User Manual
Chapter 6
GFK-1742F
Jan 2020
Non-Programmed Motion
164
Find Home Routine for Home Switch
If initiated from a position on the positive side of the home switch, in which case the home
switch must be OPEN (Logic 0), the Find Home routine starts with step 1 below. (All of the
first several steps of the following routine are necessary to allow for a variety of possible
home switch designs and starting positions.) If the Find Home routine is initiated from a
position on the negative side of the home switch, in which case the home switch must be
CLOSED (Logic 1), the routine starts with step 3 below.
1.
The axis is moved in the negative direction at the configured Find Home Velocity
until the Home Switch input closes.
2.
The axis decelerates and stops.
3.
The axis is accelerated in the positive direction and moved at the configured Find
Home Velocity until the Home Switch input opens.
4.
The axis decelerates and stops.
5.
The axis is accelerated in the negative direction and moved at the configured Final
Home Velocity until the Home Switch input closes.
6.
The axis continues negative motion at the configured Final Home Velocity until a
marker pulse is sensed. The marker establishes the home reference position.
7.
The axis decelerates and stops (at a position past the marker pulse).
8.
The axis is moved, at the current Jog Velocity, the number of user units specified by
the Home Offset value from the home reference position. If Home Offset = 0, the
axis moves back to the position of the marker pulse.
9.
The axis decelerates and stops.
10.
The DSM314 sets the Commanded Position and Actual Position %AI status words to
the configured Home Position value. Finally, the DSM314 sets the Position Valid %I
bit to indicate the home cycle is complete.
Home Switch Example
Many different home switch designs are possible. The switch may be normally open or
normally closed and may be mounted in one of several possible locations. The example
given in this section illustrates a fairly common arrangement used for linear axes. In the
following picture, the home switch is a normally open proximity switch, mounted near the
end of the machine slide’s travel range (i
n the negative direction). The imaginary line that
divides the home switch’s positive and negative sides is the home switch’s operating point,
located approximately on the switch’s centerline. If the machine slide travels in the negative
direction far enough so that the right-hand edge of the home switch cam causes the home
switch to close, we consider the machine slide as having crossed over to the “negative side”
of the home switch. The home switch cam is long enough so that while the machine slide is
on the negative side of the home switch, it will keep the normally open home switch closed.