galvo steper miror

Hello friends
I am thinking about this problem. Currently the galvo on the market is very expensive and its control and alignment is quite complicated. I found the Marlin open source 3D printer can integrate and write more code to take advantage of stepper motors to replace galvo for Resin printing. Replacement for SLA printers that are using galvo today.
I am having an idea to develop stepper motor as galvo to move the laser
I am also having difficulty in writing structural code to control this stepper motor in Marlin system can someone suggest me the problem? Or someone can help me, I can pay the person who can implement this idea

... forget moving the mirrors directly connected to the stepper shaft -- even with high resolution microstepping it's not reliable enough to set the position exact linear - there wold be "displacement waves" around the fullstep-positions.

I've built something similar with servos with super-high gearing (400:1 and 800:1) and corresponding encoders on the motor shaft - here a related thread in the German forum:
[reprap.org]

The servo-drivers were controlled by STEP+DIR, as common steppers, so not this different (the drivers made the closed-loop on their own) - and even with this high gearing they were capable of speeds up to 1m/s ... so even faster with lower gearing ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Can you suggest me how to write code to control it in Marlin. I want to try it and see how it works

... I've used the software unmodified - simple XY-movements with "G0" for positioning and "G1" for engraving (positioning with äquidistant laser pulses).

All the "adjustment" was made with an external software, which konverted the XY-koordinates to G-moves, adjusted for the nonlinearity of the galvos (cushion distortion) and for the F-value, which defines, how many extruder-steps per mm, what was 1:1 sent to the laser-controller to pulse the laser ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

can i reference your code in Marlin or not?

... you can use Marlin unmodified for testing - it's pretty all simply XY-G-codes for positioning the two motors and the STEP-pulse of the extruder stepper fed to the laser ... you have only to adjust the steps/mm for the XY and E-values.

For "exact" positining you have to calculate/compensate the "cushion distortion" of the mirrors, what's depending on your special setup ... this can be measured and adjusted with a linear equation ...

Edited 1 time(s). Last edit at 09/01/2021 09:23AM by VDX.

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

thank you so much