Corexy calibration/compensation
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Hi,
As I said in another post, I'm going to change from a delta printer, to a corexy. I'm curious what the effect of calibration and compensation is.Let's dream a little, and assume, that the bed is a perfect plane. This model has 3 motors on the Z axis, and with 3 points a geometrically defined plane
In a Corexy, CALIBRATION
When your computer tells Duet to calibrate the printer, it takes the z-coordinate reading at various points on the bed. And with those readings, what does he do:
A- (mechanical solutions) moves the different Z motors, so that the new plane through which the bed passes is at the same time distance from the tip of the nozzle.
Or
B- (software solutión) It does not move the motors, it adjusts in real time the distance from the bed to the nozzle so that it is always the same or very similar
It seems more reasonable to use solution A... But not all Corexy have, 3 Z engines. I think the smaller models of only have 1, the normal is 2 ... I think. So the solution is A, it won't always be possible
Does Duet do one thing or another depending on the engines you have in Z? Do you have to adjust the position in Z, mechanically (moving each individual motor) so that the difference of Z is the minimum possible? Or Duet takes care of it
In a Corexy, COMPENSATION.
Duet, according to what is set in config.g, takes the Z coordinate of a matrix of points, which although the calibration has been perfect, this will detect if the bed is not a perfect plane, if it is curved, like a dome or inverse. And when you're printing, adjust the position of the Z-axis, in real time, to try to keep the same distance to the bed where it is in X and Y. With calibration, errors in Z are absorbed, due to flatness problems in the bed
Is reality similar to my assumptions? Any resources (url) where I can find information about this
Thx
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@peirof You haven't considered the third and best option. Starting with your "dream" that the build platform is a perfect plane, then you don't need to apply any compensation or software adjustments at all. You can simply home Z and print. Software flatness or levelling are simply tools to compensate for poor mechanical design or construction. If you buy a cheap kit, and you decide not to correct it's mechanical imperfections, then you will need to use software compensation. But if you build the machine properly, and the build platform is flat, level and stays that way, then you don't need any form of compensation. It isn't difficult to do, but does take a little time. But the initial time spent will be saved over and over again by never having to probe and adjust every time you cycle the power and/or start another print. Trust me - I have had both types of machine and never having to compensate for poor mechanical design or construction, is so much better and saves a huge amount of time.
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If you have 2, 3 or 4 independent Z steppers RRF firmware can do Automatic Bed Leveling (ABL) as you described, where adjustments are made to individual Z steppers to get the bed as level as possible.
Also the firmware can do Mesh Bed Compensation (MBC) which involves probing the bed in a grid and gathering data about Z adjustments that need to be made in real time during printing.
The two features are independent.
All of my printers use MBC but only one of them has multiple Z steppers (3) to allow use of ABL.
The two
