Sunday, August 29, 2021

The problem with string

 It is, of course, well known that everybody loves string, except when you are 3D printing. In the clocks that I've made recently, there is often a lot of stringing between gear teeth which are close together. It doesn't take much to clean it up: a few gentle swipes with a piece of sandpaper generally does the trick. However, there's always some residue left behind. The common advice is to lower the printing temperature, so I did a quick check to see if this helps. I selected a gear with 18 teeth, printed it at different temperatures and counted how many of the gaps between the teeth had significant stringing. "Significant" is a bit subjective here; roughly, I mean I would feel obliged to clean it up. Here's the results:

You probably can't make out too much in this picture. The counts of stringy teeth were:

  • 210C: 10
  • 205C: 10 or 11
  • 200C: 4 to 6
  • 195C: 3
  • 190C: 3
So this validates that a lower temperature helps. 210C is the Prusa default for PLA and I think they use it to ensure a good flow. I'll certainly consider lower temperatures in future.

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