OK, I will start from the thought that maybe we're trying too hard to get the level sensing by using switches and probes and the like.
Working from the premise that the bed is a piece of aluminium or ply, with a heater of some sort on it, and then a sheet of "suitable" float glass clip mounted on that, if I read it correctly, the object of the exercise is to then use a levelling system to determine if the hot end is travelling at the correct height above the glass to successfully deposit the print across the printing area.
So, why are we not using the brass nozzle of the hot end as the sensor, using an electronic return capability from the print bed, which in simplest form is a piece of aluminium of known thickness placed on top of the glass. The float glass is level, so the intention is to adjust the glass level so that the hot end is the same height above the bed across all of the print area, which initially is a calibration issue that may require adjusting the bed position using levelling screws, and then after checking the zero position has not moved, it is then a mechanical issue related to the design of the device, so tweaks are used in the firmware to get the head to move accurately above the surface.
So, how about if the piece of loose plate is one side of a circuit on the RAMPS, or similar, and the calibration sequence goes something like turn hot end off, etc, and then adjust z at centre of print circle so that it just touches the plate, which can be completely automatic under firmware/programme control. As a check, Move up 5, and down 4 several times, then move down to just contact the plate again, and make sure that the Z distance has not changed and the contact between the hot end and the plate happens at the same position. That's the Z max less the thickness of the calibration plate determined. There might be some upper X Y & Z implications in here if they are significantly off position, maybe there's a case for having a centre spot on the lower sensor that would determine if the hot end was correctly finding the middle of the printing area accurately, or if there was/is an upper sensor calibration issue. Going back to the days of mechanical computer printers, (yeah I AM that old), the lateral position was determined by driving right till it stalled, and then drive left to the zero position, not using steppers it's true, but I'm sure a similar concept could work, the XY&Z could be set maybe 5 steps from the end of track, so when end of track is sensed, drive at slow and low power to the upper mechanical limit, and then back 20 steps to make sure the sensor is in the right place, and then the lower calibration has a chance of being somewhere close to where it should be.
Then, move out of the centre, and calibrate on the 3 tower axes, first to see if the plate is level, and then to see if the mechanical movements are accurate, for all 3 towers, and then if we want to get really fancy, at the mid points between each tower.
I don't have the beginnings of a clue which parameters would have to be adjusted within the firmware to save the corrections, or even if the firmware as presently constructed would be capable of holding and using these corrections, but the beauty of this concept (I think) is that it's repeatable, and checkable, and can be re run at any time if anything changes, even as a check of accuracy or belt wear or whatever, and the only change after the calibration has been run is to change the overall Z depth to take out the thickness of the plate used for calibrating. Another option would be a second piece of glass with tin foil stuck carefully to one side so that it will provide a smooth surface for calibrating.
The same concept could work with using a piece of paper on a go no go method, but that would require a lot more user intervention to step down till it jams at each location, if it could be done with the hot end effectively making the circuit to the plate, the programme itself should be capable of determining the correction information, which can then be fed into the system, if it can't be captured automatically, which might be the case if the data transfer system is one way, which it may well be.
Am I missing something, or would this be another way to get the delta side of things set up for accurate printing with very little user intervention?
I will be travelling this route very soon, the order for the parts is in, and the hotend will be ready in a few days, so I'm motivated to get my printer working reliably and accurately as quickly as possible, I'd like to use my grey matter before i hit snags where ever possible, rather than having to spend time working out if I even have an issue that needs solving
Steve
Working from the premise that the bed is a piece of aluminium or ply, with a heater of some sort on it, and then a sheet of "suitable" float glass clip mounted on that, if I read it correctly, the object of the exercise is to then use a levelling system to determine if the hot end is travelling at the correct height above the glass to successfully deposit the print across the printing area.
So, why are we not using the brass nozzle of the hot end as the sensor, using an electronic return capability from the print bed, which in simplest form is a piece of aluminium of known thickness placed on top of the glass. The float glass is level, so the intention is to adjust the glass level so that the hot end is the same height above the bed across all of the print area, which initially is a calibration issue that may require adjusting the bed position using levelling screws, and then after checking the zero position has not moved, it is then a mechanical issue related to the design of the device, so tweaks are used in the firmware to get the head to move accurately above the surface.
So, how about if the piece of loose plate is one side of a circuit on the RAMPS, or similar, and the calibration sequence goes something like turn hot end off, etc, and then adjust z at centre of print circle so that it just touches the plate, which can be completely automatic under firmware/programme control. As a check, Move up 5, and down 4 several times, then move down to just contact the plate again, and make sure that the Z distance has not changed and the contact between the hot end and the plate happens at the same position. That's the Z max less the thickness of the calibration plate determined. There might be some upper X Y & Z implications in here if they are significantly off position, maybe there's a case for having a centre spot on the lower sensor that would determine if the hot end was correctly finding the middle of the printing area accurately, or if there was/is an upper sensor calibration issue. Going back to the days of mechanical computer printers, (yeah I AM that old), the lateral position was determined by driving right till it stalled, and then drive left to the zero position, not using steppers it's true, but I'm sure a similar concept could work, the XY&Z could be set maybe 5 steps from the end of track, so when end of track is sensed, drive at slow and low power to the upper mechanical limit, and then back 20 steps to make sure the sensor is in the right place, and then the lower calibration has a chance of being somewhere close to where it should be.
Then, move out of the centre, and calibrate on the 3 tower axes, first to see if the plate is level, and then to see if the mechanical movements are accurate, for all 3 towers, and then if we want to get really fancy, at the mid points between each tower.
I don't have the beginnings of a clue which parameters would have to be adjusted within the firmware to save the corrections, or even if the firmware as presently constructed would be capable of holding and using these corrections, but the beauty of this concept (I think) is that it's repeatable, and checkable, and can be re run at any time if anything changes, even as a check of accuracy or belt wear or whatever, and the only change after the calibration has been run is to change the overall Z depth to take out the thickness of the plate used for calibrating. Another option would be a second piece of glass with tin foil stuck carefully to one side so that it will provide a smooth surface for calibrating.
The same concept could work with using a piece of paper on a go no go method, but that would require a lot more user intervention to step down till it jams at each location, if it could be done with the hot end effectively making the circuit to the plate, the programme itself should be capable of determining the correction information, which can then be fed into the system, if it can't be captured automatically, which might be the case if the data transfer system is one way, which it may well be.
Am I missing something, or would this be another way to get the delta side of things set up for accurate printing with very little user intervention?
I will be travelling this route very soon, the order for the parts is in, and the hotend will be ready in a few days, so I'm motivated to get my printer working reliably and accurately as quickly as possible, I'd like to use my grey matter before i hit snags where ever possible, rather than having to spend time working out if I even have an issue that needs solving
Steve