Increasing the force of a pneumatic cylinder

In a previous model I used 3 inch air spring (rated to lift 600 pounds). It just doesn't quite do the job.

Look at these air bags www.savatrade.com

My first thought was a bladder device that I think you already referred to as an "air spring". These can go to large diameters and still be thin in what sounds like a confined space.

Another thought is supplying higher pressure air. If you are not able to supply higher pressure air to your devices with a bigger compressor, maybe you could consider a pressure multiplier on the supply line to the air springs. They probably make different types but I have seen them that are just a compressed air driven, dual diaphragm (diaphragms are different sizes) pump that uses say 60 psi air to generate 100 psi air at less volume.

It goes without saying that whatever pressure you supply to to the devices has to be within their design limit.

The obvious is answer either More cylinders or increased Bore size. If that is not possible then increased PRESSURE is one way to increase FORCE.

An Air Compressor designed to operate at higher pressure would be one way of getting higher air pressure and are available from several compressor manufacturers.

Several manufacturers make Air Intensifiers that raise Air Pressure by using a reciprocating air cylinder to drive another same size or smaller bore air cylinder that has check valves on its outlet ports that allow plant air into the pumping chambers and check valves to allow the air at increased pressure to exit to the work reservoir.

If you run out of oomph with pneumatics, is a hydraulic system an option?

I have thought about using hydraulics but these moulds are moved through the building as they are built. So one would have to have ether a small pump unit or one that could just be hooked up at point of use.

Flat hydraulic cylinders are compact, lightweight and very strong. Most come with hand pumps and flexi hoses with quick fit connectors so you could use these systems in your factory as well.

Try searching for body work hydraulics or machinery moving hydraulics as these are also used in those fields.

Good luck.

Yeah...! Sounds smart idea too. With hydraulic jacketing or some similary tool we can easy that trouble down the road as well. Good Thinking..

We got the Picture...!

MC

It strikes me that our friend is in a hurry to break the freshly formed piece by applying more and more force, until succeeding. As far as I know, broken pieces are worthless. Now, the form is somewhat flexible, and the freshly made piece is usually somewhat more flexible. So, when he starts to peel them apart at one edge only, They should peel apart gradually, If the proper separator layer was laid down properly in the first place.

I saw complete (and somewhat fragile) aircraft parts lifted out without any brute force.

I aggree, anti stick compound layers which are cross directionally laid before any gelcoat goes on and if the shape is correct, the moulded piece should just come out easy peasy. If you need force, you are doing it wrong, I say, you are doing it all wrong boy.

Don't forget as well that if your moulded half is still in the mould and you push somewhere in the middle, it will bend and suck even harder on the edges by creating a vacuum. Push on the edge and it peels of no problems.

This parts are just raw fiberglass no gelcoat is used, it is a structrual reinforcement only it will not be seen when the boat is finished. We already use a release agent, due to the required design there is just no way to peel the part fromthe edges only. I will try to post a sketch this weekend to better illiustrate what we are doing.

This is cool stuff here:

All good very informative for this case. Lot of good suff and ideas here. You are do very wise definetly. After seen all these great ideas the only thing that PoP-Up from top of my head will be to integrate like a Rack/Pinion Gear or so in order to increase the power if they have to use the same Piston. But definetly I dont know if there room enougth for this adapter here. To me you all got a great answers for this situation as well. Smarts Buddys..!

Crank it Up;

MC

This is the mold that we are currently using, it is made framed with plywood and then has a layer of fiberglass sprayed on, then a gelcoat finish, the green residue is a paste release agent. (I have to make one out of sheet metal). It is no small task to "pull" these parts. if you do not have a good mold that is properly prepared it can be almost imposible, at best it is still not an easy part to pull.

I don't know if it is suitable for this mould but could you put air nozzles on the outside and force air between the mould and the piece you have made?

Maybe construct some pockets you can remove from the outside after setting of the eppoxy and than fill those with compressed air or something.

Or even better, incorporate some air bags in the side of the mould and blow them up.

We are already using blow holes in the moulds, you probably can't see them in the pic but each mold has 6 to 12 depending on the size.

In that case I think the blow holes surface needs increasing. One way to do that is to use a removeable insert that creates a larger pocket around the nozzle. This way the pressure gets multiplied over the larger size of the hole.

Either way it does look if your part will always be a bugger to get out as it is too convoluted. If splitting the part is not an option due to strength, could you split the mould in easier parts and peel the mould of the part in stead of the other way around?

If this is a production item, I would venture to suggest putting a greater draft angle on the mold and rounding corners, adding fillets etc to help release. This is obviously extra cost/time but if you are making them regularly it will save in the long run.

Presumably if you have to apply a lot of force you are running the risk of damaging the part or the mold....

Hey you could throw in some buzzwords.. like 'design for manufacture' etc and give yourself a promotion and an MBA.

Del

This is not a big production item maybe 4 to 6 a month. They are having problems pull the parts now so I(always looking to improve) am trying to eliminate as many problems as I can as I am building this new mold.

Yes if we apply to much force there is a risk of damaging the part, I just have to find the right combination of force and improvements to the mold to make the seperation as "painless" as possible.

I didn't design the original part. However on the moulds that I have already made I have done as you suggested, rounding the outside corners and adding fillets to inside corners. I may however look at increasing the draft angles, if possible.

Hind sight (as they say) is 20/20 so i like to look at as many options as possible prior to building something like this.

i've supplied water in lieu of air in a case similar to this and, believe me, it worked.

WE have used water on other dificult parts as well, but usually only as a last result, as this makes a big mess in the building.

Escape Pod:

Since you have already tried drilled blow holes and want to use your in-house air supply, my suggestion is to build a small aluminum jig lifted from an electric hoist (straight piece of aluminum tube with lift hooks at either end). The aluminum jig would be outfitted with several suction cups along the length of the tube and tied into a vacuum module which would then be plugged into your air drop. Operation of the suction cups would be from a manual valve mounted directly on the jig or remotely like a hoist pendant. Removal of the piece would be accomplished by:

1) Making sure mould is fastened securely to plant floor and

2) Attaching vacuum cups to piece and turning on vacuum.

3) Applying pulling force with hoist.

This would allow you to move the piece anywhere in your factory while still maintaining a vacuum on the part. You will just need an air hose long enough to move the piece from the mould area to the assembly/cleanup area. You can keep adding suction cups until part separates out cleanly from mould. Some testing would be required. This is something that you could probably build yourself fairly cheaply with purchased parts from your local pneumatics supplier.

If you can give me a better (bigger pic) and the direction of pull on the mould or even better some pics of your workers removing a piece then I can model up then jig and send it to you to give you a better idea of what I am thinking about.

UFG

I hadn't thought of that, however I have used vaccum lifts in previous jobs. This is an interesting idea, something to think about. Thanks.

Cheers, let me know how it goes or if you need any help.

I designed a similar jig for HONDA that went on the end of a robot

and placed windshields on to vans.

Your provided picture was very helpful, and gave an idea, that is easy to test without a full layup.

To recap, once the part is cured and ready to pull, it resists the removal by the strong suction between them. The almost parallel sides would have to slide most of their length long before the suction breaks. That is a difficult, high force operation. And we deal with an already existing mold, with minimum modification possible. So these are a given.

Even with such restrictions my overwhelming favorite is still peeling them apart (breaking the vacuum suction) section by section. And I propose that by easy handwork. Let focus on the triangular stiffening board first. Let us also agree not to damage the form in any way. But extension of it is still possible, as any layup on that will be trimmed off with the customary edge trimmings anyhow. Build an, say, 3" by 3" triangular or earlobe shaped extension to the bottom tip of the form. It should have a wedge shape. Full thickness at the form, and maybe 1/2" at the tip. (Making a quick and dirty copy of only this triangular section, you can proceed fearlessly and experiment cheap and dirty. As you notice I am a big believer of the quick / cheap/ dirty, before, possibly messing up a full moldig form).

Let assume, that a normal layup schedule calls for 3 layers of glass on the piece. Then over that earlobe add one or two more triangle. This gets NOT laid up tight to the triangle, just hangs down. The add-on is just for strenght. When everything is said and done, you just might not need the added layers after all. When cured, this allows a prybar or some such to break vacuum between the vertical layup and form. When you do the same thing in the full form, you break vacuum on all vertical layups first by hand and prybar, before lifting the piece out, where now mostly only the horizontal surfaces stick. With the extensions the prybar does not damage the surfaces needed to remain clean.

You might want to look into an air over oil cylinder. There is two stages involved. The first stage is throughout most of the stroke the force is like a pneumatic cylinder but the in second stage through a smaller portion of the stroke the force is much higher.

Thanks to all for the great ideas! You have given me a lot of things to try.

To all that are interested in the outcome, let me know and I will keep you updated on the progress. As this is a "spare time project" it will probably be at least a month in the making.

Again thanks for all your ideas!

Can I suggest two possibilities

#1: "turn the problem on its side".

Inside the restricted space, you could have clyinders with orientation parallel to the part surface pushing wedges between tapered surfaces (wedging them apart) giving increased separation force to the mould and also allowing large surface area for engagement.

#2: Modify the mould to have removable inserts in the low draft areas so that the mould can be stripped in portions and then the final assembly removed from the skeleton of the mould.

Hope this helps, just another view on possibilities.