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Several blocks are invoked and executed at the beginning of each procedure (the procedure header). It is important to understand their order, as well as the type of information that is available in each one. This becomes especially critical in 4/5X positioning post-processors.
A procedure starts with the following sequence of blocks (in that order).
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Block |
Comments |
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BEGINNING OF PROC: |
Additional variables available with GPP2. |
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ORIGIN CHANGE: |
Optional (only if origin has changed from last procedure). |
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TOOL CHANGE |
Optional (only if tool has changed from last procedure). |
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START PROC: |
Last block before the connection motions. |
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Connection Blocks |
A series of blocks that take the tool to the procedure start point (tool above the first actual cutting point, and properly oriented). See discussions about GPP2 connections. |
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PROC FIRST POINT: |
A block just before the actual procedure motions start. |
Note that some of the blocks generated by old GPP are missing here (For example, FEED, SPIN, COOLANT). These blocks are not needed in GPP2.
Instead, the complete information regarding the feed rate (MCH_FEED), spindle settings (SPIN_DIR and SPIN_SPEED), and the procedure coolant (MCH_COOL) are provided as new variables in the BEGINNING OF PROC block. The data is used later, whenever appropriate for the specific post processor and machine.
Notes:
START PROC is a convenient place to do things just before the motions start. For instance, the spindle may be turned on. If subroutines are used for each procedure, this may also be a good place to redirect the output and open a subroutine header (For example, "O101").
While ORIGIN CHANGE and TOOL CHANGE are optional, START PROC is guaranteed to be invoked by GPP2.
PROC FIRST POINT is the place where the actual procedure motions are about to start. After that block, GPP2 will perform the final approach to the material. It may be a convenient place to turn the coolant on.
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