Diagnose the Program-Start Position Error
The reported Fanuc 6M installation could run programs safely only after returning the machine to its reference position. The available evidence points to the operator-panel ABS/INC or Manual/Absolute toggle: its position determines whether the control tracks position changes made during manual jogging. On this machine, changing that toggle resolved the problem.
Do not assume the correct physical switch direction from the label alone. Machine-tool builders may implement this function differently, so prove its behavior with a controlled positioning test before running a production program.
Test Whether Manual Motion Is Tracked
- Move to a clear test area and use MDI to command
G00 G90 X0 Y0. - Record or mark the resulting machine position.
- Jog away from that position manually.
- Run the same MDI command again:
G00 G90 X0 Y0. - If the machine returns to the original point, the ABS/INC or Manual/Absolute switch is in the required tracking state. If it does not, change the switch position and repeat the test with adequate clearance.
This test directly checks the behavior that matters: whether manual jogging changes the control's retained absolute position. Keep rapid motion clear of fixtures, tools, and stock during the test.
Verify Work and Tool Offsets
| Program element | Evidence-supported check | Risk if incorrect |
|---|---|---|
G54 |
Confirm that its X and Y values contain the intended work offset. The reported setup kept G54 Z at zero. | An absent or incorrect work offset can send X or Y toward an unintended location. |
G43 H1 |
Confirm that the tool-offset page contains the intended H1 value. The reported machine used negative H values. | An incorrect tool-length value can produce unintended Z motion. |
G90 |
Confirm absolute programming before the first positioned move. | An unintended positioning mode changes how commanded coordinates are interpreted. |
G91 G28 |
The supplied ending sequence used incremental mode with G28 for the return moves. | Changing the mode or return sequence without proving it can alter the machine path. |
The reported offset conventions are machine-specific observations, not universal Fanuc 6M requirements. Verify the active work coordinate, tool-length sign convention, and clearances on the actual machine before cycle start.
Determine Whether DNC Is Available
The machine could send and receive programs through its PC connection, but the evidence does not establish that it supports DNC execution. One suggestion mentions changing an unspecified setting-page parameter and running in tape mode, but no parameter identifier, option status, interface configuration, or verified procedure is provided. Do not change an unidentified parameter.
Confirm DNC capability from the machine's option documentation, parameter records, and available operating modes. Existing RS-232 transfer proves communications capability only; it does not, by itself, prove that the control can execute a program continuously from the external source.
FAQ
Why does a Fanuc 6M program start from the wrong position after jogging?
The ABS/INC or Manual/Absolute toggle may be set so the control does not retain manual position shifts as expected. Test it by commanding G00 G90 X0 Y0, jogging away, and commanding the same block again.
What offsets should I check before starting this Fanuc 6M program?
Verify the X and Y entries in G54 and the tool-length value selected by G43 H1. The reported installation used G54 Z equal to zero and negative H values, but those conventions must be confirmed on the specific machine.
Does RS-232 program transfer prove that a Fanuc 6M supports DNC?
No. Sending and receiving programs confirms serial transfer, but the evidence does not confirm DNC execution; verify the installed option, operating mode, documentation, and parameter record without changing unidentified parameters.
