Form4 critical mixer failure

Support & Troubleshooting
1

Form 4 user here.

Got this printer 2 years ago and it worked great for about 6 months. Then it consistently failed on every single print, it can’t get past checking for debris. The flex build platform is colliding with the mixer on every print no matter what the material. Specifically, it lowers the build platform, moves the mixer arm, then lowers the build platform. That’s when it hits the mixer arm and has this loud clicking sound.

I was able to alleviate the issue for the past year by setting the z-offset to 540 um. But I performed a build platform alignment and now even with the z-offset maxed out and the platform still collides with the mixer when checking for debris. I have checked this with a new tank, mixer and a different build platform.

I suspect it’s something in the platform sensors or the firmware because when I could get it to print, and I printed directly onto the platform, no raft, the first few layers were absolutely squished, even with the z-offset high.

Any recommendations? Otherwise I’m strapping :firecracker: to it and leaving it outside Formlab’s offices.

2

Sounds very puzzling indeed.

the closest related discussions I was able to find were -

I know I am stating the obvious but - how about reaching out to Formlabs Support? Have you reached out before in the last 2 years?

3

I did.

They had me run through all the steps in Form 4 and Form 4L generation error messages | Formlabs

For both Error 1.1.6: Mixer detected debris and Error 1.1.7: Build platform detected debris.

Neither procedure produced any different result. I did submit a support request in Nov 2025 but I never heard back. I figure it was because we don’t have a service contract (it expired last year).

4

Hi @matthew_henry ,

I’m a Customer Support Manager for Formlabs, and I’d like to discuss how to get your printer working again with you, as well as your previous Service interactions. I’ll be reaching out.

5

A simple fix is stop using the flex build platform and see if your having the same issue with a regular build platform

6

I considered that and took the flex plate off the build platform and reran the align build platform. But it did not help, the build platform still crashes into the mixer.

7

I think I know what your problem is here, I have experienced the same. Check under the rear wear strips in the back of the resin tank. Lift it up and see if there is an accumulation of cured resin. I believe this causes the mixer to “ride” up and pinch itself on the build plate. I chased this issue for days before figuring it out.

8

The cause of this seems to be a bad LPU, I replaced the LPU, cleaned the wear strip and it started working.

9

I checked that out. None of my resin tanks had any cured resin underneath the wear strips.

10

Formlabs just sent me a mixer rebuild kit. I swapped out the parts and have done a couple of test prints without the mixer crashing. I will test print a few more times by the end of this week to see if the build platform will crash into the mixer still.