J1/J1s: the two print heads do not line up or bed calibration fails

Symptom

On a Snapmaker J1 or J1s, the layers of the two materials are shifted relative to each other, or calibration fails: the bed keeps rising and the nozzle presses into it, calibration fails without the nozzle ever touching the bed, or the bed drops intermittently during the process.

Likely causes, from most to least likely

1. The XY offset between the two extruders has not been calibrated, or a hot end was replaced without redoing bed levelling and the XY and Z offset calibrations.
2. Material left on the nozzle, or filament loaded during calibration, distorting the contact.
3. If the nozzle presses into the bed: there is no continuity between the hot end probe signal and the nozzle, often because of too much blue threadlocker on the hot end board screws (conduction goes through them).
4. The print head flat cable (FFC) is bent or damaged, or its connection to the board is loose or skewed.
5. If it fails without touching the bed: the black fan wire of the left hot end (or the right one, if the bed also drops) is worn or pressed against the casing, or that hot end's PT100 sensor is damaged.

Checks to tell which one it is

• Watch the calibration: does the nozzle press into the bed, fail without touching the gold pads on the bed, or does the bed drop intermittently? Each case points to a different cause.
• With the printer off, use a multimeter in continuity mode between the first pin of the hot end board (the probe signal) and the heater block.
• Check the FFC flat cable: not bent, and seated straight and firmly in its connector.
• Think back to whether you replaced or reinstalled a hot end since the last calibration.

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. Clean and unload before calibrating

   Unload the filament from both extruders and remove any material from the nozzles, taking care if they are hot. Snapmaker recommends calibrating with no filament loaded.

   Check: The nozzles are clean before you start.

   If that does not fix it: Repeat the calibration; if the nozzle presses into the bed, check the hot end continuity (next step).

2. Hot end continuity

   Switch off and unplug. Set the multimeter to continuity, black probe on the first pin of the hot end board and red probe on the heater block. If there is no continuity, loosen the two lower hot end board screws, remove the excess blue threadlocker and tighten them again; measure once more.

   Check: There is continuity between the signal pin and the heater block.

   If that does not fix it: If there was continuity already, the hot end is not the problem: check the FFC cable (next step).

3. Check the FFC cable

   With the printer off, check that the FFC flat cable is not bent or damaged and that its connection to the board is not loose or skewed; reconnect it perfectly straight.

   Check: Calibration completes and the nozzle stops when it touches the bed.

   If that does not fix it: Contact Snapmaker support with photos or videos of what you have tried.

4. Fails without touching the bed

   With the printer off, check the black fan wire of the left hot end; if the bed was also dropping, check the right one. If the insulation is worn or the wire is pressed down and touches the casing, it can trigger the signal before the nozzle touches the bed.

   Check: The wire is intact and does not touch the casing, and the nozzle reaches the bed pads.

   If that does not fix it: If the wire is damaged, or it is fine but the fault continues (it may be that hot end's PT100 sensor), contact Snapmaker support.

5. Redo levelling and offsets

   After replacing a hot end, or if the materials come out shifted, redo from the Calibration menu the heated bed levelling (Heated Bed Leveling) and the Z and XY offset calibrations. For the XY offset: Calibration → XY Offset Calibration → Start; both extruders touch the bed in turn and the machine calculates the offset.

   Check: All calibrations finish without errors.

   If that does not fix it: Check the result with the verification model (next step).

6. Check the result

   Run Calibration Check → Start, follow the screen and inspect the verification model the machine prints.

   Check: The verification model shows no shift between materials.

   If that does not fix it: Repeat the calibrations; if the offset persists, contact Snapmaker support.

Prevention

• Always calibrate with clean nozzles and no filament loaded.
• When you replace a hot end, redo bed levelling and the XY and Z offset calibrations before printing.
• Handle the FFC flat cable carefully when working on the print head: do not bend it.

Still not fixed?

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Printers it applies to

The Snapmaker J1 family: J1s.

Official sources

This guide summarises the official documentation linked here:

• How to resolve J1(s) heated bed calibration failures · Snapmaker
• XY offset calibration (J1/J1s) · Snapmaker
• Replacing the hot end (J1/J1s) · Snapmaker
• Calibration check (J1/J1s) · Snapmaker