Did you know you can improve machine efficiency without reducing productivity by selecting pneumatic valves and pressure regulators strategically? Many times, the compressed air delivered to a work point is at a higher pressure than required.
The key to reducing compressed air consumption is reducing the pressure supplied to the machine without affecting force and torque. How can you accomplish such seemingly contradictory goals? Here are six options to consider:
Option One: The clamp-press pneumatic circuit
If we disregard friction, the force in a clamp or the torque in a pneumatic system is directly proportional to the pressure applied to it. More pressure means more force. Regulators are often employed to limit pressure supplied to a circuit or actuator, often a single one for the entire application.
However, some circumstances merit lower force requirements for a portion of operations, which presents an opportunity to increase efficiency.
A clamp-press circuit (Fig.1) can help in these situations. Clamping force is adjusted dynamically depending on the size and nature of the part. In this example, the filter-regulator unit supplies 70 psi (4.8 bar) to the directional control valve, which is a push button operated, spring returned, 2-position, 5-ported, 4-way valve.
That same regulator also supplies pressure to the secondary regulator. The main regulator then controls the force of the double-acting press cylinder.
What the additional regulator does is achieve independent control of the clamping force. It can be reduced to 50 psi (3.5 bar) and connected to the directional control valve. When in operation, the clamp cylinder directional valve will extend only to the necessary pressure to move the cylinder. When in position, the pressure in its base can only reach 50 psi (3.5 bar).
This approach limits the force generated by the clamp cylinder and can be employed in any multiple force system.
Option Two: The differential pressure circuit
The “non-work” portion of a use-cycle represents a significant savings area. Often, the pressure used in non-work portions is the same as in the “work” portions. Reducing the “non-work” pressure can save significant amounts of energy and increase machine efficiency.
Here the circuit (Fig. 2) shows a differential pressure circuit that can accomplish this. It consists of an inline air filter with an automatic drain, two relieving type regulators, a double-acting cylinder and a push button, spring returned, 2-position, 3-way directional valve.
In this circuit, the work portion requires 80 psi (5.5 bar), but little force is needed to retract the cylinder, so it is low pressure. To accomplish this, secondary regulator, between the outlet of the primary regulator and the head end port of the cylinder, is set at 20 psi (1.4 bar). It functions as a reduced pressure air spring for the returning piston and some external load.
However, there’s a potential problem with this circuit. If the pressure at the head-end of the pneumatic cylinder exceeds 20 psi (1.4 bar), the cylinder will extend slowly and with reduced force. Exhaust air would be forced through the venting port of secondary regulator.
This is because the secondary regulator is continuously supplied by the primary regulator at 80 psi (5.5 bar). Moreover, reverse flow through the secondary regulator cannot occur.
To avoid this circuit (Fig. 3) demonstrates how you can take a different approach by placing a quick exhaust valve between the secondary regulator and the end port of the cylinder. Pressure in the head-end, in this setup, exhausts through the quick exhaust, not the regulator’s vent port.
Thus, as during retraction of the cylinder, the quick exhaust shuttle shifts automatically to its exhaust port. This directs the 20 psi (1.4 bar) required into the head-end of the cylinder.
Article contributed by Bill Service, marketing manager, Pneumatic Division, Parker Hannifin Corporation.
Much of this content was first published as a contributing article from Parker Hannifin in Hydraulics and Pneumatics as “Simple Circuits Provide Big Benefits”