Pack/Hold

[NskNsk]

Hi,
I haven't fully understand about injection molding cycle steps.I'm trying to understand it.
Is Pack and hold one or two step?
I have read about IMM cycle. Accordion to that,Pack and hold step is sub step of injection step.It compensate cooled parts in mold.This sub step start position named as Transfer position.

Am I correct?If wrong correct me.

[Airwinghma]

Greetings;




I have read about IMM cycle. Accordion to that,Pack and hold step is sub step of injection step.It compensate cooled parts in mold.This sub step start position named as Transfer position.
During the injection phase you have the Fill segment, High speed and PSI to fill the part out to 85-95% quickly, then when the transfer position is made it changes to the Hold segment, low psi to finish out the part without over packing it.

Yes the starting point for the HOLD/Pack segment is the transfer point, but some processes might transfer on Time, pressure or position, position being the most reliable/repeatable.


Is Pack and hold one or two step? During the hold segment you can set up multiple PSI and Time step, some machines and people call the first hold step as Pack.



.It compensate cooled parts in mold Not sure what you are asking here but after the hold segment has timed out and the injection phase has completed, the cooling stage starts.

Scott

[NskNsk]

yes,I know.injection phase can optimize for several steps.called as profile..
According to your explanation,we should fill 85-95% quickly in injection phase using profiles or using one step.
What happen to remaining percentage? Is Pack process fill out remaining?

As I know,melted material cooled down when touching mold surface.in that time decrease material volume.therefore,we should fill that decreased volume using pack step.
Am I correct?

In hold step,pressure is 0. screw rotation is stopped.what happen in hold step?

thanks

[Airwinghma]

Greetings;


According to your explanation,we should fill 85-95% quickly in injection phase using profiles or using one step. As a rule I use only one fill step, or profile unless a mold requires it(voice of the process), it is easier to process that way.

What happen to remaining percentage? Is Pack process fill out remaining? Yes the remaining % is completed during the Hold/Pack segment.


As I know,melted material cooled down when touching mold surface.in that time decrease material volume.therefore,we should fill that decreased volume using pack step.
Am I correct? NO, the boundary layer of material (melted material cooled down when touching mold surface) always happens, that's why you fill fast. Make sure to pay attention to your mold temperature as it will affect the fill segment.


In hold step,pressure is 0. screw rotation is stopped.what happen in hold step? Nothing but wasting time, 0 PSI in a hold segment equals zero hold, basically cooling time.

Scott