Calibration of steps Per mm

Helle everybody!

I have my x carve up and running, and have had for a while now.
However, I wanted to calibrate it. And I used the method with the ruler and then moving the spindle.

I measured it out and calculated my steps per mm and it was spot on.

However when I cut a test piece, it’s a bit off the specification.

If I use this to calculate the steps per mm, I can get excellent cuts. However now its overshooting if I check the steps via the ruler method. Is this acceptable ? Or should I dig deeper for a more serious issue?

Consider the spindle have no sideways load when you just use a ruler to measure, when you are cutting the tool have sideways forces applied to is and this may cause deflection. So I presume your carved piece is slightly undersized? By how much?


The piece cut was a simple profile of 150x50.

The x length was roughly 0.4-0.5mm off and the y axis was 0.8-1.0mm off

After I corrected the steps according to that piece, it was within 0.1of specifications

However if this is due to the forces alllied from cutting, wouldn’t that mean that is a variable changing from each cut to cut? I mean the forces might be bigger if I cut oak, or aluminum and therefore resulting in a wrong cut?

New belts will stretch out after a few days, so you may need to re-tighten your belts - this is normal.

Triple check your pulleys. A little bit of “wiggle” can result in a backlash errors that will manifest as things being just a little “off” (Ridges too thin, holes too big)

I use a longest ruler I can over the longest distance, then re-check it with shorter intervals.

I HIGLY recommend you invest in a pair of digital calipers, they will make your life so much easier. I recently saw some in the ruler section at Lowe’s or you can get them on line.
Then use them to measure your bits. One major culprit for inaccurate cuts after you have calibrated your steps is incorrect bit size. Many “1/4” bits purchased on-line are actually 6mm and not 6.35mm. So measure your bit so you have the correct diameter to enter into your CAD program.

Thank you for all your responses.

How tight should the belts be?

I do own a digital caliber - but use a regular one when calibrating.

Guess I’m adjusting the steps per mm back to what was right for the no load method.

I’ve checked the pulleys and there seems to be no wiggle in them.

Yes, but you would normally adjust cutting speed/depth per pass according to material so the sideways load will remain reasonable similar. Getting your machine properly tuned is a process that do take time, because materials settle/need readjustments to stay tuned etc. Finding your system sweet spot regarding optimum cut rate is also part of this.

End mill run out is also mentioned and may be a major factor of your size discrepancy.

So could the small differences be due to runout?

Hello friend …I checked again about microstepping and now I can explain you my actual problem. I am using Arduno Uno with protneer CNC shield version 3.5 .Earlier I was using DRV 4988 stepper driver that had heating problem even at that time it was making 4 times moovement then I replace the driver with TB 6560 .The problem comes here ,the TB6560 has manual switch to change microstepping.Now on 1/16 step its making half of the given size .The jumper setting on CNC sheild are fixed for 1/8 microstepping… do I need to change jumper setting on CNC sheild to 1/16 microstepping?

Actualy my x carve was moving 4 times on all axis

In an attempt to bring this back to topic.

Could the differences in the cut be due to runout?

Yes, atleast a part of it.
There are four factors at play, actual movement, tool run out, tool deflection and actual (real) bit diameter.

Thank you!

I never really thought about the diameter of the bit could vary :confused:

I guess I should double check the diameter !

The jumper setting is same as you mentioned but the moovement on x and Y axis is more than 4 times …so what should I do??

Sorry …actually I started the topic but dint get reply so I came here bcz this thread was live

No problem :slight_smile:

Ive got something to move forward with! Thanks :slight_smile:

Hey Guys!

So, new testing has begun! I’ve carved out the same profile as before mentioned (150x50) And the X length ( 150mm) is Pretty good… It measures in at 150.04mm.

However the y length (50mm) is 49.3…
I’ve checked pullyes, belts, wheels and pots :frowning:
The steps are perfect when measured with a ruler / Caliper.

Do you guys have any suggestions? :frowning:

Is it too much trouble to do another test piece, done at half the cutting speed used for the previous test?

Each axis may respond differently to sideway forces.

Not at all :slight_smile:

I’ll check back later today! Thank you!

So, a new cut was made - With half the speed. And it still showed the same variation :confused: