User`s manual

Non-Programmed Motion
GFK-1742A Chapter 6 Non-Programmed Motion 6-3
6
adjustment and setup of these positions and for the “find home” routine, which requires that its
final move be in the negative direction.
Distance is also provided between the overtravel limit position and the positive stop. Enough
distance should be allowed here to prevent the machine slide from hitting the positive stop. The
correct distance needs to be greater than the worst-case stopping distance required by the machine
slide after it reaches the overtravel limit position.
In this example, the machine slide’s working range is on the positive side of the home switch. If
the DSM’s
Home Position
parameter was set to 0, this would simplify programming absolute
positioning commands since only positive numbers would be used.
Often, the home position needs to be set to an exact distance from a reference point on the
machine. To facilitate this adjustment, the home switch cam could be made with slotted mounting
holes that would allow a coarse adjustment of the cam to bring the calibration to within one turn
of the encoder. Then, the small remaining distance would be accurately measured and the value
obtained would be entered into the DSM’s
Home Offset
parameter.
+
-
D
irection
M
achine Slide
Positive
Stop
Home Switch Cam
H
ome Switch
Machine
Frame
N
egative Overtravel Position
H
ome Position
45741.cvs
Figure 6-1. Home Switch Example
Move+ and Move– Modes
If
Find Home Mode
is configured as MOVE+ or MOVE–, the first encoder marker pulse
encountered when moving in the appropriate direction (positive for MOVE+, negative for
MOVE–) after the find home command is given is used to establish the exact location. In this
mode, the operator usually jogs the axis to a position close (within one revolution of the encoder)