Injection molding 1

[zpxp09]

I have a part that is being injection molded in a 66 Nylon resin. This part is prone to what the industry calls "jetting" is there anyone out there that can give processing advice on how to eliminate jetting?

 

[dhuffy]

ZPXP09,

Good day. Yes Nylon can jet and also drool from the nozzle so you may want to ensure that you have a nylon nozzle tip to prevent the drooling. In order to help the jetting, there are a few options depending on the stage you are in (is the mold built, being designed, or is the part only designed).

I would recommend gating into a region where there is a wall right near the gate to help prevent jetting (or atleast minimize it). This may cause sticking issues depending on the part design due to overpacking near that wall.

The gate design alone can help - too small of a gate will cause jetting. I experienced jetting with a PC material and opened the gate up by only 0.006" and it stopped the jetting problems.

As far as processing, I would try to slow the speed down as the material enters and passes through the gate initially. Then step the speed back up once the nylon enters the cavity. This may cause flow lines in the part depending on its sensitivity.

You may want to try one or a combination of these. Good luck and I hope this helped.

Dave

 

[zpxp09]

Hello Dave,
Thanks for your comments on jetting. I've had a chance to process this tool since I wrote the thread (yes the tool was already done) and you're right, the impressions that were gated where there was a wall that impinged the entry of the resin did mould better. The tool owner is in the process of making tool modifications based on what you have said and we should be out of the mud on this one soon. Thanks for your help.

P.S. I hope you get this reply as this is the first time I have participated in this forum and haven't yet figured out how to reply to people who post me. zpxp09@aol.com

 

[dhuffy]

Glad I could help. Good luck with the tool changes.