No correct dimensions of a square when engraving

Hello people:),

I am new to laser engraving and several days ago i bought a laser engraver, the scupfun s9. I installed lightburn(trail version) on my windows 10 laptop and then i tried to cut a 10x10mm little box for testing. But i can not make each sqaure 10x10 mm.

With lightburn a made 6 boxes of 10 mm. Snapt every box to the grid. When i engrave the box on 270GSM paper the dimesions are slightly off. As you can see in de picture the first sqaure is bigger, roughly 10,05mm, the second, thirth and fouth square are excactly 10 mm on the x-axis. The top and buttom square are 10,05 mm and as you can see they don’t line up perfectly with the other squares to make a little box.

I have tried to calibrate the x-axis and y-axis but that did not work.

Also as you can see mostly close too the end off corners the line is not smooth, first i thought it was the table so i put it on the ground but that didn’t make any difference.

I hope someone can help me with this problem.


Is the picture the result of burning all the boxes in a single pass? Or you burned each box, one at a time?

I suggest you check your belt tension. I suspect you’re overtensioned on one or both axes.

Also, please share .lbrn2 file. Your image looks fine but there might be something going on in the design that’s not obvious.

Hello @berainlb thanks for your quick respons,

The picture was burned in one single pass.
I will have a look at the belts tension.

I added the .lbrn2 file.
Littlebox.lbrn2 (5.6 KB)

Your file looks fine. The issues you’re seeing are most certainly hardware related. If not the belt tension then possibly stepper configuration.

One other possibility that occurred to me. Is it possible that the frame of your laser is out of square?

I tried to loosening the belt tension on the X en Y-axis but still i get the same results.

What do you mean by stepper configuration? Can i change them if so where can i do that?

I checked the laser and the frame but i think they are ok, can not see any parts that are not straigh or not correctly aligned.

I find it odd that the first box is not ok, than three boxes are ok and on the side the boxes are not oke.

Maybe I can contact the supplier, maybe they know what it’s about or that they have come across this more often.

Stepper can be configured in GRBL settings but I’d suggest holding off on that until you get guidance from the supplier.

I actually don’t think any of the boxes are quite right. Although the XY dimensions may be correct, they all look skewed (like parallelograms) at least from the image.

Give us an update after discussing with your supplier. Good luck.

Thanks for your effort.

I will contact the supplier and wait what they will say…
i will post their answer when i get a reaction.

Thanks again

The stepper motor drivers in CNC machines can be set to provide varying amount of rotation per pulse. If you draw a near vertical line but offset one end 0.5mm in X direction it should come out perfectly straight. However if the machine has low resolution you will see a stair stepping shape to the line. See what a horizontal line looks like also.

Hello @dean448,

I don’t have a CNC machine. But a laser engraver machine. I don’t know if this makes any difference.
I don’t know exactly what you mean by “If you draw a near vertical line but offset one end 0.5mm in X direction it should come out perfectly straight”.

You mean that i have to draw a line next to the “little box” that i drew?

Hello @berainlb,

I got an answer from the retailer. Not very satisfying

Hey,Dear friend
Please tighten the belt a bit,and Set the speed lower ,it will be more stable.

Best regards

I will try again to tighten the belt(s) but i don’t think that is the answer for my problem.
I can’t test it until next Tuesday.

I do tend to think that the problem is mechanical, likely to do with belt tension. The belts should not be under significant tension and definitely not like a spring. It should be just tight enough to remove any slack and any sagging.

What speed did you burn this at? I doubt that’s the main issue here but good to rule out all variables.

My point is that all our machines are digital where a computer needs to find location based on pulses. Pulses can be fine or course depending on what speed and accuracy you are trying to achieve. In a stepper machine there is a trade off.

In the end the machine was probably built to whatever specs they were trying to hit and the resolution is set to the highest levels that those components will achieve. By engraving a line just off horizontal or vertical you can see how poor the resolution is. So is the machine capable of hitting a location between 10.0 and 10.05? If the slide travels .05 per step then it can’t do better.

Since all laser cutters are timing belt based ,there isn’t any slippage so belt tension will only help if it’s really loose. Don’t over tighten the belt.

Next tuesday or wednesday i can try to tension or losen the ingraver belts. Hope it helps.

The speed that i used was 900 mm/m and power was set to 100%

ok, i do understand what your are saying. I will try to make some horizontal and vertical lines. And see how the resolution is. I know that an ingraver that cost 300euro has it limitations. But i will try to tighten/loosening the belts next tuesday or wednesday hope it helps.

While a true statement in general, in this particular case there should be zero reason you won’t be able to tune this to get a very nice result with very accurate dimensions.

Send an update once you’re able and we can keep tuning.

wobbles are mentioned at the end of this guide

Just a quick question…\you don’t have a KERF 0.5 set do you?


Hello @LazerArt,

I don’t know i will have to check tuesday
i will let you know.

@LazerArt i have no kerf offset.

@Kachnik, thanks i did lower the acceleration speed and the lines are much more smoother. As you can see in the picture.

@berainlb, @dean448, @LazerArt i have tried to tighten or loosening the belts. I also lowered the acceleration speed but none of them did work. As you can see i can engrave “perfect” straight lines and the five boxes next to each other looks fine, but when i add one box on top of another the dimensions are off.

boxes.lbrn2 (8.7 KB)