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45 Degree Overhang Problems (And I print Sloooow!)

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I've heard as a rule of thumb that 45 degree angle pieces are able to be printed cleanly without any support material. I've searched the forums and found a variety of recommendations that I have mostly implemented, such as lowering the temperature, increasing the fan speed, slowing the print speed down, and making all the print speeds the same so there's no acceleration (should probably mess with flow rate to account for slower speeds as well... but I don't think that's main issue as described later) But I still can't get a clean print as shown below.

Note: This piece in this photos uses smaller than 45 degree angles, but is indicative of the issues I'm having with 45 degree pieces as well. What's infuriating is that part of the print is beautiful! Before descending into a mess.

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I've been watching the prints to see if I can discern what is causing the problem. Although I can't upload a video I'll try to describe the problem. It seems to me like the printer prints the outer two layers first at slow speeds and fairly cleanly. However, it then fills in the remaining center section quickly. My infill was set to 20% and I thought maybe that low density was causing very quick, sporatic filament placement and that motion was causing the issues. However, I also tried printing at 100% infill and still had the same issue. And I wouldn't think that such a skinny piece would need infill anyway...

I've noticed on vertical prints that the printer tends to do an inside out build that results in very clean results. I don't know why this angled print is doing the outer layers, and then moving to the innermost one... I don't think I changed any settings.

Is this piece simply too skinny to print cleanly? Any reason why the printer wouldn't build from the inside out to allow for the least amount of agitation after the final outermost layer has been set?

Thank you!

IMG_0131.thumb.JPG.fbe58e38c03a0af4b2c1b83d103b3fcb.JPG

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Speed and temp go together. So if you print really slow you need to lower the temperature too. Try 10C less and ofc fans at 100% for something so thin.

 

I have been. The ultimaker PLA says a range of 195-240 and I've been printing at 195. Do you think I should keep going lower or start messing with the flow % instead?

Anyway to prevent the printer from filling in the center last, and instead do an inside out print?

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If everything is working fine and the filament is exactly the size it says, you should not change flow unless is a filament that works better with more extrusion (like some special filaments). You can go down yo 170 max since that's the minimum extrusion temperature. But to get a felling of the 'ok' temperature get a basic profile and if you change the speed lets say from 50 to 40mm/s you can change the temp 5C (as a figuratively idea). So all depends on how fast/slow you print.

For some filaments like some white colors you need to find the sweet spot where everything works nice. Other colors/brands respond different. If you make changes to speeds, you should adjust the temperature to keep a good high quality.

Ofc is very important to get good cooling for pla specially since it needs as much air as possible to cooldown and avoid bad looking overhangs or areas exposed to too much heat.

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In your case I don't think slower speed is the solution, but enough time to let the previous layer to cool before you print the next. Low temperature and higher cooling.

If you think the infill is ruining the print you could always print with a thicker shell. It is some time since I used Cura, but I think you can also lower the infill print speed.

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