Controlling Pneumatic Cylinder Speed
Great tip for controlling pneumatic cylinder speed from our partners at Proportion-Air! Contact JH Bennett for application assistance!
Air over oil? Nope – air only!
Air over oil is the traditional method for pneumatic cylinder speed control applications. This is accomplished via a reservoir of oil, driven by air pressure on the top of the oil through a needle valve to control the speed. With a Proportion-Air F-Series mass flow controller, the traditional reservoir of oil is not necessary. The speed of your cylinder can be controlled with only compressed air.
It is virtually impossible to control the speed of a pneumatic cylinder and adjust that speed as the cylinder is traveling.
Unless – your pneumatic cylinder is controlled using a Proportion-Air FA-Series closed-loop mass flow control valve. This product is so fast to respond you can adjust speed on the fly. Literally.
It may sound too good to be true, but this is an extremely repeatable claim.
How the FA-Series Controls Pneumatic Cylinder Speed The Proportion-Air closed system valve is extremely precise. The mass flow of air leaving the pneumatic cylinder (to atmosphere) is controlled with the combination of an electronic mass flow control valve, a mass flow monitor, traditional four-way/five-port solenoid valve and sometimes an additional electronic pressure regulator. The solenoid valve is used to change the cylinder direction between extend and retract. But regardless of whether the pneumatic cylinder is extending or retracting, the speed of extension or retraction is always being controlled by the electronic flow control package by metering out the exhaust from the pneumatic cylinder.
Because the electronic set point command to the pneumatic cylinder can be varied, the velocity can be varied on the fly. A soft start and a soft stop can be programmed into the PLC, and this can really decrease wear and tear on the pneumatic cylinder.
One customer had a rodless cylinder (as the name implies, it has no piston rod and is constructed with a slide table assembly mounted directly above the piston with a lip onto which you can bolt something and move it back and forth). The customer wanted to move this rodless cylinder as fast as physically possibly and control the deceleration so that parts didn’t go flying off. They used proximity sensors – electronic devices that sense when the piston passed the location of the sensor, sending a message to the computer indicating when to throttle back to half speed, again at quarter speed, and then shut off. Once it gets to those throttle back positions, it repeats each time – because the Proportion-Air product is fast enough.
In addition to repeatability, the cost of the Proportion-Air system in an air system is much less than electro-mechanically driven systems. Air is expensive to generate, but in the grand scheme of things, the capital outlay is much less.
You can find the original article and other great information from Proportion-Air here.
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