HEIDENHAIN CNC Pilot 4290 - Manual (Page 175)

HEIDENHAIN CNC PILOT 4290 163
4.12 Special Functions
Controlled parting using spindle monitoring G991
The controlled parting function (cut-off control) prevents collisions
caused by incomplete parting processes. G991 controls the parting
process by monitoring the speed difference between the two spindles.
The spindles are connected in terms of actuation via the workpiece.
After the parting process has been completed, the spindles rotate
independently of each other. Speed differences and monitoring time
are stored in machine parameters 808, 858, ... They can be changed
with G992.
The CNC PILOT writes the monitoring result into variable V300.
Specify the path to be monitored in ”return path R” and define
whether the path before the workpiece is cut off or the return path is
to be monitored (see illustration).
Parameters
R:
Return path (radius value)
■ No entry: The speed difference between the spindles running
synchronously is checked (one-time check) .
■ R>0: ”Remaining path before the parting operation” is
monitored.
■ R<0: ”Return path” is monitored – the monitoring function is
activated when the return path begins and is deactivated when
the value ”-R” is reached.
Programming controlled parting:
Cut off the workpiece.
Activate the monitoring function for the path of traverse with G917.
Move the workpiece with G1 after it has been cut off.
The CNC PILOT checks the lag error and stores the result in variable
V300.
Evaluate variable V300.
Test results
G917 produces satisfactory results provided that:
■ With rough chucking jaws, n < 3000 rpm.
■ With smooth chucking jaws, n < 2000 rpm.
■ Clamping pressure of > 10 bar.
Programming notes:
■ Program G917 and G1 in one block
■ Program G1 as follows:
■ With ”parting control”: Path >0.5 mm (to permit a
result of monitoring)
■ When checking for smooth parting control: Path <
width of the parting tool
■ Result in variable V300
■ 0: Workpiece has not been cut off correctly/
smoothly (lag error has been detected).
■ 1: Workpiece has been cut off correctly/smoothly
(no lag error has been detected).
■ G917 generates an interpreter stop.
■ Parting control with G917 is preferable to G991.
■ Tool breakage might result in speed differences which in
turn might affect the monitoring result. It is therefore
advisable to monitor the reverse path too.
Continued
Programming notes:
■ Program constant cutting speed G96.
■ Program G991 and G1 (path before the parting
operation or return path) in one block.
■ Result stored in V300:
■ 0: Workpiece not cut off
■ 1: Workpiece cut off
■ G991 generates an interpreter stop.