Prints are coming out too big so I am trying to dial in the right steps per unit.
I'm down to 75 steps per unit and prints are still oversized. This seems wrong as I'd expect this number to be at least 80.
At 75 the Z axis becomes 310mm. This seems wrong.

Does anyone know the stepper resolution for the NEMA 17s this printer ships with?

40mm calibration block is printing 40.4mm using 75 steps per unit.
20mm is printing 20.2mm so its a linear error which points to the step size.

Quote
KevinS
40mm calibration block is printing 40.4mm using 75 steps per unit.
20mm is printing 20.2mm so its a linear error which points to the step size.

It only points to the step size if the height is also wrong by the same factor. Adjust the steps/mm to get the correct height. Normally it is 80 if you have 20-tooth pulleys and GT2 belts, or 100 if you have 16-tooth pulleys. Once you have the height correct, adjust diagonal rod length to change the XY size.

Edited 1 time(s). Last edit at 11/12/2015 05:11PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks.

That's actually a big help. I found that by pushing a digital caliper down with the effector, these need to be around 81.25. It seemed to me the height was also too big but my cal object is only 10mm high so any error might be in the "noise floor"

Quote
KevinS
Thanks.

That's actually a big help. I found that by pushing a digital caliper down with the effector, these need to be around 81.25. It seemed to me the height was also too big but my cal object is only 10mm high so any error might be in the "noise floor"

FT usually send 20 tooth pulleys, so 80steps/mm should be correct.
If you want to be extra certain, count the teeth. (assuming it is GT2), if 20 then 80 steps/mm if 16 then 100steps/mm (not 16 as dc42 mentioned earlier, that must have been a typo :-) )

80 is where I had them set initially before going on this goose chase.