Prusa i3 help

[Jester]

I recently purchased two used Prusa i3's a MK2 and an MK2 upgraded to MK2.5S

The upgraded one does not work and I'm looking for a forum where I can get info on how to fix it. I'm new to 3D printing but I'm an engineer so pretty good at fixing things.

So if someone can suggest a forum that would have some Prusa experts, or if someone here has some expertise that would be great. I posted on the Prusa forum, but have had no response to my question.

Details of problem:

Extruder correctly finds home, but then fails at begining of XYZ calibration with "Calibration failed, check axes"

This is a i3 MK2S upgraded to a MK2.5S (with metal plate)

Firmware:

I tried both 3.8.1 and 3.13.2  same results

When I select Calibration | Auto Home,  the PINDA sensor is very close to centered in the target.

When I select Calibrate XYZ, after setting the top Z, the extruder comes down well left of the target (perhaps that's normal I'm not sure) but then stops and throws error  "Calibration failed, check axes"

The PINDA sensor light turns off just as the extruder approaches the table, but then it stops and throws the error.

 

Not sure what to do next?

[jfb]

Try the prusa forums at https://forum.prusa3d.com/ and more specifically
https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk2-5s-mk2-5/

[aeberbach]

Definitely Prusa forums as jfb suggested.

But also... XYZ calibration fails are usually due to incorrect tension, worn or ungreased bearings, misaligned rods (Y axis especially) or something in the path of the extruder. A cable tie incorrectly placed on the cable bundle of the X axis is a really common problem. But in the case of a MK2 I would probably suspect belts and bearings. I don't known if the MK2 shipped with hardened steel rods, can you see any wear in them or are they still a uniform mirror polish?

If the printer is turned off you can probably manually rotate the two Z axis screws by hand to bring the carriage right to the top of its travel. Does it go that high when the self-calibration is happening? Is the print plate sitting down where it should be or has it been raised higher somehow? The axes all want to see a minimum amount of travel from one end to the other and they need to perform the travel without detecting excessive current from the steppers during travel (possibly due to worn rods or bearings or belt too tight where a belt is involved).