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?

Hi Mihir,
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.

Hi Kirk
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.

Hi Mihir, I have worked with chilled air cooing, set up is more massive and result is not promising. In my opinion it will not be able to help much, but you might have to add in massive chiller, or other cooling devises to cool the air.

it may change the Internal grain/fiber structure. just like the steel , if you cool it in different temperature, it will show you different result. what's your product look like? if it is very thick, please consider air Gas-assisted molding. most of the part can reduce the cycle time by improving the struture design,mold design,,,etc.

It is not the cooling system or the medium which constitutes the product's cycle time...probably the coefficient of specific heat of a polymer leads to cycle time...too much cooling too less cooling is not that much important...

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.

Hi Bala
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.

Why am I so suspicious about this method of cooling?
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.