1. IENG 475: Computer-Controlled Manufacturing Systems
IENG Lecture 10
Relay and Pneumatic (Fluid) Control Logic
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems
(c) 2006, D.H. Jensen

2. IENG 475: Computer-Controlled Manufacturing Systems
Assignment
Assignment
Begin HW 04. Do this in teams of 1 – 2 persons.
Turn in ONE scanned/digital PDF file with Subject Line: IENG 475 HW 04 and CC your partner (if any!)
Select Project and Start Product Design
Be ready to select a project – by end of lab next week.
Begin documentation of team project.
Most of the routing information will be pulled from your MasterCAM files, and you can pull images from the SolidWorks files.
Remember to collect timing data as you go!
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

3. IENG 475: Computer-Controlled Manufacturing Systems
Relays (Switches)
Specification:
Poles & Throws
Making (N.O.) / Breaking (N.C.)
Latching (toggle) / Non-latching (momentary)
Transfer between low power logic controls and high power energy controls
Coil Nomenclature:
“relay” (< 10 A)
“power relay” ( A)
“contactor” (> 30 A)
“starters” (Overload protection, thermal)
Potential problem: “contact bounce”
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

4. IENG 475: Computer-Controlled Manufacturing Systems
Switch Nomenclature
Poles – number of individual complete circuits switched at a time
Throws – number of positions for each pole
Normally Open / Normally Closed – stable position (if there is only one)
Latching / Momentary – stays in position / returns to normal position NO NC
COM
Single Pole, Single Throw, Normally Open, Latching
Single Pole, Single Throw, Normally Closed, Momentary
Single Pole, Double Throw, Latching
SPST - NO Latching
SPST – NC Momentary
SPDT – Latching (Toggle) NO NC
COM
Double Pole, Single Throw, Normally Open, Latching
Double Pole, Single Throw, Normally Open, Momentary
Double Pole, Double Throw, Latching
DPST - NO Latching
DPST – NO Momentary
DPDT – Latching (Toggle)
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

5. IENG 475: Computer-Controlled Manufacturing Systems
Wire Logic
Review: Current flows from source to ground
“AND” (•):
c = a•b
“OR” (+):
c = a + b
“NOT” ( ¯ ):
c = a c b a c b a c a
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

6. IENG 475: Computer-Controlled Manufacturing Systems
Wire Logic
Example: Missile engine (e) should start only when the President (a) orders it fired and both range officers (b and c) concur with the order. Once fired, the engine should stay on unless the self-destruct (d) is activated.
e = [ ( a • b • c ) + e ] • d b a e d c
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

7. IENG 475: Computer-Controlled Manufacturing Systems
Pneumatics
Why use Pneumatic Controls?
Can withstand stalling without damage
Explosion proof
Generate little heat (at point of operation)
No shock hazard
Can operate underwater with minimal problems
Can obtain high speeds
Can obtain medium sized forces
Switching Sense:
Normally Not-Passing / Normally Passing
Compare with N.O. / N.C. for electrical switching
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

8. IENG 475: Computer-Controlled Manufacturing Systems
System View
Components of a shop pneumatic system:
compressor
receiver
main line
branch line
outlet
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

9. IENG 475: Computer-Controlled Manufacturing Systems
ISO Symbology
Air flow paths are shown as solid lines.
Valve ports are shown on the outside of one of the position squares, denoting the normal position.
Flow paths within the valves are shown as arrows.
Terminations are shown as lines with a short “cap” line perpendicular to the end (T).
Exhaust ports are shown as lines terminated with a “outward” pointing triangle.
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

10. Signal / Control Valves
Number of ports may be counted from the lines exiting the normal position square
Number of squares is the number of positions
Example: 3/2 manually actuated signal valve
Function is evident by shifting position squares
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

11. IENG 475: Computer-Controlled Manufacturing Systems
Valve Actuation
General (Manual) Actuation
Mechanical Actuation
Solenoid Actuation
Air Actuation
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

12. IENG 475: Computer-Controlled Manufacturing Systems
Logic Valves
(OR gate) Shuttle Valve
(AND gate) Two Pressure Valve
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

13. Single Acting Cylinder
To extend the cylinder, air flows in the port side, compressing the spring side...
To retract the cylinder, air flows out the port side, releasing the spring side.
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

14. Double Acting Cylinder
To extend the cylinder, air flows in the left side, exhausting the right side...
To retract the cylinder, air enters on the right side, exhausting the left side.
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

15. IENG 475: Computer-Controlled Manufacturing Systems
Speed Controls
Two types:
Manually Operated
Operator controlled flow
Needle Valves
ISO Preferred
Flow rate is set once*
Closing a valve slows operation in BOTH directions!
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

16. IENG 475: Computer-Controlled Manufacturing Systems
Miscellaneous
Check Valve (a control valve):
Permits flow in only one direction
Pressure Sources:
Compressor (fixed displacement shown)
Must be running to generate pressure
General Pressure Source
Usually a Receiver
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems

17. ISO Pneumatic Diagrams
From top to bottom, component layers are:
Actuators
Speed Controls
Control Valves
Logic Valves
Signal Valves
Pressure Supply
11/16/2018
IENG 475: Computer-Controlled Manufacturing Systems