prototype method

[par1]

I need to order 20-25 prototype plastic parts for testing.
Can anyone suggest economic prototype method? (famililar with SlA/SLS but its limted for very few qty)

Also, can anyone tell me the difference between Silicon RTV & Vaccum forming in terms of prototype method. Suggest, any website/book, if need.

 

[Theophilus]

RTV is great for those quantities, particularly since you can use a variety of complex forms and materials (I used to create molds and parts with this method quite a lot). RTV molds can tolerate slight undercuts since the silicone is often flexible enough to allow the part to release from the mold without damage to part or mold. However, RTV molds only last for 15-30 parts, depending on the complexity of your parts.

Vacuum forming is great if your form is simple enough to function with this process--much less expensive than RTV molds and castings per part. Undercuts are not well tolerated since the plastic will lock around the buck in undercut areas. Also, you'll want 3-5 degrees of draft on lots of your part faces for a quick, simple release from the buck. After that, you'll need to trim away the excess material (can create a template or other method).

The answer to your question is probably driven by the geometry of your part more than anything else.



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[par1]

Thanks for reply, For the RTV Silicon mold,

make SLA Master pattern; Pour the silicon rubber around the pattern & Urethane can be used to fill the part.

I should have more clarified question at the first time,

(1) The question is does Vaccum forming having similar process like RTV Silicon mold?

(2)Does the typical cycle time for RTV & Vaccum form
process is same?

 

[Theophilus]

No, they're not remotely similar. Cure times for urethanes are a bit temperature and material dependent, but you'll often need to wait a matter of hours per mold cycle for a part.

For vacuum forming, you cannot begin to approach the level of detail that RTV parts can yield (I can see my fingerprint oil from the master part on some polished parts out of the mold), but the per-piece cost is typically much less. Vacuum-formed parts only need to cool enough to hold their form before removal, so the cycle time can be quite short if using thin material.

Check wikipedia.com for better details of each process.



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[par1]

Once again thnks !

I didn't get much useful info. But, what I understood is as below:

So If we arrange to suck the heated plastic against the master pattern & it generates the shape of the pattern. Allow it to cool & have your part ready.

Doesn't it looks like Thermo form part rather than vaccum form part? or its same?

 

[patprimmer]

The major differences are that:-

With vacuum forming you use thermoplastic sheet, heat it in an oven then place it over a fairly simple mould, seal the edges of the sheet to a flat surface that is part of the mould then suck the air out of the gap between the mould and the softened plastic sheet.

With RTV moulds, you mix two liquid components that react to form a thermoset plastic. The liquid is poured into the mould and allowed to set. Between mixing the liquids and pouring the mixed liquid into the mould you might use several methods to remove air from the mix. These are time, and/or vacuum or centrifuge.



Regards

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[Theophilus]

What patprimmer said.

Plus, vacuum forming is a subset of thermoforming.



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.