Code 75501: [Channel %1: ] HSLC: CC_FASTON_CONT velocity too high
Issue Description & Safety Warning
The Siemens SINUMERIK 840D CNC has triggered a critical [Channel %1: ] HSLC: CC_FASTON_CONT velocity too high 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
Parameters: %1 = Channel number Definitions: The path-related switching signal output switched on by the part rogramm command CC_FASTON_CONT( PAT H_DISTANCE_ON, PATH_DISTANCE_OFF ) cannot output all switching signals correctly at the current velocity. Reason: A maximum of one switching edge can be output per IPO cycle (see $MN_IPO_CYCLE_TIME ). The current path velocity is so high that there is more than one switching edge to be output within one path distance PATH_DISTANCE_ON or PATH_DISTANCE_OFF. Example: IPO cycle = 2ms ( position-control cycle = 1ms ) PATH_DISTANCE_ON = 0.667 PATH_DISTANCE_OFF = 0.667 Maximum path velocity in which no switching edges are lost: 20000 mm/min When alarm 75501 occurs, the function skips the out put of two successive switching edges. This does not affect the position of subsequent switching edges. Note: Whether the ommission of a signal from the pr evious switching signal l eaves a high or low level present, is purely coincidental. Reaction: Alarm display. Remedy: - Lengthen the operating travels programmed in the command CC_FASTON_CONT - Program the path velocity or reduce it with the override switch - Set a shorter IPO cycle (machine manufacturer only) Program Continuation: Clear alarm with the Delete key or NC START.
Source: SINUMERIK 840D sl / 840Di sl / SINAMICS S120 Diagnostics Manual (DAsl, 03/2009)
Last reviewed: 2026-07-01 · Verified against the manufacturer’s official documentation.
About Siemens SINUMERIK 840D CNC Alarms
Siemens controllers include extensive self-diagnostics that flag or halt the machine when a fault is detected. Error code 75501 on the SINUMERIK 840D CNC identifies one specific fault condition — its documented cause and the official corrective steps are listed above, sourced from Siemens's service documentation. Always confirm against the manual for your exact machine configuration and follow LOTO procedures before servicing.
Complete Alarm List: 4014 Siemens SINUMERIK 840D CNC codes.
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