"KICK" force exerted from a hydraulic cylinder

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Summary:

would like to calculate force on bearings for guide bar of "H" frame press.
Hello,I am building a press that will squeeze hot steel ,back off .5"push hot steel in further and repeat.The cylinder is 4" bore , 1.375"rod and travel is 8" (the majority of squeeze will be at 5"of extension)at a max of 2500PSI. 20200917_193040[1].jpg my question is when putting @15 tons straight down what will the sideways kick bearings have to withstand.I am asking how would I calculate this.
Thank you,
Mikey
 

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  • #2
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Welcome, Mikey! :cool:

In theory, if everything is perfectly aligned, those bearings will not feel any of the pressing force.
Depending on the geometry of the slider and the bearings guides, and of how out of center the pressed part is located, a relatively small percentage of the pressing force could go sideways and on the bearings.

Do you have more details and dimensions to show us?
 
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  • #3
Baluncore
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my question is when putting @15 tons straight down what will the sideways kick bearings have to withstand.I am asking how would I calculate this.
You show a pin at the rod end of the cylinder. That will permit an alignment error in the upper anvil of the press. When the bottom roller on one side advances before the other side, it will cause an alignment error. That will apply an infinite compressive force to two diagonal guide rollers, and the rails.

Depending on the number of degrees of freedom needed for the upper anvil, Either;

1. Increase the length of the upper anvil and use two rollers only on each side, or;

2. Reduce the number of rollers to one on each side of the upper anvil so the diagonal cannot become longer. Spring load the upper anvil on the rod so it remains square until it contacts the work, then it can re-align as hydraulic pressure is applied.
 
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  • #4
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I have more details ,so much more I think I should have added"doodler" in my profile! I was thinking that with good alignment there should not be much pressure on the bearings,and other makers of presses like this all use an 'H" section of steel sort of almost clamped to the frame and accept that it will somewhat slide along it and add grease or oil where it rubs.I feel there could be wheels there and maybe bearings if there were a calculation of THE pressure applied.Heres more details,the frame is an"I" beam I will cut the center out of to any size to fit the guide . 20200918_045422[1].jpg 20200918_000518[1].jpg 20200918_043030[1].jpg 20200917_001003[1].jpg The will be .875 bolts mostly lining the inside of the frame that I might add additional guide rail to,heres what I have.
Thanks ,
Mikey
 
  • #5
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I couldn't figure how to rotate the doodles,sorry
 
  • #6
Baluncore
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Look at the piston in an IC engine. The skirt of the piston keeps the piston aligned in the cylinder. The gudgeon pin crosses the piston and controls one direction of piston tilt while allowing movement in the other. You need to do the same in your design.

The upper anvil guide is attached with a pin. The anvil needs to have more height, so when the rod is retracted, (at the top), the moving guide extension can pass up either side of the cylinder end. You must make it higher than it is wide. You may only need one roller on each side, not three. The roller should be low down to stop the bottom corner catching on the guide. Retracting the rod should not be as risky with longer guides. If you have three or more rollers on each side, ask yourself what the middle roller(s) are there for.

You must prevent high asymmetric forces being applied to the anvil and hence the rod since rods under compression tend to bend, so the rod seal may then be damaged by side forces. You might benefit by fixing the rod in a deep guide hole, with a pin there only to stop the guide falling off. You can reduce rod side forces by having more freedom of alignment at the upper end of the cylinder.

Don't post several doodles. Post one diagram with numbered parts so we know what we are discussing and can unambiguously refer to the parts.
 
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  • #7
256bits
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steel sort of almost clamped to the frame and accept that it will somewhat slide along it and add grease or oil where it rubs.I feel there could be wheels there and maybe bearings
Sliding is OK and is simple.
Rolling bearings adds another part to fail and/or wear out, complicates the design.

Note: the cylinder rod itself doesn't have rolling bearings ( maybe yours does ?? ) to keep the alignment.
1600508520874.png
 
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  • #8
Baluncore
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Invert the design to see other solutions. Consider what would happen if you turned the cylinder upside down.

Advantages; The cylinder could be held in a long guide so alignment of the upper anvil is no longer a problem. The hydraulic rod and rod seal are away from the hot steel. Position of the rod end at the top has no side or bending forces.

Disadvantages. You would need two flexible hoses for the hydraulic fluid.
 
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  • #9
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I looked at images of a piston in cylinder and get the higher than wider thoughts.I am surely complicating the design.I can add rollers later,if I want
 
  • #10
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Do you mean push down with opposite end,I like it.Man I need a new pencil,I think Im going to skip bearings and go for just a slide.
 
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  • #11
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Is this for something like a coining operation? The full 0.5" stroke seems unnecessarily long; is it possible to reduce that?
 
  • #12
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It is for forging hot steel.I actually, returned the cylinder and ordered another with a larger rod.I am now using a 4.5 bore with a 2" rod at 1700 PSI for aprox 27,000 lbs force.This new cylinder has a threaded rod 1.875"-12 TPI 3inces long and I am going to redesign the guide system which should be easier without a clevis on the pushing end.I will get some dimensions posted soon.
 
  • #13
jrmichler
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I am going to redesign the guide system which should be easier without a clevis on the pushing end
It is a mistake to connect a forging die directly to the cylinder rod without a clevis or alignment coupler in between. Even if you have perfect alignment between the cylinder and die, everything moves under load, so it becomes misaligned when in operation. If you do not want a clevis at each end of the cylinder, you could use a base mounted cylinder with an alignment coupler on the rod. See page 9 in this catalog: https://www.parker.com/Literature/Industrial Cylinder/cylinder/cat/english/HY08-1300-1_NA_ACCY.pdf. That solution assumes that the pusher / forging die will maintain alignment under the worst case off center load by itself, without depending on the cylinder. Hydraulic cylinders are designed to push and pull, but not to hold loads into alignment.
 
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