Z-Axis Configuration Issues

I have an interesting Issue. I custom built the Machine, 17.5 x 41.5 cut area. I know it is an odd size, but that is my fault due to miscalculating. The issue I am having is with the Z-Axis, I have it setup near each corner of the bed, and it is connected by the GT2x6MM Belt, 2000mm approx belt length. Before I got the proper controller and got it configured, i had a standard Motor w, Push button up and down functions.

I now have upgraded to use the Z-Axis feature on the controller, but i am running into issues due to belt slippage. I have it as tight as I can get it, but it still slips and misses steps, causing bed tilt, and jammed movement. I am looking at redoing it to use 4 Pancake Stepper motors (1 per corner) with the TR8x8 350MM threaded rod attached to each motor. I need to know if the stepper controller will handle 4 motors attached to it.

Motor type: STEPPERONLINE 17HS08-1004S
Stepper Driver: Cloudray DM 542s
Ruida Controller: RDC6445s(EC)

Any help or suggestions is greatly appreciated.

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This may be due to trying to accelerate or move the Z axis too fast, so that the motors cannot provide enough torque. Before buying more hardware, check the existing configuration to make sure you’re not asking the motors to do more than is possible.

With the power turned off, verify that you can turn the motor shaft with your fingers feeling smooth motion over the entire range of Z axis travel. If it’s hard to move by hand, the motors will have difficulty, too.

Make sure the step/mm calibration is correct. You can get a good approximation by arithmetic:

  • Count the number of teeth around the motor drive pulley
  • Count the number of teeth around the leadscrew pulley
  • Measure the leadscrew thread lead (mm/rev)
  • Read the motor driver step/rev from the DIP switches
step/mm = (leadscrew teeth / motor teeth) * (motor step/rev) / (leadscrew lead)

Set the Z axis speed to 100 mm/min and the acceleration to 1000 mm/s², which should be low enough to avoid problems; you can increase them after everything works.

See if doing that improves the situation …



The tooth count is 20 for both, the rod is 8mm per revolution. And for turning by hamd, it is doable, little tight, but doable.

The stepper driver should be around 5000 step/rev. If so, the 8 mm lead makes it something like 625 step/mm.

At 100 mm/min, the controller is ticking along at 11 k step/s, which is reasonable.

Check the stepper driver, run the numbers, and see what pops out: slower will definitely be better.


Forgive me for being dumb here, so i adjust this on the Stepper driver. That is the part i am trying to figure out. What switches go where. I know part is in LB/CONFIG. But i am not surs about this portion.

The first time you go through this, it’s awful. The second time, not so bad. The third time, you wonder why anybody has any trouble with it at all. :grin:

The front of the driver has All The Numbers:

The 17HS08-1004S motor datasheet says it runs at 1 A. You
look at the Current Table on the driver, wherein the first line says 1.0 A peak corresponds to SW1 SW2 SW3 = ON ON ON. The DIP switches between the green connector block are numbered, so you set 1 2 3 = ON.

To set 5000 step/rev, look at the Pulse/rev Table to find that line: SW5 SW6 SW7 SW8 = OFF OFF ON OFF. Peer at the DIP switches, then set those four switches appropriately.

SW4 controls the current when the motor has been idle for a while. Set it OFF to maintain half the current set by SW1=3 and it’ll probably work fine. You can set it ON to maintain full current to be absolutely sure the Z axis can’t override the motor, but try it the other way first.

Now you must tell the controller what you’ve done. I mistakenly thought you were dealing with a GRBL controller, despite your very clear note it’s a Ruida, so it uses µm/step rather than GRBL’s step/mm.

The leadscrew moves 8 mm/rev = 8000 µm/rev, so:

1.6 µm/step = (8000 µm/rev) / (5000 step/rev)

Fire up LightBurn, go to Edit → Machine Settings → Vendor Settings, agree you won’t break anything, then set the Z axis distance/step to 1.6 µm/step.

While you’re in there, set the Z axis maximum speed to 100 mm/s and the acceleration to 1000 mm/s². You already have homing turned on and, presumably, it’s trying to home toward the switch.

Write the new values to the controller and it should do a home cycle the next time you turn it on.

Report what happens!

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Will apply changes tomorrow and report, however i think i have a bed alignment issue also. That has to be fixed before any of these changes go into play.

I have already gotten the new lead screws and all motors and parts. So they will be installed tomorrow morning.

Small addition:

If in doubt, you can have 4 controllers wired in parallel (control signals), then each driver only handles one stepper and still all of them run simultaneously.

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It appears that the motors i have are the 1amp, so the controller.handles it fine. The issue i am continually having is getting everything lined up proplely.

The concept is to use the motors on the bottom of the bed, with 300mm screw drive connected directly to the motor. The motor will be mounted using the flat motor mounts. The issue i am having with this is either the motors or the rods seem fo have a wobble and keeps jamming the motors. Another issue is fhe bearing blocks i have are to short to keep the alignment.

Any suggestions will be appreciated.

Several problems will prevent this from working as well as you want.

In general, stepper motor bearings are not designed for thrust loading, so you can’t rest the platform on the motors through the leadscrews. The usual practice is a thrust bearing at the bottom of each leadscrew, with a belt drive turning all of them in unison.

However, four leadscrews in rigid bearings make the platform kinematically overconstrained. Unless all the leadscrews are perfectly straight and parallel, the platform will jam as it moves, because the bearings don’t allow any motion in the XY plane.

Unfortunately, cheap leadscrews (of the type we civilians can afford) are never straight and may have sketchy threads, so there’s no practical way to align all of them at once.

The usual practice involves fixing one leadscrew in a rigid mount, with the others in flexible mounts that allow a little XY motion. The follower nuts also require compliant mounts, because an (inevitable) bend in any screw will jam the nuts.

Setting up the mechanical bits is a gnarly problem!

The problem is not the total current, but that the driver cannot control the motor winding currents in more than one motor wired in parallel. It’s done all the time with low-end 3D printers, because it works Well Enough™ at those relatively low speeds and loadings, but you won’t see it in CNC machines.

Ed, you mentioned having flexable bearing mounts, this is what i need, i have gotten the belt setup, and Apparently have. Littld bend…

As far as the 4motor approach, i am testing it, just as a ti.e.experime t.

Something like a silicone or nylon shoulder washer or sleeve bearing would allow a little XY motion, although sorting through the Amazon offerings defeats me at the moment.

The idea is to allow a little controlled motion, without unwanted slop.

I have e perimented with the 4 motor setup. I have straight rods, new motors, good concept. But am lackinv the expertise to make it all work togethef properly. So i am backing down to a w motor setup. Both at front of laser with a belt connecting to the rear. (520mm) maybe this will work better. And maybe it will be better control, and alignment.

Ths big issue is getting everything aligned perfectly. Top to bottom, front and back and so on.

My next option will be to use 2 8x8 sizzor lift tables, attached to the bed and each other, and put a motor on them.

I have a custom laser also. My z belt was slipping teeth. I made a 3d printed bracket to hold an idler pulley. I positioned the idlers so that they increased the wrap angle on the z axis pulleys. This stopped the teeth slipping issue. I have a 2mm pitch 6mm wide belt and 4 lead screws.


Sounds something like i initially had, 4 lead screws, 10mm belt/gears, idler pullys attached directly to the t-slot on 1 end making a wide “v” for tension. Other end had the motor and wide angle with 2 idler pullies 1.5 cm apart with belt wrapped around them going to motor pulley.

When functioning, it went Down fine, and started slipping near the bottom, goi g up, i had to put upward pressure on it to get it to move. I am thinking i had bad lead screws or bad alignment of the screws. Could even be bad method of attaching to the t-slot bed. It did not have any movement/flexability in it.

If you can, send me a the specs of what you made, maybe i can get some ideas…

I had this problem as well. I could with much effort move the belt with my hands but it was too much for the motor. I finally figured out that the lead screw bearings are supposed to be “floating” in the retainers and don’t from the factory. I had to de-install the lead screw and bearing pillow block from the z bed and with the lead screw through the bearing, move the bearing all around until it loosened up. It will the mount on the Z bed without binding and the motor should move the table now no problem. Here is the link to my “bearing retainer” that Aliexpress calls a Bore Ball Bearing Pillow Block Mounted Support. If you use something like this what I described might be causing your problem as well…


Below is a youtube on the process:

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