Flow marks using polycarbonate.

Good afternoon sir,
Thanking you very much ,Icheck and come back to you sir.

Are you filling too fast?

All we run is pc in our shop.
When we fill too fast we get those marks that you
are talking about.
super slow cycles are the cure.
.10 ips to .50 ips usually helps

I thought I would note for the people who are always on this forum; ie, Brent, Rick Batey, Crusty, Brett and others. This is the first picture I have seen used on this forum and I noticed all the responsed guessed the same problem. This really helped solve(?) this issue. I know I am stating the obvious. But, how many more pictures will we see?

Tom R.

while i taugh everything was there ... something got up my mind .. you want a make sure feeding use 3/4 of cooling time or as some very small shot needs , add a feeding delay to get the feeding as close as possible to the end of cooling . The less long PC stays in the barrel, less chance are that youll have injection marks...

A nice start up would be to get string from the sprue and then get a decompress that will prevent it without getting it too long

After looking at your part I would like to make the following comments.
1. Make sure the dryer is properly working. Dry material for 3-4 hours @ 250 F prior to processing.

2. Check your actual melt temperature. Most Polycarbonate material run around 550 - 600 F depending on what grade you are using. Check with supplier for their recommendations.

3. If possible slow down the ram velocity. Profile injection may help.

4. Raise the mold temperature most suppliers will recommend 140 -180 F. Again depends on grade of material I have seen some companies use oil heaters in the 200 F plus range.

5. Not sure of the gate location. You maybe getting gate shear from a gate to small. Most gate sizes for Polycarbonate are 50 60% of nominal wall.

Hope this helps you.

Robert

Unless it is dried in a dryer. What is the dewpoint? It does look like moisture.

I agree, these look like silver streaks or crazing, common sympton related to degreaded material (running to hot) or hot material hitting a cold surface.
Polycarbonate, If there is moisture in the material don't use it as regrind, you can not reuse regrind PC that was wet.

are you sure its s flow mark and not delamtion of the matl. matl. could be to hot. or mold to cold?