Description of tasks
Your employer has decided to automate the riveting process in the production. In the
riveting two pieces of metal are connected together by steel rivets. The mechanical
departement of the company has planned and build a prototype of riveting machine.
Your goal is to plan and automate the pneumatic and electric control of the machine according to
the safety regulations.
The device has three pneumatic acting actuators.
3
1 2
1) Fastener
-Single acting cylinder, which keeps the riveted component in place
-Cylinder has no limit switches, only pressure switch , which controls correct
working pressure.
-Control of the cylinder is made by pneumatically operated 3/2 way valve.
2) Support cylinder
- When the component is secured in its place by fastener cylinder, double acting support
cylinder moves forward and supports the component during the riveting.
-Cylinder has two mechanical micro limit switches to control the forward and backward
positions of the piston.
-Control of the cylinder is made by electrically operated 5/2 way valve with
two solenoids.
3) Riveting cylinder
- Double acting cylinder has two reed proximity switches to control the forward and
backward positions of the piston.
-When component is secured in its place and the support cylinder is in the forward position,
this riveting cylinder makes four strokes.
-Control of the cylinder is made by solenoid operated 5/2 way valve with spring return.
The first task is to design, document, and connect the fastener cylinders peumatic control circuit.
For safety reasons, the control of the fastener shall be a pneumatic two-hand control.
-Fastener cylinder moves forward when two manually controlled pneumatic valves are pressed
simultaneously.
-Cylinder returns in its original position if one or the other of the manually controlled valves is
released.
-Cylinders speed of the movement is controlled by one way flow control valve. Adjust the speed of
movement so that the time from backward to forward position is 3 seconds.
Task 1:Fulfill the pneumatic control circuit below by given symbols. Simulate the circuit by
fluidsim. Then make the real connections to the pneumatic board and test it. Working pressure is
4,2 bar.
Task 2: Next we will add solenoid valve and auxiliary relays to the fasteners control circuit. This is
done by adding solenoid valve, pressure switch , relays and suitable push button.
-Next to the cylinders air connection is added pressure switch P1 which triggers when a
suitable working pressure is reached. Connect the signal wire to normally closed (NO)
contact of the pressure switch. Triggerin pressure is 4.0 bar.
Pressure switch controls relay K1. Make a hold circuit to the relay. Relay controls
solenoid Y1 so that fastener cylinder leaves forward position when the suitable working
pressure is reached.
Connect pushbutton S1 to the circuit by which the hold circuit could be released.
Fullfill next pneumatic and electric circuits with given symbols. Test these circuits with
fluidsim. Then make the real connections to the pneumatic board.
Fullfill the electric control circuit and missing component identification marks.
Task 3 : PLC control of riveting machine. (Programming part of this task is optional,
if you are not familiar with codesys enviroment you can also use demo program in the monitor
mode).
Program the sequence according to the description below using codesys programming
platform.
Sequence:
-Attach the component using pneumatic two-hand control valves.
-When the working pressure is ok., pressure switch triggers and hold
circuit keeps the fastener cylinder in the front position.
-Indicator light H1 lights up.
-You are now able to start the automatic drive by pressing start button S2.
-When you press the start button indicator light H2 lights up and automatic
sequence starts:
-support cylinder moves front position.
-when the support cylinder is in its front position riveting cylinder
makes 4 front and back moves.
-when the riveting cylinder has made 4 moves and has come
to the back position , support cylinder moves back.
-when the support cylinder is in the back position incator ligth
H2 goes off and the sequence ends.
-New sequence starts by pressing S2
Other rules:
-Automatic drive is possible only when fastener cylinder is ready
-H1 lights up only when working pressure is at the right level.
-H2 lights only during the automatic sequence.
-If the working pressure of fastener cylinder goes down during automatic sequence,
all cylinders returns at their starting positions and the sequence stops.
Make the pneumatic connections of the cylinders according to the pneumatic diagrams below to the
pneumatic board.
Connect electric control circuit of the plc according to the input and output diagrams.
Push buttons and indicator lights you can find from the festo module descriped below.
Input diagram:
:
Output diagram