For those of you who were involved with my last issue, First Layer Issues, you will be happy to know that I have fixed that.
But now I all of a sudden have another issue and I can’t quite pinpoint why. I am getting layer shifts all over the place. But its not always a sudden layer shift, but more like gradual shifting over time to where the whole part is pretty much tilted.
These two parts are the same exact part. The first one on the left you can see is tilting to the right. So my immediate reaction was to check the XY belts and I tightened them up a bit. Printed the same part again and now its tilted to the left.
So then I changed the filament and printed a test cube.
The test cube you can see is pretty wavy. The layers are shifting all over. What could be causing this I wonder? I can’t visibly or audibly notice anything weird going on, it just prints weird. I did notice one thing, the stepper motor on the right is much hotter than the one on the left. Not sure why or if that would mean anything, but it is a fact that I now know.
Well, I gave it the ol’ turn it off and turn it back on trick. I came back into work this morning, turned it on, printed that same part like the white ones in the pictures above and it printed perfectly straight layers. Didn’t change anything.
It’s back. I had some pretty bad layer shifts on my most recent print.
I have checked the grub screws and checked that the machine moves around freely by hand moving the print head around. Nothing seems to be catching or grabbing anywhere. What other factors may be contributing that I should troubleshoot?
Going back to the stepper temps, is it odd that the right one is much hotter than the left? Do I have some current issues all of a sudden?
Problems that go away by themselves come back by themselves, too.
Layer shifts in CoreXY machines do tend to happen at 45° angles, since that’s what happens when one motor skips steps. that didn’t look like the issue you were having so kind of weird.
I had my Repeat move the magnetic sheet on the bed once, which produced some pretty funky results.
The motor temp differential is also kind of weird. If they’re both set to the same current, the temperatures should be similar.
Best would be if you can catch it when it happens, to see if you can hear anything.
Are your belts too tight? That can cause shifting on a CoreXY. Is there a target belt frequency for this printer? If not you could get a reading and compare it to someone else’s to see if you’re in the ballpark.
Just printed this. You can see that it did actually shift along both axes (45deg shift). You can see it through the letter X and also along the closest side to the camera.
So now that we have confirmed that, what assumptions can we make? One of the steppers skipping?
It’s possible they are bit too tight, I can try loosening slightly and printing again. I am not sure how to test the tension in the belt, I just go by what it feels like to me.
You can identify the motor that is skipping (Or the pulley that is slipping) while it’s doing the rectilinear infill, you’ll see that when it moves at 45° one motor/belt is moving and the other only ticks when it goes tot he next line. Observing that will tell you which belt is having trouble. (My instinct tells me that it will be the one with the hotter motor, which is working harder somehow.)
You said that it’s the right hand side? I know with mine, the belt pulleys at the back for the right hand side motor had a little binding in them in the back corners. I had to file down the back corner parts in order to allow them to spin freely. I think Ryan has made adjustments to those parts, as the pulleys have seemed to increase a little in size of the flange piece. The pulleys dragging would explain a bit.
Another possible cause of drag is having the M5 scews/nuts too tight either in the back corner pieces, or in the slider pieces for the Y rails. one motor or the other, will be determined by the upper or lower pulleys. I found that it was pretty easy to overtighten the lower pulleys on the slide pieces.
This would all make sense if this was happening right out the gate. But I have 40+ print hours on the machine already and it has developed this sickness.
It may seem like overkill, but I am considering rebuilding the entire machine. I want to redo the bed support and I want to use the new printed parts Ryan has released. I think a full reset couldn’t hurt, just a lot of work. If I then still have issues, then I would be confused.
You should go by the sound of the belt, not the feel.
You measure the tension with an app like Gates Carbon Drive w/ the Motorcyle setting or a guitar tuner that displays Hz. Position the print carriage in the center of the machine (this might not be necessary but it is what I do.) Find the area of the machine where the individual lengths of belt are equal (looks like the back on the MP3DP maybe?) and pluck one of the belts. You should get a frequency reading in Hz. Pluck the other belt and it should be very close to the same as the other belt. If not, adjust, home the machine (important) and test again. Try to get as close as you can within a few Hz.
As far as target Hz for this printer I don’t know. Maybe someone has tested this on their machine and could give you an idea of where they sit. I think 110Hz might be a good starting point.
