RE: unclear expressions...

From: Brock Hinzmann (
Date: Thu Oct 30 1997 - 22:48:05 EET


Part of the confusion lies in the tendency of the people on this mailing
list to borrow terms from other industries, but then to use those terms
only in a very narrow context, recognizing among themselves that the terms
are somewhat ambiguous. I'll probably get some disagreement from my
colleagues, but here is my attempt at defining the terms you mentioned:

The term Rapid Prototyping predates the SLA and other so-called RP
machines by at least several years. The IC, PCB, and software industries all use
the term as well, to describe a quickly-made, early version of a new
product, which can be tested in a simulation, to see if a new idea will work.
At one time, I believe we decided it was a very clever marketing person at
DTM, who first borrowed the term RP to describe that company's machines.
As we have argued many times on this mailing list, the terms rapid and
prototype are relative, depending upon the industry, hence, the lack of
clarity. Some people use the term to refer to the entire process, from idea
generation through to manufacturing, but I will use RP below to refer only to
the set of machines we discuss on this mailing list. In this context, RP
is the direct conversion of any arbitrary 3-D CAD model from the computer
screen to a physical part.

Free Form Fabrication allows arbitrary shapes and forms to be made,
distinguishing it from traditional forms of fabrication, such as milling or CNC
machining, which require line of site and are, thus, not quite as free in
the forms that can be made by those methods. Since most products are
still made by traditional methods, the advantage of RP is still not fully
employed by industry, except in some injection molded products, which leads to
some lack of clarity there as well. The hope of the RP industry is that
RP technology will mature to be truly free form fabrication of finished
products, which will give greater meaning to this term.

3-D Printing means WYSIWYG (what you see is what you get), except that it
is in three dimensions, rather than two. In other words, what you see on
the computer screen in 3-D is what you get when you push the print button.
It is not yet as simple as with 2-D desktop printers, but some people
have used the term for some time to refer to RP and 3-D printing has picked
up in usage as the new concept modelers and low-end RP machines have come
onto the market and the equipment vendors are looking for a new term to
distinguish themselves from the more expensive RP machines.

Rapid Tooling is in use by the RP community to refer to new methods of
using RP patterns and models or even parts straight out of an RP machine to
get a tool to make a part in production materials, eliminating one or more
steps in the traditional methods for making such tools. Any number of RP
methods can claim usefulness in attacking one step in the tooling process
or another, which may be why it seems unclear to you, but it is an
important management concept that is really driving the RP industry at the

CAM (computer-aided manufacturing) is not particularly an RP term and
involves a whole host of different technologies. It implies that computers
are in use to control some or all of the manufacturing processes in a
factory. It is often linked to the term CAD (computer-aided design), wherein the
design of a product to be manufactured is created on a computer and the
design can then be downloaded into a CAM system to make the final product.
CAE (computer-aided engineering) implies that you are able to test and
alter engineering specifications of the CAD model in the computer, ensuring
that what goes to the CAM system is manufacturable and useful. CAD, CAE,
and CAM all seemed like such simple solutions to the process when the terms
were first coined, but any number of new computerized processes and
methods have been added and are still being added, in order to make up for

If this message hasn't made things even more unclear, then you are indeed
smarter than I. Perhaps as others attempt to respond to your message,
some patterns of definitions will begin to appear.

Brock Hinzmann

Werdinius Christian wrote:
>In this maillist and in the the whole RP-world many expressions are
>Sometimes as synonyms, sometimes with different meanings.
>They are:
>* Rapid Prototyping
>* Free Form Fabrication
>* 3D printing
>* rapid tooling
>* CAM
>* and probably some more...
>Are there any clear definations ?
>I think it would be a good thing for further discussion if someone could
>make this clear.
>with best regards from

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