Pnuematic Foot Pedal

[Mike OMelia]

I hate buying anything without asking you guys first. I need a pnuematic foot pedal to control a pencil grinder jig I am building. I'm not looking for the best of the best, but something that is strong, durable, controllable and affordable. Ideas appreaciated!

Thanks

Mike

[Stephen Cherry]

fleabay has a bunch of them.

[Mike OMelia]

OK, looking at them. Many varieties. What does "2 position" mean? Just on/off? Or are they variable? What does "3 way", "4 way", etc mean?

Thanks!

Mike

[Stephen Cherry]

http://www.grainger.com/Grainger/wwg/catalogPDF.shtml


page 3762 has the diagrams and explanations

to read the diagrams, imagine the little blocks with flow paths sliding between the ports.

[Mike OMelia]

Thank you Stephen.

Mike

[Alan Schaffter]

I'm a bit slow to understand stuff like that, so I find the Grainger explanations and diagrams lacking. I don't have a link, but I would research SMC solenoid air valves. They are a major worldwide supplier of pneumatic automation equipment and if I remember had better explanations of pneumatic valve operation and symbology. I used SMC valves purchased on Ebay for my auto blast gates.

My blast gates use bi-directional pneumatic cylinders and are powered in both directions. The valves I needed and you may also need are are classified as 2/5 (or 5/2?)- two direction, five port: Pressure inlet, (A) pressure out, (B) pressure out, (A) vent, (B) vent. The reason for two vents is that when the (A) side is pressurized, the (B) side MUST be vented and visa-versa (otherwise a bidirectional cylinder won't work). You can find tons of solenoid air valves on Ebay in 12 and 24 VDC and 110V, 220VAC but you need to know what you are looking for so learn the terminology first. I bought 24VDC valves so I could hook them up with low voltage bell wire and control them with low capacity switches (in my case current sensor switches). You will want to look at the rating of whatever mechanical switch you plan to use as your foot switch.

Some of my valves had ported bodies with female threads ready for fittings, like the one on the left, others came as part of a multi-valve manifold like the one in the center and right. After disassembling the manifold I fabricated plastic "cheeks" to cover the manifold ports so I could install the inlet fittings. I just drilled holes for the vents. Plastic barbed fittings are mounted in threaded ports are on the back (right side) of the manifold block segment. It is easier if you can find the smaller valves with integral threaded ports.

http://www.ncwoodworker.net/pp/data/1329/medium/IMG_2991.jpg

One of my blast gate SMC valves. All five ports are visible. Brass screen mufflers are mounted to the vent ports- while they quiet the valve some, my main reason to use them was to keep out spiders! I use flow restrictor valves on the pressure inlets to slow gate actuation speed:

http://www.ncwoodworker.net/pp/data/500/medium/P4280025.JPG

http://www.ncwoodworker.net/pp/data/500/medium/P4280022.JPG

[Stephen Cherry]

SMC makes what I would consider to be pneumatics of the highest possible quality. Super well made, but make sure your air is clean and dry. When I was an engineer, we would use smc pnumatics with manifolds of 16 valves controlled with a plc. It was a little pricey, but super easy to contol everything, BUT it tool some head scratching to get all the parts right.

[Mike OMelia]

Ya know, all I really want is a foot pedal that will allow me to control a pencil grinder, with variable speed. I find all of this technically difficult to absorb. If someone can tell me what I need without lots of technical detail, I would greatly appreciate it. Yes, I asked for detail, but it turns out to be more than I expected given my relatively simple application.

Thanks! (Sheepish grin)

Mike

[Alan Schaffter]

Ya know, all I really want is a foot pedal that will allow me to control a pencil grinder, with variable speed. I find all of this technically difficult to absorb. If someone can tell me what I need without lots of technical detail, I would greatly appreciate it. Yes, I asked for detail, but it turns out to be more than I expected given my relatively simple application.

Thanks! (Sheepish grin)

Mike

Ah, you are talking about a pneumatic Dremel kinda tool. That is totally different. You can do it mechanically with a foot operated, variable flow restrictor. I don't know if such a thing exists in the commercial world, but you could connect a standard ball valve to a pedal. You'll need a valve that operates smoothly and might need to rig up a linkage or gearing to reduce the amount of rotation needed to go from open to closed to something less than the normal 90°. You'll also likely need a spring to return the valve to the off position. Also, you could replace the lever with a large diameter wheel that you control by rotating it with your foot. Going the electro-mechanical way could get really expensive.

[Stephen Cherry]

Ya know, all I really want is a foot pedal that will allow me to control a pencil grinder, with variable speed. I find all of this technically difficult to absorb. If someone can tell me what I need without lots of technical detail, I would greatly appreciate it. Yes, I asked for detail, but it turns out to be more than I expected given my relatively simple application.

Thanks! (Sheepish grin)

Mike

THe problem is that it is no small task to match up the characteristic of a valve to the air needs of the grinder. It's possible to do it using the cv of the valve, and the air use of the grinder, but it would take some doing. The easier way would be to find what you want, and try to duplicate it. Or to buy a few valves, and see which one works.

I would think the place to start is a valve with the same size ports as the grinder.

[Mike OMelia]

Come on guys! Seriously? :) I have a pencil grinder. 54,000 rpms max. Connected to a 60 gallon compressor. I just want to be able to use a foot pedal to turn it on and off and control speed. Is this really that difficult? I go looking and there is all this 2 position, 2 way, 3 way etc stuff. Surely someone out there can help me? :) :)

[Jerry Bruette]

What you're looking for is flow control. I don't know of any foot pedal controlled valves that are also flow control.

The 2-way valve you refer to is only air on and air off to one port. The 3-way valve would be air on and air off to two seperate ports. It would be used for the extend and retract of a air cylinder or a pneutmatic actuator that would open and close a ball or butterfly valve.

[Mike OMelia]

What you're looking for is flow control. I don't know of any foot pedal controlled valves that are also flow control.

The 2-way valve you refer to is only air on and air off to one port. The 3-way valve would be air on and air off to two seperate ports. It would be used for the extend and retract of a air cylinder or a pneutmatic actuator that would open and close a ball or butterfly valve.

OK. Got it. On/off only. That will do as well. Though such a thing must exist since dentist's drills rev up and down, though I am not sure if that is foot control. I don't want to make this any more complicated. I will get a 2-way pedal.

Mike

[Jerry Bruette]

Did a search on McMaster-Carr and they have spring return ball valves that you could probably adapt to a foot pedal type mechanism. Foot might get tired quick though from holding it open.

McMaster item #4088T8 kinda pricey too.

[Alan Schaffter]

And don't forget to set aside enough money for the SMC consulting fees! :D:D:D:D

[Peter Quinn]

At work we have an air nozzle for blowing chips on the bridgeport, its a simple thumbscrew type thing that goes in line just in front of the air nozzle. So there is your variable speed. I think they sell them in Master Carr. Add a simple on/off foot pedal as described above, problem solved. My die grinder has a paddle on it to control on off like a pneumatic ROS, but that certainly causes you to loose some control, I could see the advantage of being able to control speed independent of the device you are holding. But does it need to happen on the fly while you work, or is it more of a setting you change between operations? Most ROS have a type of toggle switch on them that restricts air flow to reduce speed

Something like this may work. http://www.mcmaster.com/#air-flow-control-valves/=k713ua

[Mike OMelia]

Well. I think what we are bumping into here is my ignorance. I guess I don't really need speed control. Just thought it was possible. On/off is just fine. Guess I was thinking "electrically"

Mike

[Ronald Blue]

It seems like an air brake valve would do the trick. After all the braking power is modulated dependent on how far its depressed. They are pretty dependable and don't require "clean" air to work dependably.

[Bill ThompsonNM]

Google
air pressure control foot pedal

or better:
air regulator foot control