EUCHNER Handheld Operating Unit and Electronic Handwheel Field Troubleshooting Guide

Mechanical determination mechanism: using a toothed rotor and roller spring structure, with 100 positioning points per turn. Lightweight structure and shallow installation depth. Representative models: HWA (center fixed), HWB (three-point fixed). The packaging is usually in units of 10 or 5 pieces (model suffix/V10,/V05).

Both methods have a pulse count of 100 or 25 per cycle (two channels output orthogonally and can be multiplied). The output circuit can choose RS422 differential signal (A,/A, B,/B, suitable for Siemens system) or push-pull output (A, B, suitable for Fanuc system).

Chapter 2 Common Fault Phenomena and Systematic Diagnosis

2.1 Handheld operating unit: The whole machine has no response or some functions are missing

Phenomenon: After inserting the connector, the device cannot recognize the handheld box; Emergency stop is invalid; Enable switch has no response; The screen coordinates do not change when the handwheel rotates.

Cause investigation:

Cable problem (highest probability ≥ 70%): Spiral and direct cables are frequently bent, and the core wire breaks at the solder joint inside the plug or inside the cable. Common breakpoints are located within 150mm of the entrance at both ends of the spiral or at the plug welding point.

Oxidation or damage of plug pins: 23/26/28/35 pin circular connectors have poor contact in humid or corrosive environments.

Enable switch contact failure: After tens of thousands of presses, the contact resistance increases (normally<0.1 Ω), causing the safety circuit to fail to close.

Emergency stop button not reset: After the emergency stop button is pressed, it does not rotate to reset, and the internal normally closed contacts are still disconnected.

Diagnostic steps:

Measure the pins corresponding to key signals on the connector using a multimeter in the resistance range: emergency stop two pairs of normally closed contacts (should be<0.5 Ω), handwheel power supply 5V and 0V (no short circuit). Measure the resistance of the wires inside the spiral. If any wire is disconnected, it is considered a broken wire.

Swap and test the handheld box with similar devices that are working normally to quickly isolate faults.

If the enable switch is pressed to the second position and no 24V signal (or 0V change) is measured on the corresponding pin, then disassemble the housing (professional tools are required) to check the switch contacts.

2.2 Unstable Handwheel Pulse Output or Incorrect Counting Direction

Phenomenon: When the handwheel rotates, the machine axis moves discontinuously, bounces, or moves in the opposite direction; The magnification selection switch gear is invalid.

Reason:

The magnetic steel of the magnetic positioning handwheel falls off (rare, but will fail after strong impact).

The handwheel output circuit is damaged (RS422 driver or push-pull output chip burned out).

Phase error or reversed wiring of A/B phase signals (confusion between A and/B, B and/A).

The input interface of the controller is not configured for differential reception or the filtering parameters do not match.

diagnosis:

Measure the output of the handwheel using an oscilloscope or multimeter in frequency range: Rotate the handwheel to generate a square wave with a phase difference of 90 ° between phases A and B. The amplitude should be 5V (RS422) or close to the power supply voltage (push-pull). If there is no signal, it indicates that the electronic components inside the handwheel are damaged.

Check encoder interface matching: Siemens CNC systems typically require RS422 differential signals (A,/A, B,/B), while Fanuc systems mostly accept push-pull signals (A, B). Mixing can lead to directional errors or loss of pulses.

Replace the handwheel unit or handwheel module of the same model (HKB/HKD can be replaced separately) for testing.

2.3 The system does not stop after pressing the emergency stop button

Phenomenon: Even after pressing the emergency stop red button, the machine tool can still move.

Severity: ★★★★★ (Safety function failure, must be stopped immediately)

Reason:

The emergency stop contact is not correctly connected to the safety circuit (normally open/normally closed reversed).

Contact sintering after long-term use (high current inductive load).

The emergency stop button does not use a "forced disconnection" structure (EUCHNER emergency stop complies with EN ISO 13850, with two pairs of normally closed contacts for positive drive inside, which theoretically will not fail). But if the external relay contacts are stuck, the power supply can still be maintained after the emergency stop is cut off.

Diagnosis and Solution:

Remove the emergency stop button module and measure the terminals with a multimeter: when released, it should be 0 Ω (normally closed), and when pressed, it should be infinite. If there is still continuity after pressing, the emergency stop module needs to be replaced (such as 096298 long, 106435 short, or 073985).

Confirm that the emergency stop signal is set as a normally closed input in the controller. If the wrong configuration is set to normally open, emergency stop cannot be detected even when disconnected.