Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 616)

Cylindrical Grinding Fixed Cycles
Chapter 17
17-42
ATTENTION: Overcutting of the shoulder can occur when a
micro-feed is performed on an angled-wheel grinder operating
in G16.4 two step angled wheel grinder mode. All micro-feed
motion in G16.4 mode occurs on the W axis. No transformation
of Z axis motion occurs. This means micro-feed on the W axis
can exceed the actual programmed Z axis endpoint causing
overcutting of the parts shoulder.
R
I
Q
Start Point
X
Micro-Feed
Part
Required Diameter
After the W axis reaches the programmed fine plunge
endpoint (X), the part diameter was still too large because of
wheel wear. The micro-feed took over extending the fine feed
plunge on the W axis until a probe fired telling the control that
X was at the required diameter. Since no Z transformation
took place the part diameter is at specification however
overcutting occurred on the part shoulder (Z axis).
W
X
Z
Required
Shoulder
Typically the skip signal for a fine plunge is performed by an external
device measuring the current part diameter such as a gage. In this case
when the actual desired plunge depth is reached, the gage fires indicating
to the control to abort the fine plunge operation. The system installer
determines in AMP the maximum length of the micro-feed portion of the
fine feed. If no skip signal is received before the control reaches the AMP
maximum micro-feed length, the control proceeds on with spark out and
blend operations from this new plunge depth.
The system installer can write PAL to modify the offset tables for the new
wheel diameter. In this example the control will calculate the difference
between the programmed X depth and the actual X depth when the skip
signal was received. This value is then subtracted from the currently active
wheel diameter table value.
END OF CHAPTER