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step calibration

Posted by kelvinmead 
step calibration
February 08, 2017 10:24AM
prusa, i3 pro b, copy

i think, or calibration in general.

after printing beautifully an iPhone case, the phone doesn't fit.

so i printed some (3) 30x20x10 mm oblongs.

and my prints are all pretty much the same.

X, meant to be 30, is 29.52mm
Y, should be 20, and is 19.77mm
Z, should be 10, and is10.18mm

i know i can adjust the xsteps steps etc,

X and Y are 78.74
Z is 2560

but whats the system of tweaking? is there a formula, or do i blindly add 10 and see what prints?
Re: step calibration
February 08, 2017 03:32PM
ah ha!

i have a formula that works for the x and y, dunno about z... that seems more like magic.

anyway,

if you print a few 30x20x10 mm blocks (so you don't just guess on 1) and then measure them you can recalibrate your x and ysteps/mm

so;

new steps = current steps X (what it should be / what it is)

so, the preset is 78.74, my print was printed at 30mm and it was 29.52mm (average of 3 prints)

so the calc is;

new steps = 78.74 X (30 / 29.52)
new steps = 80.02

you can input this into your host software with

G92 X80.02,

then M500 to save to eeprom, and then M501 to check.

if you can't save to eeprom, like me... then you can drop a line;

G92 X80.02 Y79.46 at the beginning of every print.
Re: step calibration
February 08, 2017 05:10PM
The above method works well for the e steps and thats about it. Use this calculator to calculate your true steps per mm

[www.prusaprinters.org]

If your print is still off, look at belt tension or maybe speed settings or stepper current.

Tom does a good job of explaining why the above method is old and out dated

[www.youtube.com]

See also the reprap calibration guide

[reprap.org]
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