6 inch bore pneumatic cylinders

[George-H]

Hello,

I have been building low tonnage (15-20) press brakes using 6 inch bore pneumatic cylinders. I have been using Bimba cylinders and have been very happy with the quality and performance but they cost just under $1000 Canadian dollars each, I use 2 per press so the cost is high. My sales have been growing so now I’m looking to optimize my design a bit further and lower the costs of these cylinders as they make up a very large portion of the manufacturing costs.

I have searched for a more cost effective alternative, but no luck so far…. I’m posting on the forum seeking anyone that might be able to suggest a more cost effective alternative?

The cylinder needs to be 6 inch bore, 10 inch stroke and ideally have an oversized cylinder rod.

Any thoughts????

Thanks for your time!

 

[4GSR]

By the time you buy a piece of honed ID material, a polished rod, end caps, seals and other components, that cylinder is going to cost you more than $1000 to make. IMO. I think you are better off working with Bimbo on pricing and go from there.

 

[DDoug]

Hello,

I have been building low tonnage (15-20) press brakes using 6 inch bore pneumatic cylinders. I have been using Bimba cylinders and have been very happy with the quality and performance but they cost just under $1000 Canadian dollars each, I use 2 per press so the cost is high. My sales have been growing so now I’m looking to optimize my design a bit further and lower the costs of these cylinders as they make up a very large portion of the manufacturing costs.

I have searched for a more cost effective alternative, but no luck so far…. I’m posting on the forum seeking anyone that might be able to suggest a more cost effective alternative?

The cylinder needs to be 6 inch bore, 10 inch stroke and ideally have an oversized cylinder rod.

Any thoughts????

Thanks for your time!

Post up some pix of the machine.

 

[Scruffy887]

My 2 cents. Spend the time to get serious numbers to make them yourself. If that part is a big nut then you need to pound the bushes to find the parts you cannot make, and invest in the parts you can make. BTGTTshirt.
Or get Bimba to work with you. Like tell them what you need and if they want your business.

 

[Orange Vise]

Is air over hydraulic an option?

 

[DanielG]

Have you looked at what Atek does? Their cylinders are custom and dead simple and obviously work very well in pneumatic press brakes. It's a very non-standard design. The cylinder is fixed, the piston is hinged to the rod, and there's no head on the rod side.

 

[George-H]

My 2 cents. Spend the time to get serious numbers to make them yourself. If that part is a big nut then you need to pound the bushes to find the parts you cannot make, and invest in the parts you can make. BTGTTshirt.
Or get Bimba to work with you. Like tell them what you need and if they want your business.

My local Bimba rep has told me they will start giving me discounts when I begin to buy 50 cylinders at a time, he didn't say how much of a discount they would provide if I was to order 50. At this point 50 would be too much, I only go through 4-6 per month as I am only able to manufacture 2-3 machines per month. I could definitely push harder to get Bimba to work with me, so I will try that.

I am currently in the midst of putting together numbers for building my own cylinders. I would prefer not to go down this route at this point as I would rather spend R&D time on other aspects of the machine, but I am open to the option. I have pricing on everything except the honed aluminum tubing... Once I get final pricing I will post a BOM for the cylinders in case anyone is interested.

Is air over hydraulic an option?

In the early stages of prototyping these machines I made a few different air over oil presses... I could never get an air/oil system to work well. The main problem was the flow velocity through the oil lines... Massive ID's are required on the oil lines to allow the oil to flow fast enough to move two 6 inch bore cylinders the full 10 inch stroke. Special reservoirs are also required for the oil which were expensive. Overall I decided to abandon the air/oil concept.

Have you looked at what Atek does? Their cylinders are custom and dead simple and obviously work very well in pneumatic press brakes. It's a very non-standard design. The cylinder is fixed, the piston is hinged to the rod, and there's no head on the rod side.

Yes I have seen Atek machines, they're awesome! Their approach is great, large bore single acting steel cylinder with pivoting rod, they rely on gravity to return the ram back up after each bend, its a genius design in my opinion.

My approach requires a double acting cylinder, so Atek's approach would not work for me. I wanted some basic CNC (more specifically NC) control of the ram positioning and speed in both directions, so a single acting cylinder is not possible.

 

[Orange Vise]

I have pricing on everything except the honed aluminum tubing... Once I get final pricing I will post a BOM for the cylinders in case anyone is interested.

Does it necessarily need to be honed?

Minor leakage shouldn't really affect performance since it's just air and not a pressure/vacuum vessel.

 

[4GSR]

1026 DOM tubing with smooth ID finish may be a lot cheaper than aluminum tubing. 1026 DOM comes in honed ID too. Just saying.

 

[DanielG]

Check out STC pneumatics (not SMC). Not as nice as Bimba, but cheaper

 

[George-H]

Does it necessarily need to be honed?

Minor leakage shouldn't really affect performance since it's just air and not a pressure/vacuum vessel.

You raise a very interesting point... I am unsure about this, I have zero experience manufacturing air cylinders. I do agree that minor leakage should not be a problem at all. My main concern would be the seals wearing out against a rough walled tube when compared against a honed tube. But perhaps I am overthinking that a bit? Any insight?

1026 DOM tubing with smooth ID finish may be a lot cheaper than aluminum tubing. 1026 DOM comes in honed ID too. Just saying.

Thanks for this suggestion. I think it might be worth a shot to order some of this tube and make some prototype's.

Check out STC pneumatics (not SMC). Not as nice as Bimba, but cheaper

This is great! I have not come across STC in my searches. I just checked their site and their cylinders are VERY well priced. 125mm bore x 250mm stroke cylinder is $355 USD and 160mm bore x 250mm stroke is $579 USD. That is quite a bit better than Bimba. Do you have any experience using STC? Any chance you might be able to comment on why you think they are not as nice as Bimba? It looks like Bimba might have a step up in terms of "fit and finish", but in regards to performance... any insight?? Regardless I will absolutely order a cylinder to test with.

 

[George-H]

I'll likely end up making some prototype cylinders sooner rather than later. As per the suggestions above I will try tubing that is not honed, rather just has a smooth ID. Any suggestions for what I may do to prepare the ID of the tubing? Perhaps run a 120-240 grit flap wheel through the ID to give it a light "polish" and a thorough cleaning?

 

[Strostkovy]

How difficult is honing? I've always been fond of those extruded aluminum body cylinders with the flanged seal retainers and counterbored bolt holes

 

[ratbldr427]

Call or look on line for CRC hydraulic products. They specialise on all parts to build cylinders. The last 4" honed cylinder tubing wasn't any or very little more than DOM. They have everything you need.
About that 4" tubing I bought I think 20'. Had it on the steel rack marked do not use Hyd tubing only and had the ends plugged.
Came in one morning and noticed it in the saw. Cut into 4' lengths. I asked who is building cylinders?" Cylinders? No that's for some guard rails in finishing." In the same rack was some black iron pipe 4" & 6" we use for that. Idiots, must be why I have so much gray hair,
CRC not to be confused with the chemical co.

 

[DanielG]

This is great! I have not come across STC in my searches. I just checked their site and their cylinders are VERY well priced. 125mm bore x 250mm stroke cylinder is $355 USD and 160mm bore x 250mm stroke is $579 USD. That is quite a bit better than Bimba. Do you have any experience using STC? Any chance you might be able to comment on why you think they are not as nice as Bimba? It looks like Bimba might have a step up in terms of "fit and finish", but in regards to performance... any insight?? Regardless I will absolutely order a cylinder to test with.

I haven't used their cylinders before. We used to use their valves for prototypes and test benches, and then use SMC or Camozzi for the final stuff we built for the customer. They were good quality and we never had any failures. I just know that the distributor, who was also our Bimba and Camozzi distributor, viewed them as a step below.

 

[Garwood]

I would hone the tubing. I use a Sunnen AN-112. It would do a 6" bore fine with a heavy duty drill to drive it. 220 stones would be good for finishing. Talk to sunnen about honing fluid.

 

[Orange Vise]

You raise a very interesting point... I am unsure about this, I have zero experience manufacturing air cylinders. I do agree that minor leakage should not be a problem at all. My main concern would be the seals wearing out against a rough walled tube when compared against a honed tube. But perhaps I am overthinking that a bit? Any insight?

I guess it's less about whether to hone it or not (honing isn't a particularly expensive process), and more about getting a good finish over hitting a very accurate dimension.

 

[4GSR]

I used to buy honed ID tubing from these guys down in Houston many years ago. I see they have a place up in WI. Not saying they are the cheepiest, but always had what we needed on the floor without waiting on it.

Scot Industries - Tubing Products

Edit: Just noticed they have a facility in Canada, too.

Scot Industries

 

[George-H]

How difficult is honing? I've always been fond of those extruded aluminum body cylinders with the flanged seal retainers and counterbored bolt holes

I am not sure on the difficulty of the honing process, I've never done it, but it seems like it can be achieved with hand tools? My goal is just a very smooth ID, I think if you are after a precision ID dimension/tolerance the honing process may be more involved. I myself prefer the aluminum cylinders as well, I am a bit worried about using steel and having the ID rust from my customers hooking up these presses to air compressors without an air dryer.

I used to buy honed ID tubing from these guys down in Houston many years ago. I see they have a place up in WI. Not saying they are the cheepiest, but always had what we needed on the floor without waiting on it.

Scot Industries - Tubing Products

Edit: Just noticed they have a facility in Canada, too.

Scot Industries

Its funny you bring these guys up, my shop is located a 5 minute drive from their location in Canada. I've sent them an RFQ for some honed/plated pneumatic cylinder tubing. No price yet.

 

[George-H]

So I am getting close to having a final BOM for building my own cylinders, I'll post when complete. As of right now it is looking like cylinders from STC may be just slightly more expensive than if I build my own. I don't own a CNC lathe, or even a manual lathe, so the largest cost at the moment for building my own cylinders is the cost to have a local shop make me the pistons and thread the cylinder rod on a CNC lathe, am I crazy to interpolate the pistons on my HAAS haha!!??

Ill keep trucking away and report my results