Pneumatic Air Cylinder

[ukracer]

Any experts on air cylinders.?

I need to produce a fair amount of Torque on a couple of repetitive operations.
I THINK stepper motors might work on the longer travel.
But the shorter ones need to produce explosive short amount of larger torque.

I will try and video the process later today..

The one I am less confident about is the Arbour Press I have converted into a die press.

It would be much easier to use one of these.

But I am guessing that these produce more Torque. But would be harder to mount.

 

[mtt.tr]

The force produced is a direct result of pressure over the piston diameter

What would be best to know would be the force you need, as if you oversize the cylinder the process will be slower and potentially use more air than is ideal for max efficiency.

 

[voipio]

Torque is rotational. Does that mean the air cylinder has to produce rotation in something? Explosive force would require a sudden increase in pressure in the cylinder, implying a reservoir and high speed valve very close to the air cylinder. A spring-driven plunger pulled back relatively slowly by a cylinder and a trigger mechanism to release the spring might be better, and if it's torque you're after, how about putting in an impact wrench?

 

[bricol]

Neither of those will produce "torque" unless you connect them to lever on the end of a supported shaft, so they rotate it.

As said - force is simply air pressure over the area of the piston - and less force on the retract due to the piston rod taking away area.

 

[8ob]

A few things to bare in mind with pneumatic cylinders,we use them on pto equipment. The pistons don't last long slamming to the beginning or end of their stroke so external positive stops just short of max travel are needed both ways. Also worth regulating the pressure so its just enough to do the job and consider a one/two way external damper to soften action .

Bob

 

[bricol]

A few things to bare in mind with pneumatic cylinders,we use them on pto equipment. The pistons don't last long slamming to the beginning or end of their stroke so external positive stops just short of max travel are needed both ways. Also worth regulating the pressure so its just enough to do the job and consider a one/two way external damper to soften action .

Bob

Specifiy them with internal cushions - lot smoother. Another trick, if you don't need the speed created by high air pressure, but do need the force, regulate the exhaust air instead of the pressurised supply.

 

[hotponyshoes]

I messed about with a few cylinders making a cheese press.
Watch out when you buy one as some of them have some sort of inbuilt flow control so the pistons come out at the same speed regardless of what air pressure you feed them with so might not be quick enough for what you want.

 

[ukracer]

Ok guys thanks for all replies.
These videos might show you more about what I am trying to achieve.
Admittedly it's not exactly hard work for the RSI is not far away every day.

Dropbox

www.dropbox.com

Dropbox

www.dropbox.com

Dropbox

www.dropbox.com

 

[hotponyshoes]

For those first 2 videos,
I reckon it's going to be quicker to do it bu hand than wait for a cylinder to expand/retract plus pressing the pedal/buttons.
With that second video you will definitely be quicker by hand unless you rig up 2 pistons so you can run a 2nd shorter travel.

Unless you are thinking of making a powered guillotine and having a blade press down rather than slide across?

For the 3rd video,
Do you actually need that short sharp jab on the handle?
What happens if you pull the handle in a controlled manner?
I would think a sharp die with the correct clearance should slice through that nicely without shocking it through.
If it would then a pneumatic press would be perfect for that job

 

[bricol]

For those first 2 videos,
I reckon it's going to be quicker to do it bu hand than wait for a cylinder to expand/retract plus pressing the pedal/buttons.
With that second video you will definitely be quicker by hand unless you rig up 2 pistons so you can run a 2nd shorter travel.

Unless you are thinking of making a powered guillotine and having a blade press down rather than slide across?

For the 3rd video,
Do you actually need that short sharp jab on the handle?
What happens if you pull the handle in a controlled manner?
I would think a sharp die with the correct clearance should slice through that nicely without shocking it through.
If it would then a pneumatic press would be perfect for that job

Pretty much said it.

Proper punch/die design would assist in lowering the force required. All feasible to drive pneumatically, but would need some consideration of safety - no good speeding it up if the first thing you do is remove your finger tips . . .

If its an on-going work job though, I'd be tempted to look at subbing that out to a gasket maker or similar - CNC cut all that off the roll/sheet. By the time you've bought the pneumatics, made the supports, enclosures, control gear . . .

 

[hotponyshoes]

If you do need a sharp shock for the press then an electric solonide might be a better option?
I don't know how much thrust a big one can produce (or how much big ones cost) but you could probably stick a load of small ones between a couple of plates to get whatever you need.

Another thing that would be easy to do is measure how much torque it takes to pull the handle down and see how much a stepper/servo motor would be as that should be able to run pretty quick cycle times.
Having said that, if it is something you do a lot off I would be looking at making a rolling die cutter that you could just feed rolls into rather than trying to adapt something that's already been adapted once....

 

[Screwdriver]

Punching that material would be a lot easier if you had a spring loaded clamp that presses down on the workpiece and holds it before the punch hits it.

 

[James1979]

Not much to add but have you thought about a punch which is concave which is sharpened around the edges? Like a paper punch.

Also, with the air side of things how about an accumulator? That should give you more burst than a flow but I think controlled with a decent cutter would be better.

 

[m_c]

Having watched those videos, it's not really a process that will be made quicker by simply automating the cutting, but I'm going to guess by the support on your elbow, you're maybe not aiming to simply make the process quicker?

A lot will depend on how many of these things you're cutting, and how much you're willing to invest to automate it.

You really need to work out the forces involved.
The cuts, I'm not sure a stepper motor would work all that well, given the force I'd guess is needed. I'd probably look at a servo motor with reduction.
I'm also guessing this isn't a commercial venture, in which case safety systems would be a major concern, but even for personal use, I'd have it controlled by some kind of system that only runs when the go button is pressed.
I'd likely use some basic CNC controller that can be programmed with the start/end points, and give acceleration/deceleration at the start/finish to avoid overshooting switches, and give smoother operation.
Mechanically, I'd probably just use a basic toothed belt type of setup.

For the punching, again you'd need to work out the force needed.
As has been said, a sharp punch will make it easier, and I'd guess a short travel pneumatic cylinder would work.

 

[ukracer]

Ok guys I am 6 rolls in today......worn out my cutter holder. So printing a new one.

Will reply in detail later.

 

[hotponyshoes]

It would be easy to work out the forces involved with a set of fishing scales
Or even a bucket of water land some string

 

[500e]

1/ Why does it require both left & right movement to cut, you should be able to cut left to right, feed material, cut right to left.
3/ A bench or frame that is stiffer will make the punch opp easier your effort is going to waste with the flex on punch frame

 

[8ob]

Cant help but think the sheet material would cut easier and quicker on a treadle guillotine which would leave both hands free, possibly cutting two or three at a time. The arbor press needs a stop on it so it only travels the amount needed to punch the hole and not turned back to its rest each time, personally I would of made a hydraulic foot operated punch which again would do multiples at a time and leave both hands free.

Bob

 

[500e]

As you say wasted movement on press Bob,both in handle movement & whole press bouncing, but dies need to be better as well, don't know how multiple sheets would react.
A good sharp treadle guillotine should cut 2/3 if not more