IENG 475 - Lecture 12
Relay and Pneumatic
(Fluid) Control Logic
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
1
Assignment


Assignment
• Begin HW 04.
Do this in teams of 1 – 2 persons.
Complete Product Design & Cut Personal Parts
• Finish programming verification & cut individual
parts – by end of lab 24 APR.
• Begin documentation of team project, ASAP.
Most of the routing information can be pulled from
your MasterCAM files, and you can pull images
from the SolidWorks files.
• Remember to collect timing data as you go!
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
2
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”
(10 - 30 A)
“contactor”
(> 30 A)
“starters” (Overload protection, thermal)
Potential problem: “contact bounce”
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
3
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 one)
Latching / Momentary – stays in position / returns to normal position
NC
NO
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)
NC
NO
NC
NO
COM
COM
Double Pole, Single Throw,
Normally Open, Latching
Double Pole, Single Throw,
Normally Open, Momentary
DPST - NO Latching
DPST – NO Momentary
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
Double Pole, Double Throw,
Latching
DPDT – Latching (Toggle)
4
Wire Logic


Review: Current flows
from source to ground
“AND” (•):
•

c = a•b
“OR” (+):
•
a
a
b
c
c
c=a+b
b

“NOT” ( ¯ ):
•
c=a
4/13/2015
a
IENG 475: Computer-Controlled
Manufacturing Systems
c
5
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
a
b
c
d
e
e
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
6
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
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
7
System View

Components of a shop pneumatic system:
• compressor
• receiver
• main line
• branch line
• outlet
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
8
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.
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
9
Signal / Control Valves

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
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
10
Valve Actuation

General (Manual) Actuation

Mechanical Actuation

Solenoid Actuation

Air Actuation
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
11
Logic Valves

(OR gate) Shuttle Valve

(AND gate) Two Pressure Valve
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
12
Dual 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.
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
13
ISO Pneumatic Diagrams

From top to bottom, component layers are:
• Actuators
• Speed Controls*
• Control Valves
• Logic Valves
• Signal Valves
• Pressure Supply
* not discussed in handout
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
14
Questions & Issues

Lab:
• Computer-Aided Milling/3-D Printer/Laser Operations
• Finish CAD/CAM work
• Personal design parts (by lab this week, in team folder)
• Lathe/3-D Print part (at least 1 per team, in team folder)
• Mill Part (at least 1 per team, in team folder)
• Laser Engraver (at least 1 per team, in team folder)
• Drill Part (1 per team, organize with team)
• Perform CNC Milling & Turning, Engraving, Drilling
• All parts – timing!
4/13/2015
IENG 475: Computer-Controlled
Manufacturing Systems
15