RE:
I don't know exactly why, but after i build my kit, i never had the problem of the calibration failed. Even a the first start, with gap at the right and without tuning the belt with the app, just screw the tensioner by eyes to be roughly identical.
After the first start, i use a belt tensioner (see photo) to ensure that both side are at the same tension (2.3 (my Bambulab P1S is at 2.4 so i use aproximatly the same)
I use one time the Prusa web Hz to set both at 85hz, but when i control with my tensioner, the belt have not the same setting.
Maybe the position of the belt inside the closed area, with one pulley higher than the other, who is closer to the frame, make the "sound" différent, and when both are at the same Hz on the app, the tension is différent and that's why calibration failed.
It just a supposition to help people to try something différent.
RE: Failed Y-calibration of a new CoreOne
I don't know exactly why, but after i build my kit, i never had the problem of the calibration failed. Even a the first start, with gap at the right and without tuning the belt with the app, just screw the tensioner by eyes to be roughly identical.
After the first start, i use a belt tensioner (see photo) to ensure that both side are at the same tension (2.3 (my Bambulab P1S is at 2.4 so i use aproximatly the same)
I use one time the Prusa web Hz to set both at 85hz, but when i control with my tensioner, the belt have not the same setting.
Maybe the position of the belt inside the closed area, with one pulley higher than the other, who is closer to the frame, make the "sound" différent, and when both are at the same Hz on the app, the tension is différent and that's why calibration failed.
It just a supposition to help people to try something différent.
It's that your design? Can it be downloaded somewhere?
RE: Failed Y-calibration of a new CoreOne
Not my design, i found it on Voron forum, and you can download all needed here :
https://github.com/Diyshift/3D-Printer/tree/main/GT2%20Belt%20Tension%20Meter
RE: Failed Y-calibration of a new CoreOne
Scratch last post, not working. It started all good, but like something changed and it started to mess printing, so I stopped it. Tried to re-print and it didn't pass calibration again.
You might have seen it in the other threads -- two potential influences have been mentioned recently, by two different users:
(a) Placing the printer on a wobbly base may contribute to calibration failures.
(b) Calibration was found to work after a cold start, but then failed in subsequent prints once the printer was warmed up.
You could try to eliminate (a) by placing the printer on the floor for testing. There's not much you can do about (b), but it may help to keep an eye on this and check whether the behavior is really correlated with temperature.
Ultimately I think Prusa needs to provide a firmware fix which makes this calibration more robust. I am not quite sure why they need a super-exact XY position reference anyway -- resuming after power failure is the only scenario I can think of -- so they could make this "precise homing" optional. And I don't see why it should be impossible to obtain sufficiently accurate Stallguard readings in a more robust way.
RE: Failed Y-calibration of a new CoreOne
My final post. I had really disturbing chat and I will name guy here Daniel or Daniele, he was not professional for sure. Repeating things and blaming me for going in circles. He actually said, if I did what support told me and didn't solve my issue, it is logical to assume it is my fault. Telling me that it is not known issue and no reports.
MY SOLUTION ON THE END:
After we both lost patience, he transferred me to other support. He said, only repair is to bend X axis or to return it so they do it, that it will need some force. I asked what would happen if I break it or bend it too much, he said I can return it. So I did it. It took some force, not too much, as my right side was 3-4mm off, I pressed left side inside and right side towards me, slowly but with more and more force, as soon as I felt that I bent it a bit, I stopped, checked and repeated it few times until it was around 1 mm gap.
That gap vanished once I tunned belt to 85 / 85, that is it. Not sure will X axis stay like this, but I'm done, if this will not be long term solution I will return it.
RE: Failed Y-calibration of a new CoreOne
Sorry, but it’s just not good enough. I refuse to pay a premium price, then still have to resort to hit or miss bending or shimming of parts to rectify what seems to be emerging as a pretty common issue.
After some more to-ing and fro-ing with support, they have now finally agreed that they will send me out the appropriate box and packaging to return my built kit, so at least that’s something.
RE: Failed Y-calibration of a new CoreOne
After a 3h Session with support, I also decided to not spend more time in looking for "potential" fixes. We agreed that I send back the printer (how will hopefully soon communicated) and they repair it and send it back. Let´s see if this works out without any issues.
RE: Failed Y-calibration of a new CoreOne
When I first assembled my kit there was about a 1mm gap on one side, but I have to say, without ever having read this thread beforehand, that it seemed rather intuitive that this could be fixed with a little judiciously applied brute force. I suspect that Jürgen's posts had planted the idea in my head, but it absolutely felt like the correct thing to do. Perhaps that's because building the kit gives you a good idea what the gantry squareness depends on. I have no reason to believe that this should be considered a temporary or unacceptable fix.
RE: Failed Y-calibration of a new CoreOne
Everyone has their own perspective on this.
Prusa could have made it easy for itself and simply increased the tolerance for a successful check.
Probably nobody would have noticed.
When assembling the kit, you notice that the parts are designed to be easily bent.
With a CoreXY, it's simply that the belt tension is essential.
Whether this is better solved by the competition or just increases the tolerance range, who knows.
For me, it's a simple but effective design.
RE: Failed Y-calibration of a new CoreOne
I actually agree with you. But hassle to return ut. Wait for new printer is pain in the ...
If it works I hope it will pay itself in some time.
RE: Failed Y-calibration of a new CoreOne
With a CoreXY, it's simply that the belt tension is essential.
Whether this is better solved by the competition or just increases the tolerance range, who knows.
For me, it's a simple but effective design.
The competition can check belt tension in real time, because they did not skimp on a built-in accelerometer. The competition also has pretty clever spring-loaded belt tensioners which make the tensioning process semi-automatic; no tuning app or other measurement gimmicks required.
And finally, while I would expect that the competition's printers have slightly skewed gantries too -- that does not stop them from finding their XY home positions, without going into a death spiral like some Core Ones.
RE: Failed Y-calibration of a new CoreOne
Here, too, everyone has their own opinion.
When I look at the semi-automatic tensioners used by the competition, I'm not sure if it's that clever.
At least not when I look at what some people have to do to tighten the belts equally or not too tightly.
Or the fully automatic system from Creality that doesn't work reliably at all.
As far as I know, monitoring via the accelerator is only a function that warns of loose belts.
And only if it is measured before each print. Which is not the best thing for the hardware.
Yes, Prusa could have installed the sensor anyway. Or at least the option of installing it permanently.
The MK3 had a function for adjusting the tension. I think it worked via the steppers.
Personally, I much prefer the variant where I have full control.
It's a job of minutes to set the tension or check it during maintenance.
I don't have any problems with the MK4S either.
And if others have slightly skewed portals but simply pass the tests anyway, is that better now?
RE: Failed Y-calibration of a new CoreOne
And if others have slightly skewed portals but simply pass the tests anyway, is that better now?
The XY "calibration" is not meant to be a test for a skewed gantry, it's simply meant to define the homing positions for X and Y. I really think Prusa needs to fix their firmware and make this Stallguard detection work more robustly.
If you are worried about hardware strain caused by the belt resonance measurement in a Bambu printer, what are your thoughts about those Core Ones which keep banging away like a mating rabbit for minutes on end? 😛
RE: Failed Y-calibration of a new CoreOne
My Core One rarely does this, but it is certainly not beneficial.
But doing a resonance test before every print is not only not clever in terms of time.
The Klipper documentation also advises against it because of the stress.
And it doesn't change all the time either.
Unless you want to convey technical superiority to the customer.
That's exactly how I see it with the Lidar scanner.
In practice, a P1s works no worse than an X1c.
Prusa will probably improve the values in future versions.
Unfortunately, it has to be said that Prusa's firmware is anything but optimal at the beginning.
But for a long time more and more improvements are made and new functions are added.
If you look at a current product from the Chinese competition, not everything is going according to plan.
In every forum, regardless of the brand, there are problems or things that could have been solved differently.
Expecting perfection can only lead to disappointment.
RE:
The competition can check belt tension in real time, because they did not skimp on a built-in accelerometer. The competition also has pretty clever spring-loaded belt tensioners which make the tensioning process semi-automatic; no tuning app or other measurement gimmicks required.
I've been working on a few printable modifications to the CoreXY parts, including a semi-automatic belt tensioner.
Part of the reason is that my pre-assembled unit was not assembled well, and I've found three screws (so far) holding the pulleys to have stripped threads. Not sure if they overtightened them and ripped the threads right out at the factory, or if they undertightened them and the screws wallered out their holes during use. Also, the XY motor mounts on my unit do not have the hexagonal window to view and adjust the stepper pulleys, which sucks because I can't verify that everything is properly aligned and secure in there.
I was going to post a PSA thread, but I've been redesigning the parts instead. I've got two versions, one using heat set inserts and one using helicoils. Plan is to temporarily secure the loose screws by heat-staking the thread bore, print and install the new parts, verify they work well, and stick them on printables. Hopefully they'll save someone the trouble I've been through.
RE: Failed Y-calibration of a new CoreOne
I've been working on a few printable modifications to the CoreXY parts, including a semi-automatic belt tensioner.
That would be a nice upgrade! Where do you find room for the tensioners? My understanding is that one wants springs which are long compared to the required travel range of the tensioner, to ensure that the force remains essentially constant over the full adjustment range. I believe Bambu has oriented the springs parallel to the back wall?
Part of the reason is that my pre-assembled unit was not assembled well, and I've found three screws (so far) holding the pulleys to have stripped threads. Not sure if they overtightened them and ripped the threads right out at the factory, or if they undertightened them and the screws wallered out their holes during use.
I was going to post a PSA thread, but I've been redesigning the parts instead. I've got two versions, one using heat set inserts and one using helicoils. Plan is to temporarily secure the loose screws by heat-staking the thread bore, print and install the new parts, verify they work well, and stick them on printables. Hopefully they'll save someone the trouble I've been through.
Maybe (hopefully, with a view to future Prusa production!) it would be good enough to just use correctly sized holes for the self-tapping screws. In my kit build, the screws which form the idler axles in both motor mounts went in much too easily, since the holes in the PCCF parts were oversized. In the meantime, many more users have confirmed the same observation in the build instruction comments (step 5.18).
RE: Failed Y-calibration of a new CoreOne
I always like it when someone improves something or integrates new features. But I wouldn't retrofit these semi-automatic tensioners. I prefer a fine adjustment that I can control myself.
When putting it together, I also noticed that you can't apply too much force to the screws.The thread is quickly overtightened.Unfortunately, PCCF does not behave as smoothly as PTEG.
I also checked straight away to see if the screws had come loose on my printer. But everything is as it should be.But thanks for the tip, I'll have a look more often.
If there is enough space, I would even prefer these slide-in nuts. They are easy for anyone to fit.
RE: Failed Y-calibration of a new CoreOne
I’ve been experiencing bad homing with my printer, and managed to get it working reasonably by slightly over tightening the belts to remove some ‘play’ at the front left.
BUT when I moved the printer to a stronger surface, I realised that the frame of the printer is warped/distorted. The bottom left corner of the unit is slightly upturned and doesn’t sit completely flat.
I’ve started the possible returns process for this but it would be interesting for others maybe - if you’re having homing issues that can’t be resolved with normal belt tensions etc, have you looked at how flat/flush the bottom of the unit sits. As there may be a larger distortion of the entire unit than just the rails etc.
Mine was quite obvious but I wonder if subtle distortions can go unnoticed unless measured etc
RE: Failed Y-calibration of a new CoreOne
That would be a nice upgrade! Where do you find room for the tensioners? My understanding is that one wants springs which are long compared to the required travel range of the tensioner, to ensure that the force remains essentially constant over the full adjustment range. I believe Bambu has oriented the springs parallel to the back wall?
There's actually a ton of room around the existing tensioners. I’m experimenting with a bunch of different constant force mechanisms, as well as different locking mechanisms. It's sort of a design constraint free-for-all, though of course KISS is a major one.
Maybe (hopefully, with a view to future Prusa production!) it would be good enough to just use correctly sized holes for the self-tapping screws. In my kit build, the screws which form the idler axles in both motor mounts went in much too easily, since the holes in the PCCF parts were oversized. In the meantime, many more users have confirmed the same observation in the build instruction comments (step 5.18).
That’s really good to know. The main problem as I see it is that the receiving hole depth is only 3.7mm. It's odd, because these are not through-hole, whereas they could have gone up to 15.9mm on one and 4.9mm on the others. You can see what I'm talking about here:
Mechanically, a better design would have been to ditch the plastic threads (at least for the shallow ones) and simply use a longer screw to thread into the CoreXY steel plate. I don't think it would have complicated assembly much (those idler axis screws would be loose while fitting the mounts to the CoreXY plate). Otherwise, 4mm long heat set inserts or helicoils would have been much better.
RE: Failed Y-calibration of a new CoreOne
For what it's worth, here is what I've done so far:
Reached out to customer support, considering how long it took for them to get back to me (and the fact that live chat is inactive) I'm going to go out on a limb and say they are very busy. Here is our conversation:
Me: "After CoreOne assembly, y/x-axis fail calibration. X gantry is perfectly square and touches both stops at the same time. Belts are both tensioned to 85hz according to the app. I have pictures of the gantry touching the stops, as well as a 4 minute video of the calibration."
Prusa Support: "Thank you for letting us know. Please feel free to send us all your findings that will help us to understand your issue. In addition, i would try to increase the tension on the 90 Hz, in order to see if the selftest are passing on this new configuration.
Please don’t hesitate to contact us to communicate any other issues."
Me: "I’ll catch you up on what steps I have taken to troubleshoot (performing hard resets occasionally):
Belt tension: I’ve attempted calibration from 60-110hz at 5-10hz increments verifying square gantry each time to the front and back.
Pulley’s on motors are centered.
Measured x-axis linear rail, square left, center, and right.
Attempts to auto home fail.
Loosened the y-axis rods at the rear while gantry was at the front, pushed the gantry to the rear, retightened the rods.
Attempted calibration on a concrete floor.
I currently have the enclosure off the printer for easy access to everything so please let me know if I need to disassemble further."
I am waiting for their response.
Wanting to eliminate firmware from the equation, I installed all previous versions and reran calibration with no change.
Manually set the position of all three axis to "0" after electronically moving them to their maximum stops to give the printer a headstart also with no change.
Lastly, I visually inspected the wiring order of the x and y stepper motors and compared them with a picture in the assembly manual, they are correct.
One question I have for the group here, do you have a lot of grease buildup at the ends of your Y-axis rods? For me, it seems that a lot has escaped the bearings.