A SKT-700L with a Fanuc 21-i control showed slow manual rapid motion even at 100% override, while programmed G00 motion was substantially faster. The reported correction involved PMC D-data bits, not a confirmed CNC inches-per-minute parameter. Treat the addresses below as machine-specific evidence: preserve the current values and obtain the machine builder's confirmation before changing them.
Separate Manual Rapid From Programmed G00
The speed difference does not prove that the programmed rapid-rate setting is incorrect. G00 and operator-commanded manual rapid can follow different control paths. First compare the 25%, 50%, and 100% manual rapid selections. If they produce the same speed, the override inputs or PMC selection logic may not be changing state.
| Observation | Supported interpretation | Next decision |
|---|---|---|
| G00 is faster than manual rapid | The programmed rapid path operates differently from the manual path. | Investigate manual rapid selection before changing the programmed rapid rate. |
| 25%, 50%, and 100% give the same manual speed | The selected override may not be reaching or changing the PMC logic. | Monitor the relevant D-data and override states. |
| Manual speed changes after a D-data edit | The PMC data participates in manual rapid selection on this machine. | Verify every selector position and retain a rollback record. |
Evaluate the Reported PMC D-Data
On the reported SKT-700L, setting D3.7 changed the manual rapid selection described as 25% versus 50%. The reported mapping was D3.7 = 0 for 25% and D3.7 = 1 for 50%. A later edit to D3.4 increased manual rapid at the 100% selection. The evidence does not define D3.4's complete logic, prove that either address applies to every SKT-700L, or establish whether the values are protected or retained after power cycling.
- Record the original D3 byte and individual bit states before editing anything.
- With the machine secured for controlled testing, compare manual rapid behavior at 25%, 50%, and 100% while monitoring the selector and associated PMC states.
- If the machine builder confirms this mapping, test D3.7 first and verify the reported 25%/50% behavior. Evaluate D3.4 separately; do not change both bits at once during diagnosis.
- Test each axis over a clear, limited travel distance, then confirm stopping response and restore the original data immediately if selector behavior is inconsistent.
- After a controlled power cycle, confirm whether the setting persisted and recheck all manual rapid selections.
Control the Safety Risk
The machine in the evidence had its door sensors defeated, so its observed motion cannot establish safe behavior with the guarding system intact. Restore and validate the door interlocks before increasing manual rapid speed. Faster manual motion reduces available reaction time and can alter the risk created by open guarding, unexpected axis selection, or limited clearance.
Do not treat a working D-data change as proof of an approved configuration. Obtain the SKT-700L machine builder's PMC documentation or service procedure, confirm whether the data is protected, and verify the intended interaction among door state, operating mode, rapid override, and manual motion.
FAQ
Why is Fanuc 21-i manual rapid slower than G00?
The reported machine used separate PMC selection logic for manual rapid, so slow jog-area motion did not establish a problem with G00. Compare the 25%, 50%, and 100% manual selections and monitor whether their PMC states actually change.
What does Fanuc PMC bit D3.7 change on the SKT-700L?
On the reported SKT-700L, D3.7 = 0 selected 25% and D3.7 = 1 selected 50% manual rapid. Confirm the address against the machine builder's PMC documentation because the evidence does not establish a universal Fanuc mapping.
Does D3.4 increase the 100% manual rapid speed?
Enabling D3.4 increased 100% manual rapid on the reported machine, but its full definition was not provided. Record the original data, test it separately from D3.7, and verify all override positions with guarding and interlocks operational.
