Prusa Mini+ print 3% larger on the X-axis having printed perfectly for a year.  

Prusa Mini+ print 3% larger on the X-axis having printed perfectly for a year.

Hi everyone,

I'm wondering if anyone can help me as I can't figure out an issue I'm having with one of my Minis and  I'm at the point of swapping out hardware.

An example of the problem I'm having is as follows: Print a square 16x16x10mm where x & y are 16mm. Take an average measurement for x & y and the x axis is 3% out. I think this issue has been going on for a month or so.

I have 4 minis in total, 3 of which have excellent dimensional accuray. The one I'm having an issue is printing with excellent quality, with the exception of being consistently 3% out on the x axis. My current workaround is to scale the x axis down within Slicer, which I'm now testing with larger prints to see if this 3% inaccuray is consistent or perhaps it may get worse over larger distances.

Things I've tried

• Settings checked within Slicer, the same gcodes will be perfect on my other mini's so I know it's not the settings.
• Checked belt tension by running tests with it looser and or tighter to see if  it has an observeable effect of this issue.
• Checked extruder drive gear and driver gear, cleaned and tightented lugs on the drive gear.
• Fully service, replaced bearings on the X axis.

My suspicion is the X axis stepper motor is faulty, but a full factory reset and clibration of the x, y, z axis is reporting no errors.

Any ideas what this might be?

I appreciate any help in trying to resolve this issue.