Injection Molding Frequality Short Shot Problem

Are the two cavities that are flashing the short shot cavities?

Is it the same cavity every time.

Is your runner system balanced??

Tell us what you have done, so far, if anything.

We can't read your mind, and we can't see the machine.

The obvious answer is to call in a molding consultant to fix it properly.

Thx fr reply. Actually the m/c is so old n was running the same mold in without this problem so runner system is balanced.the short shot will come almost 10 cavity with different weight of shot,including these two flash cavities. When the short shot coming the next shot will be fine n run properly until next time of same problem. Fortunately now m/c is running properly scince 36 hrs. I adjust only few parameters like decrease screw retard position, decreases the cooling time.adjust the clamping pressure. But still m in search of actual prob cause n their rectification.

Are you adjusting the injection pressure or die closure pressure to control the flash problem ?, I think it would be wrong if you tried to fix it by tweaking the injection pressure/speed.

Now, about the short shot, you might need to check your dies matting surfaces for any damages and play with your zones temperature controllers and worm speed, this last one has a remarkable effect in the molten plastic temperature...

Do one change at a time.

Good luck

One possible problem- If you are in a high humidity area, the molds may be seeing condensation due to cold water cooling.

Dehumidified air blown over molds should stop this from happening. No need to "cool" the air, just DRY it out using perhaps a desiccant wheel.

You give no indication if you have water heating or cooling what the cycle time is what is the shot weight, when did you last purge, what is the material and did you dry it, when short shot happens is next shot over packed, do you weigh finished caps to see?. How many heater bands and what temp you have them at do you have a hot runner system and second stage clamping.. What is the machine is it starting from cold... all these things are factors to be considered.. given that the mould eventually runs properly I would be inclined to think a frozen gate... these can be eased by the use of a gas torch..or by increasing heat of the water but you give no indication if you have that.also you do not say if shorts are in same place and where that place is.

Water cooling temp 10 d c. Barrel heat starting from nozle is 188,205,200,190. Cycle time 19 sec shot weigh 45 g .purging 2-3 times within problem period. Material is hdpe with 25% lldpe. After short shot next shot is coming ok.it's hot runner mold with 24 cavity each cavity having temp control with additional 12 runner temp controller.m/c having 3 stages of closing with single pressure(40% in present). Currently m/c running in proper way from last 3 days. I decrease charging finish position to increase amount of melt stock.

Then like all old ladies she needs to be left alone to get on with the job, I think myself it is a runner temp problem as long as it stays the same.. do you have a thermal camera to take a picture of the core and cavity so you can see distribution pattern. If not I would highly recommend you get one I have seen so many problems that can be overcome this way check the nozzle temp is at 188 and maybe tweak it up a degree or two and check the starting temps of the barrel heaters they may be slow .. I wish you well