Pack and Hold separation?

[Suhas]

Do you typically differentiate between the pack phase and the hold phase?

[Rajaram Bhat]

Yes, Pack time is the period after Fill Phase and till the completion of material filling in to the cavity. Hold is the phase from pack to Gate sealing.

[ProcessEval]

Correct Mr.Bhat. But when processing a mold, how can one set these? How many sec for pack and how many sec for hold? What would determine that?

[rickbatey]

This issue comes from users of certain types of IMM brands. The controller has a 'Pack' time setting and a 'Hold' time setting, while many others just list a 'Hold' time. For most machines, even what they do at this point of the process is the same...So they can be used for one another. This usually shows me that you use one of the other brands of machines.
Rick.

[ProcessEval]

@Rick, but if there are number of profiles available, how does one use them? Or do we not? Also I thought we need to set the pack time till we get the correct amount of material and then hold to seal the gate off. (Suhas's book :) )

[Danny R]

Suhas' book? Where can I get this book? (hint!). Newer presses have more bells and whistles (multiple hold profiles). The impotance is to transfer consistantly and pack/hold until the gate seals off, as ProcessEval pointed out.

[rickbatey]

ProcessEval, I don't use pack or hold profiling unless I HAVE to! I want one speed and one hold speed/psi as long as I can make good parts. It makes it easier to work on, and tends to be more consistent. Remember that if your under the cycle time crunch, you can drop the hold (pack and hold) time, then bring the hold psi up to you get back to the part weight you had before.
I have used the velocity hold setting on an Engel to solve some small non-fills from time to time. I suppose that the hold speed was slow enough to allow the melt from to stop beforre it should have. Too much psi caused the mold to flash.

[ProcessEval]

Rick, I also have used only one pressure and time for years. I must try your suggestion of droping the time and bringing up the pressure. Thanks.

[skyma]

thanks for your suggestions and that just solve my urgent problem. thanks again

[NATHAN]

100% consideration of Newtons third law - The moment of Inertia. Deceleration needed before the hold phase starts for precise stop on V-P position and
ensures the fill volume was quite consistent on each cycle with this pack phase provided.Basically this pack phase was in-corporated between the fill and hold phase

[rickbatey]

Nathan-That may be above the capabilities of a molder from the South. I tend to keep the screw moving forward after switchover form injection to pack and hold (hold only to me). I don't even want to screw to hesitate or bounce at all. I will move the transfer position back if need be to see the screw velocity drop and the screw continue to move forward.
Rick.