The bed at its home position should be level with the nozzle. Setting the Bed Home position:
- Press the home all axis button in Pronterface,
- Press the Motors Off button
- Physically move the head and gantry assembly around the bed to make sure it just clears the surface and the nozzle does not dig into the tape on the bed surface.
If the bed is too high adjust the Z limit switch screw up. If the bed it too low adjust the Z limit switch screw down. One full turn of the screw is 0.8mm so only small adjustments of 1/8-1/16 of a revolution will be necessary as you get close to the correct bed height. After adjusting the limit switch screw be sure to move the bed down and fully away from the limit switch before rehoming the bed.
- Bed too close- The filament sticks to the bed and the bead of plastic pushes up around the nozzle to form ridges and an uneven surface.
- Too far away – plastic does not stick to the bed and forms more of a cylinder
- Just the right height – Plastic is extruded and pushed against the bed and sticks in place. The result is an oval shaped bead with a flat top and flat bottom with curved sides.
The final check the bed's home position is to print part of the first layer of your object, stop the print and peel that first layer off and measure it. If your slicer is set to 0.3127mm for the first layer it is OK to get a measurement of 0.3-0.35mm. If it is much thicker than you should adjust the Z limit switch screw a very small amount and rehome the Z axis. Repeat the test until you achieve the correct first layer height.