Rubber Matt has Hazy Areas

[chrisprocess]

Where is part gated?

That thing?

Definitely drying this material properly is critical - really any exposure to air for just a few minutes will absorb moisture and any cracks or air gaps in your dryer/feed system can be problematic.
(learned this the hard way).

Also working with this material I've experience better results filling on first stage - almost around 99.99999% full on first stage.
Reason is because once the material starts to slow down - it STOPS

Looking at your part I'm just imagining where the gate is, and how the flow-front would behave along part featues.
If you filled with one injection speed your flow-front would be Fast in areas with small cross section and Slow in areas with large cross section, which is bad for a material that wants to STOP when it slows down. This could cause the hazyness, maybe.

I'd recommend a shot size study and run fill-only parts at various transfer positions so you can visually see your flow-front at various stages and note any swirling/whirling that's going on. (10% full 20% full 30% full etc. etc.)
With this information you can do your best to 'profile' the injection to try to maintain the same flow-front rate across part features.

Steel surface finish also comes to mind..

[Joel JS]

Thanks Chris, and Nemanja,

Yes, Chris, you got the gate location correct!, tunnel gated, and looks ample in size, (if not too big. )

We did dry the material, and I thought that was unnecessary, only because we usually don't dry TPE. but I am NOT the expert on this stuff! I might try different drying levels as you guys suggested.

I didn't see anything much in the mold, I would clean the mold, and next shot looked the same. Playing with fill speed, I could move the hazy spots around a bit, and diminish a bit, but always in the same basic location.

I ended up going Sloooow thru gate, then FAST the rest , or the gate would also look crappy. I can't remember doing parts at 50% full, I probably did(?), but I like that idea, and will look again.

FYI - I also cut off the ribs on the back of the part, stuck them in the mold, and shot again, thinking I had at least the problem (Turbulence flowing over the ribs) clarified, but those next parts looked the same too!....

Thanks for the feedback!
Joel