Hi, I am in the process of designing a fully automatic mold to produce a gear shift type bellows although the design differs in that the wall thickness is substantially higher. Typically, the chocking ID is 108mm, whilst the undercut is 140mm. This means an undercut of 18.5mm per side with a wall thickness of around 3mm. Normally for thin wall I would simply inflate this off the core, however this is abnormal. Can anyone give me an indication whether Hytrel HTR8105BK will expand this far and return to original diameter. If not, i will have to implemet undercut demolding core which I do not really want to do. I have checked the DuPont site out with little success.
Thanks,

dezignit  

If DuPont can't help, try DSM and the equivalent grade of Arnitel.

You might get a better response by asking each of their technical departments the specific question.

Personally I don't see the wall section effecting anything other than the pressure required. The elongation to jump over the undercut will be about the same, so the recovery should be about the same.

I say about because with the higher pressure it might be a bit harder to control the dynamics of the stretch and jump process, and the TPE properties might change slightly with wall section, mainly due to different cooling (and therefore shrinkage)rates and to different ratio of cross sectional area effected by the orientation the can occur as material flows differently on the surface vs down the centre of the section.

Regards
pat   pprimmer@acay.com.au
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