manualshive.com logo in svg

Bimba PCS, User Manual, Page: 4 / 36

Share
Download
Bimba PCS User Manual Download Page 4

4

User Manual

Model PCS

Pneumatic Motion Control System

GENERAL OVERVIEW

The Bimba Pneumatic Control System (PCS) is a closed loop electronic controller with pneumatic valves that 
can move the rod or shaft of a pneumatic position feedback actuator and hold it in any desired position with 
accuracy and force. The PCS system is designed for series PFCN, PFCNL, PFC, and PFCL cylinders for linear 
motion and the Position Feedback Pneu-Turn (PTF) for rotary motion. The PFC should be ordered with the -L 
option, low friction seals, for the best positioning accuracy and smoothest operation. The standard PTF includes 
low friction seals.  

The standard PCS accepts a 0 to 10 VDC or 4 to 20mA analog command signal, jumper selectable (refer to the 
illustration on page 11).  The command signal defines the position the rod must move to. The rod stops when 
the feedback voltage from the probe is equal to the command signal.  
For example, if the application has a stroke of 10 inches and zero and span adjustments are set for zero to ten 
inches as well, then a 1 volt change in the command voltage is equal to a 1 inch movement. Similarly, a change 
in command signal of 0.005 of a volt equals a position change of 0.005 of an inch for the same 10 inch stroke 
application. If the application has a stroke of 5 inches, a change of 1 volt in the command signal represents a 
half inch movement. For rotary applications, the convention is similar. If the application has a rotation of 180 
degrees, then a 1 volt change in the command signal is equal to 18 degrees of rotation. 

The system utilizes the feedback from the actuator to close the control loop. The control loop compares the 
0-10 VDC or 4-20mA input command signal to the feedback signal from the actuator. The difference between 
the command and feedback is referred to as the error term. When the error term is zero, all valves close, 
trapping air on both sides of the actuator piston. (The error term is considered to be zero when it is within 
the deadband range. The deadband is defined in the Glossary of Terms section.) This holds the rod at its 
commanded position. If a force attempts to move the rod or shaft out of the commanded position, the system 
will react by increasing the restoring force to maintain position. Likewise, if the command signal changes, the 
system will respond to make the feedback equal the command signal.  

The actual accuracy/repeatability of the movements will depend on many factors, including 
signal noise, load, velocity, supply pressure, supply voltage, and application friction.  Refer to 
the Application Sizing charts for detailed information regarding sizing and suggestions for your 
application.

 

 

 

Summary of Contents for PCS

Page 1: ...We make things MOVE Please read this manual carefully before implementing your Pneumatic Control System Model PCS Pneumatic Motion Control System User Manual ...

Page 2: ...ssed air connections to the actuator before attempting to release or remove jammed item This symbol represents boxes that contain helpful hints and recommendations This symbol represents boxes that contain important notes reminders and items that may need special attention If full system pressure is applied with a large error signal present the actuator will attempt to instantaneously move to the ...

Page 3: ...ections 14 9 Apply 24 VDC Power 14 10 Apply Pneumatic Pressure 15 11 Set the Deadband 15 12 Command the Bimba Actuator to its Zero Position 16 13 Preliminary Zero Adjustment 16 14 Preliminary Span Adjustment 18 15 Final Zero and Span Adjustment 19 16 Decel Range Adjustment 19 Application Example 21 Specifications 22 Application Sizing and Rules of Thumb 22 Troubleshooting 24 Frequently Asked Quest...

Page 4: ...0 inch stroke application If the application has a stroke of 5 inches a change of 1 volt in the command signal represents a half inch movement For rotary applications the convention is similar If the application has a rotation of 180 degrees then a 1 volt change in the command signal is equal to 18 degrees of rotation The system utilizes the feedback from the actuator to close the control loop The...

Page 5: ...ed in process control systems for increased control in plant emissions smoke houses and similar applications Labeling The PCS system can position differently sized parts under a label applicator allowing the labeling process to continue without any down time for a setup change to adjust for product size Animatronics The PCS system can produce lifelike movements of puppets and figures such as those...

Page 6: ...n be translated into actuator displacement with the following formula CS d R t Z where CS the command signal required to achieve a desired position d the disdplacement the desired position is from the zero position R the full range of the command signal t full scale travel of the actuator Note for PTF rotary actuators with total rotation less than 180º always make t 180 Z the command signal for th...

Page 7: ... a 6 inch stroke cylinder the width of the dead band zone will be 1 10 0 02 6 or 0 012 of an inch Example 2 If the deadband is set for 20mV 0 02 of a volt for a 180º actuator the width of the deadband zone will be 1 10 0 02 180 or 0 72º PTF Note The PTF has a fixed electrical rotation span of 340 degrees This will affect some of the following adjustments and signals for PTF s with full scale rotat...

Page 8: ...a PLC I O card to receive a signal indicating that the actuator is within the Deadband zone potentially eliminating the need for an analog input card REPEATABILITY AND STABILITY It is important to understand the difference between repeatability and stability A system is considered repeatable if it comes to a stop inside the deadband zone A system is considered stable if it comes to a stop in the d...

Page 9: ...5 foot valve cables The snap track allows for easy mounting inside a larger enclosure box Mount the snap track in the enclosure and snap the PC Board in place Mount the valve manifold near the actuator Be careful to mount the manifold in a place where the valves will not be vulnerable to physical damage 3 MAKE THE PNEUMATIC CONNECTION The supply air must be 70 to 80 psi Air supply pressure affects...

Page 10: ...ter port of the valve manifold Connect the valve manifold retract port the port directly to the left of the center port when the manifold is facing you to the rod end of the cylinder For PTF rotary actuators connect this to the port on Body A for single rack models left side when the PTF shaft is facing toward you or connect to bodies A and D for double rack models lower left and upper right when ...

Page 11: ...le to the POWER terminal block TB1 on the PCS circuit board Twist the ground and shield wire together and connect to the Ground terminal do not terminate the other side of the shield For best positioning results consider using a precision relieving regulator and an air reservoir with a check valve before the regulator to ensure that there are no pressure drops to the PCS system You may want to ins...

Page 12: ...4 5 voltage specification as this will degrade system response and performance significantly For PFCN only power to the probe MUST come from 24 VDC supplied to the PCS control and NOT the 10 VDC that the PCS produces from terminal A of TB2 For PFCN only If the Q quick connect option was selected the lead from the connector to terminal A of TB2 must be removed and the lead reinserted into the 24VDC...

Page 13: ...able through the remaining bulkhead strain relief and connect the individual wires to PCS Terminal Block TB4 on the PC Board as follows Input Command Signal A positive analog input signal to the PCS control of 0 10 VDC or 4 20mA which defines the desired position of the PFC rod or PTF shaft Current Position A positive analog output voltage 0 10 VDC from the PCS which corresponds to the current pos...

Page 14: ...rom the valves to TB3 BLACK 24 VDC Connect the 2 white wires from Valves V1 and V3 to TB3 RED DIR Decreasing Direction Connect the 2 white wires from Valves V2 and V4 to TB3 GRN DIR Increasing Direction The following diagram below shows the location of the valves when looking down at them 8 CHECK ALL ELECTRICAL AND PNEUMATIC CONNECTIONS Make sure all pneumatic connections to the actuator and PCS a...

Page 15: ...aise the pressure to the normal operating pressure 70 to 80 psi If the actuator does not move it may already be at the zero position 11 SET THE DEADBAND The Deadband should initially be set according to the Application Sizing Chart Move switch SW1 on the PC Board from the NORMAL to the SET position see illustration on page 11 and the photo below Set the digital voltmeter to DC volts and measure th...

Page 16: ...currently set beyond the desired retracted or rotational position Adjust the Zero potentiometer CCW slowly until the red LED goes off If the zero potentiometer was adjusted too far and the actuator moved away from zero adjust the Zero potentiometer CW just enough to move the actuator back to the zero position If adjusted too far the red LED will come back on Both LEDs should be off when set correc...

Page 17: ...stment from being made properly We will address this in the Span adjustment section if necessary If the zero potentiometer was adjusted too far and the actuator moved away from zero adjust the Zero potentiometer CW just enough to move the actuator back to the zero position If adjusted too far the red LED will come back on Both LEDs should be off when set correctly This ends the preliminary Zero ad...

Page 18: ...ts the full scale position the green LED will continue to flicker even when the adjustment is no longer being turned Now adjust the Span CW just enough to turn off the green LED Both LEDs should be off when set correctly This ends the Preliminary Span adjustment PTF rotary actuators less than 180 degrees of rotation Using the command signal CS formula defined in the Main Control section of the Glo...

Page 19: ...ed by setting the Main control to the zero position signal 0 volts 0 mA or 4 mA and repeating Step 12 being careful to make very small adjustments as the setting should already be very close Now recheck Step 13 and make any small adjustment that may be necessary This completes the final Zero and Span adjustments 16 DECEL RANGE ADJUSTMENT Low Decel settings provide fastest speeds High Decel setting...

Page 20: ... too big Moves in the Decreasing Direction Towards Zero The red LED will be on while moving in the decreasing direction As the actuator tries to stop at its commanded position the green LED may come on or flicker If so the Decel Range is too small On the other hand if the actuator seems to take a long time to stop at its commanded position and the green LED never comes on then the Decel Range is t...

Page 21: ... 2 x 10 7 5 0 2 667 VDC Command Input Signal If a 4 20 mA signal is used the command input signal would be calculated as follows CS 2 x 16 7 5 4 8 267 mA Command Input Signal PTF Example Suppose we have just finished the installation procedure for a Bimba PTF Rotary actuator with 200 degrees of rotation and a 0 10 VDC command input signal There is a zero rotational hard stop at 10 degrees of rotat...

Page 22: ... AVERAGE VELOCITY MAXIMUM EXTERNAL FRICTION ZERO FRICTION DEADBAND 1 2 MAXIMUM FRICTION DEADBAND MAXIMUM FRICTION DEADBEAD MINIMUM STEP PFC 09 1 1 16 PCS 1 2 to 7 1 lb 2 75 in sec 5 pounds 50mV NA NA 0 080 PFC 09 1 1 16 PCS 1 8 to 24 30 pounds 4 00 in sec 5 pounds 40mV 80mV 160mV 0 20 0 39 PFC 17 1 1 2 PCS 1 1 to 3 2 lbs 2 50 in sec zero 25mV NA NA 0 040 PFC 17 1 1 2 PCS 2 4 to 24 50 pounds 5 50 i...

Page 23: ...e 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 As Mass increases Velocity decreases up to 20 As Friction increases Velocity decreases up to 20 As Pressure decreases Velocity decreases up to 20 Increased Friction decreases repeatability Maximum e...

Page 24: ... lines to proper ports if necessary Problem Dip Switch SW1 Deadband adjustment is in the Set position Solution Move Dip Switch SW1 to the Normal position Problem No feedback signal from the actuator Solution Verify proper connection of the feedback cable to the PCS using Figure 2 If the connection is correct use a digital voltmeter and verify that there is 10 VDC present across the PCS Sensor term...

Page 25: ...d signal that has less than 5 mV of ripple Employ proper wiring techniques to ensure signal noise is kept to a minimum use shielded cables proper grounding methods etc Problem The Electrical Power Supply is supplying less than the required 23 5 VDC Utilize a DC power supply that can supply the minimum 23 5 VDC required by the PCS At voltages less than 23 5 VDC the system performance will degrade S...

Page 26: ...m Excess friction is being exerted by application components Solution Reduce the friction to levels outlined in the installation section of the manual External friction may change as system components wear over time Misalignment between the actuator and guiding system may cause binding and increase friction to unacceptable levels Problem Varying loads in application Solution Stabilize the load var...

Page 27: ...inimum 23 5 VDC required by the PCS At voltages less than 23 5 VDC the system performance will degrade Problem Decreased velocity due to flow control misadjustment Solution Some applications require flow controls to limit velocity in order to attain required repeatability The flow controls may have been adjusted after initial settings were made Re adjust to proper settings Problem Excess friction ...

Page 28: ... Improper actuator lubrication Solution Lubricate actuator with recommended lubrication See actuator catalog for recommendations THE RED OR GREEN LED WILL NOT TURN OFF Problem The Red LED will not turn off Solution The PCS electrical zero is set beyond the mechanical zero Adjust the PCS zero setting to correspond with the mechanical zero If a mechanical stop was added or changed after the initial ...

Page 29: ... 5 microns Problem Possibly Nothing Solution The actuators and valves are built to minimize leakage but not to totally eliminate it If a stable positioned actuator drifts toward the edge of the system deadband the PCS will pulse to maintain position If the deadband is set very narrow this correction will be more frequent FREQUENTLY ASKED QUESTIONS Question Are there Default Settings for the Deadba...

Page 30: ...30 User Manual Model PCS Pneumatic Motion Control System APPENDIX A PFC ELECTRICAL AND PNEUMATIC CONNECTIONS ...

Page 31: ...e MUST come from 24 VDC supplied to the PCS control and NOT the 10 VDC that the PCS produces from terminal A of TB2 If the Q quick connect option was selected the connection to terminal A of TB2 must be removed and the lead reinserted into the 24VDC terminal of TB1 Also insert a jumper between TB1 ground and TB2 terminal C dotted blue line Always insert a jumper between TB1 ground and TB2 terminal...

Page 32: ...32 User Manual Model PCS Pneumatic Motion Control System PT ELECTRICAL AND PNEUMATIC CONNECTIONS Note For Single Rack Models Use Only Bodies A and B ...

Page 33: ...ut 3 Using a 3 8 inch wrench carefully unscrew the exposed delrin nut the back end of the probe When all the threads are free pull the probe out of the cylinder Examine the condition of the probe If debris from the application s environment or from dirty air lines covers the probe the wiper and rod inside the cylinder are most likely contaminated as well and replacing the entire cylinder is recomm...

Page 34: ... INTO THE CYLINDER It should slide in freely with minimal friction Hand tighten until O ring is seated then rotate ONLY turn until with the inch wrench APPLYING TOO MUCH TORQUE WILL DAMAGE THE PROBE 5 If there is a plug connector slide it into the area in the rear cap 6 Replace the rear cap and four cap screws using the torque in the table below BORE TORQUE IN LBS 09 7 17 10 31 35 50 90 70 150 ...

Page 35: ...adjustment RET CS and then the fine adjustment RET FN 4 Position the actuator to full extend at 80 psi Adjust the output to 10 V DC using the coarse adjustment EXT CS and then the fine adjustment EXT FN GROUND FEEDBACK OUTPUT 24 VDC INPUT GROUND FEEDBACK OUTPUT 24 VDC INPUT Probe Replacement The PFCN probe is not a wear part and normally will not need replacement If replacement is necessary follow...

Page 36: ...nge specifications without prior notice en 11 18 IMI Precision Engineering operates four global centres of technical excellence and a sales and service network in 50 countries as well as manufacturing capability in the USA Germany China UK Switzerland Czech Republic Mexico and Brazil For information on all IMI Precision Engineering companies visit www imi precision com Supported by distributors wo...

Reviews:

No comments