Maximum Velocity of Pneumatic Cylinder

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Well how do I measure the discharge across the pneumatic cylinder

Depends on the amount of load.More load=less speed for same pressure. Not enough info to give definitive answer.

Even without a load. The port size, air pressure, control valve size and supply line size are limiting factors.

To calculate the maximum velocity of the cylinder would require alot more information. The load if any the cylinder is seeing, the orinitation of the cylinder, if it is vertical, horizontal, or inclined. The quality of the compressed air supply, the size of the airline connecting the valve to the air source, the size of the airline connecting the valve to the cylinder, if straights or elbows are used to connect the valve and the cylinder.

Other critical things are the flow rate of the valve, if silencers are used, and if so what size are they. Is the air lubricated or unlubricated. An obvious factor in achieving the maximun speed will be the configuration of the valve, if we are exhausting air from the cylinder or if it is vented to atmosphere.

Typically a maximum piston speed between 1 m/s and 1.5 m/s would be achieveable however the longevity of the cylinder will be limited by the ability to slow the piston up within the allowable design constraints of the cylinder cushioning.

From your information, it seems that the available pneumatic pressure is 8 bar only. The actual pressure developed inside the cylinder will depend upon the load. But with maximum available pressure of 8 bar, the load the cylinder can move is 160 Kg. (Including weight of piston and piston rod) maximum. If load is more, this cylinder will not be able to move it at 8 bar.

The speed of piston will depend on the flow rate available from your storage tank at constant pressure.

Volume consumed per stroke is just 275 CC (140 mm stroke). With this much air remove from the air storage tank, pressure should not drop. If you want to move the load number of times in sequence, same reasoning applies.

Besides, the ports should be capable of transfering the air of 275 cc in required time of stroke. Say if you want to move the piston (and obviously the load) at say 0.1 second, (with effective speed of 1.4 m/sec), the piping, ports and the silencers should be of big enough size capable of transfering 2.75 litres/sec.

Here we are not considering acceleration and deceleration. Also we are neglecting the frictional losses in cylinder.

I have put directly the figure. I hope you will understand how these pigures are arrived:

Force = C/S Area X Pressure

Volume flow rate = Displace volume / time of displacement

Displaced volume = C/S Area X stroke

Pneumatic cylinders can go fast but produce a very harsh operation because the cylinder is still accelerating up to the point where it hits the end stop. This is caused by the high pressure needed to get a good acceleration and the fact that air is compressible. The cylinder keeps on accelerating even when the valve close. Flow restrictor and bumpers will be needed to obtain a satisfactory operation.

Don't forget, harsh and shaky operation will require much more maintenance. Component will loosen, fasteners will fail from mechanical stress.

The best fast machines I have seen were operating with mechanical cams pushing levers for the main movements. Pneumatic or electrical actuators were used for simple dependent motions.

If you want a reliable machine, keep it simple and don't push the components to their limits.