Calibrating mirrors and lens: step by step - nortd/lasersaur GitHub Wiki

Warning: this is a draft document. You're probably better off using https://github.com/nortd/lasersaur/wiki/Calibrating-mirrors-and-lenses for now.

Spirit level

check if machine is perfectly level

Paper tape procedure

25mm paper tape over mirror holder or lens holder (30mm is ideal).
- DO NOT stick to mirror or lens itself, only to holder!!!
trace circle around edge of mirror holder onto paper tape using pencil
burn at 15%, 2000mm/min (start with 6mm, burn longer if needed to see anything)
remove tape
paste onto paper, document and measure. Some hints:
- divide A4 sheets into 24 squares (4 horizontal x6 vertical)
- paste in the direction of tape from mirrors (horizontal or vertical)
- document:
  - (x0,y0) and (xmax, ymax) direction on tape from lens
  - beam intensity (x mm at 15% & 2000mm/min)
  - adjustments made (example: "1/4 turn left, 1/2 turn up")
turn top mirror holder knob left for higher, right for lower
turn bottom mirror holder knob left for left, right for right
repeat until correct

Calibrate M1 position

tape over M1
check if burn is 3.5mm right of center horizontally (=~depth of mirror in holder, think of Pythagoras)
adjust t-slot position of M1 holder accordingly
check if burn is +-3mm above center vertically
adjust laser tube position (TODO: how? more or less rubber wrapping tape in holder?)

Calibrate M1 angle on x0 side

tape panel and target laser beam through the hole
M2 hole needs to be +- 3.5mm right of center
tape M2, burn at (0,0), adjust M1
tape M2, burn at (0,0) and (0,600)
change angle of M1 or horizontal and vertical position of M1 or M2
laser beam has to be parallel to y axis

Calibrate M2 angle

M3 hole needs to be +-3.5mm above center
tape M3, burn at (0,0) and (1200,0),
adjust M2 angle or vertical position of M3
tape M3, burn at (0,600) and (1200,600)
compare it to (0,0) and (1200,0)

Calibrate lens

take out lens from nozzle
put round cardboard at the bottom inside of nozzle
lower nozzle as low as possible
burn at (1200,600)
adjust M3 angle

First comparison run: compare burns at compare cutting area corners

The idea is to compare corners of the cutting area: first by side (x0, xmax, y0, ymax), then all four:

tape M3, burn at (0,0) and (0,600)
tape M3, burn at (0,0) and (1200,0)
tape M3, burn at (0,600) and (1200,600)
tape M3, burn at (1200,0) and (1200,600)
tape M3, burn at (0,0), (0,600), (1200,0) and (1200,600)

This will help you see more clearly.

Draw the vertical deviation in perspective for the x0 and the xmax side of the cutting area. Is it going up or down? On both sides?
Draw the horizontal deviation in perspective for the x0 and the xmax side of the cutting area. Is it going left or right? On both sides?
Draw the vertical deviation in perspective for the y0 and the ymax side of the cutting area. Is it going up or down? On both sides?
Draw the vertical deviation in perspective for the y0 and the ymax side of the cutting area. Is it going up or down? On both sides?

Calibrate M2 angle on y600 side

M3 hole needs to be +-3.5mm above center
tape M3, burn at (0,600), adjust M2
tape M3, burn at (200,600), adjust M2
tape M3, burn at (400,600), adjust M2
tape M3, burn at (600,600), adjust M2
tape M3, burn at (800,600), adjust M2
tape M3, burn at (1000,600), adjust M2
tape M3, burn at (1200,600), adjust M2
tape M3, burn at (0,600) and (1200,600)

Second comparison run: compare burns at cutting area corners

tape M3, burn at (0,0) and (0,600)
tape M3, burn at (0,0) and (1200,0)
tape M3, burn at (0,600) and (1200,600)
tape M3, burn at (1200,0) and (1200,600)
tape M3, burn at (0,0), (0,600), (1200,0) and (1200,600)
compare to first comparison run
you might see some obviously wrong things comparing these. if so, fix them.

This will help you see more clearly.

Draw the vertical deviation in perspective for the x0 and the xmax side of the cutting area. Is it going up or down? On both sides?
Draw the horizontal deviation in perspective for the x0 and the xmax side of the cutting area. Is it going left or right? On both sides?
Draw the vertical deviation in perspective for the y0 and the ymax side of the cutting area. Is it going up or down? On both sides?
Draw the vertical deviation in perspective for the y0 and the ymax side of the cutting area. Is it going up or down? On both sides?

Calibrate M1 angle on x1200 side using paper tape procedure

M2 hole needs to be +- 3.5mm right of and 3mm above center
tape M2, burn at (1200,0), adjust M1
tape M2, burn at (1200,200), adjust M1
tape M2, burn at (1200,400), adjust M1
tape M2, burn at (1200,600), adjust M1
tape M2, burn at (1200,0) and (1200,600)

Note It is important to do this optimisation last, as the (1200,600) spot will always be the weakest point of the laser cutter. You want to optimise for correctness in this corner!

Third comparison run: compare burns at cutting area corners

tape M3, burn at (0,0) and (0,600)
tape M3, burn at (0,0) and (1200,0)
tape M3, burn at (0,600) and (1200,600)
tape M3, burn at (1200,0) and (1200,600)
tape M3, burn at (0,0), (0,600), (1200,0) and (1200,600)
compare to first comparison run
you might see some obviously wrong things comparing these. if so, fix them.

Draw the deviations out again as before.

Calibrate lens on y0 side

Calibrate lens on x0 side

Fourth comparison run: compare burns at cutting area corners

Calibrate lens on ymax side

Fifth comparison run: compare burns at cutting area corners

Calibrate lens on xmax side

Sixth comparison run: compare burns at cutting area corners

Note It is important to optimise for (1200,600) last and most, as the (1200,600) spot will always be the weakest point of the laser cutter. You want to optimise for correctness in this corner!