G31: Skip function

Overview

• Performs a linear move to the given position until the skip signal is activated or the commanded position is reached
  • Motion stops on the rising edge of the Skip signal, and then waits for a Done signal:
    1. CompassMotionProcessor function block sets Active to 1 at the start of the G31 move.
    2. iCube code asserts the Skip signal, triggering motion to stop.
    3. Next, the latched position data is filled in by the PLC, and made available in G-Code.
    4. The position data is read in Machine Coordinate system, saved to NC.SysVars.G31.MCS struct.
    5. The position data is converted from MCS to the currently active Local Coordinate System and is saved to NC.SysVars.G31.LCS struct.
    6. Finally, the PLC resets the Active signal allowing the next block to execute.
    7. It is a blocking command, CompassNC stops processing until G31 command is completed.
    8. If the final position is reached without triggering the Skip signal, the G31 motion is complete, Active is reset and the next block is executed.
  • Motion lookahead stops when encountered to wait for completion of this move.

Command Format

• Syntax: G31 X... Y... Z... F...
  • Specifying Coordinate System
    • MCS (G53) G31 G53 X... Y... Z... F...
  • Feed Rate F...
    • If omitted uses the last modal non-rapid feed rate.

Accessing G31 Trigger's Recorded Position

• The positions are recorded in Machine Coordinate System (MCS) and then converted to a Local Coordinate System (LCS) using the active offsets.
  • X Latch Position
    • Latch position captured and filled in by PLC
    • Available in G-Code as #<NC.SysVars.G31.MCS.X>
    • Available in G-Code as #<NC.SysVars.G31.LCS.X>
  • Y Latch Position
    • Latch position captured and filled in by PLC
    • Available in G-Code as #<NC.SysVars.G31.MCS.Y>
    • Available in G-Code as #<NC.SysVars.G31.LCS.Y>
  • Z Latch Position
    • Latch position captured and filled in by PLC
    • Available in G-Code as#<NC.SysVars.G31.MCS.Z>
    • Available in G-Code as#<NC.SysVars.G31.LCS.Z>
  • Aux1 Latch Position
    • Latch position captured and filled in by PLC
    • Available in G-Code as #<NC.SysVars.G31.MCS.Aux1>
    • Available in G-Code as #<NC.SysVars.G31.LCS.Aux1>

Examples

N1 G90 G17 G21
N2 G52 X0 Y0 Z0            
N3 G43 P0            
N10 G0 X0.0 Y0.0 Z0.0 F12000            
N12 G31 X100 F200  // Perform a linear Skip Move in a currently active coordinate system.            
#1001 = # <NC.SysVars.G31.LCS.X> // Save recorded X coordinate to a 1001 variable            
N14 G1 Y100 F12000            
G1 X0 Y0            
G1 X[#1001] // Use recorded X position as a target position.            
M30

Warnings

• Do not use G31 with G40, G41, G42: Tool Radius Offset active.

Details

• The Skip motion can be commanded in Machine or Local CS, using the same G53 or G1 commands next to the G31, see samples above.
• The position recorded is saved in a MCS struct and then converted and saved to the LCS struct. Both sets are accessable using # <NC.SysVars.G31.LCS.X> ( Y,Z, Aux1 ) and # <NC.SysVars.G31.MCS.X> ( Y,Z, Aux1 ) commands.; If you have any frames enabled (G54-G59), these positions will be different.
• For example: To measure a tool length using the sensor mounted on the machine frame, command the motion in Machine CS, use G53 G31 motion command and read the value from NC.SysVars.G31.MCS.
• For example: To measure a pocket that was just machined, while in a Local CS, use G1 G31 motion command and read the value from NC.SysVars.G31.LCS.

See Also:

• Parameter Table
• G53: Non Modal MCS Linear Move