y axis slipping?

[sthone]

When it's making the "GRGRGRGRGRGT" sound.... does it look/sound like whats seen/heard in this Video?

If so..... for me it turned out just be be a bad or loose wire going to the motor. I made a clamp seen here and haven't had the problem since.

-Steve

[ednisley]

still print like this

As Sherlock put it, "when you have eliminated the impossible, whatever remains, however improbable, must be the truth".

Your description shows the Y axis stepper motor stalls: "then GRGRGRGRGRGT Y motor grinds (like the sound it makes when commanded past limit)". That happens when the motor can't produce enough torque to move the platform, which can have several causes:

• Acceleration too high
• Speed too high
• Mechanical interference
• Motor current too low
• Wiring problem
• Print irregularity snagging the nozzle

The firmware reloads haven't solved the problem. Assuming you haven't modified the acceleration settings in the startup G-Code, then the acceleration is OK. Reduce the acceleration by a factor of four, either in the firmware or startup code, to be sure that's not the cause.

If you're using the same XY speeds as before, the speed should be OK. You can reduce the non-printing ("travel") speed by a factor of four to eliminate that possibility.

The firmware reloads set the motor current to the default value, which should suffice. If the Y axis motor is uncomfortably warm, the current is about right.

It is possible that the cable to the Y axis motor has an intermittent fatigue failure, because it does move vertically during the course of the print. That hasn't happened to anybody else, so I'd say it's unlikely, but you can check for it by bending the cable at the obvious anchor points; if the motor stalls as you flex the cable, you've found the problem.

Verify that the Y axis motor cable is firmly seated into the connector on the motor.

You're printing PETG, so the most likely cause of a motor stall is the nozzle hitting a lump of cooled plastic. That tends to happen on corners, where the nozzle changes direction, transfers a glob of accumulated PETG hairs to the print, and then whacks into the lump on the next layer. Most of the objects you've shown have plenty of corners where that can happen.

Because you're using black PETG, which tends to conceal many sins, you may not notice the globs building up. After you've reduced the acceleration & travel speed, devote an hour to watching while the most troublesome object builds: if the surface of every layer isn't absolutely flat, then I think the problem will be staring you in the face.

PETG is very sensitive to over-extrusion: too much plastic is a Bad Thing, because it causes excessive stringing that accumulates on the nozzle. If you haven't calibrated the extrusion multiplier lately, do that to see if it improves the layer surfaces.

Basically, I think you've eliminated all the hardware & firmware causes, so now you're looking for causes arising in the prints. I'm pretty sure you can print calibration cubes all day long without any problem, which means you must pay critical attention to what's happening during the printing process.

Good hunting!

[dobart]

Hi Steve, that does sound (a bit) like it; I've checked the connections and reseated the cable a few times, everything looks good with a voltmeter.

What gets me is that it ONLY takes place at the first Y motion of a new layer. Not in the middle of anything; it's repeatable almost exactly from print to print as well.

Thank you for the advice!

[dobart]

Hi Ed!

I've been printing successfully with PETG since I got the machine; early prints would curl, and the head would bump into them, but even at that stage there were no stutters, the hot end would smooth over the bump or simply knock the piece off the bed (!). I based my profile on a successful one posted here.

A month or two into it, last september or so, I finally got all my ducks in a row to print PETG dead flat with no warping. THEN, 4 months later, this pops up. I haven't changed anything in my setup, there's no warping; and I'm baffled as to why it's happening with parts I've produced tons of, as well as any new test prints etc. My last round with service involved me sending them my gcode but I haven't heard back. (checked it on a 3rd party gcode viewer and it looks fine).

Machine prints all axes just fine, does a Z step, moves X direction, GRRRRRRT at start of Y move, and then prints entire layer normally (never errors noisily at any other point in the print).
Error may or may not occur on subsequent steps, can be 1mm to half an inch at a time (only in Y direction, mostly away from motor, but has happened in a 'toward the motor' step as well). This happens wether or not the head is extruding anything at all. Tested out the cable, checked board fuses and connections etc; belt, wear, rubbing things... al the usual suspects.

Thanks for the guidelines!

[ednisley]

baffled as to why it's happening with parts I've produced tons of

Because it fails during non-printing moves (which is new news), then it's a motor overload problem. The actual cause is most likely mechanical, but … let's start with the symptom and work backwards.

Reduce the Y axis acceleration (*) by a factor of 100-ish, verify that the problem has Gone Away, then increase the acceleration by factors of 2-ish until it returns, then back off by a factor of 2.

For example, if the acceleration is now 3000, drop it to 30, then go upward: 30, 50, 100, 200, 400, 800…

Printing should be perfect at 30, albeit much slower. If a print fails when you set the acceleration to, say, 800, then set it to 400, whereupon printing should once again work fine.

Report back on what happens…

(*) Directly in firmware or using G-Code, as you prefer.

[dobart]

Running that test now, wondering why the motor would overload only on that single motion and never at any other time in a layer. I assume it's the first or second printing motion of the new layer.

Like so: layer complete, Z step, X motion (printing?) RGRGRGRGRGRGRGT Y motion (printing?) layer offset error.

EDIT TO ADD: watching it fail a test after readjusting the belt tension, it also only fails in layers that have infill, fwiw. It won't fail on the first solid layers.

[dobart]

Slow print errored as well, running one now with a different infill (full honeycomb vs fast honeycomb); the grinding sound is much reduced but still occurs, again only when a layer ands, and the Z step happens and the first subsequent motion is X; then a tiny brrt on the Y motor and the print continues with the first motion in the Y direction.

[zemlin]

Do you have anything for a Layer Change script? Mine has always been blank.

[ednisley]

Slow print errored as well

Have you done the Y axis acceleration test?

Without those numbers, we're not going anywhere.

[dobart]

Hi Zemlin, no nothing in there for a script on my end either