3- Fixed Cycles on the Mill - Rules
|For a canned cycle to operate correctly, the programmer needs to know the code words that the cycle uses. The following is an example of how a G81 canned cycle is properly written:
G81 X1. Y1. Z-.50 R.1F6. G99
G98 tells the tool to retract to the initial plane.
G99 tells the tool to retract to the rapid plane when the cycle is finished. Canned cycles already retract to the R plane but a G99 is a safe way to remember where the tool is going after it has completed the operation. Using G99 cancels G98 and visa versa.
G98 and G99 can be inserted in block of code anywhere in the canned cycle. This allows the programmer to shift at will between planes.
Note: the rapid plane is sometimes called the "retract plane" but the R word is used the same
Canned cycles are modal. Once they are turned on they stay on until cancelled. This means that every block of code after the start of a canned cycle will be interpreted as being part of that canned cycle process.
Always use a G80 command to cancel a canned cycle (note that the G80 is used after all movements are completed in the example on the next page). If not cancelled with a G80 command, every movement after the intended hole(s) may machine more unwanted holes or crash the machine.
All canned cycles will:
Here is an example of a properly written G81 canned cycle to drill four holes.