How to improve / fix Z woobble

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Commonly called « Z Woobble » on most of reprap forums, this phenomenon is very frequent when you assemble a reprap 3D printer.

Often, this phenomenon can appear after a while whithout even knowing why or what we did.

There are always at least 1 or many reasons why this happens.

When we have this effect at the begining it can be time consuming or challenging to find out how to fix it.

What is Z Woobble?

A deposit 3d printer, is printing layers on top of the previous layers.

In a perfect world, all the layers are perfectly aligned and we have a perfect wall finish.

In reality, we can often have Z Wooble, it means that the layers are miss aligned and we have some « waves » on the sides of the prints.

If we look closely under light we can see a periodic pattern repeating itself.

If we look even closer we can see that the layers seems to be layered correctly but the height of each layer may vary slightly.

Le plastique s’écrase par moment et se détend à d’autres endroits.

If we place our threaded rod in front of a long print we can clearly see the pattern matching with the thread.

Causes:

The identified causes so far are numerous, that’s why we can often accumulate them, making things challenging to fix.

Here are the causes we could identified so far:

  • Threaded rod are not parallel to themselves or to the guiding smooth rods.
  • The X belt tensioner is applying force on the Z axis smooth rods instead of the X axis smooth rods. THe smooth rods will then bend slightly enought to generate the issue.
  • The extruder is not calibrated. (EStep/mm not calibrated),The amount of plastic is too much or not enought making the plastic deposing irrugular.
  • The X carriage is not moving smoothly on the Z direction. One of the side is moving before the other side and the movement is not linear anymore.
  • One of the threaded rod is blocked when the axis is going down.(often when we are using auto bed leveling)
  • Auto bed leveling is compensating too much. meaning that one of the Z axis side is higher that the other side based on the heatbed. Use a flat object in order to adjust the height on both sides of the z axis to greatly diminish the compensation of auto bed leveling.
  • The filament is periodically blocked, impacting the plastic flow.
  • The extruder is sleepering on the filament. This impacts the plastic flow.
  • The layer height is too high or too low according to your nozzle diameter.
  • The filament diameter is not uniform and may vary a lot. Here again the plastic flow will be impacted.
  • One of the Z axis nuts have slack.
  • At least one of the nuts or the threaded rods are worn.In this case the best is to change both Threaded rods and Nuts on both sides.
  • The top of the threaded rod is constrained/ Threaded rods are never perfectly straight. constraining the top of the threaded rods will impact the guiding rods. Freeing the top of the threaded rods can fix the wooble effects.

Feel free to come back to us if you know some other causes and possible fixes.