I don't know how many of you were able to attend the recent Modern Mold and
Tooling show at McCormick Place in Chicago. It was very good for the budding
rapid tooling industry to be included with the big boys in the tooling
business. There were many of us their showing our different processes and
there was much interest. Most of the seminars were very informative. I
especially enjoyed the one on DTM Rapid Steel 2 and soon to be 3. We finally
have some friendly competition for the 3D Keltool process which I'm glad to
see. In the Rapid tooling seminar there were 5 or 6 speakers on the panel of
which I was one. Each with a different process and all very good. The last
speaker was Tom Mueller who with Dr. Paul Jacobs put together a presentation
showing the accuracy limitations of RP/RT methods. The presentation was very
slick and seemingly well presented. They went through and did some kind of
study on a bunch of SLA parts measuring the accuracy. Then using the
shrinkage and possible warpage of each of the different rapid tooling
processes they plotted out the accuracy curves of each type of Rapid Tooling
process. Their conclusion was that SLA could not be used to build rapid
tooling and that the inherent accuracy of all the Rapid tooling techniques
were not accurate enough to even hold plus or minus .030" on even a 3 inch
piece. I beg to differ with them and feel their conclusions were very flawed
and biased. The study they did on the SLA parts was done mostly on older SLA
250 and 500 type machines all with Somos resins. My company builds SLA Master
patterns on a regular basis for tooling masters. We have shipped over 300
jobs in the last year and a half. We do not recommend the use of Somos resin
for Tooling Masters. We only recommend SL5510 resin it is the only resin
rigid and stable enough that we know of to do the task. We also only
recommend making tooling masters on 3500 machines or the newer 7000 machines.
The 3500 series has the laser mounted directly above the vat and it is apt to
give the most accuracy of all the 3D Systems designs. The SLA 7000 with the
.001 layer thickness gives the best replication over curved surfaces. I'm
sure 3D Systems and others are working very hard on the next generation of
machines which will open up whole new avenues for Rapid Tooling as well. We
have 3D Systems technicians come in and tune our laser every three months. We
also do weekly test builds to insure the accuracy of our equipment. In
practice we find that most SLA master patterns measure within .002-.003 of
the desired dimensions in the X and Y. There is an inherent difficulty with Z
steps that forces the Z levels to only be accurate as the slice thickness. We
typically leave stock in areas where Z depth is critical. We attempt to do
all cavity masters in the center of the vat and try very hard not to mix
tooling builds with part builds. We have to know at all times the exact
diameter of the laser spot to insure the correct laser offset values. We
highly recommend that the Tooling masters be finished only by master
craftsman. Finishing SLA masters is almost equal to finishing CNC cut EDM
electrodes the step downs are usually about the same. So the moldmakers have
no trouble finishing and certifying the master patterns. My family has been
in the tooling business for many generations as far as we can trace several
hundred years. As a family legacy I was required to finish several complex
pieces to a tolerance not to exceed plus or minus .0002" without the use of
any machine tools of any kind. My father a master craftsman himself carefully
inspected all my work and when he was satisfied with my ability gave me his
cherished tool box and tools. Which I will in turn give to my three sons as
they will have to pass the same test along with bachelers degrees in
Engineering. A toolmaker is not worth much if he cannot finish anything to
precise dimensions. This is all really a moot point anyway because all molds
built in the mold industry are fully guaranteed to meet customer
specifications. This is how the mold business works. The moldmaker does not
get final payment until the final molded product meets the customers
specifications. This means if the tolerances required are very loose the
mold will be relatively inexpensive. If the tolerances are very tight the
mold will cost much more. Some molds we have build cost in excess of a
million dollars. Any moldmaker worth his stuff will always know exactly where
the critical dimensions are and make sure there is stock there for final
tweaking and finishing. What we do when presenting 3D keltool process as an
alternative is we ask the customer to let us know exactly which dimension we
are required to hold to exact numbers and which dimensions can be relaxed. We
are always up front with the limitations and make sure the customer is very
aware of what he is getting. The number of critical dimensions have a direct
bearing on the final price. We have built 3D Keltool molds for automotive
certified production molds. The cost was not very much less than a
conventional mold because we had to certify each dimension. On the other hand
we have built other molds using 3D Keltool Process which the customer was
willing to accept whatever we were able to provide as long as the part
functions. These molds were able to be delivered much more quickly and
inexpensively, aproximatly half the cost of any other method available today.
In practice we have found the 3D Keltool process to hold pretty true to the
advertised accuracy of .002"inch / per inch accuracy. This does not mean that
every block that comes out meets these specifications. In reality we have
nearly 20% losses using our process. We have stringent inspection standards
in place all developed by 3D Systems, and if the block does not meet the
specifications it is failed. The customer never sees these blocks however.
This is all a part of doing business. Any dimensions that have to be held to
a closer tolerance have machining stock left and are finished via EDM or CNC.
As I said earlier all molds are completely guaranteed at all times to meet
customer specification. If they do not we do not get paid until they do. We
have at times had to put double or even triple the quoted amount into molds
to satisfy customer demands. This is our loss however not the customers. This
is the way this business works and perhaps if Mr Mueller had understood the
business a little better he wouldn't have gone belly up. I feel their
presentation did a great injustice to our struggling industry. I am at a loss
as to what gain they had whilst they were sitting there giggling through
their presentation. But personally I was hurt by it. This industry is
struggling badly enough without having to endure this nonsense. I really
don't know the history between these guys and 3D Systems, DTM, or the other
struggling rapid tooling companies and I don't really care. All I know is
they threw a devastating blow to our industry with that presentation and it
appears only to satisfy some sick vendetta. I also am irritated at Modern
Tool and molding to allow two member of their editorial board to present at
their own conference. Especially such a devastating and unfounded bashing of
our industry with no opportunity for rebuttal. Pen in hand you have not
heard the end of this issue from me. My company has invested millions into
this RP/RT industry trying to help develop it into something great. And I am
not about to let a couple of grumpy old men destroy it for the rest of us.
Bob Morton
Fusion Engineering
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