When printing several objects, I recently encountered a problem that arises when the structure in itself is relatively thin or the support towers have a small surface: the printhead would in motion tend to knock one or more over as it traveled or catch at them and create layer shift.

How can I avoid collisions with the already printed parts of a layer?


The problem was twofold:

  1. Lack of bed adhesion due to the small contact surface
  2. motion into the already printed objects.

The quick and dirty way was to change two settings:

  • Print with a small (3 mm) brim to stick the supports to the print and provide more surface. Other materials than PLA may need considerably more brim!
  • Activate Z-Hop to force the nozzle to lift over the print when traveling

These tricks don't solve issues with very thin structures or in all cases. In those cases, it can be mandatory to increase the structure's (support) thickness or change the alignment.

  • 1
    $\begingroup$ This will help, but for thin vertical rods, the lateral force during deposition can cause bending of the structure, leading to effective random layer shift. No way around that other than to print in a different orientation or build in a "scaffolding." $\endgroup$ – Carl Witthoft Oct 1 '18 at 18:01

For the Creality Ender 3, I had the same collision problem and after a while I found it was because of the X-axis not being level.

I found right hand side was more than 3-4 mm below the left side when the Z-axis height exceeds around 8-10 cm. Below that, the two sides were even. I made some calibration by turning the eccentric nuts of the wheels and tighten them.

If you use Creality Ender 3, that might be the problem. Take a ruler and check between base extrusions and X-axis left/right hand sides at different Z heights.


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