Re: [rp-ml] Question for Moldflow (and similar) users about famous molding case

Date: Thu Sep 15 2005 - 23:34:15 EEST

Hello Alex,

here my late 5 cents.

Simulation is well established for critical tooling work. e.g. for metal
stamping and plastic injection production processes.
The simulation is based on CAD data, typical material properties and
process properties. An experienced user is also required to get good

As the material and the process properties are complex and vary with the
batch, time, temperature, you name it, rework of the tooling in pilot
production is still very common.

Scanning can define the reworked tooling geometry and the deviation of the
actual product from CAD data.

If a simulation software can "import" the captured data and "compare" these
data with the CAD data and the "first guess" tooling data, the simulation
software should be able to come up with an "educated" guess how to rework
the tool to get good results. In addition the feedback information from the
scanner can be used to "adjust" the material and process parameters for
succeeding simulations.

Most simulation software providers are still busy developing their
mathematical models and nice user interfaces. Simple tests are made to
extract material and process parameters to enhance the model calculations.
Some providers would not like to be offended by the deviation between their
simulation result and the real product form.

Power users will have to push the simulation software developers to make
use of the available feedback data to get more precise simulation results
and more target oriented rework. But even in the future, using all
available resources, pilot production and first article inspection will
still be necessary.

With best regards (from the scanner side)

Ernst Mueller
GOM International AG
Bremgarterstr. 89b Tel. ++41 56 631 04 04
8967 Widen Fax:++41 56 631 04 07
CH - Switzerland

             "Alex Do"
             Sent by: To
             owner-rp-ml@rapid <>
             12.09.2005 07:40 [rp-ml] Question for Moldflow (and
                                       similar) users about famous molding
             Please respond to

There is a famous case about the Oral-B CrossAction toothbrush that was
published in Mechanical Engineering 2001 ... basically after all the fancy
design when they went to mold the part, it unexpectedly warped 0.2" after
cooling. To solve the problem they re-designed the part with a counter
warp so that when it cooled it took its intended shape.

I've been unable to test out mold analysis software (can't get a license),
but I wonder would it have solved or quantitatively predicted that problem?
It seems like they still would have needed to see how much it warped by to
make an educated guess about how to redesign the part.

Thanks for the feedback ... just gathering data for a paper on SL injection
molding I'm writing.


Alexander Do
Research Assistant
Ford Prototyping Studio
University of California, Berkeley
2117 Etcheverry Hall
Berkeley, CA 94720-1750
(510) 643 9486

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