Bimba PCS - Manual (Page 23)

www.bimba.com Technical Assistance: 800-44-BIMBA 23
• 80 psi air supply.
• Minimum of 23.5 VDC provided to the PCS.
• Clean Command Signal for Main Control. (<5mV noise/ripple)
• Leak free system (The system will actually perform well with some system
leakage, however, the best performance is with no leakage).
• Short (<18 inches), hard air lines (nylon) between the valves and the actuator.
• No backlash in the system.
• Horizontally guided load. The system can handle vertical or inclined loads and
still meet the minimum deadband specified above, however, the velocity may be
effected by up to 40%.
Typical “Rules of Thumb”:
• Deviations from the recommended parameters, such as air pressure, power supply
voltage, external friction, etc, will negatively effect system performance.
However, the system may still perform adequately for your application.
• Applications with loads less than 10% of actuator capacity and strokes greater
than 4 inches will yield better repeatability than the minimum Deadband shown in
the sizing table above.
• Reducing actuator velocity by use of Flow Controls may enable the Deadband to
be adjusted tighter for a given application. The Flow Controls must be inserted
into the exhaust ports of the valve manifold, NOT in the actuator.
• Oversizing the actuator for a given application typically yields better
repeatability.
• Generically, following are relative influences on velocity:
o
As Mass increases, Velocity decreases (up to 20%)
o
As Friction increases, Velocity decreases (up to 20%)
o
As Pressure decreases, Velocity decreases (up to 20%)
• Increased Friction decreases repeatability. Maximum external friction should not
exceed 20% of the maximum rated payload. Any external friction in the
application will degrade system performance. Ensure the system is aligned
properly to any guiding systems. Misalignment will cause external application
friction.
• A borderline solution can be effective through any/all of the following:
o
sacrificing performance in one area for another,
o
limiting velocity with external flow controls,
o
diligently employing the rules of thumb, located in the Bag of Tricks
portion of this report,
o
employing a small central portion of a longer probe,
o
using a larger bore cylinder.
• The PCS system is not best suited for applications where accurate velocity control
is needed by controlling the rate of command signal change. Flow controls can be
used if lower velocities are required.
Do not allow the PCS valves to stay on for prolonged time periods
unless the valves are well ventilated, as they may overheat
potentially causing damage to the valves.