# Looking for newbie help



## Rraven (Sep 24, 2013)

Ok this has everything to do with pneumatics but nothing to do with props... but I'm building a tool at my shop and I require control of a roller. I want to raise and lower the roller and also be able to apply varable pressure with the roller. example Roller starts in the raised position, I then lower it to a work surface. Then I can increase the pressure applied by the roller say 2-4 bar. Am I using the correct terms and explaining my needs? and advise or help as to valve to use and or type of cylinders would be great.


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## bfjou812 (Aug 15, 2008)

It can be done, you don't say how you want to vary the pressure,manually or automatically, or if when you raise the pressure does it need to stay at the increased value or flucuate? A lot more information is needed.


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## Haunted Spider (Sep 6, 2010)

I am going to take a stab at this. You need to find a valve that is used to raise and lower air bags on cars. This is a manual solenoid 3 way valve that you push one way and it adds pressure, let go and it stops and push the other way and it lets the pressure out. 

Add a pressure gauge in line past the solenoid valve and you can see what pressure you are at. A simple calculation of the pressure will tell you how many pounds of lift you have on your cylinder giving you a variable pressure on the roller. 

You are going to want a single acting cylinder for this as a double will want to shoot up and down quickly. The single will allow you to use the 3 way solenoid as well as bleed the air off slowly if you want to bring down the pressure a bit. 

The cylinder size you need will depend on the height you want to lift the roller to and how much pressure you want to apply. A few vendors on here sell multiple cylinders of different sizes and can help you with the pressure and size you need to achieve. They are listed in inches of throw so find one that fits your bill. 

Ok, thats all I have.


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## Hippofeet (Nov 26, 2012)

Rraven,

I make some pneumatic tooling every now and then (cutting machines, bottle fillers, and sundry) on the side, and I think Haunted Spider covered it fairly well. If you know the pressure you need, in bar, then I would convert it to PSI, that's what most of us speak. You can calculate cylinder force by force equals pressure times area.

So for a 1 inch cylinder that would be pressure (say 100 PSI) times bore area (3.14 times .5 squared is .785) so force equals 78.5 Pounds.

I always want my needed force to be less than the max of my cylinder, so I would go bigger than what I might calculate I need, so if I calculate I need a 2 inch cylinder, I buy a 2.50. 

If the force you need requires a very expensive or large cylinder, you can use a lever and a cylinder with a longer stroke (but smaller bore) to increase the force, but remember that there is an angle vector in there, so if you push or pull against an angle less than around 30 degrees, you radically change the amount of force needed to overcome the initial resistance, and get a stroke, with pneumatics anyway, that is slow to begin, and then shifts speed unpredictably through the remainder of the stroke, as the force required to move the lever drops off the cliff.


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## Rraven (Sep 24, 2013)

Thank for all the replies and I'm going to re-read each one several times. but to clarify, what I do is wide format printing including billboards and vehicle wraps. One issue I have is mounting vinyl graphics to rigid substrates in a quick efficient way. I'm wanting to convert my 72" x 186" light table to a pressurized application roller mounted to a manual travel beam. I was thinking that I may need a pony bottle that I would use to raise and lower the roller, then use a regulator to adjust the working pressure.


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## Hippofeet (Nov 26, 2012)

Gotcha.

I would probably go with 2 double acting cylinders, DC coil 4 way solenoids, a simple on/off push button switch, and a pressure regulator mounted on the beam on the standing side of the table, with coil airline festoonage. I would have the solenoids plumbed so that ON is down, assuming that the roller would spend more time in the UP position. Just looking to extend coil life by choosing whatever position of roller gives the lesser time of coil activation.

You could use single acting, they would retract with spring pressure, but I would still go with double acting, with speed control mufflers on the solenoid exhausts, to give a nice gentle up and down, and be able to time the two cylinders. It would be difficult for me to design an arm that long that exerted even pressure across that distance with one cylinder.

Why the pony bottle? The only air loss in the system would be during the up or down stroke, the loss would be minimal, I would think even a small 2 or 3 gallon compressor would do it easily, as long as it could reach a pressure to give you a good, bubble free roll. The pressure required for that, I can't even guess at.

How strong is the surface of the light table? Is it a nice thick plexi?


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## Rraven (Sep 24, 2013)

@ Hippofeet the thought for the pony bottle was it would be needed for the raising or lowering of the roller, seeing no pressure is being applied at that initial point in time. I'll research your suggestions so I can try to sort out the plumbing. As to the light table it's 6 feet wide and 15-1/2 feel long and you can walk on it. But I'll be retro fitting it with new side lit LED panels.


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## Hippofeet (Nov 26, 2012)

Sounds really nice, Rraven. Good luck, I'm a bit jealous. I love making stuff like that. Good looking, good working automation (or semi, in this case) is a pleasure all on its own, even more so when its done by your own hands.

If it's not too much trouble, and if you are still around, shoot me some pics when you are finished, I would like to see the end result.


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## Rraven (Sep 24, 2013)

Not a problem, it may take a week or so for me to sort out the design details. I'm receiving a new digital press on monday. God I love toys and blinking lights lol


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