Chilled air cooling of injection molds in place of water
One of the injection molding machine manufacturers claim that chilled air-jet cooling of molds will reduce cooling cycle drastically. However, in such case what will happen to the product property? Any one has experience on such technology?
All I can assure you is the plastic material manufactures will only guarentee their material properties if the process is run per their recommendations - particularly proper mold and melt temperatures. It sounds like they are proposing processing outside recomendations in an effort to reduce cycle time. Not sure why you would want to run outside recommendations and risk your quality and the performance of the part?
Hope this helps.
I am also worried about the post-molding implications.
At present PP-HP+High loading of CaCo3 base component (weight:5.5 kgs) molded using a 1300 T machine with a total cycle time of approx.90 Sce (cooling time is approx. 60 Sce). It is claimed that "chilled-air-jet cooling" of mold can reduce the cooling time to 30 Sce. This may help to increase productivity.
I want to know, whether any one has practical experience on such system.
The only thing which is important is residual stress....from the polymer compounding, development of mould, selection of machine etc...should be focussed on the residual pressure and temp.....
I was trying by putting small probes of pressure and temperature in ejection pins can give the exact processing parameters....
I will definately recommend gas assisted injection for faster cycle time.
As you mentioned, residual stresses are the important factor, I agree with you. PP being a semi-crystalline polymer, consideration of build-up residual stress during cooling is more important. It is more so, when the cross-section is quite thick and the product design is complicated, where differential cooling factor play a major role.
That may be the reason, theoretically it is said that slow cooling of the component under presser is the best. However, commercially that is not possible.
The 'mass' of a fluid (air, water, liquid-sodium etc) decides the capability of the fluid to transfer heat.
'Gut' feel tells me that whilst a gas will flow easier through the cooling labyrinths, this will be negated by the poor heat transfer, and also lead to uneven cooling across the mould.