Self test failed. Verify the Length of Y axes
Dear all,after assembled my prusa. I did the self-test. fans ok. X axis ok.
Y-axis: no. the printer says to check the length of the Y axis.
The bed continue to move. But it arrived at the end.
What should I do? from the manual I don't understand how to change the length.
thanks
RE: Self test failed. Verify the Length of Y axes
Good morning,
I believe the printer is trying to say that the measured length of the Y axis is unexpectedly short.....
can you check that nothing is preventing the Y carriage moving the full 210mm front to back,
is the cable bundle restricting movement?
is the Belt fixture on the underside of the Y platform on the correct way round?
Are the bearings running freely?
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Self test failed. Verify the Length of Y axes
The movement it.s good, but it.s like that the bed wants to pass the limits.
RE: Self test failed. Verify the Length of Y axes
RE: Self test failed. Verify the Length of Y axes
is the Y axis operating the Y endstop switch at the back of it's travel range?
you should be able to confirm operation using the LCD Menu!
regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Self test failed. Verify the Length of Y axes
Now it.s ok.
I put the belt back on. creating more tension. then I stiffened the pulley by tightening the screws.
RE: Self test failed. Verify the Length of Y axes
Good news
Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Self test failed. Verify the Length of Y axes - check "Belt status" values
We had the opposite problem. It seemed okay when we went to "Settings/Move Axis/Move Y" and it would go all the way back and forth. "Calibrate/Auto Home" worked (most of the time) too. Nothing seemed to be getting in the way, yet the "Calibrate/Self Test" and "Calibrate/Belt test" both failed repeatedly. Typically the Y Axis would give a little jerk and immediately stop (no matter where it started from), then give a failure message, something about "Y Axis length".
After two days of checking this and that (including browsing these forums) and getting nowhere, my son (the owner of the printer) found a reference to the belt tension numbers on https://help.prusa3d.com/glossary/belt-tension_1597
"If you have an MK3 or MK3S you can go to the LCD menu -> Support -> Belt Status. The values should not be under 240 and above 300, but there is no unique ideal value. The lower the number, the more tight the belt is.
If your value is under (or close to) 240, you need to loosen the belt
If your value over (or close to) 300, you need to tighten the belt"
That was a big piece of the puzzle. It turned out that we were getting numbers like 275 for X and 68 for Y, so the Y-axis belt was way too tight. It sounds like the motor controller (?) itself was putting a halt to the test, not any obstruction in the path. It failed to mention anything about belt tension in the "Belt test" results. Oh, it did display a number while the test was running, but we mistook it for a (dubious) Y-Axis distance from [0,0], and we had no hint as to what it really meant, even after reading section 6.3.4 of the user manual many times.
Unfortunately, when he assembled it he had cut the belt too short with the belt tension adjustment already positioned for minimum tension, so we could not loosen further it by the proper method.
My work-around was to swap out the two M3x10 screws on the Y-belt idler with two M3x14 from the spares. This gave me enough room to drop in two pieces of zip-tie scraps between the Y-belt idler and the front plate of the frame. After I torqued them down again, this still left me with room to slacken the belt tension with the M3x30 screw on the belt tensioner under the Y-carriage.
Once we got both of the "Belt status" values within range, it passed the "Belt test" and, finally, the "Self test". Pretty soon though, I should find some material (sheet aluminum or some such) that I can punch two holes in and replace as a shim plate instead of the zip-tie scraps. I'm concerned about the long-term effects of the uneven stresses on the Y-belt idler, on either side of the zip-tie scraps.
The "Pre-flight Check" really should have us checking the "Belt status" before running the general "Self test" routine, and explaining what it signifies.