Aerotech UNIDEX 600 Series, User Manual

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Parameters U600 User’s Guide
C-64
Aerotech, Inc.
Version 1.4
From point A to point B, the X axis moves at 600 inches/min, or 10 inches/sec, and the Y
axis moves at 0 inches/sec. But, from point B to point C, X travels at 0 inches/sec, and Y
at 10 inches/sec. So, at point B, both the X and Y axes are subjected to a “instantaneous”
change of velocity of 10 inches/sec. The velocity change cannot of course be
“instantaneous”, and the controller will make that change of velocity (for each axis) in
one millisecond, so the X axis will generate an acceleration of 10,000 inches/sec squared,
and the Y axis will generate a deceleration of 10,000 inches/sec squared. However, if the
BlendMaxAccelLinearIPS2 parameter is set to 1,000 inches/sec squared, then the
controller will force deceleration to a velocity of 60 inches/minute, at point B, therefore
generating only a 1,000 inches/second squared acceleration/deceleration.
C.4.8.3. Blending Limitations of BlendMaxAccelLinearIPS2 and
BlendMaxAccelRotaryDPS2 Task Parameters
There are certain conditions where a G9 will be enforced, regardless of the value of this
parameter. There are some instances where this parameter will not work properly, due to
limitations in the look-ahead process.
If G301 mode is active, the controller will look-ahead multiple moves, and slowdown
many moves before the change in velocity. However, the maximum number of moves
ahead of the CNC block, the controller is able to slow down as determined by the
MaxLookAheadMoves task parameter. Also, there are also some other instances where
this parameter will do nothing, due to limitations in the look-ahead process.
Note that a G9 (decelerate to zero velocity) will be enforced, regardless of the value of
this parameter, if you execute a G92 command, are in G109 mode, or have a G9 on the
line.
If a G8 is on the CNC program line, this parameter will have no effect.
C.4.8.4. Calculating the value for the BlendMaxAccelLinearIPS2
and BlendMaxAccelRotaryDPS2 Task Parameters
These parameters should be set to the maximum value that does not cause excessive
excitation to the mechanics, adversely affecting part quality. The exact value required for
your system must ultimately be determined by trial and error; dependant upon your
mechanics, support structure, part geometry, required accuracy, etc. They may be set to
the lesser value of the two axes ACCELRATE axis parameters, as a very rough starting
point. The ACCELRATE axis parameter must be converted from machine counts /
second / second to inches / second / second, as follows:
BlendMaxAccelLinearIPS2 <= ACCELRATE / CntsPerInch
BlendMaxAccelRotaryDPS2 <= ACCELRATE / CntsPerDeg