MINI+: wrong first layer height, Live Adjust Z at its limit or Z rises while leveling (SuperPINDA)

Symptom

On the MINI+ the first layer is too high or too squished, Live Adjust Z reaches -2.000 and the nozzle is still too far away, or during homing or mesh bed leveling the Z axis suddenly moves up, sometimes several times, before coming down.

Likely causes, from most to least likely

1. The first layer calibration has not been done or does not match the current sheet or nozzle (nozzle change, extruder or axis changes, or the printer was moved).
2. The SuperPINDA (or M.I.N.D.A.) sits too low in its holder, so the Live Adjust Z range is not enough to bring the nozzle close.
3. The sensor or its cable fails intermittently (the cable can be damaged by overtightened cable ties), which makes the Z axis rise during leveling.

Checks to tell which one it is

• Check the Live Adjust Z value: Prusa quotes -0.400 to -1.900 as a common range; if you reach -2.000 and the nozzle is still not close enough, the sensor is too low.
• Raise Z about 10 cm, open Info → Sensor info and look at M.I.N.D.A.: it must read 0 with the red LED on and change to 1, with the LED off, when you put a thin metal object underneath.
• With the metal object underneath, move the X axis from side to side while wiggling the cable wrap: the value must stay at 1 and the LED off.

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Calibrate the first layer

   Start Control → Calibrations & Tests → First Layer calibration. Turn the knob counter-clockwise to bring the nozzle closer (more negative values) until the lines are slightly flattened. If you have several sheets, store a calibration for each one in the steel sheet profiles (Steel sheets).

   Check: The surface is even, with no gaps or ridges between lines.

   If that does not fix it: During a print you can fine-tune with Control → Live Adjust Z; on the MINI+ that value is kept for later prints.

2. Raise the sensor if you reach -2.000

   With the printer off and cold, loosen the sensor holder screw, raise the sensor slightly (0.5 to 1 mm, according to Prusa), tighten the screw again and repeat the first layer calibration starting from zero.

   Check: The calibration gives a correct first layer without reaching the limit.

   If that does not fix it: If the value is still odd or changes from one time to the next, test the sensor (next step).

3. Test the sensor and its cable

   Do the metal object test in Info → Sensor info while moving the X axis and wiggling the cable wrap. Check that no cable tie squeezes the sensor cable too hard.

   Check: Neither the value nor the LED flickers anywhere along the travel.

   If that does not fix it: If it flickers or Z still rises during leveling, the sensor or the cable is damaged: replace it following Prusa's guide or contact their support.

Prevention

• Repeat the first layer calibration after changing the nozzle, modifying the extruder or an axis, or moving the printer.
• Use a steel sheet profile for each sheet, because their thickness differs.
• Do not overtighten the cable ties on the sensor cable.

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Printers it applies to

The Prusa MINI family: MINI+.

Official sources

This guide summarises the official documentation linked here:

• First Layer Calibration (MINI/MINI+) · Prusa Research
• M.I.N.D.A./SuperPINDA sensor testing (MINI/MINI+) · Prusa Research
• LCD menu (MINI/MINI+) · Prusa Research
• Live adjust Z · Prusa Research