+x

 

Warren (Staff) - 9/12/2018 1:29:32 PM

The basic principle is the same except that expansion and contraction due to the heat cycle are very important here.  Ideally you need to minimise or take into account the difference in CTE of the mould and part.

Imagine your mould above in aluminium, the aluminium and carbon would expand as it is heated, then the carbon cures and the heat is turned off.  As the temperature drops, the aluminium will contract more than the carbon meaning the inner mould will probably self release but the outer mould will grip the part making the release very hard if not impossible.   With a composite mould, for example, that issue would be significantly reduced. You could tweak the mould design to aid release and take this into account.

+x

 

Hanaldo - 9/13/2018 1:57:04 AM

Demoulding hot will increase print through and can effect gloss retention. So you will lose a bit of your surface finish.

+x

 

quinn - 9/12/2018 1:43:38 PM

+x

 

Warren (Staff) - 9/12/2018 1:29:32 PM

The basic principle is the same except that expansion and contraction due to the heat cycle are very important here.  Ideally you need to minimise or take into account the difference in CTE of the mould and part.

Imagine your mould above in aluminium, the aluminium and carbon would expand as it is heated, then the carbon cures and the heat is turned off.  As the temperature drops, the aluminium will contract more than the carbon meaning the inner mould will probably self release but the outer mould will grip the part making the release very hard if not impossible.   With a composite mould, for example, that issue would be significantly reduced. You could tweak the mould design to aid release and take this into account.

Ah, didn't think about that. Couple questions, is it a bad thing for the male mold to shrink and release during ramp down? Will it affect the surface of the part, or is it already fully cured at the point you start ramping down and won't really cause harm? Second question, for addressing female mold shrinkage onto a part, can it be demolded at a higher temp to try and avoid the mold shrinking down on it? Or is it just too hard on the part to not have a proper slow ramp down inside both molds?