P
USH
C
ORP,
I
NC.
AFD92
Manual
16
6.0.2 Wrist Mount
If the
AFD92
is not always horizontal and changes orientation, then two system
variables have to be considered when achieving a desired output force: the Process
Equipment Weight carried by the AFD and the angle of the Carriage with respect to
gravity. The angle of the Carriage must be known so that the Process Equipment
Weight can be compensated for. The Process Equipment Weight includes the AFD
Carriage weight. This value can be back calculated from the area and pressure in the
pneumatic actuator. The best method to determine the Process Equipment Weight is
with a calibrated load cell. The angle of the Carriage to the gravity vector is defined as
shown below in Figure 9.
Figure 9. Definition of the carriage angle.
The
AFD92
is available in two configurations, the AFD91, and the AFD92. The AFD91
has a pair of single-acting pneumatic actuators, so it may only apply positive forces.
The AFD92 has two pairs of single-acting actuators acting in opposite directions. This
allows the AFD92 to apply both positive and negative forces. The area of the pair of
cylinders is 2.6 in
2
(1677 mm
2
) so, for every 1.0 psi (0.07 bar) of supply pressure the
AFD applies 2.6 lbs. (166 N/Bar) of force. This makes the
AFD92
very easy to setup.
To apply a 40 lbs. (178 N) force just set the supply pressure to 15.4 psi (1.1 Bar). This,
however, does require the user to supply one (the AFD92 requires two) precision
pressure regulator to accurately adjust the applied force. The pressure regulator may
be either manually or electrically controlled. Electrically controlled regulators are
normally the proportional type, which outputs a pressure that is scaled to a voltage input.
The force output repeatability and resolution is directly related to the quality of the
pneumatic regulator.
Copyright
PushCorp, Inc.
2006. All rights reserved
