pneumatic piston speed?

[DiaaHamdy]

Hi guys,
If I have a Piston cylinder with a diameter of 20 mm, a stroke of 125 mm and an operating pressure of 4 bars and I need to estimate the velocity of the piston but I don't know the time,(like to calculate it from this formula F=P*A and V=a*t)so could any one please helps me .Thanks

 

[BigInch]

you do know the time. Revolutions/MINUTE

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[hydtools]

What is the mass you are accelerating? F=ma
You know F. a = F/m
Use kinematic equations to relate stroke travel, acceleration, velocity and time. Take the case of constant acceleration, for example. And assume air flow is sufficient to maintain pressure P. s = 1/2 * a * t^2 v = a * t

Ted

 

[imcjoek]

If the piston velocity is sufficiently high (which I'd guess it is, if velocity is important enough to calculate?), the effect of pressure drop in the various fittings will make a simple constant pressure assumption invalid.

Try the manufacturer if it is an off the shelf part. I've run across at least one air cylinder manufacturer (Tolomatic) that has documentation on calculating piston velocity available.

 

[israelkk]

hydtools

Why to assume air flow is sufficient to maintain pressure? The pressure inside the piston can (needs to) be calculated with the movement of the piston by simulating the flow inside the piston too.

 

[BigInch]

The easiest way is to set a time over which you want the piston to travel the stroke length. Otherwise you're back on the mass, acceleration, velocity route.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[hydtools]

israelkk, because it is the simplest case, maximum flow and maximum pressure. The results will be the maximum expectation for a first order of magnitude look without calculating pressure drops and air expansion in the cylinder.

Ted

 

[israelkk]

hydtools

You are correct that this is the top speed case but DiaaHamdy need to practically estimate/calculate the actual speed not the maximum theoretical speed. I have seen robot arms speed much lower than expected because the designer failed to involve the actual flow rate into the cylinder as the result of the tubes inner diameter, valve orifices, cylinder inside volume and gas properties.

 

[hydtools]

israelkk, to your point, we need more information from DiaaHamdy. Otherwise, assuming/guessing is all we can do.

Ted