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PC Overhangs and Bridges  

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Lukas
(@lukas-6)
Eminent Member
PC Overhangs and Bridges

Hi,

I wanted to try some new material and decided to go for PC. The one I am using currently is Polymax PC. I am using an adhesive designed for PC to counter the adhesion issues which worked out great and simple objects look good.

However once I went for something with overhangs, even easy ones look really terrible (see attached picture of a calicat). I also get quite a lot of stringing but I guess I have to increase the retraction a bit. 

Settings:
.2mm layer height (same problem with .15)
110° Bed / 260° Nozzle (in enclosure)
30-50mm/s
10% cooling, 30% for bridges
.8mm retraction

What would you suggest to try to counter that problem?

Posted : 30/03/2022 8:58 am
Thejiral
(@thejiral)
Reputable Member
RE:

I have no experience with Polymax PC (blend) but with Prusament PC Blend. With the latter 45°overhangs aren't a problem. I don't know if Polymax PC is trickier in these regards but printing slower should definitely help. What is the perimeter and outer perimeter printing speed? Reduce it. 

According to manufacturer's recommendations, you can print up to 10°C cooler but that could possibly ruin layer adhesion. Polymax PC is printed generally at rather low temperatures for a PC blend. 

Cooling more would certainly help overhangs (front overhang looks a lot nicer than back overhangs). Again, this can also ruin layer adhesion potentially but you could give 20% parts fan cooling a try. 

This post was modified 6 months ago by Thejiral

Mk3s MMU2s, Voron 0.1

Posted : 30/03/2022 10:51 am
Lukas
(@lukas-6)
Eminent Member
Topic starter answered:
RE: PC Overhangs and Bridges

Thanks for the input, I just started a test print with 15-30mm/s print speed and more cooling fan (I'll see how good the adhesive is now :D). I think I do not really want to reduce the temperature too much since, like you said, the layer adhesion will get worse and worse ... But if this print "fails" i will do a temperature tower and see what happens below 260°.

I also got a spool of Prusament PC blend. Polymax was the one I decided to start with. I will compare it with the Prusament.

Posted : 30/03/2022 12:45 pm
Lukas
(@lukas-6)
Eminent Member
Topic starter answered:
RE: PC Overhangs and Bridges

The print is done and looks not perfect but a lot better. I will now try to lower the temperature by another 5° and check the layer adhesion.

Thanks again for the input.

Posted : 30/03/2022 2:26 pm
Thejiral
(@thejiral)
Reputable Member
RE: PC Overhangs and Bridges

Generally speaking I like to dial at the speed if there is an issue with overhangs. Time is easy to give and you can substantially improve overhangs without compromising adhesion. Another thing that can help and inflate print time even more 😉 is reducing layer hight, maybe down to 0.1 mm. Than the overhang steps are also shorter.

Of course, that is not a good strategy if you are trying to be as efficient as possible but I don't mind time if it gives me better quality.

Mk3s MMU2s, Voron 0.1

Posted : 30/03/2022 5:36 pm
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