SINUMERIK 840C TEA File Transfer: Cloning for 1:1 CNC Machines

Overview: When a Backup File Becomes a Liability

Two Hyundai HIT18S lathes, mechanically and electrically identical (a "1:1" pair), sit on a shop floor. One runs perfectly on its original SINUMERIK 840C control; the other has been chasing alarms that look suspiciously like corrupted compensation or tool data. The temptation is to pull the working machine's .TEA file and drop it onto the sick one. In principle this is supported on a 1:1 configuration. In practice it is a procedure with several pitfalls, and the field experience distilled below is intentionally conservative: confirm with the machine builder (Hyundai) before any cross-load, and treat every step below as a procedure to be executed with the original control on standby in case the target control refuses to boot after the transfer.

The information in this article is anchored against the official SINUMERIK 840C Programming Guide (Software Version 2, 3, 4, 5 and 6, Edition 09.2001) from Siemens Industry Online Support, plus field reports from technicians who have physically executed the procedure on Hyundai HIT-series machines. Where the Siemens documentation and field practice diverge, the field practice is called out explicitly.

What the TEA File Actually Contains

On the SINUMERIK 840C, files with the .TEA extension belong to the family of tool/zero-point compensation records. They are not the part program (which lives under .MPF / .SPF), nor the machine data (which is held in .TEA-class records only after an explicit data-class export on some SW versions — see "Ambiguity Note" below).

Prerequisites Before You Move a Single Byte

Three prerequisites must be satisfied before any cable is plugged in. Skip any of them and the most likely outcome is a control that refuses to load the file and emits alarms on the next reset.

1. Confirm 1:1 mechanical and electrical identity. The two Hyundai HIT18S lathes must share the same spindle motor, feed drives, axis configuration, and option-bit set. Hyundai's machine serial number plate and the option sticker on the 840C NCU should be compared. If one machine has an optional steady-rest encoder or tailstock probe that the other lacks, the cloned TEA file will reference non-existent hardware.
2. Confirm matching software versions. Both 840C controls should report the same NC software version (e.g. SW 4.x, SW 5.x, SW 6.x per the Programming Guide edition coverage). Mixed-version cloning can be performed in some cases (e.g. SW 5 to SW 6) only when the higher-version control has been commissioned for downward compatibility — this is not automatic.
3. Take a full backup of the target control before loading the donor file. If the transfer bricks the TEA loader, you need the original to revert. Use whichever interface you plan to use for the transfer to dump the target's current data first.

Hardware You Will Need

Method A — Parallel Cable + FX Software (Field-Confirmed)

The parallel method is the only one in the source material that an end-user has confirmed executing successfully. The procedure below generalises from that report and from the 840C Programming Guide data-handling chapters.

Step-by-step procedure

1. Power down both controls. Cycle the donor machine to OFF, wait 30 seconds for the NCU to discharge, then power it ON to standby (no NC Start). The receiving machine remains powered down.
2. Connect the parallel cable between the PC running FX and the 840C's parallel port (typically the X121/X122 port on the operator panel backplane — verify against the machine-specific wiring diagram; Hyundai HIT18S varies by build year).
3. Boot FX in service mode and select the source control profile (HIT18S, NC SW version reported by the donor 840C).
4. Issue a backup read of the donor control. In FX this is the Data In/Out → Backup → Read NC path. Capture the full backup, not just the .TEA you suspect — the TEA file references MD numbers whose context only exists in the full backup.
5. Visually verify the captured backup contains the expected .TEA entry and that the file size is non-zero. A zero-byte .TEA is a sign the source control could not enumerate the data class — abort the transfer and re-examine the source.
6. Power up the receiving machine to standby. Connect the parallel cable to the receiving 840C's matching port.
7. Issue a restore write to the receiving control. In FX: Data In/Out → Restore → Write NC. Monitor the progress bar — a typical full NC restore on a 840C takes 4–8 minutes over parallel; abort if no progress registers within 90 seconds.
8. When the restore reports success, do NOT NC-Start. Power-cycle the receiving control (OFF, count to 30, ON to standby) so the new data is read from non-volatile storage on the cold boot path.
9. Enter the 840C's commissioning menu and verify the option-bit set matches the machine serial plate. Any mismatch here is the most common cause of post-restore alarms.
10. Run a dry-cycle in JOG through all axes to confirm referencing, then MDI a no-cut spindle rotation before any production G-code is loaded.

Verification checklist (parallel method)

Method B — Serial Cable + PCWIN (Reported, Not Field-Confirmed in Source)

The serial method using PCWIN (the older Siemens DOS-based PC-side counterpart to FX) was mentioned in the field report but not personally tested by the participants. Treat the procedure below as a synthesised procedure consistent with the 840C Programming Guide's data-transfer chapters; verify each step against the specific SW version of the target control before relying on it.

Step-by-step procedure

1. Identify the 840C's serial port configuration. From the HMI: Commissioning → Serial Interface. Note baud rate, parity, data bits, stop bits, and X-on/X-off vs. RTS/CTS handshaking. Typical 840C default is 9600,8,N,1 with X-on/X-off.
2. Match PCWIN COM-port settings to the 840C exactly. Mismatched handshake is the single most common cause of "PCWIN connects, transfer starts, then stalls at 0%" failures.
3. Connect a null-modem RS-232 cable between the PC's COM port and the 840C's serial port (typically X101 or X102 on the operator panel). The cable must be a null modem, not a straight-through — pins 2/3 crossed, 4/5 crossed, 6/20 crossed on a DB25 implementation.
4. On the 840C, initiate the send side. In Data In/Out → Send, select the .TEA file (or the full backup if available). The 840C will print READY on its serial port and wait for the PC handshake.
5. In PCWIN, issue Receive NC Data. The transfer runs at the negotiated baud rate; at 9600 baud a full NC backup is ~25–35 minutes, so plan around production.
6. On the receiving machine, repeat the steps above but with Data In/Out → Receive on the 840C and Send NC Data in PCWIN.
7. Cold-boot the receiver exactly as in Method A, step 8.

Method C — Floppy Transfer (No PC Required)

If neither a parallel nor a serial-equipped PC is on hand, the 840C's built-in floppy drive (when fitted) can move individual .TEA files. This is the cleanest method for a TEA-only transfer because it bypasses any PC-side tool version skew.

1. Insert a DOS-formatted DSHD floppy in the donor 840C's drive.
2. HMI: Data In/Out → Floppy → Read Out. Select the .TEA file.
3. Verify on the HMI file browser that the file landed on the floppy with the expected size.
4. Move the floppy to the receiving machine. Data In/Out → Floppy → Read In.
5. Confirm overwrite prompt; then cold-boot.

Post-Transfer Alarm Conditions

Troubleshooting Matrix

Field-Proven Caveats Specific to the Hyundai HIT18S

The Hyundai HIT18S uses a Hyundai-specific option-bit set layered on top of the standard 840C option bits. When a donor file is loaded onto a receiver, the receiver's option-bit set must be re-asserted via the Hyundai commissioning procedure before the loaded TEA will be honoured. This is a documented Hyundai step, not a Siemens step, and skipping it is the single most common reason "the file loaded fine but nothing works" outcomes are reported in the field.

A second caveat: the HIT18S uses a tailstock that, on some build years, is monitored through an auxiliary encoder that registers in the TEA bundle. If the receiver does not have the same tailstock option, the encoder address will point to a non-existent module and the 840C will refuse to come out of standby on the first reference attempt.

Pre-Transfer Documentation You Should Capture

Before initiating any transfer, snapshot the following on both machines. If the transfer fails irrecoverably, this snapshot is your rollback path.

• NC software version displayed at boot
• PLC software version (from Commissioning → PLC → Version)
• Drive firmware versions for every axis and spindle
• Active option-bit set as a printed HMI screenshot
• Full tool list with D-offsets and H-numbers
• Zero-point (G54–G59) shift values
• Saved compensation tables (pitch, sag, backlash)
• Current MD dump, exported to floppy

Frequently Asked Questions