230-0482

Power down and disconnect handwheel

Set NC STOP, power off TNC control, and carefully disconnect the handwheel cable from the HR port.

Always power down completely before disconnecting handwheel cables to prevent damage to TNC inputs.

Disassemble handwheel housing

Remove the handwheel cover screws and carefully separate the housing to access the internal rotary encoder assembly.

Take photos before disassembly to ensure proper reassembly of encoder positioning.

Clean encoder components

Use lint-free cloth with isopropyl alcohol to clean the encoder disc, LED, and photodiode surfaces. Ensure no residue remains on optical surfaces.

Do not use compressed air which can drive contaminants deeper into encoder assembly.

Reassemble and test

Reassemble handwheel, reconnect to TNC, power up and test handwheel operation in MOD 1 (Manual) mode to verify alarm clearance.

Visual inspection of encoder disc

With handwheel disassembled, inspect the encoder disc for cracks, scratches, or missing segments that would interrupt optical signal transmission.

Use a magnifying glass to detect hairline cracks that may not be visible to naked eye.

Test LED and photodiode function

Using a multimeter, verify LED illumination and photodiode response. LED should show forward voltage drop of ~1.7V, photodiode should show resistance change with light blocking.

Use appropriate current limiting when testing LED to prevent damage.

Replace damaged components

If encoder disc is damaged, replace entire encoder assembly. If LED/photodiode failed, replace individual components maintaining exact positioning.

Order genuine Heidenhain encoder parts using the handwheel model number for proper signal compatibility.

Calibrate encoder alignment

Ensure proper air gap (typically 0.5-1.0mm) between encoder disc and optical components before final assembly.

Inspect handwheel cable connections

Check connector at handwheel end and HR input on TNC for corrosion, bent pins, or loose connections. Verify proper seating of all connections.

Wiggle cable while monitoring for alarm to identify intermittent connection issues.

Clean connector contacts

Use contact cleaner and fine brush to clean all connector pins and sockets. Apply thin coat of dielectric grease to prevent future corrosion.

Ensure complete drying of contact cleaner before reconnection to prevent short circuits.

Check cable continuity

Using multimeter, verify continuity of all conductors in handwheel cable from handwheel connector to TNC HR input pins.

Refer to TNC installation manual for proper HR connector pinout for your specific handwheel model.

Secure connections and test

Ensure all connections are tight, properly seated, and strain reliefs are secure. Test handwheel operation through full range of motion.

Access handwheel parameters

Enter MOD 2 (Machine Parameters), navigate to handwheel configuration section (typically MP7xxx series parameters).

Document current parameter values before making changes for easy restoration if needed.

Verify handwheel type setting

Check parameter for handwheel %3 type matches actual handwheel model (HR410, HR420, etc.). Verify encoder resolution parameter matches handwheel specifications.

Incorrect handwheel type parameters can cause permanent damage to handwheel electronics.

Reset handwheel parameters

If parameters are incorrect, set to proper values per handwheel documentation, save parameters, and perform TNC restart to initialize new settings.

Consult TNC parameter manual for your specific control version as parameter numbers may vary between TNC models.