Posts: 86
Joined: Sat Mar 16, 2013 10:27 pm

Trouble at the Top.

Wed Apr 24, 2013 10:19 pm

I have been having problems when I get to the top of something where the area is quite small that I end up with a blob.
I am guessing it is because there isn't time for the layers to cool before I start the next one.

Any Ideas on how to fix this.
P.25-1.JPG (206.71 KiB) Viewed 2250 times

Site Admin
Posts: 304
Joined: Sun Feb 10, 2013 8:28 pm

Re: Trouble at the Top.

Thu Apr 25, 2013 6:26 am

This is very common for parts like this. If you look in thingiverse for pictures of this calibration pyramid, you'll see hundreds with the same problem. And yes, you are correct, it's just lack of cooling at the very top. Here's a few suggestions for ways we have been able to improve printing of extremely small layers like that:
  • Lower your extruder temperature by 10-15 degrees - Some of the best calibration pyramids I have ever seen with PLA were printed at 175 or 170 degrees. A lower temperature lets the layers cool faster and helps the plastic solidify quicker. In Creator you could even slice the part, preview it by-layer, and find out the layer number where the part really starts to narrow. Then go into the Temperature tab of your FFF settings and start lowering the temperature near that layer using additional setpoints.
  • Improve your cooling fan - Very small parts like this need as much cooling as you can give them! This is one of the big reasons you see people attaching ducts to their cooling fans to help concentrate the cooling fan air near the extruder tip. You might try adding a similar duct to your M2 fan for parts like this, or even look at installing a second fan. Both would help.
  • Try printing the same part in ABS instead of PLA - It wasn't clear from your post, but if you are printing with PLA, you might want to try printing the same part with ABS. ABS is typically less stringy and can solidify quicker because of its higher glass transition temperature. It's the same reason why bridging is sometimes much easier with ABS instead of PLA.
  • Print 2 at once - Obviously printing multiple parts at once means that the hot extruder will have to move away from the part momentarily while it prints the other part. We commonly solve cooling issues by just printing 2 copies of the same part simultaneously.
Hope that helps!

Posts: 86
Joined: Sat Mar 16, 2013 10:27 pm

Re: Trouble at the Top.

Thu Apr 25, 2013 3:18 pm

I had thought about adding a small tower off to the side as a second part.

Looks like there something for future improvement. Possibly under cooling if slowing to X% doesn't get you to min layer time then do ????.

Keep up the good work.

Posts: 86
Joined: Sat Mar 16, 2013 10:27 pm

Re: Trouble at the Top.

Thu Apr 25, 2013 10:31 pm

I used the same settings as above but I printed a small tube beside the pyramid.
Layer .25 Temp 183.

P.25-2.JPG (146.53 KiB) Viewed 2215 times
So this will work until you can come up with something. Also it still gets a bit sketchy when it prints a small layer right on top of the layer that just finished instead of starting the layer over on an area that has cooled but it seemed to work.

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