Re: Knee for z-axis control? pnuematic actuator

>
>
> I like this idea alot. Does anyone know how to calculate the size

of

> the accumulator that would be needed based on the different

cylinder

> diameters and strokes?
>
> Thanks
> David

If you figure your actuator (piston) diameter and stroke for your
most rapid movements, ie: drilling lots of holes.

and calculate the repetitive rate for drilling, you can easily
calculate air volume. If your actuator is running at 80 PSI and
your compressor tank is 120 psi.

An example is a 4 inch dia actuator with 80 psi. That is 0.087 sq ft.

Say your holes are 2 inches of travel. Each piston stroke would be
0.174 cubic feet.

10 holes a minute would use 1.74 cubic feet of air. An air
compressor should have a duty cycle of less than 33%, so triple the
air volume to 5.2 CFM.

Since the air tank will not bleed dry, but go from 120 to 90 psi, all
you need to know is how to calculate the volume of air at 120 psi and
at 90 psi in a storage tank.

Since we know 1 atmosphere is 14.7 psi and that at 2 atmospheres the
volume is half and at 3, it is 1/3 and so on.

90 PSI is roughly 6 atmospheres and 120 psi is roughly 8
atmospheres. So, you will lose 2 atmospheres in a pressure tank as
it goes from 120 to 90 psi.

Those two atmospheres should have a volume of 3 times your use, or as
we figured 5.2 cubic feet.

7.48 gallons is 1 cubic foot so 5.2 x 7.48 = 38.9 gallon tank.

A typical commercial tank would be an 80 gallon tank so would be
almost exactly 6 times the volume needed.

Now, as for calculating hose sizes to meet your speed requirements,
I'll leave that to another post.



Dave