Concept Modeling

From: Rolf Hubert (
Date: Sun Feb 04 1996 - 19:46:49 EET

I'm somewhat confused, perhaps all the experts on this forum can enlighten me.

In the Mechanical Engineering - January 1996 issue, it presents the MJM and
other ink-jet type systems. This particular article focuses on "Rapid concept
modelers". Concept is the key. Are we to assume that engineers can no longer
see their creation on their sofisticated workstations with their sofisticated

"Engineers can conceive their idea, design it in CAD, and without leaving the
CAD workstation build a physical model of their concept as easily as creating
a paper print or plot." The problem is they are not building their concept
which by the way was a smooth representation on their CAD workstation.

Am I to assume that your goal is to build a concept model, show it around the
room and then perhaps decide to build another on a more accurate machine? In
1988, 3D Systems built a concept modeler. This system built models with poor
accuracy, poor surface finish, and with poor materials. The engineering
community demanded more. A spokesman for Ford said that we need a desk top
system that builds precision parts and sells for under $25,000.00.

A vice president for 3D Systems said "we expect explosive growth in this
area". Of course, purchase a concept modeler and still have the requirement
to build another model on the SLA 250, 350, 500 or whatever else they expect
to give you. 3D Systems has certainly given credit to all those engineers
that cannot visualize what they have created on their $!00,000.00 workstation.

Am I hearing that 3D Systems is now using a thermal plastic? How is it
possible that this ink-jet type system from 3D Systems weighs 700 pounds,
certainly a wonderful addition to your office or as some will put it, a
network add-on?

The concept modeler gives a new meaning to productivity, let's build it twice
or perhaps even more! Give the engineer some credit, build it once on a
machine that builds dimensionaly accurate smooth parts. The Sanders Model
Maker can build and slice at .0005, .00075, .0015, .002, .0025, .003, .004 and
soon at .005 inches or 0.012, 0.018, 0.037, 0.05, 0.62, 0.075, 0.1 mm

The article states that Sanders has created a niche market, jewelry. If
Sanders catered only to the jewelry industry, why is our machine a 6 inch
cubed. Has anyone seen rings or braclets or whatever that was that large? If
you are interested in building something that doesn't require sanding, try the
Sanders machine. One of our many non jewelry customers sent us a STL file
created by Delcam of a shower head. We produced it at .0015 inches or 0.037
mm. The model was in 2 parts. They said "this was the first time this model
was produced and actually fit together." The model required no post
processing and was extremely smooth.

Tom Sorovetz said that the MJM system is now applicable for mom and pop shops,
HOW? Mom and Pop operations are forced to produce perpect parts quickly. How
is it possible that they can even think of affording to do models more than
once? The MJM system has a way to go and when it starts producing
dimensionaly accurate smooth parts, it will probably be stepping on a few more
patents already in existence and in use.

And of course, let's not forget Terry Wohler's statement that "raster is
better". That is perhaps true if you are interested in rough parts. Let's
start building parts that are no longer useable in the real world. Let's have
meetings where we're passing around models with stairstepping and all other
kinds of imperfections. Wouldn't it make far more sense to create the final
model and know that the imperfection was in the design rather than the concept
Rolf Hubert
Sanders Prototype, Inc

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