HEIDENHAIN TNC 407 (243 020) Technical Manual - Manual (Page 273)

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TNC 407/TNC 415/TNC 425 6 Display and operation 01.98
6.8 Return to the contour
With the HEIDENHAIN contouring control it is possible to resume an interrupted program, or to
make a block scan up to a predetermined block number (see User's Manual).
These functions must be enabled by machine parameters and the PLC program must
be changed accordingly.
Markers inform the PLC about the individual conditions during the resumption of the program or
block scan. Depending on these markers, certain functions can be enabled in the PLC-program (e.g.
operating the axis-direction keys in "Manual operation").
M2018 is set if the "MANUAL OPERATION" soft key is pressed.
M2019 is set if the "Return to contour" function is activated with the "RESTORE POSITION" soft key.
M2059 is set if the "RESTORE AT N" soft key is pressed. M2059 is reset if the "RESTORE
POSITION" or "INTERNAL STOP" soft key is pressed.
During the block scan the PLC positioning commands are only included in the calculation if they are
also executed. The TOOL CALL block usually releases PLC positioning commands for the tool
change position. If these movements are to be offset in the block scan, the absolute position must
be entered referenced to the machine datum in MP951.x and the offset must be activated for
specific axes with MP7450.
When using random selection in the central tool memory (see section "Tool change"), an alteration of
the position numbers in the tool memory must be avoided during block scan. This is transmitted
from the PLC to the NC by marker M2612.
Machine parameter MP7680 can be used to select whether the block scan may be interrupted by a
programmed STOP or M06 and whether the programmed dwell time should be taken into account
during the block scan.
The feed for returning to the contour is specifically defined in machine parameter MP4220.X. This
machine parameter is also used to set a number in the PLC (see "PLC description.")
MP4220 Feed for "Return to the contour"
Entry: 10 to 30 000  
mm
min
MP4220.0 X axis
MP4220.1 Y axis
MP4220.2 Z axis
MP4220.3 4th axis
MP4220.4 5th axis