Z motor skipping issues

Having a issue with my Z steppers / Lead Screw. When going up I can lose steps. I have checked all connections and they look good. If I let the lead screw fall through the XZ Plate it aligns with the coupler. If I use WD40 Dry Lube with PTFE it will improve for like 5 minutes. I think my issue is the drivers. I sourced my own parts but I did not tune the steppers. How do I check if this is my issue?

you can see some of the issue that came up in my recent make

I should also note that I can easily stop the machine with my hand. I have also had a zip tie stop it too (I know I’m sorry Ryan, I hadn’t cut them all by that point)

Wops this is what I get for posting late with a headache… forgot my machine details

Skr Pro 1.2
TMC2209 Drivers
Nema 17 (84 oz in)
12v 5A Power
T8 8mm Lead Screws (300mm because it was what was available at the time, maybe make a bigger plate in the future for foam cutting? I don’t think the extra size is causing the issue, right?)

I’m going to try and tune them here at lunch if I can get away. Will update as I go. Any help appreciated

Okay. Got 10 minutes of shop time before something called me out. I adjusted the driver by a 1/4 turn which is another 1/4 from full (ambitious I know). How to I properly test the temp. I have a laser temperature thingy I use for work. But do I just engage the steppers and wait around. Is it better to initiate a long move? How long is good enough for the test?

Once tuned I did move it around 15 times or so and the stepper still felt cold (thought initially I would know if I did something super wrong just by feel)

Ryan and I demonstrated pretty well that the steppers do have enough power to easily lift another 7-20kg without giving in, but in general there are two possibilities of losing steps: one is that you are losing a lot of steps suddenly, then it is either binding, too fast or too weak, or you are, as it was the case with me, gradually losing steps. I had to change something in my firmware so the driver waits for a pulse for the next command, I know that the Jackpot has got the same setting, don’t know about the SKR though.

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It is a rapid loss of steps, like it’s missing torque to move the lead screw. It is more commonly when the core is closer to the spoilboard vs higher up but does happen higher up as well just not as often. After turning up the steppers I couldn’t cause the issue, but as stated I didn’t have a lot of testing time.

It also happens more with slow feed rates

The skr pro tells the tmc 2209 drivers what to set the current. You can see what they are set to by sending M122 from a computer. You can change the values with M906. The value you change in M906 should take effect immediately and reset when you cycle power. If you want to keep the new setting, you have to save to eeprom with M500. A change of 50mA can be enough to change it. The TMC drivers can also reduce the max current if they get too hot. The actual max is in M122. If you see that dropping, then you need to cool your drivers.

The set current is going through the motor all the time. I haven’t ever tested it, but I believe it will be just as hot when moving as stationary. Philipp put a temperature strip from a fish tank as a great visual indicator of temperature. At least I think it was him. Otherwise, put on some masking tape and hit it with a touchless thermometer. You don’t need terribly accurate readings. Under 59C is a rule of thumb.

The default settings shouldn’t be skipping though. Is your gantry enormous or do you have a lot bolted on, or a full sized router?

Friction can really add a lot to the leadscrew. If it isn’t aligned perfectly, it will bind. I always use grease from a tube of white lithium that I bought 10 years ago. Same stuff I use on my 3D printer.

You don’t want to hear this, but an intermittent wiring issue can also cause skipped steps only when raising the gantry. If one coil is broken, the motor can wind down by jumping from one spot on the coil to the next, but it can’t jump up. I hope it isn’t this, because it can be a real pain. The TMC drivers can sometimes detect an open loop and report that in the response from M122. There are columns for ola and olb. Those are open loop warnings from coil a and b. If you ever see those flags true while the motors are engaged, check your wiring. S2g is short to ground, and not as common IMO.

Kobalt router, 55” rails, there is a metal outlet mounted onto the Xmax side, the issue has proximately been on Xmin side during slower operations (5mm/sec or less). If it has momentum I can’t get it to happen. I haven’t had a chance to test it again after adjusting the potentiometer but if it’s software controlled I didn’t do anything but open the gateway.

Edit: I also feel like if it was a broke stepper coil the issue would be more common and not resolve with lubricants. Or are you referring to something wrong with the board itself like a partially blown moffset/etc?

The intermittent wiring issue is not broken all the time. It is sort of a catch all diagnosis. I’ve had it where one ons the crimps was bad. It would work fine, but the connector would change due to heat or something would give a small tug on a cable and it would skip. I agree that a completely broke cable would not show like this.

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After initiating m122 I get

M906 x900 y900 z900
Connection to all steppers was reported as ok
Rms current is 887 (I’m assuming this is related)
Max current is 1251

This is really odd. I cannot get the issue to replicate after adjusting the screw on the drivers. I just spent the last 20 or so minutes running it at different speeds up and down, and at different heights, without issue. Could those Potentiometer screws limit the flow as well as the software? It seems really odd to me I can’t replicate the issue after that. I have a cut planned for today so we’ll have to see if it changes while cutting.

How many starts on the 300mm lead screw? This affects torque needed to lift the gantry.

I’m not sure what you mean by starts but this is the one I bought

Lead Screw Length: 350mm
Lead of thread: 8mm
Lead Screw diameter: 8mm
Lead Screw spacing: 2mm

Edit 1: Oh just read on what starts is, I don’t think its listed on amazon. I will go look when I get back in there
Edit 2: Looks like 2 starts

Isn’t the default driver current 800 in the firmware? I think that is the sweet spot for speed and torque.

I take it back. It’s a 4 start got physical in there vs the photos.

Also interesting development. I did not lose any steps during the carve but I did when Estlcam issued g28 Z on tool changes. Only on tool changes, but not on all of them. Coincidence?

I haven’t changed anything firmware yet, and my understanding is more is more, allows for more speed and more torque at lower speeds when you increase. The issue is getting it to the max without overheating the stepper. Ryan sets it to a comfortable but conservative level (at least that’s what I remember reading)

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I think you’re right. Although, I did have to tune mine down to 700 at one point to keep the temps where I wanted them during the summer. I must be thinking of higher speeds where you lose torque the faster you’re moving.

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Interesting development. I increased the current slowly from 800-1200 as I increase the current my max increases as well. Set at 1200 my max is now 1636

Is this expected that the max is always 400 more than current?

Also what is the amount of time I should test for with steppers engaged? I’m going 30 minutes right now and they are still cool (not cold so I know something is happening)


What are your Z axis rapid speeds, and what is your plunge speed?

Can you very easily move both Z axis screws all the way up with your fingers when the board is not plugged in? If it binds at all or it is hard by hand your steppers don’t stand a chance. This could be a missalignment issue. Dry lube is not always the best use something greasy.

I stopped at 1200 so I am not sure if I should increase until the max current stops increasing, or if anyone has any ideas why I’m experiencing this/what I should do next on that front

480 in Estlcam (8mm/sec?…brain math)
Plunge I have at 3mm/sec

No binding, I will say though that the side that fails most often is a little harder to turn, not by much but noticeable

At the top and the bottom?

Normally this is high enough to start melting things or thermal throttling so I assume something else is wrong. Best to post pictures so we can see your wiring and jumpers. What firmware did you flash?

What does M119 say?

If this is the case you have firmware or binding issues for sure.

The release was in march I think? I downloaded it in September.

Here is what I got

x_min: open
y_min: open
y2_min: open
z_max: open
z2_max: open
z_probe: open

I changed the current back to 800 but here’s m122 before I did (at least with what I believe are the relevant parts)

x y y2 z z2
set current 1200 1200 1200 1200 1200
RMS current 1160 1160 1160 1160 1160
Max current 1636 1636 1636 1636 1636
Run current 20/31 20/31 20/31 20/31 20/31
Hold current 16/31 16/31 16/31 16/31 16/31

All connections tested ok

missed this. its just in general. I did notice if I bottom out the travel that it binds but I don’t think that’s alignment right?