graemeian
3rd June 2016, 04:48 PM
I have read literature on Injection molding and I want to present my molding process to the forum to see if there is anything wrong with the process.
I am using simple A-B molds and I remove the sprue afterwards.
Speed is not a major issue but part stability is
I use a static nozzle
Small parts drop in a bin automatically and I sometimes get several hours of hands off run time before a part needs to be flicked out of the mold.
Large parts are different.
Here it goes.
Close the heated mold.
When clamp pressure reaches a certain value, inject resin.
After the screw has stopped advancing, continue pushing screw for 2-20 seconds.
Start a setting timer
***
Rewind screw to start position using back pressure.
When timer finishes...
retract screw a few mm to prevent drooling
retract nozzle a mm or so or drop pressure to reduce heat transfer. (on some materials such PVC, I leave the nozzle advance under force and put a piece of card stock between nozzle and sprue bushing)
open clamp.
eject part
draw heat and fumes away with ducting along with PID controlled heating element to get constant mold temperature
Play on internet and clean up area near machine while machine is running
repeat
At ***, I sometimes do the following
Dwell
Increase clamp pressure (coining)
Sometimes coining happens after the screw rewinds
Thank you.
I am using simple A-B molds and I remove the sprue afterwards.
Speed is not a major issue but part stability is
I use a static nozzle
Small parts drop in a bin automatically and I sometimes get several hours of hands off run time before a part needs to be flicked out of the mold.
Large parts are different.
Here it goes.
Close the heated mold.
When clamp pressure reaches a certain value, inject resin.
After the screw has stopped advancing, continue pushing screw for 2-20 seconds.
Start a setting timer
***
Rewind screw to start position using back pressure.
When timer finishes...
retract screw a few mm to prevent drooling
retract nozzle a mm or so or drop pressure to reduce heat transfer. (on some materials such PVC, I leave the nozzle advance under force and put a piece of card stock between nozzle and sprue bushing)
open clamp.
eject part
draw heat and fumes away with ducting along with PID controlled heating element to get constant mold temperature
Play on internet and clean up area near machine while machine is running
repeat
At ***, I sometimes do the following
Dwell
Increase clamp pressure (coining)
Sometimes coining happens after the screw rewinds
Thank you.