Stepper motor stalls / vibrates upon direction change

Hi,

I am lifting a 6,2 kg bed on my CoreXY printer with a NEMA 23 stepper 20/40 reduction with belt pulleys and 2 mm pitch rods. It all runs very smoothly and I can trim the motor down to 0.5A and still it works nicely. But when changing direction it either makes a vibrating noise but continues, or it stalls completely and keeps vibrating untill I cut the power. During this stall, I can turn the pulleys by hand easily. It is as if something is out of phase. When I change direction "manually", jogging down and then up, it works fine. But now that I run (smoothieware) the M32 autolevel command, it the bed goes up to the sensor nicely, goes down, but when it wants to go up again the problem occours.

I hope someone can help me out, it's really annoying now the whole printer is done and only this keeps me from printing...

Cheers,

Hugo

Edited 2 time(s). Last edit at 12/16/2017 04:59PM by HugoW.

Just changed X and Y acceleration from 3000 m/s2 to 1000, and Z acceleration from 300 down to 50. The problem is smaller, now, not gone. Strange thing is, this printer has worked in this config before without problems. I only changed from microswitch Z-probe to induction probe.

[EDIT] A clip, of course the problem was minimal when the camera was on...

Clip on youtube, don't know how to embed

[/EDIT]

Hugo

Edited 2 time(s). Last edit at 12/16/2017 05:13PM by HugoW.

Are you trying to drive it too fast?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I just noticed when watching the clip again, the problem seems to occour when the Z-movement stops. Check 0:18, 0:22 and 0:26 of the clip.

I'll check the speeds, they are the standard in the 3-point probe cycle in Smoothieware. [CHECKED] 4 mm/s quick homing, 2 mm/s slow. [/CHECKED]

[EDIT] I've changed the acceleration of X and Y back up, those don't matter. I changed Z acceleration down to 10. Now all movements go well, except for the last stop of the G32 cycle. There it just stops 0.8 mm short of where it should and vibrates. BTW, this very slow acceleration does make for smoooooooth movements, it looks nice. I will next try to up the motor current. I go from 1.0 to 1.5A, big step, just to try.[/EDIT]

Cheers,

Hugo

Edited 2 time(s). Last edit at 12/17/2017 02:05AM by HugoW.

It seems you have some backlash issues when the bed moves smoothly at 0.5A, but at the turning point you get some binding.
I'd check the mechanic parts before upping the current. ( that would only make the bed "jump" )

I was soooooooo hoping you were right... The two spindles run very light, I can spin them with my fingers and it's all smooth. I switched the Z motor to the second extruder port (both in the smoothieware and by changing the socket on the board), it might be in the driver, but the problem persists. I then changed that back, problem (off course) persists. Next I changed out the motor. I had a spare laying around. Problem still persists.

I tried jogging from the TFT screen, pushing +10 and -10 a couple of times fast. The bed, of course moving slower than I push the buttons, moves up and down perfectly, not stalling or humming or anything. And this happens at a higher speed than when homing. I also tried G32 homing at a different height, lowering the sensor 20 mm. Maybe something was binding ast precisely the Z homing height. Problem persists.

So I think it is;
Not in the motor
Not in the mechanical drive
Not in the driver board
Not in the smoothie-config

But where else to look?

Cheers,

Hugo

Euraka! Looking back at the list I typed above, all I could think of was firmware. So I checked and lo and behold, I found something. Last week, while trying to get the TFT to work, I upgraded the firmware of the TFT. While at Github, I saw they had an upgrade of the board's firmware as well and I guess I installed that while attempting to get the TFT going. Fortunately I keep a folder on my PC with previous versions of firmwares and configs, so I could put the previous one back and it works fine. I guess there is an issue with the G32 in the current version, but my version runs, now. Happy...

Cheers,

Hugo