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Functional testing of RP parts?

Hi Ed!

I am JB from India working in CAD Field. I just happened to visit your site when was looking for information about RP technologies in general. Congrats for doing a wonderful job. I found a wealth of info on the basics of RP in your website.

I have one question regarding RP Models.. Can you please help me?

I would like to know whether we can do a life-expectancy test on RP models, specifically, an endurance test with about 10,000 repeated cycles or so.

Secondly, How closely RP models imitate the behavior of actual plastic materials? I have a plastic part made in Acetal which has to be tested to withstand a torque test.

Whether we can directly build parts using Acetal material? If not, which RP process would you recommend... FDM or SLA... that can closely Simulate the behavior of Acetal when doing functional testing.

Thanks in advance
JB

Dear JB:

Thanks for your kind words.

In general, materials used in RP are not yet equal to engineering plastics, so if you are trying to accurately determine the life of a part, you can't easily do that by using an RP fabricated item. Also bear in mind that the mechanical form of the materials is different. Plastic shot into an injection mold has a molecular alignment which affects its mechanical properties and can't be simulated using RP. One approach people have used, however, is to use RP to make a rapid mold (often with some detail missing to save cost) and use that to shoot a few parts in the final material for testing.

There isn't any RP process that uses or closely simulates acetal at the moment, and I'd say there isn't much going on in that direction. Most of the work in stereolithography is aimed at things like polypropylene. With the above remarks in mind, your best bet is to use RP to create a mold.

Alternatively of course, you can use FDM to make pretty tough ABS and other engineering plastic parts. Stereolithography parts can also be tempered for greatly improved torque performance. See the category "Part finishing services" under the commercial listings on our site. However, as mentioned, precisely simulating final behavior of an injection molded part is questionable.

Thanks again and best regards,

Ed Grenda
Castle Island Co.
The Worldwide Guide to Rapid Prototyping

Hi Ed.

Thank you very much for your feedback. It was very helpful for me and my superiors in deciding the proper RP requirements for the part.

With regards
JB