Defect Detection for Fresh Injection Molding Solid Parts

K

KCIPOH

#1
Hello Cove members,

Good day. Our production are having a difficulty in detection of the bubble inside a solid PP white color injected part (not transparent part), at customer side, they will drill holes and put in brush furr.

If there is a bubble (size of a red bean) in our product, this will cause problem of cannot assembly the furr on the drilled holes.

I'm thinking of having the part weight as a detection point to detect whether there is a bubble inside a part but i think the weight shown will be very less and cant justified the defect.

This raw material are mix with blowing agent by our mixer.

Need inputs on this :confused:
 
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#2
Checking the weight was the first thing that occurred to me as well, but what about the reason for the bubbles? How common are they, and what is currently being done in order to avoid them altogether?

/Claes
 
B

BridgeGap

#3
For detection, part weight is the way to go, using an appropriate inspection plan.
There are scales for this, calibrated according to your needs.

And as Claes indicated, while you are utilizing an interim detection process, I'd really be looking after the root cause. Its a pretty common and easy to fix processing problem. If the technical ability of your processors is insufficient to deal with this, I'd get with your human resources department real quick.

Good luck
 
K

KCIPOH

#4
Hello Claes,

Fyi, this is the first time we have this problem with our customer and currently QC are checking 5 pcs/hr for the critical defects, i'm having to destruct the part using jigsaw during the first shot of production run each time but would it help? as for the rootcause, we are in the progress.

Thank You for inputs :)

Hello BridgeGap,

Appreciate your inputs as well :)
 

kuyakut

Involved In Discussions
#5
Hi
Does heating the part with a hot air gun cause the 'bubbles' to collapse and then reappear when the plastic cools?
This is still your main question to answer because the remedy for voids is usually different than for bubbles.
Voids are packing and cooling - bubbles are trapped gas and venting. Bubbles are ususally near the surface - voids can appear anywhere but usually near the middle of the wall.
It can be minimize by Increasing Holding Pressure and Holding Time or Increase cooling time.


Kuyakut
 
Last edited:
K

KCIPOH

#6
Hello kuyakut,

Fyi, once this part drop off from the mold, it will straight drop into a bin filled with cool water cooling by water chiller.

but i guess you are right, the defects i think i suppose to address here is void rather than air bubbles as it happened in the middle of the wall.

I'll duscuss your suggestion with my production guys and update you if any outcome.

Thanks and appreciate your inputs :yes:
 
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