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Siemens SINUMERIK Controller
Program/G-code · Intermediate · 30-120 minutes
Siemens 61284 - Block : starting point cannot be approached without collision. Pre-
Alarm 61284 fires when the SINUMERIK 840D NCK cannot safely retract the tool to the programmed starting point due to potential collision with workpiece geometry or fixture elements. This occurs during canned cycle execution (F_DRILL, F_TAP, F_GROOV, etc.) when the approach path violates machine coordinate boundaries or interference zones defined in the part program or machine data.
61284
Siemens 61284 - Block : starting point cannot be approached without collision. Pre-
Block: starting point cannot be approached without collision. Pre
The starting point cannot be approached without collisions Control reaction: Interpreter stop NC Start disable in this channel. Interface signals are set. Alarm display.
Root Cause Summary
Alarm 61284 fires when the SINUMERIK 840D NCK cannot safely retract the tool to the programmed starting point due to potential collision with workpiece geometry or fixture elements. This occurs during canned cycle execution (F_DRILL, F_TAP, F_GROOV, etc.) when the approach path violates machine coordinate boundaries or interference zones defined in the part program or machine data.
Safety
- Only qualified personnel should diagnose and clear control alarms; follow the machine builder's safety procedures and lockout/tagout where hardware work is required.
Causes and Fixes
- 1
In the part program, verify the R-plane value (clearance plane) is set sufficiently high above the workpiece. For F_DRILL and similar cycles, check that RTP (Return To Point) parameter provides adequate clearance. Increase RTP value or R-plane by 5-10mm minimum above the highest workpiece feature.
Excessive clearance plane heights may reduce cycle efficiency; coordinate with workholding design.
- 2
Check DFRAME offset in Diagnostics > Frames > DFRAME (NCK menu path: Cycle > Frame Setting). Verify that the workpiece coordinate system origin does not place the starting point inside the physical workpiece or fixture envelope.
- 3
Review machine data MD10200 (axis limits) in Parameter > Machine Data > Geometry. Ensure soft limits are not restricting the Z-axis or approach axis retract motion beyond physical constraints.
- 4
Simulate the program with SINUMERIK Operate Simulation mode (Siemens HMI) or use VERICUT post-processor to visualize the retract path and identify exact collision point.
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