Thoughts on synchronizing two cylinders?

[Bruce Beamish]

I have seen what happens to a large twin ram press when the rams get out of synch due to a load imbalance.

This was on a 200 ton press (I think) with a wide top platen. The ram connections on the platen got broken and the ends of the rams damaged.

Fortunately no one was injured just clean underwear required.

The end result was new connections on the platen and the rams shortened by about 5 inches and a mechanism to equalise the pressure between both rams fitted.

This was a commercially made press too and It didn't have this arrangement from new! I don't know any more details as It happened before I started in that shop.

It was one of the shop engineers that told me about it as he was involved in the repair and modifications.

Why they didn't replace the rams with new ones I don't know maybe it cheaper and they reckoned they could live with platen not going all the way down.

I never found it a problem I just packed things up if I needed too.

[DClaville]

if the cylinders are the same size and the flow to both are equal, same length and size of hoses and pipes it should not be possible for them to get out of synch unless the work is places so far out that one ram can move with out the guides or work raising the pressure in the one ram

 

lets say one is pressed down about 0,01mm more then the other the pressure will be higher in that one as the resistance will be more then the other ram will have to move to equalize the pressure

 

so the way I see it if you have a press with two cylinders placed apart some, so the dies surface is between the two cylinder rods and just to go for over kill there also is some prober guides you are home safe that also makes it possible to have a press with downward motion and at the same time have the cylinders in the bottom part of the machine?

 

if you imagine a half of a 4 post press with the two posts being cylinders so the press is pushing on the pull stroke of the cylinders.

 

that is how I am planning to build my press with the two long 5" cylinders I got, calculated to end up with 38tons

[Bruce Beamish]

In the situation I described above the twin ram press did have a wide platen with the rams set fairly wide apart and I was led to understand that an off centre load situation developed which led to the damage.

It may have been an an unusual or exceptional set of circumstances that let to this accident. I do not know, I wasn't present but I was relaying what I had been told by the Engineer inolved in the repairs.

[John Larson]

Allow a place for the flow equalizer.  You will want it eventually. 

[Ric Furrer]

if the cylinders are the same size and the flow to both are equal, same length and size of hoses and pipes it should not be possible for them to get out of synch unless the work is places so far out that one ram can move with out the guides or work raising the pressure in the one ram

 

lets say one is pressed down about 0,01mm more then the other the pressure will be higher in that one as the resistance will be more then the other ram will have to move to equalize the pressure

 

so the way I see it if you have a press with two cylinders placed apart some, so the dies surface is between the two cylinder rods and just to go for over kill there also is some prober guides you are home safe that also makes it possible to have a press with downward motion and at the same time have the cylinders in the bottom part of the machine?

 

if you imagine a half of a 4 post press with the two posts being cylinders so the press is pushing on the pull stroke of the cylinders.

 

that is how I am planning to build my press with the two long 5" cylinders I got, calculated to end up with 38tons

 

The two cylinder press I had (since sold) was acting up one day...one ram traveled a bit faster. The flow divider had malfunctioned and a new one fixed the issue.

It may have been caused by the bad flow divider, but maybe not.

All my future presses will have only a single cylinder. I have been lucky in locating surplus cylinders from 4-14 inches in bore. I have one that is 40" tall and 12" bore...has an 8" ram....not sure what I'll do with that one. The think is too tall to bottom mount and is about 1600 pounds.

 

Ric

[Jim Kehler]

That sounds like a bulldozer to me, we had one at the raiway with a 500 ton cylinder about 18" dia. and about a 2 foot stroke. There are a lot of jobs where horizontal just works better.

[Ric Furrer]

Jim do you think a 140-160 ton is adequate for a bulldozer?

I may wish to bend a sewing needle or 1/2" rebar and may need more push. :rolleyes:

 

Actually I worry about the seals on such cylinders...I know many are used horizontal, but I heard it was bad for the seals.

 

Ric

[Jim Kehler]

Well ... what are you planning to sew? :blink: I've done a lot of work on bulldozers from 60 to 200 ton but that said my 10 ton can do a lot when set up right and its quick.

The larger bulldozers at work were well supported and I don't recall any issues with the seals.

[Hillbillysmith]

Should not matter as the hydraulic fluid will equalize during pressing operation unless you are trying to press something with an odd shape like a pentagon, triangle, trapezoid, etc. which will create an unbalancing situation regardless. Just be sure you have a pump rated for the flow and pressure needed and enough power to back up the pump.

-Hillbilly

[Hillbillysmith]

*CLARIFICATION* multiple cylinders run from a single engine, pump, valve combination will self-equalize due to path of least resistance... Trying to run multiple cylinders with multiple power sources is a WHOLE NEW BALL GAME.

-Hillbilly