2.810 Manufacturing Processes and Systems
Welcome to 2.810
This course is about manufacturing processes. At one
level manufacturing processes can be thought of as the methods by which
we convert raw or unfinished materials into useful hardware. In
fact, often the various manufacturing processes are categorized by the
type of material which is converted, e.g. metal removal processes, polymer
processes, ceramics processes, etc. This view is represented schematically
in Fig. 1.
The processing of materials in machines can be analyzed using scientific
and engineering principles (heat transfer, solid, and fluid mechanics etc.)
to better understand these processes, to optimize and control them, and
to maximize their output. In this course, we will use results from these
analyses to understand manufacturing processes. We will identify the fundamental
physical mechanisms for each process considered, and show the relationship
between these mechanisms and the behavior of the process in terms of rate,
quality, cost, and flexibility. To do this we may have to get into some
mathematical derivations, particularly in the area of heat transfer, but
in general the emphasis will be on identifying critical physical phenomena
and describing the appropriate scaling laws.
In addition to material flow through the process, we may also consider
both the energy flow and the information flow. Energy is required
to do the work of disturbing and, in some cases, reestablishing atomic
and molecular bonds in order to change the shape, surface, and microstructure
of the material we are processing. Analysis in this area is also quite
amenable to engineering principles.
Information of several types is required in materials processing
including; 1) production information (how many parts to make, when etc.),
2) parameter setting information (temperature, pressure, time, etc.) and
3) basic structural and shape information. This later form of information
is often supplied in two distinct manners; 1) sequentially (a little bit
at a time) or 2) in parallel (all at once). The sequential processes generally
make a part by either adding (e.g. rapid prototyping) or subtraction (e.g.
machining) material a little at a time. Usually the shape information of
these processes is embodied in a software program which drives a
positioning system with a focused end effector. In contrast, parallel processes
usually use hard tooling to embody the shape information for the
part. The shape information is then imparted almost instantaneously and
everywhere for the part. This group of processes include; injection molding,
casting, forging etc. When the resulting part requires very little post-processing,
the parallel process can also be called net shape . We will use the broad
categories of sequential (including additive and subtractive) and
parallel(including net shape processes) to generalize about the various
characteristics of a process.
Note that parameter setting information (the second in our list above)
can be obtained from: experience, handbooks, engineering models, and designed
experiments. You will get first hand parameter setting experience when
you and/or members of your group operate the various processes we use in
this course. Located on the first floor of Building 35 in the Laboratory
for Manufacturing and Productivity you will find the machines to be used
in your group car project, including; 1) a 3 axis CNC Vertical Milling
Machine, 2) a 30 ton injection molding machine, and 3) a thermoforming
machine. Production type information, the first in the list above, will
be dealt with at the system level, which will be discussed shortly.
Also note that in Fig. 1 we have indicated the possibility of disturbances
to the process. These may come as variation in the various inputs, as well
as variation in the environment, operator, machine and methods. The identification
of, and elimination of disturbances is critical to manufacturing process
engineering. At this point we will also introduce the notion of feedback
information related to the performance of the process.
Viewed in another way, manufacturing processes are part of a system
to make competitive products. In fact, they are at the center of the system
for the creative development of products. This idea is shown schematically
in Fig. 2.
Here we are looking at the three steps to design a new product including
part design, process design and system design. To have a successful manufacturing
enterprise, each one of these steps must be done well. In this course we
will consider all three steps for a few well defined examples. Of course,
our emphasis will be on the process, but we will clearly show the interconnection
and interdependence of the three steps. Of critical importance in this
sequence are the communication links between part and process, and process
and system. These are marked in the figure as, 1) the engineering drawing,
and 2) the process plan, respectively. The importance of these two vehicles
for understanding processes can not be overstated. We will use them repeatedly.
Feedback to part design in order to alleviate manufacturing problems at
either the process or system level, is indicated by the dash line marked
DFM (Design for Manufacturing). In this course we will consider the manufacturing
cell as the representative unit for the system. Hence we will show how
one goes from part design, through process design to cell design and back
again for the volume production of a part or an assembly.
Our goal for 2.810 is to develop both of the process views outlined
above. In order to do this in our allotted time we will focus primarily
on 5 processes; assembly, machining, casting, injection molding, and thermoforming.
You will receive hands on experience for each of these processes through
your work on the group project. More information on the goals
of the course and the project can be found in
separate sections of this web site.
Hope to see you in class.