I think this is a question for @peopoly
I know basically what i get as an user
So due to nature of galvo system, as far from the center you go in the X/Y plane you go bigger error ocures , that is very different in X an Y axis.
So the approach is just like lead screw areal wear correction on the CNC machines.
You print something 10 mm long and you compare if it is 10.5 , then you correct coordinates in this range
same for 20, 30,40,50,60, etc
Again I am just an user
Thanks for the input. I read the docs and checked the formlabs code as well.
It seems Formlabs uses a 2D grid and interpolates (bi)lineair in XY. So they have datapoints on a XY grid.
This seems to me as most accurate; probably they get these grid values when leaving the factory?
The calibration STL in Moai is just on 2 axis. (with a smart STL that you can measure quickly btw)
So this introduces a small error in the interpolated area’s in each quadrant. However it’s a quick and flexible calibration so i think for most this would be OK. Making a more extensive calibration STL would be difficult to measure accurately
First thing i don’t understand is what Asura does with the measured values in the example:
- calculate the adjustment value. In this case, it is 61 + (62-61)/2 = 61.5
On the row Xval 61 60.6. Change it to Xval 61 61.5
If you measure 62 and it should be 61 then your position is off by 1mm. So the correction would be -1? Or am i missing it completely? Or is it because the origin in the GCode is on the lower left corner? Hence division by 2?
Second thing i’m not sure of (@Peopoly) what would be the best way to interpolate between the quadrants?
Third thing that comes to mind would be a smarter way to generate a correction table.
Wouldn’t it be possible somehow to overlay a ‘sensitive’ sheet/paper with printed rectangles of known dimension.
Then have the laser make some rectangles on this sheet/paper.
Take a photo of the sheet.
Because you know the pre-printed rectangles (and their size) and you know the GCodes for the burned in rectangles you could theoretically perform an image analysis and get a very accurate grid compensation…
Would be an ‘semi’ automated way to perform an instant calibration…
For me it do not matter how it is done as far it is giving results correct enough .
Can you do the same in gcode generation. I do not ask for the same table or STL.
Just a way to make this grid compensation on X and Y .
I am ready to spent time a make tests when and if you implement this kind of calibration .
Anyway I did already purchased formware personal licence, so I am at your disposal to make tests.
are there any updates for the calibration? would really love to start using formware but I can’t leave asura if I can’t calibrate my new slicer.
yes it’s in planning in 1-2 weeks. Had some other issues to build with higher prio.
But it’s on my todo list. I’ll give an update here once done.
Yes, every Form 1/+ printer has his own calibration grid stored in flash memory and sends it to Preform for path generation.
I recorded some test grids on UV sensitive paper, that worked well. But it is difficult to align the paper accurately on the build plate. So i think working with pre-printed rectangles would not be feasible. Maybe with some kind of jig to fasten the paper on the build plate?
Atm i think the best idea is to create a plate with an array of photodiodes that form a grid and use that for calibration.
Look at the Form 2. It has photodiodes around the tank, i think for thermal drift correction.