Scripts 2, 3 and 4 take the extruder near one of the towers. The idea then is that the
height of the extruder above the bed at that point (the z-coordinate) can be adjusted by
the calibration screw on that tower, without affecting the other towers. The z-
coordinate is not set to zero in these commands, as the extruder may crash into the
bed if the calibration is not correct.
Press the home button and see that the printer homes correctly. As each carriage
moves up, check that the wires do not get caught in the limit .The next step involves
getting an idea of how far away from the bed the zero point is, then type G1 Z100 into
the G-code box and check that the extruder moves to about 100mm above the bed.
This will also confirm that the travel distances are calibrated correctly. If the printer is
still not within 20mm of where it should be, then the printer construction should be
checked again.
Try the script 2, 3 and 4 buttons and check that the extruder moves to the correct
tower- the X tower is to the left of the display, the Y tower to the right and the Z
tower to the rear.
Press Script 1 (to centre the extruder) and try the G1 command again with lower Z
values- I would try G1 Z50, then G1 Z20, G1 Z10 and G1 Z5. If the extruder is at
least that many millimetres above the bed, then try G1 Z0 to take it to its lowest point.
This will give you an idea of how much you need to adjust the calibration screws.
If you have Z=0, move it to Z=5 with G1 Z5 before running the scripts to move the
extruder across the bed, then move it back down to measure at each corner of bed.
The M3 nuts have a thread pitch of 0.5mm, so one full turn will change the calibration
by 0.5mm. For each of the three towers, if the calibration is too far above the bed,
unscrew the calibration screw. If the extruder appears to be too close to the bed, screw
the calibration screw in. Make conservative adjustments to avoid overshooting and
check each tower even if that screw has not been adjusted, as the adjustments tend to
interact slightly. About 0.5mm clearance is a good point to start doing test prints, after
which small changes can be made to the screws between prints to fine tune the
calibration.
Overview of calibration cycle:
Home printer with G28
Use G1 Z10 to move extruder down.
Press script 2 button, note clearance- if it is more than 10mm, use G1 Z0 to move to
lowest position. Note clearance and adjust tower X screw.
G1 Z10 to move extruder away from bed.
Press script 3 button, note clearance- if it is more than 10mm, use G1 Z0 to move to
lowest position. Note clearance and adjust tower Y screw.
G1 Z10 to move extruder away from bed.
Press script 4 button, note clearance- if it is more than 10mm, use G1 Z0 to move to
lowest position. Note clearance and adjust tower Z screw.
G1 Z10 to move extruder away from bed, then press script 1 to check overall
calibration. Most printing will take place in the middle of the bed, so this is important
too.
Repeat until calibration is satisfactory.
