Re: Is this true.........?

From: Mark Kottman (
Date: Mon Dec 08 1997 - 22:52:49 EET


It is neither true or false, it is mostly a matter of perception and
semantics; what is "high volume production" or "high tech"? It's pretty
open to interpretation.

I prefer to look at the geometry of the part, and the function required
from it, and the material it will ultimitely be produced from, then
decide which is the best way to get the prototypes I need. I will never
confine myself to one fabrication method for all the different types of
parts that I need. We use SLS and SLA, but we also machine parts, or
sometimes molds, if that is the better approach. No matter what the
approach, however, time is often a critical element to us that will
often drive a decision more than cost.

Quantity of parts required is also a key element; seldom do we need only
one of anything. Rapid prototype parts are generally only a first step
in creating multiples via RTV molds or other processes. Quantity
required also plays a big part in the feasibility of machining parts. If
few parts are required of simple geometry, machining can be the fastest
method of production.

This brings me to a point that is often overlooked. Rapid prototypers
have built their business on speed. Machine shops are built around a
much older paradigm of keeping the shop full by running a backlog of
business. This backlog is generally what makes machining so much slower
than rapid prototyping. If you find a machine shop that doesn't work
that way, they can be very competitive. I have had a few experiences
where I have had large parts (18" X 26" X 4") machined from Ren-board
from my 3D CAD file, and shipped to me in a week. Considering the size
of the part, I doubt that any rapid prototype shop could have done any
better, and cost would have been many times greater.

Mark Kottman
Kimball Int'l

Elaine T. Hunt wrote:
> How common is this for most industry?
> ""As a general comment on what I have seen thus far, it appears difficult
> to justify the cost of rapid prototype parts unless they are going to
> result in high volume production or are high tech enough to warrant
> special materials and/or have difficult geometry that would be
> expensive to manufacture. Anything that could be used to dispel these
> notions,
> especially that of high cost, would help sell the RP technology to a
> broader range of industrial customers. It is difficult to inspire
> interest in a service that could cost several times more than the cost
> of conventional machining, even if you can get it done in a fraction of
> the time. Add to this the fact that most RP products have either
> strength or accuracy limitations, and the choice is usually to wait a
> few days longer and get it made out of aluminum in the shop.""
> *******************************************************************
> Opinions, suggestions, and other controversial matter VOID where prohibited.
> ******************************************************************
> Elaine T. Hunt, Director
> Clemson University Laboratory to Advance Industrial Prototyping
> 206 Fluor Daniel Bldg. Clemson, SC 29643-0925
> 864-656-0321 (voice) 864-656-4435 (fax)

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