20% GF PP Warp

I have had two tools recently come my way that are slatted for 20% GFPP. Looked at Mold Flow, both show warp tendencies and both have been warped. More than MF said but in the areas. I have tried different fill rates, hold times/pressures, water temps, and barrel temps. My conclusion is that the orientation of the fibers is causing the warp. Our corporate team suggested we do tool work to include increasing the gate size from 2mm to 4mm and rad the corners as much as possible. None of this worked either.

Shot neat PP and 20% TF PP... Warp gone. What am I missing?

Both parts are direct drops. The last part is valve gated (3 gates on a rectangle part) and I tried sequencing them to no avail. I am getting very discouraged that this material is kicking my a$$.

Thanks!

Just out of curiosity have you tried cure time ?? If so was it a big increase small ??also with pack pressures have you tried more or less?? And how are you filling it d-2 or d-3 what part percentage does each stage transfer at??

I need a more photos of part with gating. the warpage is due to glass orientation, which (maybe) can be change due to injection cascade stategy …. and materiál press in the area (maybe some area must be without holding pressure (close gate on HP). .. and tool temperature profile...

Attachment 449Attachment 450Attachment 451

This is the bin I had issues with. A change to 20% TF PP solved the issue.

I have adjusted the pack/Hold times and pressures. Cure time... I shaved 10.0s off and added 60.0s. Neither changed the warp whatsoever.

Nothing I changed made this warp any better or worse.

We are running a decoupled 2 setup.

I will post pictures of the seatback shortly.

First, you are absolutely right on this: 'My conclusion is that the orientation of the fibers is causing the warp.' Fibers orient whereas talc does not since it is a powder.

You may have tried this but the other thing I can think of is to try differential mold temps. The side towards which it is warping should have a lower temp.

Let us know.

Suhas

I tried up to 45° difference and still nothing. I was not comfortable (nor was I at this point either) running any higher for production. This was just an effort to see if the warp could be changed any.

Possible to create a cooling fixture so that the parts cannot warp while cooling?

The parts are already warped as soon as the robot drops it in the cage.

PP TF is a solution or the tool must be adjusted to compensate warping.
I am prefering Mouldflow analyse before any changes.

Is moving to a 20% glass bead filled PP an option?

What about melt temps? Entire mold hotter too? I only see on gate. Where are the others? I know this won’t run a decoupled process due to reminding me of plastic bowl lids; they look like potato chips when you mold them like you should. Since you have Valve gates I'd pack for a short time and shut them. Allowing the mold temp to lower the molded in stress and differential shrinkage. What’s the MF of the resin? Higher might help. Ask do they really need the glass fiber.
Rick

Sorry, to say but you may need to add some windage to the tool and it may be a little late - not sure.
Suhas

So again, we were able to convince the customer to switch to a talc reinforced material (TPO) on the seat back that I was having warp issues with. This will not always be a possibility, any tips for gating (size location etc) for glass filled materials?

Attachment 452Attachment 453


Sorry Rick- This is the valve gated part. the center pc is the one that is having all the warp. I have tried sequencing them, different pack times, starting to fill this panel first and last. 20% TF TPO meets all customer requirements and produces a flat part... Also better in my opinion all the way around in regards to wear on the machine and tooling.

Any advice would be appreciated.

Hi,

can you post here the process output datas and injection curve with time and preassure scale?

J.

is this warpage presented also on short shots parts?

As others have mentioned you have proven that the fibrous filler is the true root cause. Not a whole lot of processing around this issue especially with what I see as the parts design. If talc or glass beads are not a permanent option perhaps a talc/glass combination may help reduce warp.

Can gussets be added to the outside of the part to tie the flange to the intersecting walls? If so you would want to make sure to not make them too thick or it could make the issue worse. I've seen adding gussets at about 50% nominal wall thickness help with this type of warp.