Improved z axis precision by means of a 1:3 gearing. Moves the stepper from the bottom of the printer to the top. Thus, some adjustments have to be made. See instructions below!
The stock M8 screw might not be long enough for this part to fit to your printer!
Adjustment settings for the new Z-axis ratio
These are instructions for the stock Marlin firmware shipped with the K8200:
- you need to swap two of the four phases of the z-stepper to reverse the rotation:
- swap pins 1 & 2 or 3 & 4 of the z-stepper connector on the controller board
- do not swap pins 2 & 3 or 1 & 4 as this will not work
- depending on which z-arbor you have (vanilla M8x1.25 or improved TR8x1.5) change the following z-steps per mm settings (Marlin g-code):
- change stepping:
- for M8x1.25 => 7680 steps per mm z-lift:
- for TR8x1.5 => 6400 steps per mm z-lift:
- store in EEPROM
- Test these settings!
- check whether Z moves into the correct direction
- if Z moves into the wrong direction, manually press the Z-stop button to emergency stop it!
- check whether Z moves the correct distance
- placing a digital calipper between the z-arm and the top frame crossbeam and zeroing it in place should work just fine but be careful not to drive Z into the limits of the calipper!
- check whether homing Z still works; you shouldn't need to readjust Z axis.
Other things to note...
You likely need to extend the z-stepper cable... but I guess since you've already successfully built that K8200 printer you should be able to do this without any further instructions.
Oh, I forgot to mention: it requires the Z-arbor to stick out long enough at the top of the printer. With the stock M8 screw this might not work. Since I have replaced it with a TR8x1.5 of 500mm length, what sticks out at the top is more than enough to mount the large cog to the screw.