Back pressure is the amount of pressure the plastic has to exert on the screw to force it backwards, hence the name: back pressure. Increasing back pressure increases the density (the weight) of the shot (molten plastic) at the front of the screw.
thnx for video BUT i would ask about raising the back pressure u told us in the video that raising it make the part weight less while the density getting higher how is that possible i think both should getting higher Thnx
Increasing back pressure does increase part weight. I have not been in their facility to see what exactly is going on with the part weight in their particular scenario. I could speculate the back pressure is causing the plastic pressure to exceed the nozzle contact force and drooling between shots. Perhaps the hold time is shorter than needed to completely seal the gate leading to inconsistent part weight, the process could be running pressure limited causing weight inconsistencies with viscosity changes. If it's a hot runner mold the hot tip could have an internal leak. It's a guessing game without thoroughly investigating a root cause.
I've been molding for 25 years. As far as I know adding backpressure increased the shot density therefor increasing the part weight. Or maybe i've been doing it wrong all along.
Back preasure puts more material in the flights of the screw not less.
Back pressure is the amount of pressure the plastic has to exert on the screw to force it backwards, hence the name: back pressure. Increasing back pressure increases the density (the weight) of the shot (molten plastic) at the front of the screw.
thnx for video BUT
i would ask about raising the back pressure u told us in the video that raising it make the part weight less while the density getting higher how is that possible i think both should getting higher
Thnx
Increasing back pressure does increase part weight. I have not been in their facility to see what exactly is going on with the part weight in their particular scenario. I could speculate the back pressure is causing the plastic pressure to exceed the nozzle contact force and drooling between shots. Perhaps the hold time is shorter than needed to completely seal the gate leading to inconsistent part weight, the process could be running pressure limited causing weight inconsistencies with viscosity changes. If it's a hot runner mold the hot tip could have an internal leak. It's a guessing game without thoroughly investigating a root cause.
I've been molding for 25 years. As far as I know adding backpressure increased the shot density therefor increasing the part weight. Or maybe i've been doing it wrong all along.
As you are 25 years experienced, I want to speak with you sir
Your right. It’s a compression therefore increases the density
hope that you make new video about maintenance molding machine
We have a number of projects that we’re working on! Stay tuned!
GREAT WORK KEEP GOING
Thanks! We certainly will!
Hi
Hi!