Fluid power circuit construction

[Nil Skrzypczak]

Hello all,

I am a student in a trade apprenticeship program and am currently attending a pneumatics power and control course. I have been tasked with drawing up a pneumatic circuit that performs this sequence:

Pushbutton 1 and/or 2 cause cylinder 1 to extend. Cylinder 1 makes limit switch 1. Limit switch 1 extends cylinder 2. At approximately 75% of its travel, cylinder 2 makes limit switch 2, which causes cylinder 2 to decelerate for the last 25% of its travel. Pushbutton 3 returns both cylinders.

I have no idea what would causes a cylinder to slow down, could someone help?

 

[IRstuff]

I have no idea what would causes a cylinder to slow down,

Well, what made the cylinder move in the first place? And how would you get it to stop? And then, how would get the stopping to slow down?

TTFN (ta ta for now)
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[3DDave]

Typically one adds a metering orifice to the exhaust side of the cylinder. The restriction causes there to be less pressure drop so there is less force available. Notice that if the cylinder meets an obstruction, the exhaust air will continue to leak allowing the pressure differential to increase and overcome the obstruction. When the cylinder moves it will recompress the exhaust side until it again reaches the velocity where the forces balance in a steady state.

The orifice can be adjustable with a cam to drive the size so that the leak path becomes smaller as the cylinder moves.

If you have a residential door closer with the internal spring there will be a small adjusting screw to change the leak path. If you pause the door you will notice the force increases as the air leaks out. You can, if you like, turn the screw while it is closing to change the rate of closure.

Unfortunately, because air is compressible, it's not possible to guarantee the velocity profile. If, for example, the exhaust port was closed off, changing the load will cause the piston to move.

 

[Pud]

I used to have equipment where the slowing down was done with by oscillating/pulsing fast the air control valve.
Worked fine.

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[Andrea_martinez325]

I am not an expert on this, but there may be some problems in your circuit, which you may not have assessed.
One of them could be the amount of compressed air in each cylinder and another can be the type of cylinder you are working with.

I recomend you to do some research on it and see if you find a solution.
GOOD LUCK MATE!