Known restrictions

• If program is continued after block search with an offset, because it has not moved back totally to the original contour, this offset is valid till normal program end or reset. If the program is restarted again the positions do not have the offset any more.
• If a NC block for restart contains movement and technological commands, e.g. at N100, than just the remaining movement command is executed in real mode. All technological commands of block N100 are simulated (block search mode).

N90 X90
N100 X100 S1000 M3 M111
N110

If also the technological commands shall be executed the user can specify block N90 with 100 % as covered distance. The following properties must be taken into consideration with automatic return to contour:

• The axes are moving back in rapid mode in a straight line. If any obstacles are between the actual axis position and the position to continue after block search, the motion back to contour has to be generated manually.
• With active soft gantry mode the return movement is done with unlinked master and slaves, this means the axis coupling is activated after the return movement.
• Any axis exchange is only allowed if the axis are requested with implicite reading of position from interpolator (default, not in case of #CALL AX FAST).

Axes, which are moved during active block search and are released (#PUT AX) before switching to normal mode, are not moved to their last known position.

• Only the actual present axes of the channel are moving from their real positions at program start (default channel configuration) back to contour, which are known during block search off.

If during block search any new axis have been requested (#CALL AX) this axis can not be moved back automatically, because all start positions of the actual axis have to be known. Any other exchange of axes between program start and restart after block search is handled correctly.

N00 X10 Y20
N10 #CALL AX [B, 4, 3]
N20 B45 (B-axis movement not considered)
N30 #PUT AX [B]
N30 Z100
N50 #PUT AX [Z] (Z-axis released, can not be restored)
N10 #CALL AX [C, 5, 4] (C-axis not known at program start,
position must be fetched from IPO)
N30 Z100
N30 #PUT AX [X,Y]
N10 #CALL AX [X, 1, 1] [Y, 2, 0] (exchange of X/Y considered)
N100 X100 Y200 (continue normal execution after block search) 
M30

In the example above the B-axis is not moved to 45 if automatic straight back to contour is enabled. Also Z-axis is not moved to contour. C-axis is moved correct back to contour.

If program execution was interrupted and “continue at interruption point” is requested with usage of block search function, the parameters are available directly with the present state data in PLC.

If block search parameter should be determined based on the input NC program, it must be taken into consideration that contour influencing functionalities like tool radius compensation or polynomial contouring can modify target positions and block limits.