40Ton Hydraulic Press Brake

[BrooklynBravest]

So is it completely irrelevant that on the slave side cam, its 7.5" vs 6" on the pivot? Should this have been 6 x 6? I made it 7.5 just because it fit inside the frame I built. Or does it not matter whatsoever other than to reduce strain on the linkage.

[whtbaron]

I think if you want that blade to travel down evenly, everything needs to be equal.

[farmersammm]

If we flip the thing on its side, with the dot representing the fulcrum, it's easier to visualize.

Where the linkage is placed along the lever determines how much force is applied to the right side lever. Without running numbers, because I actually don't know............I'm not sure where the linkage has to be placed between the fulcrum and the cylinder. I'm not quite sure you can place it anywhere along that line, without altering things. Closer to the cylinder generates less force on the right lever, closer to the fulcrum generates more force on the right lever. This is why I figured it was a good idea to start the whole process at the right lever.

[farmersammm]

I think if you want that blade to travel down evenly, everything needs to be equal.

Yeah, travel wise..........but we need to determine just how much pressure is going to be generated at both ends of the blade. The linkage position determines this if I'm thinking right. The higher the linkage position, the less pressure overall. Actually, the higher the linkage, the harder it is for the cylinder to push. I stand corrected. See where we're going? Start with the required pressure on the right side of the blade, then work backwards.

[Munkul]

Which pivot point are you referring to?

I can see additional stress at the point around which the lever pivots, but no increase at any other point. 1" 1018 having a shear strength of around 40Ksi is able to handle it with proper pin sizing. Lever web at the pivot point, and between cylinder yoke, and pivot point, can be increased to take the strain I'd think.

Upsizing the force generated by the cylinder places strain on connections at both ends of the cylinder. This brings into question the formula you're using for the force generated by a 3" cylinder. I did a quickie online calculator search, and at 2500psi hydraulic pressure input, a 3" cylinder only puts out 17,000 pounds of force. I believe you'd have to up your pressure, or go to a bigger cylinder. (I'm using tractor hydraulic pump capabilities as a benchmark.......they generally run around 2500psi on the stuff I own)

So......we go to a bigger cylinder I guess?

I used pi x D^2 instead of pi x R^2. Sorry, fuzzy brained. I did think something was off, I had a gut feeling, but the 28.3 sq." just didn't trigger me like it should have. Instead I thought "Wow I had no idea that a 3" cylinder could exert that much force"

[Munkul]

If these relationships in terms of X, Y and Z are maintained, then the same forces are applied. Apart from friction losses which should be negligible if bushed and greased properly.
The linkage and slave top will see more applied stress than the top of the master link.

Now i see my error with the cylinder sizing, I think you're going to have to use a HUGE cylinder and some HUGE pins if you want a true 40 tons downward force on this design without massive deflection.

As said earlier, presses aren't overbuilt for bending strenths - they're overbuilt for minimizing deflection.

[farmersammm]

Ok...............here's where I'm fuzzy. It seems to me that the location of the linkage that transfers force to Blue Y determines the size of the cylinder required to come to a desired down force at all Y's. In other words, the input force for the whole system

[farmersammm]

Increasing the Z length, increases the force required to move the whole damn thing while maintaining a given force at the down links at X, and Y.

[Munkul]

Ok...............here's where I'm fuzzy. It seems to me that the location of the linkage that transfers force to Blue Y determines the size of the cylinder required to come to a desired down force at all Y's. In other words, the input force for the whole system

formula for master side leverage ratio is x / y
for slave side its x * (z / z) / y

; z cancels out.

[djd775]

The theories on multiplying, dividing, or evening out the pressure on each side of the linkage are incorrect. The division of load between the 2 parallel toggles will be solely dependent on where the load is.

You have correctly designed this so that the geometry is parallel from side to side (see first section of my scribbles below)

As for the forces, it is indeterminate unless you know the placement of the load. If the load is placed fully under the left side vertical link, then the tie link and entire right side mechanism will carry essentially nothing. If the load is fully under the right side vertical link, then the tie link will carry around 69,000 lbs, which is further multiplied by the RHS linkage to around 86,000 lbs. There are infinite possibilities between either extreme, but this calculation is sufficient for the accuracy you need. There are cases where you could load the press at the extreme end, in which case the opposite link would actually be 'lifting' on the ram to keep it level - again, probably not worth considering here.

All of this changes as the cylinder strokes and the angles change, but probably not enough to matter. If I were you, I would design such that the pictured position (all links at 90 degrees to each other) happens at the mid stroke of the cylinder. This will avoid angles getting too far out of whack, as you'll have equal rotation on either side of what's pictured.

[farmersammm]

Ok, humor me If we move the circled blue line towards the hydraulic cylinder, it's gonna require a bigger cylinder to make 40 tons at the blade.

[farmersammm]

Ok, I think I['m seeing the relationship between the distance between the whole setup. Moving the blue line upwards also extends the blue line going down to the fulcrum, making it a longer lever.

[Munkul]

Ok, I think I['m seeing the relationship between the distance between the whole setup. Moving the blue line upwards also extends the blue line going down to the fulcrum, making it a longer lever.

Yes

[Meltedmetal]

Force from the cylinder X 14/6= total force on the blade or (Force from the cylinder X 14/6)/2= total force at each side of the blade . Close enough for rock and roll, disregarding all the friction and angles etc.

[BrooklynBravest]

We’re definitely not in Kansas anymore with this thread lol.

All work on this press will always be done in the middle of the press, whenever possible.

Worth nothing the place i got the overall concept is here



And i spoke to the gentleman who built that press.

I think if you want that blade to travel down evenly, everything needs to be equal.

It can ONLY travel evenly. Other than slack in the system.

My drawing is actually animated under 100% constraints I just can’t post the animation here.

[Boostinjdm]

Ok, humor me If we move the circled blue line towards the hydraulic cylinder, it's gonna require a bigger cylinder to make 40 tons at the blade.

No, It makes zero difference to the total input/output of the system.

Raising that adjustable link up will reduce wear and tear on the link. It will also make the adjustment more fine. Lowering the link will either increase wear and tear on the link or require beefing it up. Lowering the link will make the adjustment more course.

Ideally, you'd raise the adjustment link as high as you can physically make it fit just to make it last longer.

[BrooklynBravest]

This was a commercially available one, however they took a different approach. I can’t afford the space to have a 15” cylinder overhang it. And that also requires substantial support for that cylinder attachment to not blow off the side.

[BrooklynBravest]

No, It makes zero difference to the total input/output of the system.

Raising that adjustable link up will reduce wear and tear on the link. It will also make the adjustment more fine. Lowering the link will either increase wear and tear on the link or require beefing it up. Lowering the link will make the adjustment more course.

Ideally, you'd raise the adjustment link as high as you can physically make it fit just to make it last longer.

The ONLY reason i put it where i did, was it stayed inside the constraints of the 1/2” X 12” plate being used for the cross sections. Solely aesthetic while making it as high as i could.

[Boostinjdm]

BB,

Make sure you are accounting for cylinder and punch stroke. You don't want to find that once you bend a piece you don't have enough extra clearance to remove it.

Your design is better than the Iroquois design in my opinion. You want the adjustment link in tension rather than compression as they have it. Tension keeps things straight. Compression allows parts to squirt out the sides and ruin your day.

The ONLY reason i put it where i did, was it stayed inside the constraints of the 1/2” X 12” plate being used for the cross sections. Solely aesthetic while making it as high as i could.

Good.

I saw you mention an expensive pump. Look back to my press build thread (i think you were around then). I don't remember my pump being very expensive. $100 pump + motor and valving of your choice.

[farmersammm]

No, It makes zero difference to the total input/output of the system.

Raising that adjustable link up will reduce wear and tear on the link. It will also make the adjustment more fine. Lowering the link will either increase wear and tear on the link or require beefing it up. Lowering the link will make the adjustment more course.

Ideally, you'd raise the adjustment link as high as you can physically make it fit just to make it last longer.

Yeah, I finally saw the relationship..............................."Ok, I think I['m seeing the relationship between the distance between the whole setup. Moving the blue line upwards also extends the blue line going down to the fulcrum, making it a longer lever."

[farmersammm]

This was a commercially available one, however they took a different approach. I can’t afford the space to have a 15” cylinder overhang it. And that also requires substantial support for that cylinder attachment to not blow off the side.

I like that one better. But I can see how much space it would eat up

[BrooklynBravest]

Ok here we go courtesy of the tube.




I mean so do I but it probably isn’t in the cards lol

I like that one better. But I can see how much space it would eat up

[M J D]

This was a commercially available one, however they took a different approach. I can’t afford the space to have a 15” cylinder overhang it. And that also requires substantial support for that cylinder attachment to not blow off the side.

Why not reverse one of the " cams" and put the cylinder in the center so basically " centers" the force?

[Boostinjdm]

Why not reverse one of the " cams" and put the cylinder in the center so basically " centers" the force?

So the cylinder floats? Needs a frame reference (mount) or things will go all wonky.

[BrooklynBravest]

BB,

Make sure you are accounting for cylinder and punch stroke. You don't want to find that once you bend a piece you don't have enough extra clearance to remove it.

Your design is better than the Iroquois design in my opinion. You want the adjustment link in tension rather than compression as they have it. Tension keeps things straight. Compression allows parts to squirt out the sides and ruin your day.



Good.

I saw you mention an expensive pump. Look back to my press build thread (i think you were around then). I don't remember my pump being very expensive. $100 pump + motor and valving of your choice.

I ordered a Chinese auto lift pump after someone explained to me a double acting pump is not necessary here.

Log splitter valve, to be upgraded to electronic once I prove the press works.


To your point about stroke, it has 4” of total blade travel.

Which is actually more than my swag off road setup that I’ve never had an issue removing stuff from.