Calibration help

I test printed a 20mm cube from Hollow Cube and Cube With Hole. The cube’s height is correct for both, 20mm, but when measuring the X and Y it comes out to 24mm. The hole is not a circular hole but an oval shape. The MPCNC is squared using a carpenter’s square and measuring diagonally across from each point. Here are some pictures as references. I printed out a bracket for my Ramps to put a fan on it. Well, the bracket looks great but just to wide. Do I need to make any settings in the Marlin software or is this a structural issue that I need to recheck? I triple squared it, but if there are any other suggestions then I am open to them.

  1. Did you buy everything from here?
    Not everything

a)If you didn’t or changed some things please don’t leave out any details.

b)What firmware?
Firmware is from this site

  1. Are you using end stops?

  2. Are you using all my recommended parts? yes

a) If not please list what parts you used
Most of the parts are the same but from Amazon

Are you sure you are using 16 tooth pulleys? If not you need to adjust your firmware.

I checked the package and it lists it as 16, but when I looked closer, and counted I noticed it was 20 tooth pulleys. So much for packaging. Would it be better to order 16 tooth pulleys or just stick with the 20 and make changes in the firmware?

If I make changes in the firmware would it be


Line 510: #define DEFAULT_AXIS_STEPS_PER_UNIT {200,200,4535.44,200} // default steps per unit for Ultimaker

What numbers should I be using to represent the 20 tooth pulleys?

If you don’t want to deal with getting new pulleys, you’ll change those first two numbers (x and y axis) and probably try what this calculator gives you

I took a guess at most of the other settings (mostly defaults), but w/ a 20 tooth pulley it looks like 160 might be the number.

Thanks Dahuss! I am going to comment on that line in the firmware. The firmware is lacking in comments on what parameters are representative of what. So for that line
{200, 200, 4535.44, 200} should be {X, Y, Z, ?}

So with a Nema 17 with a 1.8 degree step angle I am getting 80 steps per unit for X and Y.

I am using the formula:

steps/mm = (motor steps per rev)∗(driver microstep) / (belt pitch)∗(pulley number of teeth)
80 = (200)(16) / (2)(20)

Am I calculating this incorrectly? Because with a 16 tooth pulley that 200 should be 100 based off of the formula above.


Your calcs are for 16th stepping , double them for 32.

Thanks vicious1! I really appreciate your help and of those in this forum (dahuss). Thanks for this great design and letting everyone build it. I will post some pics of my printer once I have it printing correctly.