When i calibrate the X or Y axis it goes right to the desired distance. When I return the axis it comes back but is 5mm short
eg:send the X axis right 200mm it goes 200mm When I send the X axis left it travels 195mm
The Y axis does the same thing and it is consistent.
If anyone has had this problem I’d like to hear from you. I am using a grbl bob and nema 17 stepper motors
Sounds like you have a 5mm backlash. Check if the screws and rods are fixed. The motors might do half a turn until the belt starts moving..
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Good to hear from you. As I have been running tests this problem is in one direction. It’s compounded with the length
100mm I loose 1mm
200mm I loose 4mm
500mm I loose 10mm
this is the X axis
In the Y axis
100mm it stays 100mm
200mm I loose 2mm
500mm I loose 5mm
I have ordered lead screws I’m getting a feeling it could be a slipping problem with the belt drive system I’m using
Have you tried messing with the traveling nut on the screws first? You might also have a loose set (grub) screw on the motor shaft to lead screw coupling (this is the first thing to check).
Unless you used spray cleaner on the lead screws and did not re-lube them, I doubt you need new screws.
Because those errors vary linearly with the distance traveled, it suggests the axes need calibration:
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thank you for replying what I learned was the way I set up the belt drive it was slipping. I never have liked belt drive so I have installed lead screws and it seems to have solved the problem.
The problem I’m having now is tuning the motors, I need to increase the torque is there a way of doing this in light burn? Or is the a grble setting?
The X axis is working fine
The Y axis is telling me it has to be over 1400 spm and the Nema 17 isn’t able to do this
the cutting area of my laser is 700mm X 700mm
If you have any idea what the problem could be drop me a line
thanks
Thank you for the doc. the problem I was the way I built the belt drive it was slipping. I redesigned the laser to except lead screws and problem solved. The X axis moves without issue, the Y axis moves just as well but when I write 200mm in the requested distance the machine traveled 40mm
when I enter that number the steps needed are over 1400. The motors stall at this rate so working my way up slowly it seems the max speed the motor will turn is 1000 - 1200 steps before it stalls, I can get to 130mm when entering 200mm before the motors stall.
hope I explained this properly if you have any questions or ideas I’m happy to hear them.
Lightburn has no control of the things plugged into the controller board. It simply issues commands to the controller for position and accessory activation.
You may try increasing the stepper current. If you have a very high accel setting, it may be missing steps due to the inertia of the hardware. Enter $$ in the console, then copy the GRBL settings and paste them in a reply. We can then see if there something strange in there. Basically, do not change any settings on a maybe.
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If I understand correctly, the leadscrew drive has $101=1400 step/mm. Typical belt drives will be around $101=100 step/mm, which means the motor must spin about 14× faster to move the same distance with the leadscrew.
Stepper motors run at constant power, which means their output torque is inversely proportional to their rotation speed: power = torque × speed.
Reduce the maximum Y axis speed by a factor of ten to compensate for the increased step/mm value and the motor will produce approximately the same torque . For example, if $111=8000 mm/min for the belt drive, reduce it to $111=800 mm/min for the leadscrew.
The motor winding current sets the power level and, thus, the torque at any given speed. If you have already adjusted the current to the recommended value for the motors, then they cannot produce more torque at a given speed. Typical NEMA 17 motors run at 1.5 A, maybe 2 A, although they become alarmingly hot near their upper limit.
Leadscrew drives make sense for CNC machines that must provide force against cutting tools with relatively low feed rates, but make less sense for laser machines where the motors must overcome only the inertial load of the laser head at relatively high speeds.
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thank you for this information I have been in the cnc hobby for 16 years and just recently started with laser. Lightburn and grbl are new to me. I’m building this laser from scratch and enjoying the adventure as I progress . If there are any good self help videos you know of I’m very interested. After reading your email I can see have a lot to learn thank again for the time you take to help me
As the others already mentioned, a leadscrew design is favorable for a CNC (low speed, high torque) but usually bad for a laser, where you need high speeds but nearly no torque (no force applied between laser head and workpiece).
In your case, if changing to a belt-driven mechanics is not the preferred way, I’d exchange the leadscrew to another one with a much higher pitch. Common leadscrews have 5 or 8 mm / revolution, you might search for some that have more..
Absolutely nothing wrong with that; I know the feeling. 
I’m not much of a video guy, but a subscription to Home Shop Machinist might scratch your itch.
(Disclosure: I wrote the Along the G-Code Way column in Digital Machinist until it folded.)
As do we all! Welcome aboard …
I have ordered the belt and will switch it over
I’m building this laser from scratch so its been a great learning experience thank you for your ideas and support
The X axis is working grat its the Y axis that is giving me some problems
When I had this machine operating before on belt drive it was how I had set up the belt drive so I’ll be making some changes in how I set up the next drive system with belts
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