Hot Runner-Nozzle Heater

[Sammy101]

Jendalf,

Sorry but I dot quote understand your second instruction, are your saying that I should increase the HR temp than of the barrel with +5/-10 deg. C variance?
I appreciate if you make it clearer.

I am not sure of the system for closing and opening. I will get back to you on this.

Thank you so much!

Sammy

[Jendalf]

If you setup the temperature on the barrel 240 °C the hot runners temperature should be around 250°C generally for PP. But def. not 380!

[Sammy101]

Jendalf,

Yes. I believe that also. Perhaps the heater actual power output is already below the input value. I will consider also checking the calibration status of the heater.

Thank you!

Sammy

[rickbatey]

There is another issue that may be at work here. The hot tips grow as they are heated and on occasion they grow too tall and create thin areas in the part, which makes fill the part difficult. Also some drops have tips inside them to control freeze off and stringing/gate vestige. At times the tip inside grows too much restricting the resin flow path. This can usually be determined by measuring the assembly at temp or by visual inspection while in the mold.
Rick.

[Jendalf]

Both are possible, but heat influence on thermal behavior of the functional units of the hot runners is more probable.

note (out of theme):
I´v challenged simmilar effect. Problem here was the pneumatic controled needle malfunction due to the low temp of cooling water. The cooling water that cool down the base of the needle (that is connected to the manifold) caused the tightening of its diameter around the needle. The pneumatic wasnt able to moove with the needle (due to the friction) and that casued me short shots. Quite interesting

J

[Sammy101]

Rick and Jendalf,

Please correct me if my understanding is not inline with what you wanted to explain, but this tip expansion basically restrict flows, correct?
Does it really causes the nozzle heater got shorted easily? Does build up pressure inside the hot runner passage affects the heater itself?

Sammy

[Jendalf]

Sammy,
nothing is 100% sure here, but the heat influence is one of the most probable option. Especially because of the high temperatures set on HR.
Another thing is that if the nozzle is selfclose the function unit inside can be weared or broken or it can contain the forreign element inside (like metal).

J