Thoughts on synchronizing two cylinders?

[dan_m]

I'm going to be using two 6" cylinders for my press, since once you go above a 6" bore the price seems to jump drastically. My two cylinders cost $295 each, versus well over $1000 for any 8" I could find (two 6" cylinders is equivalent to a single 8.5"). I hadn't done any research into synchronizing them because Randy is running his parallel cylinders without any control mechanism other than the mechanical coupling of having them both attached to the plate they are moving. When I was putting together my order at Bailey last week, the guy strongly recommended getting this 50/50 flow divider/combiner: http://baileynet.com/index.php?page=Search&id=14&srchsrc=SearchBox&sbmfrmas=Submit&baileynum=270-704

It is out of stock and they don't know when it will come back, so I looked at Surplus Center for something equivalent. The flow dividers there specifically state that they are not suitable for synchronizing cylinders, and upon doing some more research I'm finding that synchronization without digital control is apparently difficult to achieve. Randy's works fine without even a flow divider though, so if anyone has experience with this I'd like to know your thoughts on the best way to go about it. Is the mechanical coupling to the plate enough, or am I risking damaging the frame if one cylinder decides its going to push more than other. And would a 50/50 flow divider help the situation, or is it useless for this application?

Some extra info that may be helpful for this, the cylinders I'm using have a 5/8" hole in the rod ends, and will be pinned to thick tabs welded onto a 2" die plate. I'm using the ibeam frame and guide system that Eric Fleming used (pictures here: http://www.flemingknives.com/largepress.htm). My beam has a flange thickness of .495", and for the ram guides I'm planning on using a 1/2" spacer with a 1" guide plate on either side (will make sense if you look at Eric's pictures). I'll make the plumbing from the control valve to each cylinder exactly the same to minimize any differences in flow to the two — rigid lines, exactly the same distance, etc. Any thoughts?

[Randy C]

My press has (2) 4 1/2" cylinders and they evened out by themselves. I was worried about the same thing but it turned out to be a non-issue. I

[ptree]

To use mechanical guiding to accomplish this takes consideration to have long enogh guides to not allow locking when the translating rams cock the ram.
There are several types of flow devider. Parker makes a gear type that works well and is near bullet proof

[kubiack]

There was a thread on IFI that dealt with this subject. I will see if I can add a link.
http://www.iforgeiron.com/topic/16384-spring-return-for-hydraulic-press/

[dan_m]

ptree, I was going to have the guides 8" tall above the 2" plate. Any thoughts on the sufficiency of that? The maximum stroke is 20".

What kind of situation am I looking at if they did go out of sync?

Thanks for the link kubiack, I'll check it out tonight as I'm about to leave for the afternoon

[ptree]

If I recall there is a guideline on long guides to prevent binding, but I don't recall where. I assume you mean the outer guides will be 8" above the plate, what size is the inner element?
Binding will make for a jerky operation at best, destroy the guide surfaces if worse, or wreck the guides in a catastrophic manner if really bad and you gain the full force of a cylinder pushing in a side load manner.
Gut says 8" on anything smaller than say 6" od on the inner element shoud not bind.

I have seen hundreds of 2 post and 4 post presses, some with one cylinder and some with 3. I did some work on a 1000 ton 3 cylinder, 4 post press at VOGT. Had about 16" posts, and about 6' long guides. I replaced it with a custom 1000 ton single cylinder, side plate design, portable press. (Portable if you have a 25 ton bridge crane overhead)

[dan_m]

I'm using WF 8x35 I-beams as the guides, photos of someone elses can be seen in the second link in the original post. Here's a screenshot from my sketchup drawing showing what I plan on doing:

The flange on the beams in .495" thick and the spacer on the guide plates is .5". Hopefully it's sturdy enough, I've already got the beams cut to length and have all the plate so redesigning it with round posts at this point isn't really an option. Plus Randy's works really well and while not the same design it uses the same principle. I just read through the post that kubiack linked to, and Fe-Wood mentioned using a bar linking the two cylinders with a piece underneath that drives the plate. That sounds pretty reasonable to me, so I might run with that idea. As designed now, it's got a maximum opening of 19" between the plates, so I can spare the extra inch or two.

EDIT: Just put that idea into sketchup and it makes no sense to me, although maybe I misinterpreted this:

I'm thinking about using 2 rams (60 tons) with a bar between them and 1 collar in the center to push from. Anyone made something like that?

Here's what I got:

I can't imagine that crossbar not bending, and putting anything under the rods defeats the purpose.

[dan_m]

Oh, and in that picture, the ram plate is 2" thick by 8" deep, and the guide plates on either side of the .5" spacer are 1" thick by 8" tall.

[kubiack]

I will be watching this build with interest as I am also planning to build a press like Randy’s in the near future but with the cylinders above as you are doing. My thoughts after reading the post I linked to earlier were that Randy has already proven that it works well without the splitter. If you keep the cylinders as close together as possible and the guide system roughly equivalent to what he has done it should also work well. Building the frame will be the same whether you use the valve or not. So why not build it and do some testing with very small loads to see if it binds. If it does you can always add the splitter valve in later or rebuild the guides and make them longer than 8”.

Fe-Wood did you build your press with two cylinders and how did it work out?

[dan_m]

Building the frame will be the same whether you use the valve or not. So why not build it and do some testing with very small loads to see if it binds. If it does you can always add the splitter valve in later or rebuild the guides and make them longer than 8”.

My thoughts as well. And in case Fe-Wood doesn't see this, I PM'd him last night and he said he ended up finding a press for cheap at an auction and never built the one he was referring to in the thread.

[jimmy seale]

we have never used a "splitter" on hydraulics because the cylinders will equlize when load is applyed. as for "play" i've seen too much and too little be a problem. one thing to be aware of is the slack you will have over the system and at the extended position, you may need to consider a mount of some type at the cylinder heads, to help keep them from bowing in the extended range. as a disclaimer i do not have a degree so this is just doghouse engeneering, just remember to have a weak link some where(usually the pressure release) to avoid a train wreck/and or injury.also on it's maiden voyage cycle it a few times to purge the system,good luck, jimmy

[kubiack]

Jimmy can you explain how the cylinders will equalize? I have no experience with hydraulics other than what I have read, mostly on this forum, and what you are saying contradicts what others have previously said. In the previous post Grant stated that the cylinder with the least resistance will want to travel ahead. Larry posted a picture of a press that the splitter valve and Richard Furrer said his press had one also.

[Frosty]

It's been quite a while since I messed with hydraulics but I'll chime it. As I recall I just plumbed a "T" in the supply and return lines, making sure the lines were larger than the orifices in the fittings. I don't recall there ever being a problem with rams out of sync unless there was air in the system. Air is easy to see as the rams get spongy and jerky. If it happens very often I put a bleader cock at the highest point in the run.

A word to the wise, I only used hydraulics in situations where we had to fix problems and make mods, I'm not now and never was trained in hydraulics so I may well be wrong all round.

Frosty the Lucky.

[dan_m]

I sent Larry an email last night since he doesn't seem to be on here too much lately. He said that he wouldn't worry about using a flow divider, that (and this is assuming I interpreted his explanation correctly, ie not to quote him) because the cylinders are so close together one can't push too much past the other one without the flow then running mostly to the one that's lagging, as the cylinder out in front is experiencing greater resistance, hence the equalization. He didn't think the cylinders running slightly apart would do any damage to the frame that couldn't happen anyway (poorly or underbuilt frame). Given that, and the fact that Randy has a nicely-working example of parallel cylinders with nothing but a mechanical connection, I'm just going to go for it. I can always add a flow divider if needed.

[peacock]

It's really a matter of the oil taking the path of least resistance. If one cyl. gets harder to push the pressure on that cyl will try to rise and the flow will decrease, if they are plumbed with equal size and length plumbing the cyl with less load will now recieve greater flow and move ahead. Now if the load(part to be pressed) is off center the cyl. on that side will load up first causing the other cyl to move faster possibly creating a bad situation. If the guides are long enough and the frame is strong enough it may just stall out, on the other hand it may send a chunk of red hot steel flying at an unknown direction. Consider the flow divider.

surplus center cat#285 page 31 upper right corner delta rotary divider

[dan_m]

Phil, any chance you could get me a part number on that? The last catalog I got from them was #284. In my catalog there's only one rotary flow divider (a Delta), rated at 21 GPM for the expensive version, but my pump is 28 GPM. The non-rotary, non-priority flow dividers seem to have GPM ranges, none of which work for me as I'm using a two stage pump, so 28 or 7 depending on the stage, and the ranges generally aren't that wide. One thing I looked at was just using a separate flow control on each cylinder, and setting them each to 14 GPM to divide the flow 50/50. I know nowhere near enough about this stuff to know if that's something that would work though.

[jimmy seale]

remember this...the more connections = more places to possably leak = a possable failure point. as stated above, they will equilize and shouldn't ever be a problem. i personaly think that adding a splitter or flow control will be a waste of money on this project, but that's up to you. i do wish you sussess on it and be sure to put up pics.

[dan_m]

I'm going to see how it works without a flow divider and add one if necessary. Starting the build tomorrow, I'll make a new thread and post pictures as I'm going.

[Randy]

peacock has it exactly right: "It's really a matter of the oil taking the path of least resistance." If it helps I've attached the front and back closeups of my press. Only problem I've had is either my measurement for the cylinder spacing or the guy who cut the plates or maybe something else caused the one cylinder to cock to the right and so there is a slight imbalance in the push. It hasn't been a problem. I should also mention that the cylinders are locked in place in the frame at the top and the bottom as they pull as well as push. Personally I wouldn't have the cylinders on the top just due to it being top heavy and having the ceiling height to accommodate them. You may have to bolt the unit to the floor where with mine I could have on casters if I wanted. But one does what he likes. I'd also recommend a limit switch to control the travel. And a must is protective sleeves for your high pressure hoses. Only cost about $3.50 a foot and can save your life and your shop.

Here's the front:



Here's the back:

[kubiack]

I was thinking cylinders on top just for the fact that the steel is stationary while you are trying to keep it square and level in the dies. It seems like punching a hole for a hammer eye would be easer if the hammer head was not moving. I have watched Randy’s videos and it does not look like this would not be a problem for most work done on the press but for some it would be. I also like how compact and how little material he used in his press. However I think if building a large base or bolting it down works fine in your shop the cylinders on top is the way to go.

Randy could you comment on using the press with your piece moving instead of stationary. If I remember correctly you said in another post that you rarely use your press for punching.

[Randy]

The key is having fences and stops, which you need to have anyway in punching. Also if you center punch your work and have a point on your punch it's not a problem at all. (the metal moving up instead of the press coming down) It's hard to eyeball anything as your dies get in the way. Everything moves so smooth that you don't get bounching around of the metal. Plus before you put the hot metal in the press you have already brought the dies down most of the way. Saves time/heat and it can all be aligned before putting in the hot metal. I was concerned at first, too, in having the metal moving up, but after the first squish I pretty much have forgotten that I'm working this way.

[dan_m]

Thanks Randy! I don't have a choice as far as mounting the cylinders on top, since mine have a 20" stroke. They're about 31" in length retracted, which means that even if you don't account for vertical space taken up by the frame, the top die (if they were bottom-mounted) would be at 51". Add the frame to that, and it'd be right about eye level. I would have preferred the cylinders on the bottom for the reasons you mentioned, but I wanted a long stroke so I could use drifts, and though 20" is overkill the cylinders were surplus so I went with what was available for pretty cheap. And I'm going with rigid lines instead of hoses, so I'll just put guards over the fittings to prevent any leaks at the joints from contacting hot metal.

[kubiack]

Thanks Randy, I guess a hammer head was not the best example for what I really had in mind. The hammer head would be fully supported by the die and once you had it aligned it is not going to move. I was really thinking of punching holes in a long bar where you have to support the one end while operating the press. If doing a series of holes you could set up in-feed and out-feed supports on either side of the press. With the dies set very close it might not be a big deal to support the material for the fraction of an inch until it is gets squeezed by the dies. Maybe it is just seeing all the commercial press made with the cylinder on top that makes it seem like that is the best way to do it.

Dan, I’m looking forward to see how you project turns out.

[Randy]

Yea, Dan, sounds like you'd have to stand on a box!

[Ironmann]

I am building several press, for sheet metal forming and trimming, we use a gear rack on each side with a set of gears on each side mounted on a shaft, turning on pillow blocks, that are bolted on your top plate, so it prevent the cylinders, from overridding each side, I have done it, by copying, someone else who is in the press building for 30 years, was a good challenge to understand, because my presses are running in the 20 to 40 tn range, which can be instant destuction on the first tryout.

 

Ironmann