Irish_Steve Wrote:
-------------------------------------------------------
> if the switch is a removable device, (which I hadn't
> completely recognised) then that may not be so
> much of an issue as I thought it might be.
It was in our case. Johann's probe is different, it is not removable but is retractable.
> I've already realised that calibration will be
> iterative, in that one change to the bed levelling
> will change other readings that have already been
> set up
The proces should not be iterative. Notice we descrite the whole system with equations and them solve them. We should have got the correct resonse at the first attempt. Anyway this did not happen and we needed 3 iterations for bed leveling withing 0.05mm. We did not try more since that is good enough for 0.2 mm layer height and we do not expect to need smaller layers.
The equation is of 4th order but I believe it should have only 2 real solutions. That is in ideal case when everything is measured precisely. Maybe the inexact measurements "break" it. Anyway it works enough to be usable. This would deserve more investigation. If you want to continue I can post the maxima notebook. Though it will take some time to review/fix comments so that even somebody else can understand the process.
> I would be the first to admit that I do
> not have enough knowledge of the cartesian Polar
> conversion systems to understand what most of the
> variable parameters actually mean, or how changing
> them will affect the device.
I doubt any delta bot uses polar coordinate system (distance, azimuth, elevation). At least Marlin and Repetier convert directly cartesian to delta. Most people seem to take the route of laser cut top and bottom plate and then they get precise tower positions. Figuring out precise diagonal rod and endstop positions is easy even without any math. Fixing tower positions manually is a bit harder, but it is not a big deal either.
The general rules are like:
* moving tower radially have biggest impact on the oposite side of tower (so if it is symetricaly high/low on the oposite side then you need to move the tower nearer/further in firmware parameters)
* moving tower diagonally have the biggest impact on the z-postion just to the left/right of the tower - one side is going up and the second one down (so if e.g. left side is up and right down then you need to move tower in firmware to the right)
This manual approach for figuring out tower positions precisely is very iterative. The math based approach idealy should not be iterative at all (but it was ... at least in our case ... although 3 cycles are not that much ... maybe we got lucky :) ).
Firmware parameters are described quite well in Configuration.h. Although it may be a quite a chalenge if you do not do software at all. There are some gotchas, e.g. comment for DELTA_SEGMENTS_PER_SECOND talks about corners precision, but it has hardly anything to do with corners, it is much more about slight imprecisions in stright lines :) or if you happen to have diagonal rod precise to a whole number of milimeters and you do not add .0 the end then compiler will unterstand it as an integer and its square root will overflow and you get delta bot which can home but cannot move :)
But mostly it is ok.
Good luck building your printer.
-------------------------------------------------------
> if the switch is a removable device, (which I hadn't
> completely recognised) then that may not be so
> much of an issue as I thought it might be.
It was in our case. Johann's probe is different, it is not removable but is retractable.
> I've already realised that calibration will be
> iterative, in that one change to the bed levelling
> will change other readings that have already been
> set up
The proces should not be iterative. Notice we descrite the whole system with equations and them solve them. We should have got the correct resonse at the first attempt. Anyway this did not happen and we needed 3 iterations for bed leveling withing 0.05mm. We did not try more since that is good enough for 0.2 mm layer height and we do not expect to need smaller layers.
The equation is of 4th order but I believe it should have only 2 real solutions. That is in ideal case when everything is measured precisely. Maybe the inexact measurements "break" it. Anyway it works enough to be usable. This would deserve more investigation. If you want to continue I can post the maxima notebook. Though it will take some time to review/fix comments so that even somebody else can understand the process.
> I would be the first to admit that I do
> not have enough knowledge of the cartesian Polar
> conversion systems to understand what most of the
> variable parameters actually mean, or how changing
> them will affect the device.
I doubt any delta bot uses polar coordinate system (distance, azimuth, elevation). At least Marlin and Repetier convert directly cartesian to delta. Most people seem to take the route of laser cut top and bottom plate and then they get precise tower positions. Figuring out precise diagonal rod and endstop positions is easy even without any math. Fixing tower positions manually is a bit harder, but it is not a big deal either.
The general rules are like:
* moving tower radially have biggest impact on the oposite side of tower (so if it is symetricaly high/low on the oposite side then you need to move the tower nearer/further in firmware parameters)
* moving tower diagonally have the biggest impact on the z-postion just to the left/right of the tower - one side is going up and the second one down (so if e.g. left side is up and right down then you need to move tower in firmware to the right)
This manual approach for figuring out tower positions precisely is very iterative. The math based approach idealy should not be iterative at all (but it was ... at least in our case ... although 3 cycles are not that much ... maybe we got lucky :) ).
Firmware parameters are described quite well in Configuration.h. Although it may be a quite a chalenge if you do not do software at all. There are some gotchas, e.g. comment for DELTA_SEGMENTS_PER_SECOND talks about corners precision, but it has hardly anything to do with corners, it is much more about slight imprecisions in stright lines :) or if you happen to have diagonal rod precise to a whole number of milimeters and you do not add .0 the end then compiler will unterstand it as an integer and its square root will overflow and you get delta bot which can home but cannot move :)
But mostly it is ok.
Good luck building your printer.