Loud Noise when using a pneumatic cylinder for push off

You didn't describe how the pushing progresses. Does the pin slide out easily? Does the pressure build up slowly until the pin just suddenly gives way?

Without seeing the equipment or knowing what you're actually doing, I can only make a couple of guesses.

If the pin is forced fit (as in really jammed in there), the bang may probably be just the pin being forced out. Can't offer a solution except to issue ear protection for the operator.

Next possibility is the sound of the cylinder piston slapping or hitting the other end of the cylinder. You may need a cylinder with built-in cushioning or a speed limiter.

It's also possible that it's the sound of the air coming out of the cylinder's exhaust. You might be able to solve that by installing a silencer (not the type used in weapons ).

Thanks very much for your response. The pin is not only force fit, a special type of glue is used to hold it in place. Thus the pressure builds up slowly until the pin suddenly gives way.

I'll try some of your suggestions and see if it helps.

Cheers.

Just out of curiosity, if the pin has been glued in, why would you force it out? I'm sure there's a good reason but I'm thinking,

"why go through all the trouble of putting it in, only to force it out later?"

I mean, if you could find a way to eliminate the installation of the pin in the first place, then you wouldn't have to remove it later.

Basically, the push off mechanism is used on components that have failed test.

Rather than throw them away, we strive to reuse them and to reuse them, we have to push off the pin and fix a new one.

The cylinder has too much stored elastic energy (in the compressed air). It's hard to envisage exactly what you describe. Can you change to a hydraulic cylinder (to give a 'stiffer' action ) , or moderate the speed with which the pin yields. It might also be down to how the whole assembly is mounted.

K

I can't use a hydraulic because of the environment. I'll try a cylinder with cushioning.

Thanks.

How about bringing in a couple of stiff springs aligned with the pin . The cylinder acts on the pin and the springs. When the pin gives , the springs will prevent sudden 'popping' action of the cylinder. The mechanism may be too complicated , but I'm guessing as to how the set-up looks.

Could be the slap of the swab at the end of the cylinder stoke. Especially if cylinder rod is being extended very quickly. Recommend a cylinder with a cushion.

"I am using pneumatic pressure at 5 bar on a 125mm bore cylinder with a stroke of 50mm to push off a pin from a component. The required force to push off the pin is typically between 5 and 7 KN."

Why not a hydraulic press? Or a compound lever? Both provide controlled movement.

A mechanical stop on the piston just after the point that the pin releases.

Just reading between the lines, it sounds like the load is released from the cylinder before the end of the stroke. Put a gage in the exhausting port of the cylinder, and read while the cylinder is under load. If the pressure is low, a cushion won't stop it from hitting as high velocity. You need to decelerate the cylinder to a low velocity prior to the piston contacting the head. If a cushion won't word, then find a place to mount a shock absorber. Check this site: www.enertrols.com. If there is no place to install a shock you will need to discuss the application with an applicatiion guy at one of the shock manufacturers. If the piston is large enough to accommodate shocks; the piston could be drilled, and tapped in 4 places for mounting shocks. To get the same stroke as before, you will have to replace the cylinder with one having enough extra stroke to compensate for the shock length. This is an extreme solution to the problem, but may be the only one if an air cylinder has to be used. Other actuators, such as hydraulic, or electro-mechanical would maintain a nearly constant velocity during load change. Air is a relatively economical solution to many motion control applications, but with any solutions, there are compromises.

Can you Chamfer the pin's trailing edge, component or both; so final 3-10mm graduates energy released as pin clears? If possible, start with small chamfer and try minimal cutting until pin clears without a sharp edge.

Opposing force may be required as you complete the stroke, as well.

Does the pin accelerate as it leaves the cylinder, presently? Is there shear pressure in effect?

The pin may accelerate when you chamfer the trailing edge.

Control of the thrust and graduated release may damper your finishing stroke.

Hi,

I had a similar problem with a pneumatic press tool. The "bang" was coming from the tooling bottoming out due to the reasons outline above. We could have tried different larger cylinders with cushioning etc. However, we fixed the problem with polyurethane stops found in Musumi press tool catalogue.

Cheap and nasty but effective solution to the problem. Maybe not suited to your application.

If you have the time and money I would first try a larger cylinder with cushioning.

Regards

How about a needle valve to limit the sudden release of compressed air on the exhaust port. You could regulate it to discharge slowly and freeflow during reset. This would act as a cushion externally rather than swapping out the entire cylinder.