May
8, 2008 – Lab Day
Members
present: Tami & Sadik
Today, Tami removed all the plated tiles from the racks. Tami
heated the back of the tiles with a blow torch and removing the solder in the
process was able to detach the times from the racks. She had to take special
care as to not scratch the Ni-W coated surface on the other side. Once the
tiles were removed, Tami wiped them down with water and eventually stored in a
Ziploc bag. Similarly, Sadik & Tami removed all the pins from the base of
the chess pieces by applying heat from a blow torch to the base of the pieces.
Initially, we explored removing the pins from the base of the pawns with a pair
of pliers but the pins were extremely difficult to remove because of the
accompanying solder. By a stroke of
genius, Tami remembered that heat broke the racks from tiles, this could be
applied to the pins in the base of the chess pieces. We decided to apply heat
to the base with the blow torch and it worked out perfectly! We simply clamped
each chess piece in the vice making sure that the pins were facing up. Then
Tami heated the base with the blow torch for about thirty seconds and Sadik pulled
the pin out with the paper towel (with relative ease). This not only showed ingenious
resourceful lab techniques but also encompassed great teamwork between Tami and
Sadik. This was very motivational after having such a hard time with the
earlier team challenges experienced a few weeks ago.
After the tiles were removed from the racks, and the pins
removed from the pieces all that was remaining was to clean the backs of the
tiles and to felt the base of the pieces. The board also needed to be
assembled.
Tami spent the evening working on cleaning the backs of the
tiles by doing the reverse of a technique that Aaron and Sadik had done to mask
the tiles originally. First, she clamped the tile and hung it over a bucket of
water. As she took the blow torch and heated the tile, any drops of solder
would fall into the water. She used a putty knife to scrape the remaining
residues and solder off the tiles while applying the blow torch. After the back
was “clean” she would release the clamp and the tile would fall into the water
to immediately cool down. She repeated the process for the 36 tiles that were
masked from the Ni-W coating.
Sadik,
Aaron, and Tami discussed the plan for the limited time left in the semester. Tami
bought the self-adhesive felt and traced the sizes over the weekend. Sadik
polished the aluminum board over the weekend.
UPCOMING
TUESDAY SCHEDULE
Tami,
Sadik, and Aaron will be assembling the board as well as cutting/attaching the
felt to the chess pieces. They will also be finalizing the poster and
presentation for the last day of class which is this upcoming Thursday.
May
6, 2008 – Lab Day
Members
present: Sadik, Tami, and Aaron
Sadik, Tami and Aaron traveled to Xtalic to finish the
plating of all the chess pieces and the tiles.
As always, we were warmly received by the company and were assisted by
Alan Lai for the day. In preparation for the plating procedure, we masked all
tiles and racked them up. Additionally,
we had attached pins to the base of the pawns and that made fixing the pieces
in the bath very easy. We went through
the plating process by first washing the pieces in the cleaning solution, passing
them through a copper electrode bath, rinsing with sulphuric acid solution and
eventually immersing the piece in a bath enriched with Nickel and Tungsten
salts. Surprisingly, we noticed some burn out on the surfaces of the plated
pieces and this was attributed to several factors including less degree of
polishing and the contact angle between the pieces and the electrodes. We
plated 16 pawns, 5 rooks, 4 knights, 4 bishops, 3 queens, 2 kings, and 36
tiles. Tami and Sadik are now experts to the Ni-W procedure after having dipped
so many pieces.
Meanwhile,
back at MIT, John worked a little lacquering the second set of tiles and
applied brown patina to the second set of chess pieces.
April
29, 2008 – Lab Day
Members
present: Sadik, Tami, and Aaron
We
explored patination. We used the brown patina and realized that when left to
dry after patinating, the surface of the pieces tarnished badly and was quite
an uncanny site. Therefore, in our second trial phase, we wiped off the patina
from the surface of the pieces. This turned out to be an ideal method and so we
used it to surface treat all the pieces and the tiles. The pieces with patina were lacquered as well
to accentuate their lustrous appearance.
April
25, 2008 – Lab Day
Members
present: Sadik, Tami, and Aaron
Over
the weekend, Tami & Sadik finished buffing all the tiles using the buffer
and readied them for electroplating. We attempted to patina the pieces and the
tiles. We also cut the final set of chess pieces that were cast from the pawn
tree using a dremel tool, sand papered the bases and polished the surfaces with
the vibratory finisher overnight. We also contacted Alan Lai from Xtalic,
informing him of our attention to plate our pieces the following week. Since we
would be plating en masse, we asked him how he would like us to stack the pieces. He advised that we mask the back of the tiles
so that the solder will not interfere with their industrial bath.
___________________________________________________________________________
One week break in lab progress as some members had to
re-learn what the word teamwork means.
April
15, 2008 – Lab Day
Members
present: Sadik, Tami, and Aaron
Lab Activities
The group was rather split
up for today’s lab session. While Aaron continued dealing with welding/brazing,
and the construction of the “tile holder”, Tami and Sadik tried their hand at
the final bit of waxwork.
Several new attachments were
ordered for the Dremel tool. Originally, we only had a small sanding bit. While
excellent for removing imperfections from the smooth, large, rounded surfaces
present on most pieces, the tool was unsuited to some of the finer areas of
detail on certain pieces. The first piece ordered was basically a tiny drill
bit which would be able to fit into these tinier grooves. Using this attachment
is actually rather difficult, given the hardness of the alloy we’re using and
the tendency for both the piece and the bit to vibrate. Clamping the piece down
doesn’t help much, as most of the shifting is simply translated into the hand
tool. In addition, a set of copper brushes was ordered. These rotating brushers
should be able to remove slight debris from the surfaces as well as begin the
polishing process. Additionally, two types of polishing wheels were ordered.
One is a simple flat disk, meant to polish blunt surfaces on the pieces, while
the other has a narrowed edge which can be used to fit into hard-to-reach
grooves on the pieces.
Upcoming Schedule
As
of this week, the group is almost definitely set on using the nickel-tungsten
coating for our white pawns. The gloss is quite nice, and the surface comes out
very smooth after treatment. We are planning to try to schedule an appointment
for the week of the 28th to coat the pieces. In the more immediate
future, we will burn out the mold made on Monday during lab on Thursday, and
then we will cast pawns on Friday. With this casting, we should have enough
pieces to complete the electroplated half of the set. The rest of the castings
should be completed the following week, and we should be in the final stages of
the project very soon. Tami and Sadik will finish the 2 molds they were working
on, in hopes that they’ll be ready to pour on Tuesday. Aaron will continue
working on the way to suspend the squares in the electroplating solution. John
will continue his work with the new dremel attachments and polishing techniques
to try to finish the pieces as nicely as possible.
April
10, 2008 – Lab Day
Members
present: Sadik, John, Tami, and Aaron
Lab Activities
After our presentation, the
group met in Mike’s office to identify pressing tasks that needed to be done to
expedite the progress of the project. It
was agreed that Aaron would explore brazing while the rest of the team shared
the responsibility of burning investment molds, ordering patinas and
experimenting with different types of patinas from Mike’s previous work on
medallions.
Setting up and burning the mold: We worked
simultaneously on three different molds that had been prepared the previous
week. Two of the molds had a cylindrical
geometry while the last mold was rectangular in shape. Like last time, we first
removed the cardboard paper that encased the ceramic using a knife. This
was done gradually by rotating the block of ceramic to unwind the cardboard
paper, similar to the way one removes the cardboard tube around a can of ready-to-bake
biscuits. After the encasement was removed, we centered the material on
two refractory bricks in a miniature furnace. Using map gas methyl
acetylene propadiene, we set the ceramic aflame. We monitored the burning
of the ceramic carefully to ensure that no cracks were being created as a
result of the flame. This is because the cracks yield localized leakage
sites on the material that will affect the mould. Once the process was
completed and the flame had died, we allowed the material to cool for a while.
The molds exploded a little, but did not crack as severely as the molds had
during the previous casting.
As the flames smoldered, we
noticed that the rectangular mold burned unevenly. The flame that burned the
mold was centralized on one half of the ceramic, burned slowly and charred the
ceramic to a lesser extent. This is attributable to the extra pair of holes in
this mold and it is very likely that the irregularity in the burning pattern is
not a function of the rectangular geometry. In order to remedy the
uncharacteristic and rather unnerving burning of the mold, Mike suggested we
use a refractory brick as support to incline the brick at angle of 45°. Mike’s
insight turned out to be extremely helpful as it maximized the surface area of
the mold engulfed by the flames. Shortly
after this critical step, we successfully completed the burning of all three
molds.
Patina Exploration: We tried different patina solutions to decipher which
surface finishes worked well and which ones were simply an aesthetic faux pas.
Three different patina solutions were used. The first solution was a black
patina solution (although it had a deceptive blue look that clearly belied its
surface finish) that works well for copper, brass and bronze. The second solution was pewter suitable for
only brass and copper alloys and a brown solution that also worked well for
copper and brass. All three solutions were purchased from Sur-Fin Chemical
Corporation. Before depositing the
patinas onto the surface of the pawns, we wiped down the pawns with a metal
conditioner called Sur-Clean 400. The metal conditioner cleaned the surfaces
and by rinsing with some water, we removed residual particles that tend to clog
the pores of the pawns. For all three solutions, we poured a small amount of
solution into a cup and immersed the pawn into the solution for amount five
minutes. We allowed the pawn to adsorb the solution until there was a vivid
color change and dried it on the bench for about ten minutes. As expected, the
pawn in the black patina solution turned black while the pawn in the pewter
solution gained an astonishing yet radiant pewter look. The pawn in the brown
solution turned a rather dramatic brown.
We lacquered all the pawns with flat lacquer to enhance the luster of
the pawns.
Impressed by the variation
in the results, we juxtaposed the electrolytically plated pawn with all the
pawns covered in the patina and discussed which pawn best complemented the
plated pawn. We deliberated ad nauseam on the choice of pawns; clearly, we were
torn between what our hearts wanted and what our hearts needed. In the end,
Shakeel’s prefrosh (an avid learner who was seemingly engrossed in foundry
work) delivered us from our quandary and made the executive decision for the
team. Save for John, it turns out that everyone in the team agreed with the
prefrosh that the plated pawn was best complemented by the dark brown pawn. We
are still figuring out which way to go with the surface treatment of the pawns
and are weighing several options. For example, according to one school of
thought, application of a high gloss lacquer instead of a flat lacquer will
make the sample more lustrous and will eliminate the aesthetic mismatch that
John was concerned about (definitely a valid point).
Brazing: Aaron
explored several techniques for brazing metals. The reason for this is that in
order to electroplate the small plates which we will inlay into the machined
board, we will need to align them in a sort of grid or matrix during the
plating process. The sharp corners and edges of the squares cause “burning”
which leads to a discoloration of the coating at these points. By positioning
the pieces close together, we can avoid this burning effect since the electric
field lines of neighboring pieces will interact.
Casting: Poured
the 3 molds which had been burned out the day before. After some cooling, the
pieces were removed from the hardened investment. It was found that of the
total of about 28 pieces, 18 were of “useable” quality. There is much touching
up that needs to be done, but an order has been placed for special tool bits
that should help with removal of excess metal and smoothing of the surface. We
prepared another 2 molds (of 6 pieces each) for casting. We mixed and poured
the investment over the waxes, and the investment should be ready to burn out
later in the week.
Upcoming Schedule
Next
week, we will continue with surface treatment and will commence assembly of the
chessboard where we will use epoxy to in lay the brass squares in the aluminum
frame. Additionally, Tami and Sadik will prepare another investment mold on
their own, to create the final few pieces we should need to complete the chess
set. Later in the week we will cast molds and then early next week we should be
finishing up with our casting of these new molds.
April
8, 2008 – Lab Day
Members
present: Sadik, John, Tami, and Aaron
Lab Activities
After Aaron fixed the
machine over the weekend, we thought it wise to do further work with the
injection molder in order to gain further experience with the tool. During our initial experience with the
machine, although the group members learned many of the functions, we were
unable to produce anything when the problem showed up. Aaron worked with Sadik &
Tami to assemble the machine by screwing all the removed frames together. The process was fraught with some
difficulties as we had to ensure that all connections were air tight and
wouldn’t leak after a while.
We encountered some water
leakages here and there but as engineers, we remained unfazed by the
setbacks. We worked tirelessly to screw
on very airtight tubes and finally managed to ensure that there was no water.
However, we were a little too diligent in this task. One of the small
connectors broke off, meaning we wouldn’t be able to use the water to heal the
mold. After going through the painstaking assembly, it seemed a shame not to
injection mold anything ourselves. Thus after cleaning up some of the water and
ensuring that there was no further leakage, we went ahead with some cold
castings of the various “dogbones” in the particular mold we had loaded. We
noticed that because of the low temperature of the mold, and because of the
thin parts we were trying to create, the material solidified before completely
filling the mold. As a result, our dogbones didn’t fill fully and a disk-like
piece ended up filling in an elliptical shape. Still, we had some experience
with the machine and performed the injection molding several times.
Afterwards, we had to go
through the arduous task of disassembling the connections for all the hoses on
the machine. Although it was pretty challenging, it was a true test of our
tenacity and problem solving skills, particular in maneuvering the oversized
wrenches in close quarters. We all got a lot of hands on experience with tools
that they weren’t used to, and overall they felt it was both a rewarding and
entertaining experience.
Upcoming Schedule
Our
plan for this coming week is to cast the next set of pieces, which should
hopefully be our major casting of the semester. We will need to do one more,
but it should only include about half a dozen pieces or so if we’re lucky with
this casting. We’re going to bake the molds on Thursday during lab in the
basement, and then hopefully cast on Friday.
April
3, 2008 – Lab Day
Members
present: Sadik, John, Tami, and Aaron
Lab Activities
Today, we traveled to Dr. Schuh’s company, Xtallic, located in
Westborough to surface treat five of our samples. Upon arrival, we were warmly received by the
employees at Xtallic and given a guided tour by a Materials Engineer at the
firm called Alan Lai. Alan chaperoned us
throughout the day and gave us all the assistance we needed. As discussed earlier, the type of surface
treatment we performed was electrolytic plating, specifically, nickel with
tungsten tuned electrolytic plating.
Following Alan’s counsel, we connected our samples to electrical leads
by attaching them firmly to a pair of scissor-like holders. We used a taught
piece of wire to hold the grippers shut and grasp the piece by its edges.
Initially we tried tapping our samples by using a drill to create a hole at the
base of the pawns into which we could insert a small screw. However, the severe
hardness of our samples didn’t make this possible giving the machining
capabilities of their lab. One of the workers offered to fetch us harder tips,
but ultimately we decided that grasping the pieces on the edges would be
sufficient for our purposes.
Using an estimated pawn surface area of 70 square centimeters, one of
the Xtallic employees calculated the parameters for electroplating using
top-secret proprietary information.
After calculating the surface area and inputting the current and voltage
parameters, we subjected the pawn to serial cleaning where the pawn was passed
through multiple tanks containing different four different solutions. The first tank was a cleaning solution that
contained standard industrial solvents used for cleaning. Additionally the tank
was sonicated. The second tank was also
a cleaning solution but unlike the first tank, it had a greater concentration
of solvents that ensured thorough cleaning of the surface of the material. The third tank was filled with copper
electro-cleaner solution and connected to a rectifier that regulated the
current flow. The fourth tank contained a 10% by volume sulphuric acid
solution. The final tank, in which the Nickel and Tungsten salts were in
solution, was equipped with a rectifier to control the wave form. This allows to company to obtain precise
control of the grain size of the nanocrystalline surface structure by
controlling how much of each metal is deposited. Unlike most other plating
processed, which utilize DC, Xtallic uses AC to obtain their fine control of
the final product. The steps for coating the first pawn can be summarized as
follows:
- Attach the pawn to a
holder. Immobilize the pawn firmly
such that it doesn’t threaten to give way during successive dipping in
solutions.
- Wash the pawn with water to
remove any foreign matter from the surface. This can be done by simply placing the
pawn under a tap and drenching it with the gushing running water.
- With the aid of a clip, dip the
pawn in a cleaning solution for about 5minutes. The pawn should be
strategically placed between the anodes to maximize contact with the
solution.
- Remove the pawn from the
solution and rinse it thoroughly with water. This rids the surface of dirt
particles and other surface impurities.
- Place the washed pawn into a
beaker containing water and transport it to the second tank containing the
higher concentration of cleaning solvent.
- Remove the pawn from the beaker
and lower it into the tank. Use a clip to affix the pawn in the
solution. The pawn is left in the
solution for about 10minutes. The solution in this tank is ultimately
responsible for completing the cleaning process. By the time the pawn is
removed, most of the dirt particles on the surface and other clogged
particles would have been removed from the pawn.
- Gently remove the pawn from the
tank and wash it with water.
- Momentarily place the pawn into
the third containing the copper electro-cleaner. Hold the pawn down for about twenty
seconds making sure that the pawn is positioned between the anodes in
order to maximize electrolytic contact.
(Note: The tank is connected to a rectifier that produces 0.1A of
current per square centimeter.) Here, one notices the formation of bubbles
as a result of the evolution of hydrogen gas. The pawn is removed after 20
seconds. Due to the short stay in
the solution, the pawn can be dangled over the tank by hand instead of
clipping.
- Remove the pawn from the tank
and wash it thoroughly with water.
- Place the washed pawn in the
fourth tank containing 10 % sulphuric acid for about twenty seconds and
transfer it back into a beaker of water.
- This time around, wash the pawn
with tap water and deionized water in quick succession.
- Lower the pawn into the final
tank containing the metal salts, organic chemicals, acids, and other
top-secret goodies that we’re not allowed to know about. Under the
settings used for our particular surface area, the pawn remains in the
bath for about 11minutes. The parameters for electroplating use one
waveform for the first 10 minutes to deposit the bulk of the material,
while a second waveform us used to deposit a slightly different surface
layer that helps prevent corrosion.
- Finally, remove the pawn from
the solution, wash under the tap, and savor its beauty!
We plated three pawns. Two of the pawns
turned out the same but the third pawn was less lustrous because we roughened
the surface using a coarse brush before plating. Polishing affects the luster of the plated
pawns because the smoother the surface of the material, the better incident light
is reflected off the surface. Thus smoother pawns will yield mirror like
surfaces. The coatings we used were set for 4 microns in thickness, which
should provide more than enough durability for our pieces.
Over the weekend, Aaron spend long hours
working under the injection molder. He managed to identify the problem with the
machine as a circuit board which converts analog inputs to digital signals. One
of the contacts appears to be malfunctioning, which corresponds to the switch
from which we get no response. Fortunately, that particular function isn’t
necessary to return the machine to “standard position” and set it into
automatic mode for injection molding (an issue we hadn’t realized last week).
Thus, Aaron was able to produce several plastic pawns and carries them around
with him at all times. One can only imagine his feeling of pride.
Upcoming Schedule
This
coming week, we will perform castings towards the end of the week. We’ll fire the molds on Thursday most likely.
Tomorrow the group will continue work on various odds and ends needed for the
project involving machining, planning, wax-work, etc… Time will likely be split
between Mike’s office, the foundry, and the machine shop upstairs.
April
1, 2008 – Lab Day
Members
present: Sadik, John, Tami, and Aaron
Lab Activities
We met to commence
injecting molding. Injection molding is a fabrication technique used for making
pieces comprising both thermoplastic and thermosetting materials. This
intricate manufacturing process is carried out by injecting highly pressurized
molten plastic into a mold. The mold is usually the negative image of the
desired product outline. In our case, we
precision machined our mold using the CNC mill from a purchased slab of
Aluminum. We were excited to learn about injection molding because it is a
commonly used manufacturing process and has several uses ranging from the
production of small components to enormous parts of machinery. Injection
molding can achieve an IT Grade of about 9-14. The IT Grade by definition is
the "tolerance a given process can produce for a given dimension".
Some of the commonly used
thermoplastic materials include polystyrene, polyamide, polypropylene and
polyvinyl chloride. The plastic used depends on the nature of the work being
done because each plastic has its own set of advantages and disadvantages. For
example, polystyrene is inexpensive but also lacks mechanical strength and so
it won’t be as strong. For our work, we
ordered three types of plastics: High Density Polyethylene (HDPE), high impact
polystyrene and polypropylene. A
detailed description of the polymers can be found in the order sheets posted in
this document. An excess was ordered such that the department has a supply for
future students. Also, ordering in bulk simply makes more economic sense.
After an overview of the
machine, we started the injection molding process. The machine we used was a
Battenfeld Unilog 1020 injection molder manufactured in
After returning downstairs,
we managed to load the molds into the carrier and we tested that the mold
closed appropriately by operating the machine in manual mode. Aaron continued
his orientation of the machine, explaining the built in manufacturer safeties
which require that you cycle through the emergency stop knob, the shielding,
etc… before you can proceed. As we worked on the process, we noticed that the
controls weren’t responding when trying to use the hydraulic system to align
the device. We were unable to shift the device at all, although we were able to
melt material and successfully flow it through.
We also couldn’t engage the
machine in automatic mode because we received an “error 19”. Upon looking in
the user manual, we found that the device wasn’t appropriately registering as
prepared for use. We believe this has to do with the malfunctioning command
preventing the motion of the knob in one direction. Additionally, we noticed
that when both opening and closing the mold, the pressure gauge on the front of
the injection molder would respond by reading a built up of pressure. When
activating the broken switch however, we found that the motor did not respond
at all. The initial thought was that it might be the switch, so we switched
switches to test this hypothesis. We still couldn’t get the machine to work,
and as such, as concluded the problem must lie within the machine.
Upcoming Schedule
On
Thursday, we will present a brief update and then we will rush over to
Professor Schuh’s surface treatment company in order to nickel electroplate
several of our pawns. We must remember to bring lab coats, as they don’t have
enough spares for all of us to do hands on work. I figure I’ll forget this
unless I put it in the progress report. We can remove this sentence later.
Mar
20, 2008 – Lab Day
Members
present: Sadik, Tami, John, and Aaron
Lab Activities
The group met with Yin Lin
for SEM analysis in the Course 3 SEM lab located in building 13. The samples examined were the as received
brass ingot and a cast metal piece taken from the base of a pawn. The SEM analysis was performed to determine
the elemental composition of each sample. We generated spectra for the samples
and determined the relative composition of each element present in the
sample. Based on the spectra, we learned
that the elements in the samples were Al, Sn, Mn, Fe, Ni, Cu and Zn with Cu and
Zinc being the most abundant constituents.
For
the as received sample, shown in Figure 1, the SEM spectrum indicated that the
percentage of copper was 64 while the percentage of iron was 40 with the
remaining trace elements accounting for the remaining composition. Pictured below, the as received sample showed
a dendritic phase interspersed with black spots. Figure 2 shows the distribution of the
elements in the cross section examined.
Figure 1: Cross section of as received
sample
Figure 2: SEM Spectrum for
as received sample
As expected, after casting,
the percentage of copper and zinc in the metal decreased. However, comparatively, the amount of zinc
lost was significantly greater than the amount of copper. The percentage of copper
was found to be 57 and the composition of zinc had decreased to 34%. Figure 3 below illustrates the expected
changes in the amounts of zinc and copper.
This is primarily due to the emission of zinc in the form of zinc fumes
during the melting of the brass ingot in the crucible. Counter to what we initially hypothesized,
many of the black spots seen in the micrographs represent iron inclusions that
are usually incorporated into the material during processing in order to
surface harden the metal. There were voids present in our cast sample however,
just far fewer than we had initially anticipated. These voids appeared to have
slightly light and hazy boundaries in the images, as opposed to the dark and
distinct edges of the iron inclusions.
Figure 3: SEM spectrum of
cast piece taken from the base of pawn
We explored different
locations on the samples to gather more data on the relative changes in
composition as a result of casting. A
complete list of the plots and their corresponding scan sites can be found at: ftp://prism.mit.edu/3.042-spring08/alldata.pdf
After the SEM analysis, we
proceeded to divide up pending tasks.
Sadik worked on cutting a thicker slice of cast metal from the base of a
pawn on the pawn tree. This piece was
delivered to Yin Lin and will undergo SEM analysis. The results from this experiment will
corroborate our data from the recent SEM analysis. Tami cut small pieces of
brass ingot using the horizontal band saw while Aaron completed the machining
of the board using the CNC mill. John
spent the rest of the day preparing pawns and fixing pawn trees in an attempt
to salvage the remainder of the pieces used in the failed investment pouring
attempt.
Lastly, the group discussed
the prospect of visiting Dr. Schuh’s outfit together to surface treat our cast
pawn pieces. We agreed to undertake the
assignment immediately after Spring break during a lab period.
Upcoming Schedule
This Tuesday, we will meet in Mike’s
office to perfect injection molding of a plastic chess piece. Sadik, Tami, and
John will attempt to operate the injection molder independently under Aaron’s
guidance. Also, we will select and prepare our samples for surface treatment
which we should be performing on Thursday. Finally we will discuss SEM results
from sample submitted to Yin Lin before Spring break and juxtapose the results
with previous SEM results.
Mar
18, 2008 – Lab Day
Members
present: Sadik, John, Tami, and Aaron
Lab Activities
The day began with Yin Lin explaining
the steps involved in preparing our samples for X-Ray Diffraction to each of
the team members. She discussed how she methodically cut two thin pieces from
the as-received brass ingot and the cast alloy, placed them on two slides and
later mounted them under an optical microscope.
A close inspection of the sample taken from the cast pawn tree revealed
quite an interesting result. We found that in the as-received sample, there was
much more alpha phase copper present than in the cast sample. Additionally, the
cast sample had many air bubbles present. We agreed that this lack of alpha
phase is likely due to a fast cooling rate in the area which we took the sample
from, and that by sawing off another piece from the cast pawn tree in a thicker
area, we should be able to find more alpha. This is because, by virtue of its
position and surface area, during casting, diffusion heat occurs at a
relatively slower rate at the sprew which is thicker, than the thinner gates
leading to each individual pawn. Also, the sprew is at the center of the
ceramic. On the other hand, the sample taken from the base of the pawn is near
the surface of the ceramic and was in closer proximity to the water we dumped
the mold into, so cooling and diffusion occurs much faster there.
Tami brought the piece to
the analysis lab. Below we see an image of the first cut being made. Notice the
position from which we are gathering the sample is located between the two rows
of pawns, near the center of the mold.
With the aid of the optical
microscope, we noted the differences in the microstructure between the two
samples. A juxtaposition of the electron micrographs of the two samples
revealed that there two distinct phases; an alpha phase and a beta phase. The alpha phase comprises a cluster of
dendrites while the beta phase consists of large grains. (Figure 1)
BETA
PHASE BETA
PHASE ALPHA
PHASE
Figure 1: a. As
received (50X) b. cast alloy
(50X) (base of pawn)
From the micrographs above
we see that for a sample taken from the base of pawn, there is virtually no
alpha phase after casting the metal. Note that we get some alpha phase. We
predict that there should be slightly more alpha phase in a sample taken from
the sprew for the reasons mentioned to earlier. There is more diffusion time
and slower cooling near the sprew so there is enough time for dendrite
formation and subsequently we get more alpha phase.
Additionally, courtesy of
Yin Lin, we obtained data on micro-hardness of the as received sample and the
cast metal taken from the sprew. The
results obtained are as follows:
Table 1: Results of Hardness Tests
|
As received sample taken
from brass ingot |
1. Alpha phase has an
average HV of 115.96 with a 10g load and an average diagonal of is 12.8
microns 2. Beta phase has an
average HV 146.1, with 10g load the average length of diagonal: 11.24
microns |
|
Cast sample taken from
sprew. |
1. Since there is
virtually no alpha phase, indentation is impossible. 2. Beta phase has an
average HV of 152.6 with 10g load and an average diagonal of 11.1 microns. |
The results summarized in
Figure 1 above shows that the alpha phase is harder than the beta phase. Additionally, the beta phase for the as
received sample is softer than the beta phase of the cast metal. This is
unexpected, because of the loss of zinc during casting in the form of zinc
fumes which should weaken the material. We will be able to postulate the
reasons for this better after performing a compositional analysis on the
samples. See an image of the copper-tin phase diagram below:
Sand blasting:
We also sand blasted a couple
of pawns in the labs. The process was
done to smoothen, clean and shape the surfaces of the pawns. This was done by
directing a jet of abrasive particles across the surface of the pawns and this
produced an even finish. The resulting
pawns had a very smooth surface but retained blemishes caused by trapped air
bubbles. The pawns themselves discolor slightly, likely from a combination of a
rougher surface finish and sand becoming imbedded into imperfections. So far,
we have three different “colors” of pawns, as evidenced by the image below. The
far left pawn is “as cast”, and has not been smoothed at all. The pawn in the
middle has been sand blasted, and then washed down with water. The pawn to the
far right has been polished using the vibratory finisher, causing a slight
discoloration. This is perhaps due to a change in the surface
topography/roughness of the metal, as well as some oxidation occuring as a
result of the polishing lubricant.
Lastly,
the mold which last week did not set properly. We believe that there was a
problem with the mixing of the catalyst, which could account for the fact that
the ceramic didn’t harden. We essentually found that the material was like wet
sand on the inside of the mold. The wax pieces were removed from the molds, and
salvaged for a investment setting. See an image of the destroyed molds below.
Upcoming Schedule
We
are scheduling a meeting with Prof. Chris Schuh to use the facilities in order
to electro plate some pawns. Right now we are planning to head over either the Tuesday
or Thursday after spring break as a group. There was some discussion of going
this Friday, however Tami will be out of town and was rather excited about
being able to experience the process herself.
On
Thursday, we will be starting the class by heading down to the UGTL where we
will perform analysis on the samples of metal taken. We have time reserved on
an SEM. After this, we will spend the rest of the day in the foundry working on
creating investment molds. Our plan is to cast some molds over the weekend and
at the beginning of next week, and allow them to dry for the duration of the
break, and then to do a major casting the week after spring break. This way we
should be able to produce a good number of pieces during a single casting
session.
Mar
13, 2008 – Lab Day
Members
present: Tami, Sadik, John, and Aaron
Lab Activities
We worked on cutting off the
pawns from the cast pawn tree using a saw. This was done by securing the pawn
tree firmly in a vice and clamping it at an angle that allowed free movement of
the saw. The pieces were cut systematically
with care taken not to dent adjacent pieces.
Occasionally, the tree was removed from the vice and rotated in order to
adjust the cutting angle. Below is an image of Sadik hard at work removing our
pawns from the tree manually with a saw.
In all, ten pieces were
cut. He also sawed off a small piece of
alloy located at the base of a well formed pawn with no blemishes. This piece was wrapped up and sent to the
X-Ray Diffraction lab for composition and elemental analysis. Additionally, Sadik used the horizontal and
vertical band saws in tandem to cut out a small piece of the as received brass
ingot. The first phase of the cut using
the horizontal band saw was done as follows:
- First, the desired section of the brass ingot
was marked with a sharpie.
- The hefty brass ingot was placed in the vice of
the saw such that a small section of the ingot protruded outside of the
vice.
- The lubricant outlet was pressed and coolant
gushed onto the edges of the blade.
- The motor was pulled to lower the blade of the
saw and subsequently, cut the brass.
- Cutting continued gradually until the piece was
cut.
Once the piece was cut out
with the horizontal band saw, Sadik used the vertical band saw to cut out a
very small piece of brass. This procedure was relatively simple. It was done as
follows:
- The thin cutting blade was inspected for any
dents.
- The machine was switched on.
- Satisfied with the cutting edge, the brass piece
was pressed down flat on the surface of the stage and gently driven
through the activated blade until the piece was cut.
Finally, the small brass
piece was sent to the X-Ray Diffraction lab for composition analysis. The purpose of the X-Ray analysis is to
determine how the composition of the brass ingot changes as a result of the
casting process. So by comparing the
composition of the brass piece obtained from the casting tree and the piece
obtained from the ingot, we can scientifically determine the changes in
composition as a function of casting. Furthermore, we can quantitatively and
qualitatively explain the changes in the relative composition of the alloy post
casting.
On Thursday, under the
tutelage of Yin Lin, we will perform the X-Ray Diffraction Analysis and
characterize our samples.
We also proceded to pour two
additional investment molds, for casting this week. The procedure for
investment pouring used was the same as the last time, although both molds were
made smaller. One mold was cylindrical, while the other was box-shaped. After
the investment was poured, we sanded the bases of the pawns until they were
sufficiently smoothed to be polished using the grinder in the foundry.
Afterwards, the pieces were placed in the vibratory finisher overnight to be
polished. Below is an image of the grinder used to smooth the bases of the
pawns so that they sit flat on a surface.
Aaron worked on the initial
machining for the design of the injection molded pawn we are planning in the
future.
Upcoming Schedule
On
Tuesday, we will likely meet with Dr. Schuh to discuss surface treatment of our
cast pieces. We will strategize about
how to procede with surface treatments. Additionally, we would like to fire the
investment molds cast last week to prepare them for pouring.
Mar
12, 2008 – Wednesday Afternoon
Members
present: Sadik, John, Aaron, and Tami
Note:
As evidenced by the picture below, today we all wore our safety gear.
Casting: On
Wednesday, March 12, 2008, we inspected the machined board from Tuesday and the
group discussed the intricacies of the board at length. We agreed that the
board was machined as desired with a border of about 0.1 inches between the
brass and aluminum for aesthetic reasons. Below is an image of the machined
aluminum pocket, along with the metallic squares layed into place to get an
idea of how the final board will look.
We then proceeded to cast. We used a
Before melting, we pre-heated the brass pieces in the
crucible to remove residual moisture trapped as a result of processing during
manufacturing. This step is essential
because water in the brass pieces during melting causes a steam explosion that
will derail the casting process. The
crucible we used was an Inductotherm crucible connected to a series of magnetic
coils that generated a magnetic field coupled with inductance as a result of
the flow of eddy currents produced by the furnace coils connected to the
crucible. The temperature of the melt can easily be determined using a
thermocouple. However, one can easily decipher the different stages of the
melting process by observing the generation of characteristic fumes from the
melt. Naturally, different metals have specific activities that determine the
temperature at which they can be poured for casting. As a result, there exists a welter of
published literature that indicates the temperature at which melted metals can
be poured. Additionally, most
manufacturing plants can easily furnish information on the pouring temperatures
of the alloys they produce especially because the pouring temperature is also a
function of temperature and material processing. For example, Silicon-brass has an empirical
pouring temperature of 1200°C even though its melting temperature is known to
be at
Below we see a picture of the red-hot metal before it
has actually melted. Several seconds after this picture was taken, the bottom
of the ingot began to liquify and the entire ingot slowly sunk into the
crucible.
While the pre-heating was being done, we packed a
sandbox with foundry sand. Foundry sand is simply a mixture of sand, motor oil
and clay. We padded the foundry sand
down in the box, transferred our investment mould into the box and cushioned
the mould with the sand. The foundry
sand is important because it backs up the mould and prevents the mould from
leaking during casting, especially since our investment mold had actually
cracked during the firing process. Sand was packed to the top of the mold, to
ensure that leakage would not occur during casting. When the pre-heating was
complete, we melted the brass pieces in the crucible until bluish white fumes
emanated from the crucible and the resulting slurry was red hot. We used a
blanket to cover the mouth of the crucible to prevent hot droplets from
escaping and causing harm.
Eventually, when the pieces were melted, a pair of
tongs was used to pour the metal slurry into the investment situated in the
sandbox. The presence of excess alloy on the surface of the ceramic confirmed
that the mold had not leaked as we were casting, which would have caused the
level of molten metal to decrease suddenly.
We then allowed the set up to cool momentarily and transferred the
ceramic into a bucket of cold water. The set was allowed the ceramic to sizzle
in the water for a while and the ceramic was later removed from the alloy with
a hammer. The metal pawn tree with most of the ceramic material removed is
shown below. After the image was taken, we continued to remove material from
the tree while keeping it mostly submerged in water.
With extreme caution, we hammered the head of the
investment gradually until the investment came off. We chose to hammer it
because the cast metal pawn tree enclosed by the investment is pretty robust so
it is able to withstand shocks and blows.
We went through serial steps of hammering and washing the cast metal
with water until all the investment came off.
Emboldened by the successful turnout of the cast pawn
tree, we sawed off one pawn, removed blemishes at the base with a Delta Sanding
sand caster and polished thee pawn with an Ultra-Vibe A5 finisher.
Casting
Precautions:
- Exhaust ventilation systems and respirators must
be used in tandem when melting to prevent inhalation of fumes exuded by
the melt. Exposure to zinc oxide or any metallic oxide fumes for that
matter can cause metal fume fever, a malaise which may leave one
bed-ridden for weeks.
- Pre-heat your metal alloy pieces for a
considerable amount of time to remove all the moisture and hence prevent
steam explosion.
- Typically during melting, the metal solvates
hydrogen gas and the adsorbed gas is trapped in the mould. The presence of the trapped gas is
evidenced by the blemishes on the surfaces of the cast metal and because
of the surface distortions caused by the gas, it is necessary to degas.
Mar
11, 2008 – Lab Day
Members
present: Sadik, John, Aaron, and Tami
CNC Machining: Today in the lab, we divided up the work to maximize team
efficiency. Tami, Sadik and Aaron
continued machining the second half of the board using the TRAK DPM2 CNC mill
with prototrak SMX manufactured by Southwestern Industries. Like last week, we prepared the stage for
milling by removing the vice and placing the board flat on the stage. We
positioned the half of the board we were going to machine directly under the tip
of the milling tool and using the electronic interface of the machine, we set
the x, y and z coordinates for the cut.
The appropriate milling tool was inserted into the tool holder using the
in/out button on the upper-left section corner of the machine.
After setting up the machine, we selected our
starting point for the cut (which was the midpoint of the board), entered in
the parameters for the rectangular pocket we were going to machine and began
machining the board. This time around, we upped the cutting speed to 1500rpm
and this significantly reduced the cutting time without compromising the
quality of the cut. Upon completing the
machining of the board, we evened out the texture of the surface and made the material
smoother. We subsequently stored the
machined board in a cabinet to be examined the following day.
Shown below is an image of the starting cut being
made on the second half of the board. The program was run in two steps to
accommodate the large size of the pocket we need to mill, which is actually
operating near the limits of the mill’s capabilities.
Below is another image of the machining process. In
this case, we can clearly see the flakes of removed metal and the libricant
coating the surface of the board. Additionally, the clamping mechanism used to
fix the board in place is visible on either side.
Several
new sets of wax pieces were cast, and he proceded to continue with the touch-up
work on the cooled wax pieces in order to create a good set of pieces for
casting. In anticipation of the successful completion of the casting to be done
tomorrow, he began to prepare additional wax-trees to be poured with investment
on Thursday during lab. Upon the realization by Mike that the investment is
actually quite expensive, and that the explosion in the original cast was
likely caused by its large size and internally trapped water expanding as it
vaporized, we began to look at tighter, more efficient packing methods for the
pawns. One relied on squeezing the pawns into a smaller diameter tube and
placing them all in a single layer, as evidenced by the image below. The piece
was constructed by pouring a small disk of hot wax and then inserting the pawns
directly in the wax and allowing it to cool. While this process took several
iterations to complete successfully (as detatching the wax disk from its
container turned out to be a challenge), this version of the mold should save
time in the long run as we won’t have to carefully attach individual sticks of
wax together to server as runners to feed material to each piece separately.
The
second design was more traditional, but also sought to maximize the packing of
the pieces to minimize the ammount of investment needed. An image of this is
shown below. Here the pieces are angled directly out of the main sprew, and six
of them are packed into a very small area.
Upcoming Schedule
We
will cast the metal pieces this week, and begin to look at how effective the polisher
is. We are also scheduling a meeting with Prof. Schuh to talk about taking some
of our pawns over to his company to treat them with the nickel electroplating
process.
Additionally,
we plan to make this a very productive week. We will complete the machining of
the additional squares needed on the water jet, as well as cut the remainder of
the ingots on the band saw to save time in the future (so we can cast more
precisely how much material we need, without taking the time to go upstairs and
use the saw each time). Lastly we will pour investment over the two new molds,
to hopefully prepare them for casting early next week.
Mar
6, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron, and Jogn
Lab Activities
As planned, Tami, Aaron and Sadik machined the board
today using a TRAK DPM2 CNC mill with prototrak SMX manufactured by
Southwestern Industries.
First
the machine stage was readied for milling by disassembling the vice and placing
the material on the stage. The removal
of the stage allowed us to contain our material and define a machining
space. Since the size of our material
exceeded the dimensions of the stage, we decided to clamp the edges of the
material in order to maintain stability during machining. This was done by
affixing three miniature clamps along the sides of the material.
With the aid of an in/out
button on the upper-left section of the machine, the milling tool was inserted
in place. Once the tool and the material were in position, the machine’s
electronic interface was used to set the coordinates for cutting. This
was done by directing the cutting tool to the starting point of the cut such
that the x, y and z coordinates read zero. After the starting point for the cut
had been determined, we run a trial cut only to discover that the tool could
not recognize the starting point of the cut due to the vast expanse of the
board.
Faced with this challenge,
we put on our engineering thinking hats and solved it by redefining the origin
of the cut. This means that we divided the board into two equal halves and
machined the two halves separately. We
then proceeded to machine two rectangular pockets in the board.
We also poured and removed
the first few sets of wax Kings and
In addition, the shrinkage
of the wax was measured. 100 mL of hot wax was carefully measured out and
poured into a disposable container. The way was allowed to cool for two days
(the pouring was actually done on Tuesday) and the resulting cap was filled
with water to the 100 mL mark. The water needed to reach the 100 mL mark was
measured to be approximately 20 mL, and the new volume of the wax was
calculated to be at 80 mL. Thus 100 mL of hot wax tends to want to shrink to
about 80 mL of cold, solid wax. This shrinkage is actually quite a bit larger
than the 8% predicted by Mike, although there is likely some error in the
measurement. Additionally, since the wax in the melting container is in
actuality likely a combination of several different waxes, this could affect
the degree of shrinkage. The pieces themselves should not shrink however, as
the wax inside the mold cools from the outside in. Thus the wax at the surface
tends to harden first, and then solidify towards the center. If we don’t pour
additional hot wax into the mold however, we get significant shrinkage on the
gate of the wax piece. This was a brief, interesting measurement to conduct in
an attempt to characterize the wax.
Another measurement taken
was the density of the wax. A single wax pawn was found to weigh 11.7 g. This
was placed into 195 mL of water and it was found that the water displaced to
210 mL. Thus the volume of the pawn is 15 mL, giving the hardened wax a density
of 11.7/15 g/mL or 0.78 g/mL. This is less than the density of water, which was
visually confirmed by the fact that the pawn would not sink in the beaker (a
small blade had to be used to submerge the pawn completely. The submerged area
of the blade is minimal, and was not taken into account for this calculation.)
This data will be combined with the density of the investment in order to
calculate the buoyant force exerted on the wax, and ultimately the amount of
stress held by the sticky wax upon loading. Below is an image of a submerged
wax pawn during the volumetric measurement.
Lastly, we constructed a
small wooden-frame strainer in order to periodically rinse out the polishing
medium more easily. The mesh consists of small diamond holes small enough such
that the ¼ inch polishing medium doesn’t slip through. The mesh is simply
attached to the inside of a pine frame and has little handles on the end to
allow it to rest on top of the sink for the medium to dry. The simple frame is
nothing fancy, and a newer one could likely be purchased, but given the
infrequency with which the medium will need to be washed, this simple strainer
could last Mike several years.
We’ve begun to re-look at
the way in which we assemble the pawn tree, as our first tree cracked during
firing. Aaron believes the cracking has to do with the volume of ethanol being
lit on fire. Mike suggests that the molds be made as thin as possible, as
smaller molds seem to have less issues with explosions in his experience.
Depending on how well the first mold pours this week, we will look at new piece
arrangements for casting.
Upcoming Schedule
On Tuesday, we will
continue to work in the foundry and attempt to create our first metal chess
pawns. We will be meeting at 2 pm in Mike’s office.
Mar
4, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron, and John
Lab Activities
We
began the day by identifying and outlining the various lab activities and
divided by the work accordingly. We worked on some of the back-row pieces and
shared the specific waxing techniques with the rest of the team. The techniques, he explained, were a function
of the intricate shapes of the pieces. For example, due to the complex head of
the knight, one had to remove the wax piece sideways from the polyurethane
mould. Below is the distinct ways of
successfully removing the wax pieces from the respective polyurethane moulds:
Bishop: The piece is
carefully removed after making a jagged cut in the polyurethane mould and the
piece can be pulled gently from the top. The cylindrical symmetry of the bishop
makes it very similar to a pawn, and makes the wax pieces prone to air bubble
flaws at the top of the piece.
The Rook: A double cut is made in the polyurethane mould and
the piece is removed vertically to avoid any damage to the cavity at the top of
the rook. Additionally, in the case of
the rook, the polyurethane is contained in a plastic cup of similar size to
prevent wax spillage that may lead to uneven solidification of wax in the
mould. We took this precautionary measure because the presence of cuts on both
sides of the mold makes it less able to stay together on its own.
The Knight: Once
the wax sets in the polyurethane mould, make a straight cut on the side of the
mould and gently remove the piece from the side. One must be careful of the
knight’s jaw which can catch on a piece of polyurethane. Similarly, when being
poured, the jaw area is prone to air bubbles. Only a small amount of wax should
be poured into the mold and it should be tilted to allow wax to completely coat
the jaw area of the piece. Then the remainder of wax should be added and air
bubbles should be tapped out (to prevent air catching on the delicate details
of the spine).
Below
is an image of all of our polyurethane molds made to date.
Next,
we proceeded to burn the investment (ceramic) from our mould. The process was conducted under the
supervision of Mike Tarkanian. We first
removed the cardboard paper that encased the ceramic using a knife. This was done gradually by rotating the block
of ceramic to unwind the cardboard paper, similar to the way one removes the
cardboard tube around a can of ready-to-bake biscuits. After the encasement was removed, we centered
the material on two oven bricks in a miniature furnace. Using map gas methyl acetylene propadiene, we
set the ceramic aflame. We monitored the
burning of the ceramic carefully to ensure that no cracks were being created as
a result of the flame. This is because
the cracks yield localized leakage sites on the material that will affect the
mould. Once the process was completed
and the flame had died, we allowed the material to cool for a while.
Unfortunately, a major crack formed in the side of the ceramic and may have
caused damage to several of the pieces. Mike suggested that we plug the holes
with sand and cast anyway, with the hope that the internal details of the pawns
were left in tact. An image of the mold after the ethanol has been burned out
is shown below.
While
the investment was being removed, we poured new polyurethane molds for the King
and Queen. Provided these molds properly set, we will have functioning molds
for all chess pieces and can begin focusing on assembling a variety of pieces
and preparing them for casting. He also worked on producing more wax pieces in
the adjoining lab and Sadik touched up old wax pieces. Few wax pieces were
poured as the glass beaker used to pour the hot wax was damaged. We will
procure a replacement as soon as possible and continue creating waxes to
prepare molds for casting. The procedure for touching up the previously created
wax pieces was done using the guidelines from last week as follows:
- Inspect the piece to
identify all holes and ill-formed areas that need to be refilled.
- Fill an alcohol
burner with some ethanol found in the flammables cabinet.
- Gently melt a thin
stick of blue wax with the burner so that is just liquefies at the point
in contact with the flame.
- Immediately fill in
the areas on the piece riddled with defects with the drops of melted blue
wax.
- Allow the wax to seep
into the defect area for approximately a minute by setting it down.
- With the aid of a
razor/knife, carefully scrape off excess wax from the touched-up
areas. The edge of the razor should be angled tangentially on the
surface of the piece in order to selectively remove the excess wax.
Angling the blade in the radial direction simply causes the newly added
wax to break off the piece.
Meanwhile,
Aaron worked on tool alignment in preparation for the machining of the board on
Thursday. The board we are machining is actually at just about the maximum size
the machine is capable of handling. The additional piece he machined will aid
in the alignment of the board and allow the machining of the aluminum pocket to
be less painful.
Upcoming Schedule
Sadik
and Tami will use the Solid Works design of the chessboard as template to
machine the board. As the inlayed pieces were already cut on the waterjet last
week, the machining of the pocket is the second to final step towards
completion of the board. The final step would be to treat the inlayed pieces
with our final surface treatments and actually affix them into place. We will
also produce more wax pieces, as we anticipate needing many in order to cast a
complete chess set. As soon as the metal ingots arrive, we will pour our first
batch of pawns using the mold we have completed. We will then be able to polish
the pieces and arrange to begin surface treatments.
Feb
28, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron
Aaron
showed Tami and Sadik how to use the Water jet machine located in the MIT Hobby
Shop. The orientation involved set-up,
engineering design, manual and automatic operation of the water jet as well as
clean-up.
Tool Description: The Water jet is an incredibly precise cutting tool
that is able to make cuts in different types of materials. It is an essential tool for fabrication and
manufacturing parts and is capable of cutting, carving, reaming and shaping. It comprises a cutter that is connected to a
high-pressure water tank. The water in
the tank is siphoned through an adjoining nozzle and impinges the surface of
the material with brute force and ultimately cuts the material. It is worthy of note that the torrent of
water incident on the surface of the material, gradually cuts the material. The
cutting is aided by abrasives like sand which increase the force of the
water. The machine is connected to a an
electronic interface that enables the user to make engineering designs using a
software called OMAX.
Following
the overview of the machine, we proceeded to cut out 16 squares from a brass
plate.
Procedure: Following Aaron’s tutorial, Tami & Sadik
proceeded to cut out our squares from the brass plate. Summarized below are the
steps we took to make the cuts:
- First, we primed the pump. This was achieved by fetching out the
warm water in the pump and refrigerating it for a while. When the water
was sufficiently cold, we poured it into the pump taking care not to trap
any air bubbles in the pump.
- We set the machine home to (0, 0), the origin/starting point of the
cut.
- With the aid of two heavy blocks, we flattened the brass plate.
This helped us to localize the material and prevent it from moving during
the cut.
- Using the electronic interface, we used the OMAX software to design
our cut. The software allowed us to
set the start and end points of the cut, direct the cut as well as choose
the quality or finish of the cut.
- Once the parameters were set, we filled the tank with water from
the reservoir such that brass plate was completely submerged.
- Next, we flanked the machine with protective shields and hit the
“go” button.
- Finally, we traced the cut on the electronic screen and once the
cut was complete, we reached into the pool of sand with a pair of tweezers
and gently removed the cut piece.
The
team currently has enough wax pawns to perform castings for all of their
surface treatment technique tests, with a safety factor of about 1.25 for
pieces destroyed or poorly cast.
Polyurethane
molds were prepared for the Knight, Rook, and Biship. We also prepared the
“pawn tree” for investment pouring by cutting and measuring the cardboard tube
and base, and affixing the tree to the base with wax. Met with Mike on Friday
morning to go over the procedure for mixing and pouring the ceramic slush over
the wax pieces. First, enough powder to fill the entire cardboard tube was
measured out and then weighed. The powder was then mixed with ethyl alcohol and
a catalyst was added. The materials were mixed by hand (wearing large gloves)
in order to scrape the bottom and sides of the container and prevent material
from clumping at the bottom and prematurely hardening. Once the investment was
of a regular consistency, the mixture was poured over the pawn tree into the
cardboard cylinder and placed aside to dry over the weekend. Next time we need
to mix investment, and other members will then be able to handle the task in
pairs. An image of the investment poured into the cardboard tube is shown
below.
Upcoming Schedule
We will meet on Tuesday in Mike’s office and
split up into teams, tackling both the machining of the aluminum board and
dealing with the investment and wax casting in parallel. The cavity for the
inlayed pieces will be machined into the aluminum block using the CNC mill. The
investment will be sintered at high temperatures in the furnace, and prepared
for casting upon arrival of the metal. Molds will be made for the King and
Queen pieces, while the molds for the Knights, Rooks, and Bishops will be
opened and tested.
Feb
26, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron and John
Lab Activities
Touching Up Wax pieces:
Touching up of the pieces is
important because it corrects physical defects on the pieces that occur as a
result of the trapping of air bubbles in the polyurethane mould during the
pouring of wax into the mould. This process produces desirable pieces with a
uniformly smooth surface. Although the pieces are never truly perfectly smooth
like wax pieces cast without flaws, the process should allow for good results
when pouring investment and eventually casting metal pieces. The procedure for
touching up the pieces was outlined as follows:
- Inspect the piece to identify all holes and
ill-formed areas that need to be refilled.
- Fill an alcohol burner with some ethanol found
in the flammables cabinet.
- Gently melt a thin stick of blue wax with the
burner so that is just liquefies at the point in contact with the flame.
- Immediately fill in the areas on the piece
riddled with defects with the drops of melted blue wax.
- Allow the wax to seep into the defect area for
approximately a minute by setting it down.
- With the aid of a razor/knife, carefully scrape
off excess wax from the touched-up areas.
The edge of the razor should be angled tangentially on the surface
of the piece in order to selectively remove the excess wax. Angling the
blade in the radial direction simply causes the newly added wax to break
off the piece.
Meeting with Dr.Schuh:
The
group met with Dr. Schuh to discuss surface treatment options for the chess
set. We told him about our interest in
exploring different types of patinas and he gave us numerous options for
surface treatments.
Aaron
mentioned surface shooting using Professor Eagar’s facilities as one kind of
surface treatment the group was considering. Dr. Schuh explained that shooting
was a technique that was used specifically in relation to internal or residual
stresses inside the material and would not necessarily to enhance the aesthetic
quality of the material. He however went
on to discuss Electroless plating and Electrolytic plating as two
electrochemical processes that produce aesthetically appealing yet different
surface finishes.
Electroless
plating (chemical or auto-catalytic plating), entails the controlled mixture of
different chemicals in an aqueous environment without the presence of
electricity. Dr. Schuh recommended two popular types of electroless plating:
electroless copper plating and electroless nickel plating. He also showed us samples that had undergone
electroless nickel plating and we observed that the samples had a matt
appearance. He noted that our pieces
will need about 5 to 10 microns of coating on the surface. The finish on the
pieces was metallic in nature, but tended to be matte rather than shiny.
Additionally, he mentioned that this process would not hide small defects in
the pieces as readily as Electrolytic plating. An image of some electroless
nickel-plated objects are shown below.
On
the other hand, the samples Dr. Schuh showed that had undergone Electrolytic
plating had a very lustrous and sparkling appearance. See the sample image of
electrolytic plated nickel below.
As
the name suggests, Electrolytic plating is a galvanic type of plating method
that uses the underlying principle of oxidation redox reactions to make
deposits on the surface of materials. Dr.
Schuh pointed out that in electrolytic plating, an anode and a cathode are
joined by a wire in an aqueous solution. The power supply drives metal out of
solution and onto the desired surface. See a schematic of the cell below.
He
said that a bulk of our chess pieces could be plated simultaneously by placing
them in a large barrel containing aqueous solution and inserting a wire. The set up would then be constantly agitated
by turning the barrel around to ensure that diffusion of the deposited materials
is homogeneous for all the pieces in the barrel. This would fully plate the
pieces, completing and breaking the circuit depending on which pieces were in
contact when. Alternatively, we could attach a lead to the bottom of individual
pieces which could be cut off after the plating process. This would hide the
place where the physical contact would prevent metal from plating onto the
piece.
Dr.
Schuh added the caveat that the quality of work obtained from electrolytic
plating is a function of experience with the technique and therefore the
technique is empirically tuned and not necessarily driven by scientific
knowledge.
Based
on our deliberations with Dr. Schuh, we are more inclined towards electrolytic
plating for the following reasons:
·
It is relatively
easier to level out defects on the surface of the material.
·
It produces more
shine and is therefore more aesthetically appealing.
·
It is the most
common surface treatment method widely used in industry.
That said, we considered Nickel with Tungsten
tuning, copper plating and gold plating.
Below are some of the color combinations Dr. Schuh shared with us:
Blue: coat with chrome and
heat
White: Coat with nickel and
heat it
Black: Coat with black chrome and heat it
At the meeting we briefly discussed
anodizing, an electrolytic passivation process.
We learned that in anodizing, the color of oxide and thickness of oxide
determines the anodizing properties of the material. Additionally, we discovered that different
colors can be obtained from Titanium oxide by tweaking the occurrence of total
internal reflection in the oxide.
Finally, Dr. Schuh volunteered to help us
with the Nickel/Tungsten plating since he has the expertise and owns a company
that specializes in this method of surface treatment. He said that we would be
able to use his facilities to conduct the procedure ourselves. He also asked us to check out a local shop in
Upcoming Schedule
Between now and Thursday, team members will
come in to produce more wax pieces. The
goal is to produce as many defect-free pieces as possible.
On Thursday, the team is scheduled to meet
with Ken Stone for a water-jet orientation in the MIT Hobby Shop. The orientation will include operation of the
water jet machine, engineer designing of the cuts to be made using the
machine’s software, cutting out the boxes in the material and clean-up. We were
unable to conduct the meeting today because of the timing of the meeting with
Professor Schuh.
Lastly, we are expecting our investment
order to arrive by Thursday and following receipt of the order, we will proceed
to pour investment over the assembled wax pawns. We plan to begin pouring metal
next week.
Feb
24 and 25, 2008
Weekend Progress
Over the weekend, the
internal structure of the website was re-done. All the documents and files were
taken down and re-organized. They will be reposted Monday evening along with
this progress report.
Additionally, the “laboratory
notebook” section has been re-written and updated to reflect the progress made
by the group and entries have been included in approximately two day intervals.
The previous progress reports have been extended to include greater detail and
images.
More wax pawns were cast
using the three molds and following the tips suggested by John and Aaron during
there extensive pouring experimentation. About one out of every four wax pieces
cast tend to be very nearly perfect with few flaws, while two tend to have
minor flaws which can be repaired. About a quarter of the wax pieces cast are
too deformed to be repaired and are simply melted to be recast.
The cast wax pawns were
attached to small cylindrical segments of wax to create a T-shaped inlet. The
pieces were then affixed to a central hexagonal wax rod using sticky wax. See
the image below:
The reason for the
additional segment of wax sticking out beyond the pieces is to help decrease
turbulence in the final mold when the metal is poured, as well as to capture
any impurities traveling at the front of the metal flow.
A second version of the
“pawn tree” shown above was made upon the realization that we had a large
number of 6 inch diameter cardboard tubes available downstairs but not very
many of the larger 8 inch diameter tubes which would have been needed to cover
the original design. The second structure consists of a total of 12 pawns
stacked in two layers of 6 pawns each and fits inside a cardboard tube with a 6
inch diameter. The cardboard tube is used to create a vessel which contains the
investment when it is poured over the wax models. After the investment is
poured and has cured, the wax will be melted out of the mold (this occurs
during the heating phase of the curing process).
Updated Tuesday,
Feb. 26th Schedule
The original plan for this
Tuesday has been altered slightly due to scheduling issues with Professor
Schuh. We will meet with him at 3pm to discuss surface treatment techniques. As
a result, the waterjet orientation will occur later in the afternoon or may get
pushed back to Thursday depending on how long the meeting with Professor Schuh
runs.
The hobby shop Waterjet
machine has been made available to the group thanks to Aaron’s contacts, and we
should easily be able to access the machine during our Tuesday/Thursday
laboratory hours as we need it. An image of the hobby shop’s Waterjet machine
is shown below.
At 2pm, our group will meet
in the foundry to discuss investment mixing with Mike and prepare the rest of
the chess pieces for mould making. We currently have polyurethane material on
order and plan to create additional moulds as soon as the material arrives for
the remainder of the chess pieces. Piece preparation includes sanding,
polishing, and filling in grooves of the original (purchased) plastic chess
pieces, and positioning them in plastic cups.
We will also pour more wax
pawns using the currently existing moulds and touch-up the imperfect pawns as
time permits.
Feb
22 and 23, 2008
Pawn
Casting
As part of the lost wax
casting process, we have continued to produce wax pawns from the urethane
molds. At the present time we have 3 viable molds for making pawns and are
demolding parts and re-pouring wax every few hours. See the image of the molds below. Two are large
and one is small. Next to the molds are the cups used to create pressure and
prevent mold motion during wax casting.
As some pawns still come out
of the molds with small voids (caused by bubbles, see below) we have found
ourselves touching up the pawns with small flaws using the blue wax rods
(~.050” in diam.). The technique is pretty straight forward. Using a lit
alcohol lamp, heat the wax pawn for only a few seconds and do so without
melting the wax. The goal is to preheat the red wax (pawn) so that the blue wax
will better adhere to it. In a timely
manner, you then heat the tip of a blue wax rod until the tip has melted and try
to deposit any molten material directly onto the flaw in the pawn. See image below:
Repeat this process as many
times as is necessary to produce a wax “plug” that will be shaved down to the
level of the surrounding red wax. The
best tool for shaving the blue wax down is a SHARP xtacto knife. There are
plenty of fresh sharp blades in the bottom of the tub of wax tools (looks like
a cottage cheese container full of dental tools). The same blade is great for
removing any excess flash from the molding process or trimming away excess wax
caused by bubbles in the urethane molds. See image of repaired and smoothed
pawns below. Note the smooth texture of the blue wax and the small number of
flaws in the pawns.
The technique developed over the past week
for pouring wax pieces is as follows:
1)
Remove the
previously cast wax piece from the mold.
2) Be careful to remove all the wax from the mold as
anything left in there will cause a flaw in the next piece.
3) Plug in the wax melting apparatus. Be sure to put it
up on a ceramic brick as the wiring has a short in it and you can be shocked if
you don’t.
4) While the wax melts, take a sacrificial cup (Blue
plastic cup or styrofoam coffee cup) that is the same size as the urethane mold
and place the urethane mold in it. This helps to keep the mold shut when pouring
the wax later on.
5) As soon as a sufficient volume of wax is melted, pour
about ¼ of the total volume of the pawn into the mold. You’ll know if you added
too much in the next step.
6) Now turn the mold on its side (90 degrees) and rotate
the mold along its principal axis. I’ve found that doing this for 30 seconds at
about ½ rotation per second results in a good coating of wax on the surface of
the mold. If you overfilled the mold
then some wax will pour out the top of the mold and you will get burned. BE CAREFUL!!!!
7) Now place the mold upright on the table and top off
the mold with molten wax. You want the wax to the flush with the top of the
urethane.
8) Now you want to loosen any bubbles that have gotten
stuck in the wax. The best way to do this is to smack the side of the mold
until you see some bubbles come out. There is always at least one bubble. Alternatively, you can squeeze the mold in
the hoop direction to break the bubbles loose. Whichever technique you find
works for you, use it.
9) Now check that the parting line on the urethane mold
is flush at the top of the mold and along the sides.
10) After pouring, give the wax about 30-45 min to freeze
before removing the wax pawn from the mold.
11) If the pawn is good, set it aside. Occasionally you’ll
get pawns with too many flaws, throw these back into the molten wax and try
again.
12) Trim and repair any good pawns as needed and leave
them on the plate labeled “Finished Pawns.”
NOTES:
The wax is hot, if you’re
uncomfortable working with the temperatures then gloves are available in the
cabinet by the door of the foundry.
The wax is HOT. Don’t burn yourself.
This is very important.
The heating element for the wax melting
apparatus has a short in it. If you leave the metal can on the metal table you
will get shocked. It’s not fun.
Our biggest problem with the above
process is when we forget to check the alignment of the seam in the urethane
mold. This gives weird looking pieces that are not repairable.
The molten wax has a small to it. It
is also an irritant. Use the elephant trunks in the foundry to provide
ventilation of the fumes from the wax melt.
When pawns are done being
repaired, they are placed on a plate located near the molds (It has “Finished
Pawns” written on it). If you happen to get a flawless pawn from the mold
(COMPLETELY free from of all voids, excess material, or surface discolorations)
set those aside as they will be used for the final product at the middle of the
term. Our reasoning for this is that we would like to use the repaired pawns in
the process of down-selecting a surface finish and as sacrificial parts when we
start learning how to polish them with the vibratory finisher. For this reason,
there will be many pawns cast in the first attempt.
Ordering
and Materials Selection
In addition to the work done to obtain wax pawns suitable
for casting, we have also been concerned with order of materials for the
project. Specifically we’ve ordered:
McMasterCarr:
Aluminum stock – Al-6061 stock, this will be perfect
for the machining and easily anodized or electroplated for the board
Brass stock – Thin stock will allow us to use and
inlay style assemble of the board.
Locktite adhesive – This will attach brass to
aluminum and only cures in the absence of oxygen so it’s perfect for our
application.
Vibratory Finisher – We bought one that was the right
size for both the bell and the chess groups. This is a heavy duty unit with
adjustable offset on the weight and a bowl that allows us to use either wet or
dry media. Prices were compared between MSC Direct and
Storage box – I also bought a blue PP storage box
that gives us a place to store the wax patterns before they are assembled into
the wax trees.
A detailed copy of the McMaster order can be seen
under the “internal documents” section of the website HERE. (MAKE THAT A LINK)
-1/4” pyramid (Medium Grit)
-1/4” pyramid (Fine Grit)
-Dry Polishing Media for Brass
-Polishing Compound for Brass and other soft metals.
A detailed copy of the
Alchemo of
Conneticut:
Aaron spoke with an R&D
scientist (Gene Bonds) at H. Kramer & Co. (a brass smelter in the
There is only one concern
with the alloy. It is very susceptible for porosity if not cast correctly.
Their recommendation was to minimize the turbulence in the flow of liquid
within the mold. We will need to take this into account when designing the wax
pattern “tree.” Some suggestions were offered but more reading will need to be
done to understand how to minimize the turbulence in the flow. Obviously we
need to avoid sharp corners in the gates of our mold but more information is
needed before a suitable runner/gate arrangement can be settled upon. It is
uncertain if mold flow will allow us to calculate the turbulence in the flow,
but that can be looked into next week.
The local distributor for H.
Kramer is located in
At this time, it appears
that will be ordering our raw brass ingots from Alchemo in Ct. As soon as a
P.O. can be obtained the material will be ordered.
Estimation
of Amount of Material
Mike had asked us to order
100 lbs of brass because it is a common foundry material and would be used up
anyways. In the interests of cost, buying in bulk was cheaper in the long run.
We know that the chess set will not be that heavy but it’s of interest to us to
know what the final mass of the board and pieces will be.
Through solid modeling we
were able to determine that the mass of the board (Aluminum + Brass parts) will
weigh about 22.5lbs (10.2 kg). However, we don’t have solid models of the chess
pieces yet so we are unable to determine their mass. In order to determine the
mass we’ve measured the volume of the pieces and calculated the mass using the
density. We used the water displacement method to obtain the piece volume. The
chess pieces fit perfectly in a 250ml graduated cylinder (250:2). Table 1 shows
the results of those experiments.
|
Chess
Piece |
Volume
[ml] |
Weight
[g] |
|
Pawn |
10 |
83 |
|
Knight |
20 |
166 |
|
Rook |
19 |
158 |
|
Bishop |
16 |
133 |
|
King |
30 |
249 |
|
Queen |
25 |
208 |
|
|
Total: |
~4070g
[9.0lbs] |
Table 1. Estimated Mass of Chess Pieces (assuming
ρ=8.30g/cc)
Each chess set should cost
us about 9lbs of brass (excluding the gates/runners/sprue, which can be
recycled). At $5.95 per pound, the estimated raw material cost for a set of
chess pieces is $53.55
Feb
21, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron and John
Lab
Activities
Group
orientation on Computer Numerically Controlled (CNC) mill:
Aaron introduced the group to the CNC
mill and taught the team how to operate the machine as independent users. The overview included safety concerns with
the machine, insertion and removal of tooling bits, location of bits within the
lab, manual and automatic operation of the machine, and cleanup. This overview
on the CNC was important because the device will play a pivotal role in the
fabrication process of the chess board.
The CNC will be an essential tool that all members of the team have to
be conversant with. The CNC mill that
the group worked on was a TRAK DPM2 with prototrak SMX manufactured by
Southwestern Industries.
Instrument/Machine description:
The
CNC mill is a state-of-the art tool used for milling all kinds of
materials. Since the inception of the
CNC mill, older production mills have become antiquated due to the relative
ease of operation and set up of the CNC.
The machine is “designed to use modern tooling”[1]
and is equipped with an electronic interface that permits the user to upload
specific designs into the machine and the tool subsequently churns the design
under the supervision of the user.
The
software interface easily reads designs produced by engineering software
programs like CAD (Computer Aided Design) and
Operation of the CNC Machine:
The
machine is relatively simple to use. In setting up the machine for use, there
are a number of things one has to consider.
Typically, the cutting tools to be used for milling are determined by
the type of material being milled. Additionally,
the type of drilling tool to be used for the cutting is a function of the
surface finish desired for the piece.
Basically,
in using the CNC machine, the power button turns the machine on and off. Once the machine is turned on, the material to
be milled is placed on a stage with a clamp-like feature synonymous to a vice
that supports the material firmly. With
the aid of an in/out button on the upper-left section of the machine, the
milling tool can be inserted in place.
Once the tool and the material are in position, the machine’s electronic
interface can be used to set the coordinates for cutting. This is done by directing the cutting tool to
the starting point of the cut such that the x, y and z coordinates read zero.
After the starting point for the cut has been determined, the direction of the
cut is set and by pressing the “go” button, milling begins.
Like
any tool, precautionary measures have to be taken when using the CNC
lathe. It is important to always make
sure that the units of measurement specified by the CAD or
Sample Machining:
After
the orientation was complete, team members took turns in machining a slab of
Aluminum. We each inserted the aluminum into the holder and set the
coordinates, as well as set the machine to make straight level cuts and smooth
the surface of the aluminum block. An image of John and Sadik placing the
aluminum block is shown below.
Methodology:
- The CNC was turned on by the switch
- A drilling tool was selected and inserted into
the drill chock.
- Using the electronic interface, the x, y and z
coordinates were manually selected.
- The cutting parameters for the forward direction
were selected as +10mm in increments in the x-direction at a cutting rate
of 1500ppm.
- In the backward direction, the cutting
parameters were -10mm in increments in the x-direction at a cutting rate
of 1500ppm.
- The cutting was done by alternating the
directions for about 20minutes
Upcoming Schedule
1.
In order to facilitate the fabrication of the board, a detail design drawing
must be completed prior to construction. As Aaron has extensive modeling
experience, and John has worked with modeling software in the past, Tami and
Sadik expressed an interest in learning to use the software and create the
engineering drawing for the chessboard. They will download and learn to use
Solid Works by Tuesday and will update the rest of the group on their progress.
The board design should be completed by next Thursday.
2.
Next Tuesday in lab, we will set up a pawn tree and cover it with investment.
Mike has agreed to meet with us and will help us mix the material and conduct
our initial pouring. After the investment has cured, we will schedule a time
with Mike to pour the first set of pawns.
3. The team will undergo a water jet
orientation and learn how to use the water jet machine. The water jet is another cutting tool that
slices into material using the high pressure of a jet of high velocity. The
machine makes primarily two-dimensional shapes which should be ideal for
cutting the small brass squares for the chessboard.
Feb
14, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron and John
Lab Activities
Activities in Lab:
Four
3D printed pawn pieces were collected from the ZCorp 400 and dried using
compressed air to remove all the residual ceramic powder on the pieces. These steps were taken to ready the sample
for the waxing and molding. An image of the cleaning process is shown below:
Before
we proceeded, we agreed that we didn’t have to vent the final moulds because
there was no fine detail on the pawns that needed to be replicated. This decision was supported by Mike who
agreed that because of the shape and volume of the pieces, they should cast
properly without vents. The pieces were waxed carefully to ensure a smooth
surface. This step consisted of dipping the pieces into a molten wax bath for 5
minutes each, as shown in the image below:
The
pieces were placed on a make-shift dipping device fashioned out of wire mesh.
The mesh allows good coverage of the pieces in wax. Not only does the wax treatment
smooth out the surface of the pieces, but it also prevents the mold material
from penetrating the porous 3D printed piece and ruining the mold. After the
pieces were saturated with wax, they were removed and allowed to cool before
being prepared for mold casting.
Polyurethane
mold rubber, poly 74-series and poly 74-20 were mixed in a weight ratio of
1:2. The resulting solution was stirred
thoroughly to create a homogenous solution for the mold. Care was taken not to
mix too vigorously and introduce air bubbles into the polymer which would
result in a poor quality mold. After waxing, the pieces were placed on a stem
in a small cup using sticky wax and allowed to cool. The urethane solution was
gradually poured into the cup to submerse the piece. The molds were then placed on a bench to set
in the mold overnight. In the image below, Tami is pouring the solution into
one of the cups with the pawn affixed to its bottom.
Upcoming Schedule
On
02/21/2008, following feed back from our presentation in class, we intend to do
the following:
- Complete ordering of materials.
- Build more molds
- Cast dog-bones
- Literature search on surface treatments for the
chess board. The tentative list of
possible surface treatments for metal include:
1) Nickel Plating
2) Chrome Plating
3) Patina staining (at lest 4 different colors)
4) Polishing
5) Oil Blackening
6) Powder Coating
7) Anodizing (for aluminum chess board only)
And for Plastic we are considering:
1) Metallizing via electrode-less nickel plating (Very expensive)
2) Metallizing via sputtering (very cheap)
Feb
12, 2008 – Lab Day
Members
present: Tami, Sadik, Aaron and John
Lab Activities
Team
met at 2pm in 8-014 to learn the rudiments of casting. Mike taught the group how to perform sand
casting and wax casting. Additionally, he explained the two types of wax
casting: machine wax and hand-carved wax.
The lecture ended with a discussion on rubber molding.
Following
the presentation on casting, the team met to strategically plan the fabrication
components of the project. Courtesy of a
patron of Open source, the group obtained a 3D scan of a complete chess set and
the images were compared to real chess pieces (that were borrowed for the
purpose of the lab). It was agreed that
the online images were more appealing and had better aesthetic quality.
In
light of this, the group decided to feed the scanned file into the 3D printer
and 3D print about four pawns as well as the king, queen, bishop and the
rook. The 3D printing was set up and
left to run overnight. The pieces were
obtained the following morning, readied and stored for Thursday’s lab
activities.
Upcoming Schedule
On
Thursday, 02/14/2008, the group intends to wax coat and create a rubber mould
for each of the pieces mentioned above and will subsequently proceed to cast
those pieces. All these processes constitute the trial phase of the project and
based on our satisfaction with our results, we will make informed decisions on
how to proceed next Tuesday.