Nema17 Motors not turning WITH BELTS attached (all Axis, X, Y, Z)

Machine: DIY Build

Board: C3D LaserBoard

Firmware: “I have a new board and I’m using whatever it came with”

Problem/ Question: Hi Guys, I attached 2 Videos of my Z-Axis (the problem also exists on the Y and X Axis as well). On one Video you can see the Belt is “very” tight around the Nema17 Motor (which is connected to a external driver), but the motor seems that it can not pull the belt in any direction.
On the second video I just removed one belt tightener and you can see the stepper moves just fine, but of course the Z-Axis has no movement, as the belt is not tight enough.

EDIT: just noticed that I can not upload videos here -.-

Is my problem really a hardware problem? Is there a setting on the C3D LaserBoard I have to edit? Can I do something in the LightBurn Software?

I believe, that I have wired every thing properly, but not 100% sure. I added a photo as well.

The external driver connected to my Z-Axis is -->

[TB6600 Single Axis 4A CNC Schrittmotor Treibercontroller 9 ~ 40V Micro Step]

The motor for moving my Y-Axis is -->

[ACT Motor GmbH 1PC Nema17 17HS5425B Schrittmotor Dual Shaft 2.5A 48mm]

The motors for moving my X-Axis & Z-Axis is -->

Tronxy SL42STH34-1504A (NO201809065459)

Is there someone that can give me a good advice?

Thanks and regards,

Just a little update on this:

I played around with the “speed value” in light burn and changed it from 200 to just 10… and now the X and Y-Axis are running much better then before. So it seems, if the motor is turning slowly, the belts are moving pretty smooth… but I believe this is not the solution to my problem, right?

What current setting do you have the external drivers set at? Maybe try setting the current higher. That’s all I can think of to start with.

I need to check this tomorrow.
But what about the stepper ( X and Y Axis) that are directly connected to the LaserBoard?

I’m using all external drivers in my build, but I believe the current level for the built-in drivers are set in the config file. Not sure what they default to but take a look and see if these can be raised at all. Bear in mind that the onboard drivers have a limit of around 1.5A I think.

I would check to make sure all of your belts are tensioned properly. Start with a relative amount of slop and you can tighten from there. Tighter belts cause way more resistance. If you say the motors turn freely without belts, they should turn relatively easy with belts unless your gantry is excessively heavy which I doubt. Leave some play in them to start with. Your comment about the belt being very tight concerns me.

This is the button you use to upload files

But no videos uploads are possible from my computer, right?

And is there a instruction on the file on the SD-Card regarding the values?
If I have to change something there, what do I have to change and what are the effects?

I guess only photos but I have seen other people with videos. May have to post video on YouTube which is easy then you can attach a link.

Did you reset all your belt tensions looser. This can definitely be the root cause of you problem. Have you searched the posts in this forum. There is info here talking about motor current settings


See if there is a sweet spot between having the belt so tight it won’t move and not having a belt attached. Also, without the belt attached, does you carriage move freely? You may have to loosen your roller guides. You should be able to easily slide the carriage back and forth with your pinky finger without the belt attached. I really feel this is a mechanical issue. If this does not solve it, we can look at your motor currents

Alright, i also check the mechanicals and get back to you as soon at had a look at it :smiley:
Edit: but don’t forget - you just saw a video of my Z-Axis Installation. :wink:

With the belt in place on your z axis you should easily be able to turn the motor gear. Another thing to check and make sure on your z axis is that all of the screws are in sync. The table should be level. If one of the screws is leading or lagging the other 3, it will take excessive force to turn them all together

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Sorry for replying so damn late, but busy with quite some other things too.

4 days ago I checked my Z-Axis again after all you suggestions and ideas and there were a view things that helped me, get some smooth movement on slow speeds to the Z-Axis and so “ok” movement on higher speed (loosing some steps):

  • increasing the current limits on the external stepper driver WAS A BIG WIN.
  • more tension on the pulley that is attached to the NEMA17 WAS ALSO IMPORTANT
  • and a lot of mechanical tweaking of the 4 threads WAS ALMOST THE IMPORTANT THING AT ALL

I forgot to make a short video how its running, but I guess then next time I am working on this, I record a little clip.

On my Z-Axis UP and DOWN is switched when I press the buttons in the LightBurn software. I believe I have to change the two DIR wires on the motor OR on the connection to the board?

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To switch the motor’s rotation, take either A+ and A- and swap them or B+ and B- and swap them (not both). It doesn’t matter which one.

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