Inconsistent Print Accuracy with Left Nozzle on Tall Models

Bambu Lab H2 Series
1

I’ve been testing and trying to understand why my H2D printer behaves this way. It seems there may be a difference between the left and right print heads—specifically, the left one appears to lose precision when printing taller models.

The reason I suspect this is because I have a model that prints flawlessly using the right nozzle. However, when printed entirely with the left nozzle, the print randomly fails after about 50% completion. Interestingly, if I use both nozzles in a multicolor print (left and right), the print completes perfectly. It’s as if printing the entire model with the left nozzle causes a loss of precision, resulting in the nozzle striking the model and detaching it from the build plate. This issue seems to affect only tall, narrow models.

Here’s what I’ve already done:

  • Full printer calibration (the one that takes over an hour)
  • Dual nozzle precision calibration using both dark and light filaments
  • Vision Encoder calibration
  • Dried the filaments using AMS HT to maintain recommended temperature (per Bambu Lab’s guidelines)
  • Individually calibrated the filaments with correct values applied

Since this issue only occurs with specific models—especially when the entire print is done using the left nozzle—I’m unsure what to try next. This happens on both the stock firmware and the beta version I’m currently using, so I’m at a loss for why it occurs. Troubleshooting has been difficult.

Any suggestions?

2

I have a tall part that was printed using the left nozzle. During a travel move, it crossed over a tree support and I saw it hit the support one time, even though Z-hop was on and the printer was in normal Z setting with reduced infill. Retraction disabled. It seemed like the Z-hop was too slow and the travel move was too fast.

I reviewed the travel paths and saw that turning on ‘Avoid Crossing Walls’ would have stopped it from crossing the tree support where the collision happened. However, it shouldn’t have hit anything to begin with, so there’s definitely a need for improvements .

3

I have that setting enabled as well—mine is set to 50%.
I even tested with various filament types, but the result was always the same: the model was knocked over. So I believe there’s still some optimization needed for the left nozzle.
I’ve now installed their latest beta, version 01.01.02.07, so I’ll repeat the test and see if this version performs any better.
However, I have a couple of laser jobs to complete first, so the earliest I can run new tests will be tomorrow.

2 Likes
4

The jerk is currently set to 3 mm/s perhaps a higher value might help, but it’s odd that the problem is only occurring with the left nozzle.

Let’s hope the newly released firmware is an improvement. :crossed_fingers: