Rotary moving different amounts in different directions

Hello all,

I have done my best to search this issue and am coming up empty handed.

I have a HL 1060 100w with Rudia RDC6445G controller. I am using a Mansfield rotary. I have gone through the tutorials on setting up the rotary and have some success with using it. Today I am trying to tune it so it is as accurate as possible. I have reduced the y axis access to 50mm/s and max speed to 65 mm/s. The rotation is smooth and doesn’t appear to be skipping. I set the steps to 3350

My problem:

I have a tumbler on the rotary that measures 237mm. I zero the cup and give a move command in the negative direction and the cup rotates 360 degrees and stops perfectly on my zero mark. I can do this 2 or three times and it stops right on the zero mark. However, when I change directions and move the cup in a positive y direction the same 237mm it comes up about 25mm short of the zero mark. If. I make a new zero mark at this location and then rotate it again in the same direction it stops about 25mm short of that mark and so on. Any help or ideas would be greatly appreciated.

Thank you,

It sounds odd, especially it being off an inch. Can’t believe there is any way for it to have that much ‘slack’ or ‘backlash’ in there.

Don’t know how your stepper needs to be set up, but sounds like that’s not an issue.

The object diameter is of no consequence as far as a ‘wheeled’ rotary is concerned. If the steps/rotation and the gear ratio taken into account it will work. If it’s a layout, you might need to know your limits, but the rotary thinks it’s just a table.

Will it frame properly?

Make sure you’ve saved a copy of your configuration before modifying anything.

My acceleration values for the Y axis are down in the single digits. Excruciatingly slow, but sometimes it pays off. The Y axis max speed is also down in the single digits.

If you are doing this on the console, then it will be using the speed set on the controller. If you are using ‘jog’ in the move menu it will use that ‘speed’ value. Make sure they are low.

Might try lowering them and see if it makes a difference. Make sure you use the controller or Lightburn but please specify as there are many ways to ‘move it’… If it is slipping you probably cannot see it slip.

I have a PiBurn…

Good luck


Well, I don’t want to believe it either, but it was doing it. It may have been something with the specific cup. (which I don’t understand) but I ran a koozie that’s all the same diameter and It was ok. I was running a yeti water bottle, which was 268mm circumference, but the actual neck where the rollers rider was 237mm. So that’s what I used. ( I did try it with both numbers).

I changed the settings to allow for a maximum of 2000.00mm movement for the Y axis and centered it at 1000. So the cup could make several complete turns around without hitting a limit error.

I did write the configuration changes to the controller and also read them several times to make sure that what I wrote actually went over. I am controlling everything at this point via light burn. I did decrease the speeds on the actual controller panel as well though, just to be sure.

I appreciate the insight, hopefully it was just some fluke with the specific cup.

I don’t understand the preoccupation with circumference… With your type of rotary, there is no reason to know the circumference.

Only reason for that is in making the artwork, if you want it to completely go around the cup.

I understand the ‘extension’ of the Y axis, but what use is it?

Do you have art that rotates it multiple times?

Maybe I’m not experienced enough, I can’t think of anything I’ve done that needed the object to do more than one rotation and most of the time, less than one. I did some 3/4" acrylic tubes on the PiBurn…

Good luck


Not stuck on the circumference so to speak, but I need to know the circumference to know how far to tell the cup to travel around 1 turn to verify steps are set correct. Maybe there’s a different way to figure that? Main issue is that of it starts and runs an image and I want or need to run it a second time on the same cup, I can’t because they start points have moved.

The only difference between one direction and the other is the ‘dir’ bit (motor driver direction). Other than that they work the same. I don’t know of any ‘adjustments’ that are there for different directions of the axes.

That’s why I keep going back to it slipping.


I understand what you’re saying. It just seems odd to me that it will make 1 full revolution one way several times, stopping in the exact same spot but won’t make a full revolution in the other direction with the same move command and come up shorter each revolution. I can understand slippage, but I can’t wrap my head around it slipping almost an 1/8 of a revolution. Probably something I’m doing wrong. I guess I’ll have to take slomo video of it and watch

I can’t think of anything that would effect an axis in one direction.

Agreed that it sounds like it’s loosing a lot but I can’t think of any logical explanation for that type of behavior.

Have you ensured that all the set screws are snug on the motor drive?

I’m kind of a loss also…


What do you put them on the burn them?

How many did you have to purchase?


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