Learning objectives for the advanced level (TP102)
Exercise 4: Sorting packages
Learning objectives
After completing this exercise you’ll:
Be familiar with the set-up and mode of operation of a double-acting cylinder.
Be able to calculate the piston force of a double-acting cylinder for both the advance and the return strokes.
Be familiar with the set-up and mode of operation of a 5/2-way valve.
Presentation of the problem
Packages are sorted manually from a roller conveyor into large containers at a sorting station. When the containers are full, they’re removed and new containers are provided. At this point the material flow should be interrupted, but the roller conveyor continues to run. The material flow is interrupted by mechanical blocking (slide). The slide has to be operated at the sorting station.
Layout
Sorting station
Exercise 4: Sorting packages
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Parameters
A double-acting cylinder will be used, because work is carried out during both the advance and the return strokes.
Project assignment
1. Describe the set-up of a double-acting cylinder.
2. Describe the mode of operation of a 5/2-way valve.
3. Create a pneumatic circuit diagram for the package blocking slide.
4. Set up the control system.
5. Double-check the control system configuration.
6. Describe the mode of operation of the control system.
7. Create an equipment list.
Procedure
1. When the selector switch is activated, the cylinder advances and pushes the slide into the flow of material.
2. The cylinder remains in this position after releasing the selector switch and the material flow remains interrupted.
3. After turning the selector switch to its initial position, the cylinder moves to its retracted end position and the material flow is resumed. The cylinder remains in this position until the selector switch is activated again.
Safety note
Limit pressure at the service unit to a maximum of 3.5 bar (350 kPa) for this exercise.
Exercise 4: Sorting packages
Set-up of a double-acting cylinder
2 3 4 5
6 1
7
Circuit symbol and schematic diagram of a double-acting cylinder
– Compare the circuit symbol shown above with the schematic diagram of the double-acting cylinder.
Determine whether or not the two illustrations are the same.
The two illustrations are the same.
– Make a note of the characteristics of a single-acting and a double-acting cylinder designs that are the same as well as those that are different.
Both cylinder designs include cylinder barrel, piston and piston rod.
The double-acting cylinder doesn’t have a return spring.
The double-acting cylinder has 2 supply ports.
– Match the numbers from the schematic drawing with the individual components of the double-acting cylinder.
Component Designation
1 Supply port, piston chamber 2 Piston
3 Cylinder barrel
4 Supply port, piston rod chamber
5 Piston rod
6 Bearing cap
7 End cap
Exercise 4: Sorting packages
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Mode of operation of a double-acting cylinder
– Describe the mode of operation of a double-acting cylinder.
As opposed to a single-acting cylinder, more air is consumed. As the piston surfaces differ in size, the forces vary with identical pressure.
Forward stroke
Compressed air flows into the cylinder through the piston chamber supply port. Pressure is built up in the chamber and force is applied to the surface of the piston as a result. If this force exceeds static friction, the piston is advanced. Air in the piston rod chamber escapes through the port at the piston rod end.
Pressure is not built up to full force until the piston is fully advanced.
Return stroke
After reversing, air flows through the supply port at the piston rod chamber where it builds up pressure until the piston rod is retracted. Air escapes from the piston chamber through the piston chamber port.
Exercise 4: Sorting packages
Calculate the piston force for the advance and return strokes Theoretical piston force is calculated using the following formula:
Fth = A p
The following applies to double-acting cylinders:
Advance stroke Feff = (A p) – FR
– Calculate the effective piston force for the advance and return strokes of the cylinder with a working pressure of 6 bar (600 kPa).
The piston diameter of the cylinder is 20 mm and the piston rod diameter is 8 mm.
Exercise 4: Sorting packages
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Determine the requirements for the directional control valve
– Write down the requirements for the directional control valve.
Compressed air must be available in both switching positions, because the double-acting cylinder cannot be retracted without compressed air. Venting of the other cylinder chamber must be ensured in each case.
– Indicate why the directional control valve has to be actuated with a switch.
A switch has to be used because a pushbutton cannot be held in the activated position for as long as it takes to replace the containers.
Exercise 4: Sorting packages
Mode of operation of a 5/2 way valve
– Complete the circuit symbol of a manually actuated, 5/2-way valve with spring return and locking function, and enter the port designations.
2 4
3
5 1 5 4 1 2 3
Circuit symbol and schematic representation of a 5/2-way valve
– Describe the mode of operation of a 5/2-way valve when valve port 2 is connected to the piston rod end of a double-acting cylinder.
Mode of operation of a 5/2 way valve, unactuated
When the 5/2-way valve is not actuated, the return spring holds the valve in its initial position. The piston rod end of the cylinder is pressurised and the piston rod is retracted.
Mode of operation of a 5/2 way valve, actuated
When the 5/2-way valve is actuated, the force of the valve return spring is overcome and the valve is reversed. In this state, the supply port is connected to the piston end of the cylinder via the valve while the piston rod end is exhausted via the valve. Pressure which is built up at the piston end causes the piston rod to advance. As soon as the piston rod has reached its advanced end position, maximum operating pressure is built up at the piston end of the cylinder.
Actuation with a switch
If the valve is actuated with a switch, the valve remains in either of its positions until the switch is reversed again.
Exercise 4: Sorting packages
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Complete the circuit diagram
– Complete the circuit diagram shown below.
2
31
1A1
1S1
0Z2
0Z1
2 4
3
5 1
Pneumatic circuit diagram
Exercise 4: Sorting packages
Create an equipment list
In addition to the circuit diagram, complete project documentation also includes an equipment list.
– Create an equipment list by entering the required components in the table below.
Quantity Designation
1 Cylinder, double-acting
1 5/2-way valve with selector switch
1 Distributor block
1 On-off valve with filter regulator
1 Compressed air source
Exercise 4: Sorting packages
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