automatic z height detection

Weedz

Hi

i have just installed z probing to my printer and if i understand correctly the firmware needs a starting point to make the probing and starts from the height the bed is at that moment. 

isnt it possible to set the printers x and y coordinate to the middle of the bed and make a first probe and calculate everything else from that first start probe? i think that is the way marlin does it

btw i use a cartesian printer wich need to be calibrated every time because i take the top part of my heatbed to remove the print.

Repetier

With automatic bed leveing your z home position is at top. So after homing you have a working coordinate system. The error is small enough to stop shortly above the bed. Version 0.92 will go down on it's own if you are starting too high.

Depending on printer it might by easier to skip z homing and do a z-probe like you described. On other printers that may damage your z probe if you start too low because activating z probe is not possible at starting height.

You can use G30 to set Z by a single probing at your current position. So you can achieve your propsed behaviour by

G28 X0 Y0 ; Needed for correct positioning

G1 X100 Y100 F2000 ; Center position

G30 ; replace Z homing by probing

G32 ; Recompute rotation matrix

Weedz

Yeah ok I understand what you mean..... if you would have a retractable sensor with a servo you could have that problem. I have a inductive sensor so I wouldnt have that problem. Is it an option to add in the firmware maybe or is it too niche ?

I will try your solution opted and check if that works

Different question but in the line of the same as the above. Is it possible to make a grid scan? and use that as leveling compensation. I can see some movies about it on Delta printers wit Repetier but not Cartesian printers. Is it possible to make a height mapping?

Repetier

While you can make a height map with the host, the autocorrection based on stored heigt map only works for deltas. That has to do with long lines. Deltas split them into short, which is needed to follow bumps. Cartesians insert them as more efficient long lines but that makes it impossible to follow bumps. So until we start splitting cartesian moves that would not fully help.