X Axis lost torque

Having issues with my LR2. My X Axis has lost alot of torque. My usual settings are 2.6mm per pass at 15mm/s. 3.18mm endmill. Just profile cutting.

I have even reduced my setting down to 50% speed and 2mm per pass cut and it still skips steps.

I can’t find any issues. Using TMC2208 drivers and all set to 1V VREF. Increasing voltage won’t make any difference.

18V power supply running MKS GEN L.

Any ideas?

Edit: What I have tried so far.
Swapped out the TMC2208 driver for another one, same results.
Swapped out the TMC2208 driver with an A4988, same results.
Checked wiring, all is good
Sprayed and cleaned all bearings, and adjusted bolts holding the bearings on the X axis
Disconnected power to board and manually move X axis across the whole length several times, and it rolls smooth, not catching on anything.
Have just removed the X stepper and from router mount, to see if I can find anything that might not seem right, but nothing unusual there either.

I have hit a brick wall with this. To the point where I’m thinking of ordering a bigger nema17 (if there is one), and trying to find a driver that can produce a higher torque.

Any ideas are much appreciated. I really need to get this machine going this weekend.

Cheers John

Have you checked the power supply with a multimeter to see if the 18v is still 18v? You could also check the total current draw from the power supply to extrapolate roughly how much current each stepper motor is taking.
It has to be either increased friction or loss of torque and if you have checked for friction that leaves the power supply, the stepper driver or the stepper motor - one of which you have substituted…time for the other two?

Thanks Mike. I can temporarily hookup a bench power supply instead of the 18V brick. If the results are the same, it pretty much just leaves the stepper.
Can the stepper lose torque over a period of time?

Not as far as I know, providing they spin free when not powered…There is not much in them to go wrong, if a coil fails then it wont turn at all…anyway…you need the biggest, most powerful stepper motor for the X axis anyway and China needs to get its economy going again! :slight_smile:

Too right they do! lol I’ll hookup the bench supply on it tomorrow morning and see what happens. I’ll post back either way.
Thanks for your help

This may be the cause, check that the two screws are properly tightened.

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I was going to suggest pulley grub screws, or an intermittent wiring issue. I’m guessing the tmc2208 isn’t connected via uart? It can tell marlin if it detects some siring issues with TMC_DEBUG.

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Also, Hello again John! Long time no see.

Hey Jeffeb3, yeah long time. It’s unfortunate that troubles brought me here rather than just to hang out here abit, but at the moment I’m trying to find a way to get more than 24 hours in a day lol.

Grub screws are tight, no slip at all. I have pulled the stepper off the assembly and it’s definitely tight.
Nuh I’ve just got the 2208’s just plugged in, no UART. Actually I just ordered the 2209’s. They have a higher continuous curent than the 2208’s do.
I’m gonna pump the voltage up to 24V through my bench supply and give it test.
As for the wiring, I will double check it again today BUT, I can jog the X from one side to the other without jittering or stalling, it runs smooth. The problem is when it has a little force, that’s when it loses steps. Could the wiring make the stepper lose torque? Either way I will double check that again.

Yeah Roger, they’re tight mate, thank you

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I believe so. I had an issue with the Z torque on my LR, and it was only one motor. It energizes one coil, then the other, then the original, in the other direction. If you had one coil completely disconnected, I can imagine it still making the jump over the broken coil. But I don’t know how it would get started, or how much speed would be needed to jump the gap. It makes more sense in Z, because there is a constant tension towards the ground.

Your X is wired in series, right?

Are you thinking MPCNC again? lol. X is only one motor plugged straight in the usual way

Oh. Not on mine. I guess I have X and Y flipped from you.

Ahhh, that makes sense. Sorry, never thought of that. Yeah my Y is 2500mm long (the wheels side) and my X is 1300mm

So X for me is what moves the router left to right

Just wondering, based on my feeds and speeds posted in my original post, is there any way that I/we/someone can calculate the amount of force or torque needed to successfully cut at those settings? I don’t need exact figueres, but what I would like to do is do a simulation without the router on, but I’d like to put some weight on the router (if this isn’t a stupid idea) to simulate the extra load? OK the fact is, right now I can’t run the router because my wife will probably kill me or divorce me, or both, as she just got home from night shift work so she’s just gone to bed. I don’t want to waste half day waiting, so I thought if there was a way to somehow convert the torque to weight, or kg. If this is stupid, you’re allowed to laugh

So just to update, yesterday, after I re-assembled the X motor on the mount, tightened the belt, it’s back to normal. I got my torque back, WTH? The only thing I can think of that might’ve changed, is the belt got tightened maybe 1 tooth more. Could that really have been the issue here? Or do I have gremlins in my shed? lol


I have to confess. I sent the gremlins to get you back on the forums. I’ll tell them to stand down.