Y axis issues  

RE: Y axis issues

This is just a guess, but look to the drive system. Make sure your belt is tensioned properly (hold the motor still and try to move the bed to make sure the belt isn't skipping teeth). Also check the set screws (grub screws) on the z-axis motors. Tightening order is very important. With both set screws loose, first tighten the one on the flat of the motor shaft to make sure it seats flush against the flat. Then (and only then) tighten the other set screw. (If you aren't sure you followed this process on the x-axis and the extruder, you may as well check those set screws while you have the proper sized allen wrench in your hand.)

RE: Y axis issues

@sembazuru

The Mk3S does not have grub screws for the Z axis- they are integrated leadscrews.

@thomas-3 Y-axis crashes are still an issue with this machine, yes like @sembazuru said, check your Y motor pulley for looseness and tighten if needed.

If this is a newer machine, the belts will stretch a bit in the first break-in prints and need to be tensioned a bit more.

Also, if the U-bolts for the Y-axis bearings are too tight it will cause problems.

RE: Y axis issues

@joe_prints I have loosened the U bolts as I also read that can cause problems, this hasn't helped however.

It is strange since it has been working perfectly prior to this issue, so a loose belt makes sense,  I have checked the tension on the printer and it says its fine, it also feels fine according to the instruction manual. But I will tighten it and see if that helps.

Thanks for your reply.

RE: Y axis issues

Hi @thomas-3

Successfull calibration is crutial for correct function of the printer. Can you a bit more describe what does it mean it does not find home? Does it mean that the motor is not able to drive the bed into home position? This could lead to suspitcon regarding the strong  bearings friction or obstacle along the Y rod.

What are the values of Y belt tension? Numbers below 250 could indicate friction issues.

Is the temperature of the Y motor normal? You should be able to keep you hand on it.

How long was the time period between last but one and recent print you mentioned?

Try to search carefully along both Y rods, if anything like rest of the filament is not creating obstacle 

RE: Y axis issues

If there is no friction moving Y axis both directions, my guess would be that it is hitting something before reaching full rear position.

Look for zip ties and watch the cables as it moves.

If it can't reach full rear travel - it will not be able to find Home.

RE: Y axis issues

Hi @zoltan

What I mean is the print plate will not move all the way back, it only moves to half way. When I go in and move it with the dial it sounds like its crashing into something and reads -4mm so it thinks it is all the way back, but it isn't. 

The belt is reading 193 I have not felt the Y motor but will check that, Thank you.

The time period between prints was no more than 1 week.

I will try everything you have said and report back.

Thank you for your thoughts.

RE: Y axis issues

@robert-rmm200

Its not hitting anything, no obstruction at all. It thinks it is all the way back, so when it starts to print it says crash detection, unless I move the Y axis back manually before I start a print. But as I mentioned it still crashes later on in the print.

RE: Y axis issues

193 on an axis means the bearings are much too tight (they don't really mean belt tension, instead, they tell you axis friction, where higher is lower friction and better).  You want those numbers to be above 260, and ideally closer to 300.

Check the U-bols as mentioned above. They should be adjust loose until the bearings wiggle, then tighted a quarter turn - just enough the bearings no longer move.  Any tighter and they crush the bearing sheel and the rollers seize up.

Also - despite Prusa saying the bearings are lubricated, they aren't. The oil is only for shipping, and it evaporates in a few weeks leaving a dry rod/bearing which also seizes.  Greasing the bearings is best practice.

RE: Y axis issues

Posted by: @joe_prints

@sembazuru

The Mk3S does not have grub screws for the Z axis- they are integrated leadscrews.

 

Yes, silly me. That was a typo in my end. I meant to say Y-axis, the axis that was not performing well. My apologies if I confused anyone.

RE: Y axis issues

@tim-m30

Good to know, thank you.

RE: Y axis issues

Ok, so I have tried everything mentioned above, I have not tried a print yet, but I now see that both the X and Y axis will not find home.

Belt Status is    X 273     Y 284

So if I move them to half way when the machine is off, when I switch it on, they think they are home, the printer says they are at 0, when they are in fact at more like 100mm. If I manually move them home then switch on the machine they give the correct reading. 

Does it sound like an electrical or computer issue? 

Thank you in advance.

RE: Y axis issues

@thomas-3

every print starts with Home position calibration, otherwise the printer (you can move the bed or the extruder during switch off the printer anywhere) does not really know, where the bed and the extruder is positioned. After hat the bed leveling is executed in order to see how is the surface of your bed perpendicular to Z axis and how flat the surface is.

Those are the minimum requirement prerequisites of the potentially successfull print. 

What you ar saying in the previuos statement it leads me to the idea, your previous home position calibration failed due to the heavy frictions or obstacles on Y axis. Moving the bed manually do you experience any higher resistance at some position? So can you run once again the basic XYZ calibrations and let us know about the result?

Did the printer stay all the time on the same place? Any move can change the postition between axes. Do you have always the same ambient temperature in room where the printer is located?

The last what I have in mind the level of the crash detection, but this would mean there is something wrong with your Firmware. Which version of the Firmware do you have installed recently? Did you upgrade/change the Firmware before your prints started to fail?

As many as possible (even for the first look non relevant) details you provide to us in advance, less potential questions we have to rise and less crystal globe divination from our side will appear.

RE: Y axis issues

Posted by: @thomas-3

So if I move them to half way when the machine is off, when I switch it on, they think they are home, the printer says they are at 0, when they are in fact at more like 100mm. If I manually move them home then switch on the machine they give the correct reading. 

Following up on Zoltan's comments.

The printer has no absolute position encoding.  When the printer powers up, it is essentially lost, and all position info is set to zero, regardless of where the bed, extruder or Z is at.   To determine the positions, the firmware moves the extruder left until it bumps into the support; moves the bed back until it hits the read rod holder, and Z down until the PINDA triggers.  It then adjusts a bit based on cal constants stored when you did the XYZ calibration. Once it has hammered a bit and adjusted, it is now HOME at 0,0,0.

You can force a home operation via the menus, Autohome.

ps: If the printer is on and has been homed, then you move the bed or extruder, it is once again lost.  This is why recovering from a power fail can be problematic. The printer assumes it hasn't been moved - but often users bump something and the recovery fails.

RE: Y axis issues

@zoltan

When I manually moved the Y axis there was friction at about half way, well friction might be the wrong word but it took more force to slide the axis. So I have now greased the bearings and it is much smoother, strange as the printer is only a few weeks old and has a total print time of 2 day and 3 hours, I remember clearly reading in the instruction manual that the bearings DO NOT need grease. I will be swapping these bearing out for the Japanese bearings that seem to be so popular on this forum.

The first axis crash happened prior to updating my software to 3.8.1, and it crashed after the update, so I reset the printer as well and re calibrated all axis.

The printer stays in the same position and the temperature is a constant 22 /23 degrees Celsius  

I am, as I write this waiting on the first print since doing the above. So fingers crossed.

Thank you for taking the time to read and answer my questions, I really appreciate the help.

RE: Y axis issues

@tim-m30

Thanks for explaining that, It makes sense and helps me to understand where the issue is, appreciate it.