Hotrunners and air inlet

[NskNsk]

Hi Friends,

I have seen an air supply to the fix half of mold.and it has hot runner system.
sometime,If material is dirty(mixed nonferrous metals),cavity gate is stuck. In that time technician change the air direction and try to solve problem.When air flow is on,inject some material from cavity all gates.They activate activate 5/2 directional control valve manually until stuck material remove.

What is this air system?Please explain.

Thanks in advance.

[Airwinghma]

Greetings;

Sounds like your hot runner has valve gates in it that open and allows the plastic to flow into the cavities of the mold. The system is air operated and the pins are part of a piston the moves back and forth when the gates are actuated open/closed.

https://www.dme.net/catalog/DME/PDF/Hot%20Runner.pdf

The link shows some DME systems

[NskNsk]

Thanks
Is hotrunner pin cylinder double active?

[Airwinghma]

Not sure what you are asking, but the pin moves open and closed when the air is channeled to the sides of the piston, double action.

[rickbatey]

Yes it should be double acting. Never seen a valve gate gate, pneumatic or hydraulic that wasn't, but who knows!?
Rick.

[Airwinghma]

Huh, maybe a spring loaded pin , any toolmakers here

[NskNsk]

Thank
As I think,double acting method is better than spring return.Because,spring return can be stuck in material.
Anyway,Is valve gate usage only for make clear surface part without gate point(End point) marks?Is there no another advantage?
What is the moment for valve gate forward and retract in IMM cycle?

[rickbatey]

Movement time is almost nothing as the stroke is about 6mm or so. Another advantage is sequential filling of the cavity resulting in no knit lines in the part, lower required fill pressure due to sequencing and possibly reduced pack/hold time as the pin closing blocks the flow of resin back out of the cavity. But it does allow for direct gating resulting in no runners to trim off and the possibility to gate on the most critical surfaces.
Rick