Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 436)

Programming Feedrates
Chapter 18
18-10
If you use this feature simultaneously with the Dry Run feature, the
feedrates that are assigned to the External deceleration feature are used.
The feedrates for this feature are not related to the Dry Run feedrates,
although the operation of this feature is similar to Dry Run.
This feedrate is unaffected by the
<FEEDRATE OVERRIDE>
switch and the
<RAPID FEEDRATE OVERRIDE>
settings, and it operates as if the switches
are set at 100 percent. Blocks that are programmed to move at the rapid
feedrate are still executed in the rapid mode.
Use this feature to protect the machine from harsh or sudden stops. If a
very high feedrate is active at the time that a hardware overtravel occurs,
damage to the machine can result or the machine can coast past a safe
range for axis motion. If the switch is installed before the overtravel area,
the feedrate of the move is reduced and the amount of coast into the
overtravel area is much less.
If the current feedrate is less than the feedrate set for the external
deceleration feature, it is accelerated to the external deceleration feedrate.
This can cause problems with part finish or can damage the tool if this
feedrate is higher than that which the part should be cut.
WARNING: Your system installer can write PAL to allow the
operator to select the external deceleration feedrate at any time.
This means that during normal automatic operation, you can
select external deceleration and replace all feedrates in the
program with the external deceleration feedrates. This can
result in damage to the machine, part, or injury to the operator.
There are two types of axis acceleration/deceleration available. They are:
Exponential Acc/Dec
Uniform or Linear Acc/Dec
S--Curve Acc/Dec
These are used to produce smooth starting and stopping of the machines
axes and prevent damage to the machine resulting from harsh movements.
Your system installer determines the acc/dec parameter type (exponential
or linear) for some manual motion types. To determine which motion
types are configurable, refer to the following table. Refer to your system
installer’s documentation for more information about how your system is
configured.
18.3
Automatic
Acceleration/Deceleration