Selftest Error Please Check Y Axis Length  

RE: Selftest Error Please Check Y Axis Length

Try printing this gauge to adjust your belts, this is what are used to fix the problem for me. https://www.prusaprinters.org/prints/46639-tension-meter-for-the-gt2-belts-of-i3-mk3s-or-prus

RE: Selftest Error Please Check Y Axis Length

What do you mean by "bumping the front of the printer"? During a print?

If the bed stops half way during selftest and the belt tension is ok and the grub screws on the motor are properly tightened and there is nothing blocking the bed it seems to be a mechanical problem with the smooth rods and bearings.

Remove the y axis belt and check if you can move the bed freely from one end stop to the other. If the friction increases at one point one of the rods might be bend, if you have friction all along, one or more bearings might be damaged...

RE: Selftest Error Please Check Y Axis Length

What I mean by bumping the front is that the bed seems to be an inch forward of where the printer expects it to be. When moving forward to the front, the bumpers underneath hit the forward part of the rods and grinds for a few seconds (making an unpleasant noise) before starting to move back. That's when the check Y axis length error appears.

RE:

The unpleasant grinding sound is merely the sound of the stepper motor skipping / missing steps, it should cause no damage.

If the printer seems to think the Y carriage is in the wrong position, it likely has something obstructing it  when it does the home position check at the start of the print.  It does this by running the Y carriage all the way back towards the motor until it hits the rear stop.   If something blocks the movement before it gets all the way back, the printer will assume that it hit the rear stop and act like you describe, with the carriage further forward than it should be and hitting the front stop, which should never happen during printing.  Normally, the rear stop on a Mk3 series is the Left side linear bearing contacting the Left Rear smooth rod holder, while on the Mk2 series, a limit switch at the motor holder determined home position.

So, the first check is easy. Just make sure that the bed can move all the way back without obstruction until the Left Rear linear bearing contacts the end stop. It should do this at the start of a print as well. If it only goes some of the way back, something is probably obstructing it, either something hitting the Y carriage, the bed heater cable getting caught on something, something interfering with the belt or maybe a sticking linear bearing?

RE: Selftest Error Please Check Y Axis Length

Since I can't get past the alignment setup, I can't print that.

RE: Selftest Error Please Check Y Axis Length

Since I can't get past the alignment setup, I can't print that.

RE:

Mybe this will help. if you can upload a video thanks, Prusa Knowledge Base | Adjusting belt tension MK3/S (prusa3d.com)

Prusa Knowledge Base | Adjusting belt tension MK3/S (prusa3d.com)

Check movement as suggested above.  You should be able to feel any obstruction but check you have no debris in the Y axis idler; hmm, and make sure the wire bundle from the back of the print bed is not hitting the wall behind.

If none of these help try running the XYZ calibration:

https://help.prusa3d.com/en/article/xyz-calibration-mk3-mk3s-mk3s_112351

 - This isn't usually needed but perhaps your machine was shaken up in transit.

Cheerio,

RE: Selftest Error Please Check Y Axis Length

https://www.help.prusa3d.com/en/article/check-axis-length-x-y-z-mk3-s_134223  

Posted by: @john-r-4

My Y axis was bumping the front of the printer so I decided to recalibrate. It had done this before and recalibration fixed it. Now I get a message: Selftest Error Please Check Y Axis Length

Nothing is interfering with the movement of the bed. The belt seems sufficiently tight. It has about the same amount of give as the functioning X axis belt. On the self-test, it moves all the way forward easily, but only moves about half way back before it gives me the error.

This was a pre-assembled printer that I got in December 2021.

Suggestions?

RE:

Here is a video of what is happening.

RE: Selftest Error Please Check Y Axis Length

It was working for a month, then quit.

It won't let me calibrate because it stops at the initial test for the Y axis, telling me "Selftest error! Please check: Axis length Axis Y"

RE: Selftest Error Please Check Y Axis Length

Trying again with a video

RE: Selftest Error Please Check Y Axis Length

I've tried to upload a video and apparently have failed at that as well.

The belt test fails with the same Y Axis length error message.

RE:

Trying to upload a video, but it's not showing up.

RE: Selftest Error Please Check Y Axis Length

The belt status under Support says 180 for the Y Belt. The support page says if the belt is under 240 to loosen the belt. But when I loosen it, the value gets worse, not better. I wonder if something isn't wrong with my belt tensioner underneath. Here's a photo:

RE: Selftest Error Please Check Y Axis Length

To be truthful I had the same issue but I tightened it up  to show 145 - 160 took away the problem and I just left it and printed it gauge  and then adjusted it between minimum and max, I never had an issue with setup again. I could never get it to what is recommended. It just didn’t work for me still to this day. I change my belts and printed new parts but no go. I couldn’t Ever get it to hit over 160 and work. But mine print very nice with all types of filament I’ve had it for over a 2 years now. 

RE: Selftest Error Please Check Y Axis Length

I had the same issue. Turn off the printer.  Take a clean small cloth, clean the rods, then put a little WD40 on the rods with a clean cloth. Push the bed back and forth to get the oil into the bearings. This worked on mine.  

Posted by: @john-r-4

My Y axis was bumping the front of the printer so I decided to recalibrate. It had done this before and recalibration fixed it. Now I get a message: Selftest Error Please Check Y Axis Length

Nothing is interfering with the movement of the bed. The belt seems sufficiently tight. It has about the same amount of give as the functioning X axis belt. On the self-test, it moves all the way forward easily, but only moves about half way back before it gives me the error.

This was a pre-assembled printer that I got in December 2021.

Suggestions?

RE:

Posted by: @alisumer

I had the same issue. Turn off the printer.  Take a clean small cloth, clean the rods, then put a little WD40 on the rods with a clean cloth. Push the bed back and forth to get the oil into the bearings. This worked on mine.  

 

That might work once or twice, but WD40 is not a lubricant, it will dissolve what's left of lubricant in your bearings. Initially this will make them go smoothly, on the long run it will remove the lubricant completely.

Agreed, WD40 is for cleaning, not lubrication.  Either use the Prusa supplied grease or a drop of light machine oil.

You might as well bring forward your regular maintenance session:

https://help.prusa3d.com/en/article/i3-printers-regular-maintenance_2072

Cheerio,