Pneumatic circuits

Explain what pneumatics is and name two everyday devices or machines that operate on compressed air, stating what motion each one performs.

Name the basic components of a simple pneumatic circuit and explain in one sentence the function of each one.

In the diagram in the figure, there is a component marked with ?. State what component it is, what function it performs, and describe what happens to the cylinder rod when it is actuated and when it is released.

Name three machines or services in your environment that use compressed air (dentist's surgery, petrol station, street roadworks...) and explain what job pneumatics performs in each one.

Explain the difference between a single-acting cylinder and a double-acting cylinder, and describe what is observed when releasing the push button in each case.

Put the path of the air in this circuit in order: cylinder, compressor, control valve. Then, explain why the valve is placed between the air source and the cylinder and not after it.

A bus door opens and closes using a pneumatic cylinder that must push in both directions. Explain what type of cylinder and what type of valve it needs, and why a single-acting cylinder with spring return controlled by a 3/2 valve would not be suitable.

In a workshop, the rod of a single-acting cylinder extends normally when pressed, but returns very slowly when released. Analyse at least three possible causes (leaks, worn spring, dirty valve...) and explain how you would check each one.

A service unit (filter, pressure regulator, and lubricator) is usually placed before the circuit. Explain what each of its three parts does and what happens to the valves if the air arrives dirty or with uncontrolled pressure.

A double-acting cylinder is controlled by a 5/2 valve. Explain in your own words what these two numbers mean (five ports, two positions) and how the valve enables the rod to extend and retract.

To actuate a stamping press using a pneumatic cylinder, an elementary circuit is proposed with a manual push button that switches a monostable valve: pressing it lowers the press and releasing it raises it by means of a spring.

1. a) Justify why this design fails to comply with basic industrial machinery safety regulations and which pneumatic logic element (two-pressure valve or "AND" valve) must mandatorily be incorporated to implement a two-hand control for operator protection.
2. b) Design the improved circuit by describing precisely which components you would use and how you would connect the pressure lines between the push buttons, the logic valve, and the actuator.
3. c) Predict what would happen if the operator attempts to bypass the system by permanently jamming one of the two push buttons with a clamp, and reason what additional synchronism condition modern industrial safety requires.

A technical office must choose the drive system (electric or pneumatic) for two different industrial applications in a factory:

1. A positioning robotic arm for assembling microcomponents, which requires an accuracy of 0,1 mm and holding intermediate positions fixed with rigidity.

2. A pusher for a packaging area in a flour mill, where the environment contains suspended combustible dust and packages may frequently jam against the mechanical stop.

For each of the two applications, determine which of the two technologies you should choose and justify your decision by analyzing: positioning accuracy, behavior under mechanical overload stall, and ignition risk in explosive atmospheres.

Describe in words a circuit design in which two cylinders move simultaneously actuated by a single push button. Analyse what synchronization problem might arise if one carries more load than the other and how it could be mitigated.

An operator looks at the pneumatic circuit shown in the figure and claims that, in the resting position depicted, the cylinder rod will remain at an intermediate point because compressed air enters simultaneously through both chambers and the pressures balance out.

1. a) Reasonably refute the student's claim: identify the valve marked with ? (number of ports, number of positions, and type of actuation/return) and deduce in which exact position the rod will be before pressing the push button.
2. b) Describe the complete operating sequence: explain what occurs in each chamber of the cylinder while the push button is held down and what happens exactly at the instant the push button is released.
3. c) If the driven load extends with excessive acceleration and slams into the end-of-stroke stop, indicate which auxiliary component you should install, in which specific line you would place it, and in which direction to regulate only the advance speed without slowing down the retraction.