Need help calibrating 3d printers steps per milimeter

[Zerphan 0]

I have a Cheap chinise CTC prusa i3(https://www.aliexpress.com/item/4000238153166.html?spm=a2g0s.9042311.0.0.279a4c4dUEIbmR) with a anet 1.5 board which i have just flashed with optiboot and the latest marlin firmware but I am unable to work out the steps per mm. I have a 2 mm pitch on the belt and 20 teeth on the driver cogs. Can anyone help

[gr5 2,331]

Just tell it to move 10mm and measure how far it moves.  Figure out the ratio (actual distance / desired distance) and multiply that ratio by the current steps/mm.  In other words if it moves 10% too far than increase steps/mm by 10%.

 

Then repeat but with the longest distance that is reasonable for more accuracy.

[tinkergnome 929]

7 hours ago, Zerphan said:

I am unable to work out the steps per mm

 

Calculating the theoretical value (as a starting point) is fairly easy, but you need the (micro-)steps/rev of the stepper motor as well.

Simply compute the quotient of steps/rev of the motor and mm/rev of the pulley (20*2mm in your case).

 

For a common 1.8° stepper motor and 1/16 micro-stepping this would be: (200*16)/(20*2)

(assuming that all pulleys are of the same size).

 

There are online calculators for the lazy ones... 🙂

https://blog.prusaprinters.org/calculator_3416/#steppermotors

[GregValiant 1,489]

You need something more accurate that a ruler to perform the measurements.  A vernier caliper works well.

I think that not enough people pay attention to the frame of the machine.  Everything needs to be square and parallel.  A carpenters tri-square comes in handy.  If (for example) the X beam is at a slight angle then your prints will be off no matter how well the steps are calibrated.  Or if the two upright beams aren't parallel then the part will twist as it gets taller.

After the machine gets a few hours on it you will want to re-visit the calibration again as things loosen up.