Nozzel plugging

Hi all,

New day with new injection molding problem. The issue this time is nozzle plugging, we face this problem during the start-up and sometimes when the machine works in automatic. We have a valve gate hot runner and the material is PA66GF30, for the temperature I work with 290 °C as a maximum in the hot runner system. Yesterday with a mold of 4 cavities and after 4 cycles of production one of the cavities was blocked.
If there are Any suggestions that can help us to avoid this issue, I will be grateful. Thank you!!

Sounds like the most common problem with using a hotrunner system and glass filled material. The glass will eventually build up over time and plug the tip. To get something like that back flowing we typically set it to near max temp on the tool and blow compressed air into the nozzle to break up the clump of glass.

thank you, sir, I appreciate your suggestion.

The temperature set point on the valve gate is just that, a set point. Usually the actual temperature is much lower than the set point. Try getting a melt temperature reading by directly purging at each gate. You may simply be freezing off and need more heat.

Have you done a mold balance? Does the cavity that "blocks off" look balanced compared the others? This should be done with 0 pack pressure and slightly incomplete parts.

Hi,

1- Yes, I did a mold balance.
2- yes, all cavities are equal (24.70, 24.70, 24.71, 24.76 grams)
3- Yes, I did it with 0bar in pack pressure.
For the real temperature in each gate, I didn't have the equipment to measure them but while we worked with 300, 310, or 320°C in temperature we didn't have a "blocks off" in cavities during a period but after that, we have a material degradation.

My proposal is " if I can make the gate diametre larger to make the passage of glass fiber easier, my question is: the solution can work or not and what's the risques ?"

thank you,
Best regards