Z-Probe Issues

This guide helps you diagnose and fix Z-Probe problems on the Vision Miner 22IDEX V4. Z-Probe issues fall into two categories:

• Mechanical — the probe does not physically reach the dock station at the back of the machine, or the servo angle is wrong. This is solved by running the Probe Calibration macro, which adjusts the X pickup position and the servo angle. See the Z-Probe Calibration Guide for the full procedure.
• Electrical — the probe circuit has a short or open circuit, and the printer cannot detect the probe correctly. This guide walks you through the built-in self-test and manual troubleshooting for electrical issues.

Start here: if you are not sure whether your problem is mechanical or electrical, run the Z - Probe Test macro first (see 1. Running the Z-Probe Self-Test below). It will tell you exactly what is wrong.

Tools and Materials

• Something conductive — a screwdriver, hex wrench, or a short piece of wire (for the nozzle-to-bed contact test)
• Multimeter (optional — for advanced continuity checks)
• Clean cloth — for wiping magnets
• 2mm HEX - Wera Screw Driver (hex wrench) — checking magnet seating
• 2.5mm HEX - Wera Screw Driver (hex wrench) — magnet contact bypass test (included with the printer)

Z-Probe Working Principles

The Z-Probe system has three components:

1. Two magnets on the Tool 0 (T0) toolhead — these are the contact points that connect to the probe.
2. The Z-Probe body — a mechanical switch with its own pair of magnets. It sits in the dock station at the back of the machine.
3. The optocoupler PCB — a small circuit board mounted at the back of the machine, near the dock. It controls when the probe circuit is active and reports the probe state to the mainboard.

How the circuit works:

1. Circuit activation. The optocoupler PCB enables current flow between the toolhead magnets only when needed — during auto-calibration or Z-homing. The rest of the time, the circuit stays disabled for ESD protection.
2. Normally closed switch. The Z-Probe contains a normally closed switch. When attached to the toolhead and not triggered, current flows through it, completing the circuit.
3. Trigger detection. When the probe's plunger contacts the build plate, the switch opens and breaks the current. The firmware detects this change and registers the Z-height.

LED Indicators

The optocoupler PCB at the back of the machine has two LEDs that show the probe state in real time.

🟢 Green LED — Circuit Enabled

• On when the firmware activates the probe detection circuit (during homing or probing).
• Off at all other times.

🔵 Blue LED — Probe Detected

• On when the Z-Probe is attached to the toolhead and the internal switch is closed (not triggered).
• Off when the probe is triggered (plunger pressed), or when the probe is not attached.

Web Interface Monitoring

Check the probe value in the Web Interface under Machine Status or General:

• 1000 — probe detached, triggered, or circuit disabled (open circuit)
• 0 — probe attached and not triggered (closed circuit)

1. Running the Z-Probe Self-Test

The printer has a built-in self-test macro that checks every part of the Z-Probe circuit step by step. Run this first — it takes a couple of minutes and tells you exactly where the problem is.

To launch the test: open the Web Interface → Macros → System → Troubleshooting → Z - Probe Test.

Before starting, the macro asks you to remove the Z-Probe from the toolhead and make sure it is not attached to the magnets.

The test has four steps:

Step 1 — Open Circuit Check

The macro checks that the probe circuit reads open (value 1000) with the probe removed. If it reads 0 instead, there is a short circuit somewhere in the toolhead wiring. The test stops and tells you to check for a short.

→ If this step fails, go to 3. Short Circuit — Step 1 Failed.

Step 2 — Nozzle-to-Bed Contact (Left and Right)

The macro asks you to touch each nozzle to the build plate using something conductive — a screwdriver, hex wrench, or wire. You bridge the nozzle tip to the bed surface 5 times for each toolhead.

The LEDs on the optocoupler PCB give real-time feedback:

• 🔵 Blue = waiting for contact
• 🟢 Green = contact detected

The macro moves the build plate close to the nozzles so you can reach. If a nozzle fails, the test tells you which side has the problem — Left (T0), Right (T1), or both.

→ If this step fails, go to 4. Nozzle Contact Failed — Step 2 Failed.

Step 3 — Probe Attachment Detection

The macro asks you to attach the Z-Probe to the toolhead magnets. It waits up to 60 seconds for the probe to be detected (value changes from 1000 to 0).

→ If this step fails, go to 5. Probe Not Detected — Step 3 Failed.

Step 4 — Probe Click Test

With the probe attached, the macro asks you to press the probe plunger 5 times. Each press should break the circuit (value goes from 0 to 1000) and register as a click.

→ If this step fails, go to 6. Probe Click Failed — Step 4 Failed.

Test Summary

At the end, the macro shows a summary of all four steps:

If all four steps pass, the electrical circuit is working correctly. If your probe still fails to pick up or place, the problem is likely a pickup position or servo angle issue — see 2. Probe Pickup and Placement Issues below.

2. Probe Pickup and Placement Issues

If the self-test passes (all four steps green) but the probe still fails during auto-calibration or Z-homing, the pickup position or servo angle needs recalibration.

Symptoms:

• The probe does not get picked up — the toolhead does not reach the dock station at the back of the machine.
• The servo rotates to the wrong angle and the probe cannot be grabbed.
• The probe gets knocked off during placement.
• Error message: "Probe was not detected at the dock after placing"

Solution: Run the Probe Calibration macro (Macros → System → Calibration → Z Probe → Probe Calibration in the Web Interface). The macro walks you through adjusting the X pickup position and the servo angle — it only takes a few minutes. See the Z-Probe Calibration Guide for the full procedure.

Before running calibration, also check:

• Clear any filament strands, debris, or tools from the dock area and the pickup path.
• Verify the dock is securely mounted and has not shifted.

3. Short Circuit — Step 1 Failed

What happened: The probe circuit reads as closed (value 0) even though the probe is physically removed. Something inside the toolhead is short-circuiting the probe contacts.

Symptoms outside the test:

• The printer attempts Z-homing without picking up the probe, acting as if it is already attached.
• During Z-homing with the probe attached, the nozzle crashes into the bed — the printer cannot detect the trigger.
• 🔵 Blue LED stays on even with the probe removed.
• Web Interface probe value stuck at 0.

Work through these checks in order:

1. Check for conductive filament. Carbon-fiber-reinforced materials (CF-Nylon, CF-PEEK, CF-PAEK, CF-Ultem) are electrically conductive. Residual filament on the nozzle or toolhead magnets can bridge the contacts. Unload the filament and clean the nozzle and magnets thoroughly. Re-run the self-test. If the short circuit clears but you later get inconsistent or false probe readings, conductive residue may also be present inside the nozzle — see 7. Conductive Filament Residue — False Z-Probe Readings for the full solution.

2. Check Tool 0 grounding lug. Inspect the gold-colored grounding lug crimped to the T0 heater block. The lug and its wire must not touch the aluminum bracket that holds the belts, or any other metal part. This contact is the most common cause of the short circuit. Bend or reposition the wire to create clearance.

3. Inspect wiring. Follow the probe wires from the toolhead magnets back to the distribution block/PCB. Look for damaged insulation, pinched cables, or wear. Also check fan, temperature sensor, and heater wires — frayed insulation on any nearby wire can short to the probe circuit.

4. Check connections. Lightly tug each Z-Probe wire at the distribution block terminals. For push-in terminals (Wago blocks): press the tab, remove the wire, inspect for fraying or corrosion, reinsert firmly.

5. (Advanced) Check the PEEK interface screws. Remove the PEEK interface (the part joining the extruder motor to the hotend). The screws securing the hotend should be slightly recessed — not protruding past the mounting surface. Protruding screws can cause intermittent shorts. Check both T0 and T1.

6. If the short persists after all checks, contact support with your LED states and the self-test results.

4. Nozzle Contact Failed — Step 2 Failed

What happened: The probe circuit did not detect contact when you touched the nozzle to the build plate. The test tells you which side failed — Left (T0), Right (T1), or both.

• Both sides failed — likely a build plate wiring issue or a problem shared by both toolheads.
• One side failed — the problem is on that specific toolhead.

Work through these checks:

1. Make sure you are using something conductive. The screwdriver, wrench, or wire must be metal. Touch it firmly from the nozzle tip to the build plate surface — the contact must be solid.

2. Re-run the test. Sometimes a light touch does not register. Press firmly and hold for a moment.

3. Inspect wiring on the failed side. Trace the Z-Probe wires from the toolhead magnets to the distribution block. Check for loose, broken, or corroded connections.

4. Test with a magnet bypass. To determine whether the problem is in the toolhead wiring or the Z-Probe itself, short-circuit the two magnets on the toolhead directly with a wrench or screwdriver (lay it across both magnet contacts). If the probe value in the Web Interface changes from 1000 to 0, the toolhead wiring is fine — the problem is elsewhere. If it does not change, the toolhead wiring or magnet connections need to be reseated or repaired.

5. Check build plate wiring (if both sides failed). Follow the build plate ground wire to the distribution block and verify the connection is secure.

6. Contact support if the problem persists. Include the self-test results and which side(s) failed.

5. Probe Not Detected — Step 3 Failed

What happened: You attached the Z-Probe to the toolhead magnets, but the circuit did not detect it within the 60-second timeout. The value stayed at 1000 (open circuit).

Symptoms outside the test:

• The printer picks up the probe but does not recognize it.
• 🔵 Blue LED stays off even with the probe attached (while 🟢 Green is on during a probe attempt).
• Web Interface value stuck at 1000.
• Error messages: "Probe is not connected", "Probe not detected at start of placing"

Work through these checks:

1. Test the Z-Probe body with a multimeter. Set the multimeter to continuity mode. Place the probes on the two magnet contacts on the probe body:
   • Plunger up (not triggered): multimeter should beep (continuity — closed circuit).
   • Plunger pressed (triggered): no beep (open circuit).
   • If this fails, the Z-Probe Sensor Assembly is defective and needs replacement.

2. Test the probe mechanically. Press the plunger gently — you should hear and feel a crisp click. Mushy, sticky, or silent = faulty probe.

3. Bypass the probe — short the magnets directly. If you don't have a multimeter, re-run the self-test. When it asks you to attach the probe (Step 3), instead of attaching the probe, lay a wrench or screwdriver across both magnet contacts on the toolhead. If the value changes to 0, your toolhead wiring is good and the Z-Probe itself is faulty — replace the probe. If the value does not change, the toolhead wiring is the problem (recheck connections, reseat wires at the distribution block).

4. Clean the magnets. Wipe both the toolhead magnets and the probe body magnets with a clean, dry cloth. Remove filament residue, oil, or debris.

5. Check magnet seating. Using a 2 mm Hex screwdriver (hex wrench), gently check the tightness of the screws on the two magnets on the probe body and the two magnets on the toolhead. Loose magnets cause intermittent or failed connections.

6. Contact support if the probe is still not detected.

6. Probe Click Failed — Step 4 Failed

What happened: The probe is attached and detected (value 0), but pressing the plunger does not register. The value does not change from 0 to 1000 when clicked.

This means the internal switch in the Z-Probe is defective. The probe needs replacement.

Before replacing, double-check:

• Press the plunger firmly — you should hear a crisp click.
• If the click is mushy or silent, the switch mechanism is worn out.

Contact support to order a replacement probe.

7. Conductive Filament Residue — False Z-Probe Readings

Conductive filaments — carbon-fiber-filled (CF-Nylon, CF-PEEK, CF-PAEK, CF-Ultem), metal-filled, and ESD materials — can leave electrically conductive residue inside the nozzle after a print. When this residue melts and bridges electrical contact points during the next Z-homing or mesh compensation cycle, the printer registers false probe triggers and produces incorrect Z-height readings.

Symptoms:

• Z-probe gives inconsistent readings after printing with conductive filament.
• First layer is too high or too low despite correct calibration.
• Probe triggers at random heights during mesh compensation.
• Self-test passes but probing behavior is unreliable.

Prevention — Cold-Pull Retraction Feature

Firmware now includes a cold-pull retraction feature that runs automatically at the end of every print. When enabled, it:

1. Detects which nozzle(s) were active during the print (left, right, or both in mirror/duplicate mode).
2. Lowers the active nozzle temperature by 100 °C (minimum floor: 100 °C).
3. Waits for the nozzle(s) to reach the lower temperature.
4. Retracts 50 mm of filament total (30 mm cold-pull + the standard 20 mm retraction in end.g), pulling conductive material out of the heat zone.

This prevents conductive residue from remaining inside the nozzle between prints.

How the Feature Is Toggled

The feature is controlled by a single file on the SD card:

The feature is enabled by default in new firmware. Users only need to take action if they want to disable it or if they had previously removed the file.

You can also change the retraction mode through the Web Interface: Macros → System → Settings → Job End → Tools Unload.

The available modes are:

For conductive filament printing, select Heat Break Retract.

If the Problem Persists

If false readings continue even with cold-pull retraction enabled:

1. Perform a manual cold pull — heat the nozzle to printing temperature, insert filament, let it cool to 100–120 °C, then pull firmly to extract residue from the heat break.
2. Clean the nozzle tip and toolhead magnets with a dry cloth to remove any external residue.
3. If the nozzle is severely contaminated, consider replacing it or cleaning it with a torch (steel nozzles only — see the Nozzle Cleaning guide).
4. Re-run the Z-Probe Self-Test to verify the circuit is working correctly.
5. Contact support if the problem persists.

8. Manual Probe Diagnosis — Is It the Probe or the Circuit?

If you want to determine whether the problem is with the Z-Probe body (the mechanical switch) or the toolhead circuit (wiring, magnets, optocoupler) without running the full self-test, follow these steps.

Before starting: Enable the probe detection circuit. Open the Web Interface → Macros → System → Calibration → Z Probe → Enable Probe (or send M42 P4 S1 in the console). The 🟢 Green LED on the optocoupler PCB should turn on.

Test A — Attach the Probe

Attach the Z-Probe to the toolhead magnets. Check the probe value in the Web Interface:

• Value changes from 1000 to 0 — the circuit detects the probe. Proceed to Test B.
• Value stays at 1000 — the circuit does not detect the probe. Skip to Test C.

Test B — Click the Probe

With the probe attached and reading 0, press the probe plunger firmly. The value should change from 0 to 1000 while the plunger is pressed, and return to 0 when released.

• Value changes 0 → 1000 → 0 — the probe switch is working correctly. The problem is elsewhere (likely mechanical — see 2. Probe Pickup and Placement Issues).
• Value stays at 0 — the probe's internal switch is defective. The switch does not open the circuit when pressed. Replace the Z-Probe. Contact Vision Miner support.

Test C — Short the Toolhead Magnets

This test isolates whether the problem is in the toolhead circuit or in the Z-Probe body.

Remove the Z-Probe from the toolhead. Using the included 2.5 mm hex screwdriver, bridge the two magnet contacts on the toolhead probe holder — lay the screwdriver across both magnets so it touches each one simultaneously.

Check the probe value in the Web Interface:

• Value changes from 1000 to 0 — the toolhead circuit is working correctly. The problem is the Z-Probe body (defective switch or poor magnet contact on the probe side). Replace the Z-Probe. Contact Vision Miner support.
• Value stays at 1000 — the toolhead circuit has a problem. Check the magnet connections, wiring from the magnets to the distribution block, and the optocoupler PCB. See 4. Nozzle Contact Failed for detailed wiring inspection steps.

Useful Macros

The printer firmware includes several Z-Probe macros in the Web Interface. Here is a quick reference:

FAQ

Support

If you could not find an answer here, reach out to our support team.