3.5s+ upgrade, can't get x axis calibration to complete successfully - Assembly and first prints troubleshooting

RE: 3.5s+ upgrade, can't get x axis calibration to complete successfully

Looper — Wed, 04 Feb 2026 01:17:58 +0000

OK, I think I found my issue. I got a successful X Axis check.

I changed the X stepper pulley and slid it out, away from the stepper motor, just a smidge. The only thing I changed to get this to pass a test. The only thing I didn't change prior to that. Basically I tried to make sure it was tracking true with the belt.

Hope this helps someone.

RE: 3.5s+ upgrade, can't get x axis calibration to complete successfully

Looper — Tue, 03 Feb 2026 21:10:27 +0000

Posted by: @pete-6
I know this problem is posted somewhere else in these forums, but I'm having the dreaded x axis calibration failure (with no diagnostic message to help) after upgrading my 3s+ to a mk3.5s+, and changing out the pinda for the superpinda. I've literally spent hours on this at this point. here's what I've checked and tried:
* verified that zip ties are not interfering
* checked for smooth operation across the axis. rods are clean and bearings seem OK
* tried with belt "a little tight", "a little loose", "too tight", "too loose" and perfect, all have made no difference - any value between 58 and140hz onthe belt tuner
* removed screws in back end of hot end fan, they may have been contacting z axis screws (no change)
* held heat bed cable bundle aside during calibration to make sure it's not interfering
Sometimes the calibration will bounce off the left side many (>20) times, other times only a few, but I always get a fail .

I am seeing the same thing here.

Installed new 3.5s+ kit, and heat bed, on a MK3 that had been updated to a MK3S+. The MK3s+ had been printing fine and had passed all calibration test a week prior to this upgrade when I upgraded it from an MK3.

I have completely disassembled the the X/Z rods, verified bearings are in the right clock orientation, re-lubed bearings with Prusa Lube. Assembled everything and tried it with the belt too loose, too tight and just right. no improvements. still a red X on the the X axis. Nothing is hitting everything moved freely.

I have looked over the Crash docs and verified everything on that list. Anyone with any ideas?

The original MK3 had very few hours on it as I never used it much, maybe two days of print time. I bought it new to use with an MMU1 that got upgraded to an MMU2. It then sat in a corn for a few years and I just dug it out to upgrade it and the MMU2 to a MMU3. Was hoping to gain some speed with the MK3.5S+ upgrade.

3.5s+ upgrade, can't get x axis calibration to complete successfully

Pete — Mon, 19 Jan 2026 20:13:20 +0000

I know this problem is posted somewhere else in these forums, but I'm having the dreaded x axis calibration failure (with no diagnostic message to help) after upgrading my 3s+ to a mk3.5s+, and changing out the pinda for the superpinda. I've literally spent hours on this at this point. here's what I've checked and tried:

* verified that zip ties are not interfering

* checked for smooth operation across the axis. rods are clean and bearings seem OK

* tried with belt "a little tight", "a little loose", "too tight", "too loose" and perfect, all have made no difference - any value between 58 and140hz onthe belt tuner

* removed screws in back end of hot end fan, they may have been contacting z axis screws (no change)

* held heat bed cable bundle aside during calibration to make sure it's not interfering

Sometimes the calibration will bounce off the left side many (>20) times, other times only a few, but I always get a fail .