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Okuma OSP Controller
Safety · Intermediate · 20-90 minutes
Okuma OSP Alarm A 8600 - Ceiling door open/close limit SW NG
Okuma OSP alarm 8600 indicates the chip conveyor system has failed to respond properly to PLC control signals or has reported a fault condition. Most commonly caused by conveyor motor overload, broken drive chain, or PLC input/output signal issues. Typical fix involves checking conveyor mechanical operation and verifying I/O signals in the PLC diagnostic screens.
8600
Okuma OSP Alarm A 8600 - Ceiling door open/close limit SW NG
Ceiling door open/close limit SW NG
On a machine with the door interlock type S specification, the ceiling door open/close confirmation limit switch has failed or is reporting an inconsistent state. The control cannot verify the ceiling door position, so the interlock blocks operation.
Root Cause Summary
Okuma OSP alarm 8600 indicates the chip conveyor system has failed to respond properly to PLC control signals or has reported a fault condition. Most commonly caused by conveyor motor overload, broken drive chain, or PLC input/output signal issues. Typical fix involves checking conveyor mechanical operation and verifying I/O signals in the PLC diagnostic screens.
Safety
- Apply LOTO (lockout-tagout) to main machine disconnect and chip conveyor local disconnect before reaching into chip pan or conveyor belt area to clear jams - belts can auto-restart if control circuits remain energized
- Chip conveyors often operate in coolant-flooded environments; verify area is drained and use insulated tools when measuring voltage to avoid shock hazard from wet connections
- Broken carbide tooling fragments in chip buildup are extremely sharp and can cause severe lacerations; use hook tools and cut-resistant gloves when clearing jammed material
Causes and Fixes
- 1
Check Conveyor Physical Operation
Manually inspect the chip conveyor for visible jams, excessive chip buildup, or foreign objects. Look for broken chain links or misaligned guide rails that could cause binding.
Ensure machine is in emergency stop and conveyor power is locked out before manual inspection
- 2
Test Motor Overload Relay
Locate the conveyor motor starter panel and check if the thermal overload relay has tripped. Reset the overload relay if tripped and note the current setting versus motor nameplate amperage.
Overload relays often trip at 85-90% of setting, so check for gradual wear causing higher operating currents
- 3
Clear Obstruction and Test
Remove any identified obstructions or excessive chip accumulation. Manually rotate conveyor drive sprocket to verify smooth operation before restoring power and testing automatic operation.
Use proper lockout/tagout procedures when clearing mechanical obstructions
Call a technician if:
- ·PLC input/output modules require replacement
- ·Motor starter components need replacement
- ·Conveyor mechanical repairs require specialized tools
Prevention
- Implement regular chip conveyor cleaning schedule to prevent overload conditions
- Monitor conveyor motor current draw during preventive maintenance
- Keep conveyor feedback sensors clean and properly adjusted
- Maintain proper chain/belt tension per manufacturer specifications
Common Mistakes
- Assuming sensor failure without checking mechanical conveyor operation first
- Resetting overload relays repeatedly without identifying root cause of high current
- Ignoring gradual increase in conveyor operating noise that indicates developing mechanical problems
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