Code Y51-0020: Hi-acc time const unextendable
Issue Description & Safety Warning
The Mitsubishi M800/M80 CNC has triggered a critical Hi-acc time const unextendable alarm. Immediate attention from a qualified operator or maintenance technician is required to prevent secondary damage to the equipment or spoiled parts during the manufacturing cycle. Always ensure standard safety and LOTO procedures are followed before accessing electrical cabinets.
Official Troubleshooting Steps
Details High-accuracy acceleration/deceleration time constant extension option is unavailable. Remedy Adjust the setting of "#1207 G1btL" to be within the range of when the high-accuracy control time constant extension option is OFF. High-accuracy acceleration/deceleration time constant extension option is un available for a system con- figured with multiple part systems. Change the system to be m ade up of a single part system, or set the said option to OFF. Superimpos li near G0 error 0022
Source: Mitsubishi M800/M80/E80 Series Alarm/Parameter Manual (IB-1501279)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Mitsubishi M800/M80 CNC Alarms
Mitsubishi controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code Y51-0020 on the M800/M80 CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Mitsubishi's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 722 Mitsubishi M800/M80 CNC codes.
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