polymer to make sample tool

[jamesbrown]

Hello

I wonder if any of you can help me. I have been given the task to find out if it is possible to create a sample mould tool for EPS and EPP products.

I am looking for polymer blocks up to 0.5m³ that can be cnc'd to form the cavities to be bolted to some old tool plates and run. We would only require a minimum of 20 samples from this tool before it breaks.

The requirements are:
Must withstand 170°C (338°F) at 6bar (88psi) for a maximum of two minutes, whereby the temperatre drops to around 120°C and the pressure falls away. Between cycles the sample tool is not likely to drop below 100°C.

On 'normal' aluminium tools, we core vent to allow the steam to escape, however i am fairly sure this wouldnt be possible with a polymer tool, however we would need to pin vent the part or find another alternative.

If you think you can help but need a little more information, please ask.

Many thanks in anticipation
James

 

[patprimmer]

Prototype tools made of plastic are typically made of a filled epoxy like Devcon.

You need to maximise heat resistance, compressive strength at elevated temperatures, smooth finish and surface hardness.

You need to minimise mould shrinkage as the resin cures and coefficient of thermal expansion in the temperature range that it will operate at.

You need to minimise surface friction for easy mould reease.

Like I say, a specialist filled epoxy like Devcon.

Wood might also work.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[jamesbrown]

It is a slightly different process to standard plastics in the sense that you want the tool to heat up rapidly, but also dissapate the heat rapidly as the cycle draws to an end.

But thank you, 'liquid metals' are definately a viable option that i have started looking into.

As for wood, at these pressures and temperatures using steam it would more often than not warp.

 

[Compositepro]

There are lots of suppliers. Try looking here

http://www.compositesworld.com/suppliers/list.aspx?cid=317

Their sourcebook (the print version) is one of the best I've seen.