Cooling fan
Common VFD, drive, UPS, and cabinet overheating failure point.
Heidenhain TNC 640 Error Codes — What They Mean
The Heidenhain TNC 640 is a premium CNC control used on advanced 5-axis milling and mill-turn platforms. Heidenhain alarms are highly specific, but they still fall into a few broad categories: axis referencing, encoder feedback, drive faults, PLC/safety faults, and program logic problems. The exact alarm text on screen matters as much as the number.
Common Heidenhain TNC 640 Alarm Reference
| Alarm | Meaning |
|---|---|
| 100 | PLC not ready |
| 115 | Axis enable missing |
| 130 | Reference mark not found |
| 200 | Drive fault |
| 399 | Servo or drive communication issue |
| 601 | Spindle fault |
| 710 | Encoder signal fault |
| 740 | Power interruption / control voltage issue |
Common Causes by Alarm
- 100 PLC not ready — Safety chain or PLC startup issue. The control is waiting for a machine-ready signal.
- 130 reference mark — Axis has not crossed the encoder reference mark, home switch is defective, or axis movement is blocked.
- 399 drive communication — Commonly seen when a drive module loses communication or powers down unexpectedly.
- 710 encoder fault — Encoder cable damage, contamination, or failed measuring system.
- 740 power interruption — Loose control transformer connection or unstable supply.
Step-by-Step Fix
- Record the exact alarm text — Heidenhain messages are descriptive and often point directly to the subsystem.
- For 100/115 — Check safety relays, axis enable contactors, and machine-ready PLC bits.
- For 130 — Inspect reference switches and confirm axis can move freely to the reference point.
- For 399/710 — Check encoder and drive connectors for contamination and looseness.
- For 740 — Verify control voltage and inspect transformer and power supply terminals.
Parts Often Needed
| Part | Notes |
|---|---|
| Encoder cable | Common wear/failure item |
| Reference switch | For repeated homing issues |
| Control power supply | For unstable control voltage |
| Drive module | Only after connector and supply checks |
Related Resources
- Browse all CNC machine error codes — Fanuc, Haas, Mazak, Siemens, and more
- Cincinnati CNC Fault Codes — Complete Troubleshooting Guide
- CNC Alarm Reset Guide: How to Clear Alarms Safely
- CNC Machine Error Codes: Complete Troubleshooting Guide
Need Replacement Parts?
Before ordering, match the machine-control part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
The TNC 640 is usually found on expensive multi-axis equipment. Persistent drive and encoder faults should go to a Heidenhain-trained technician or the machine builder, especially if machine geometry or kinematics are involved.