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Seeking hydraulic system guru

SShep71

Cast Iron
Joined
Sep 17, 2014
Location
San Diego, Ca
Since my Chicago Dreis Krump 131-36 clutch press brake, broke, and almost took of my hand in the process it is getting an UPGRADE. I saw that Baileigh has a 3142, 31" wide 42 ton press brake. A "cute" little item, but with a 22,000 price tag. I like the size, despise the company, hate the price tag. I am going to step the game up and go from a 12 ton mechanical press brake to a 40 ton hydraulic press brake. I am going to have to dig into my stash of 1" plate that I have been hoarding for a whiles now for the new strengthening members. I have the mechanical aspects all worked out, reinforce that, weld this, strengthen that, large pin here, big bolt there, voila! I am in need of my hand being held with regard to the hydraulic system, as I never had to design a hydraulic system from scratch before I naturally have some questions.
I am trying to mimic a Piranha 6' 45ton press brake for ram velocity and such, the Piranha lists a work velocity of 19 IPM and a retract velocity of 165 IPM. I have no idea what type of pump they are running, but it seems as if it is a variable displacement pump in order to get the ram velocities mentioned, 5hp is specified for the motor.

On my monstrosity:
-The upper die will have a travel of just over 4"
-The upper die will be driven by a lever arm with a ratio of 3.68:1, that will give me plenty of safety room to hit the 40ton mark.
-The cylinders are 4x18x1.5" diam rod.
-The motor is a 10HP 3 phase motor 1750 RPM for the power
-I am going to build a baffled tank with about 25-30 gallon capacity with all the proper fluid management built into it.



Now the requested help, the pressure calculations show that I can run 1000psi from the pump in order to achieve the 40 ton target force. The pump I bought is a Eaton/Cessna gear pump but it is only a 0.6 in^3/rev displacement (originally I had planned for a 3x6 cylinder), but the pump is bought already. From what I calculated the max velocity that pump will allow for is 29 IPM at the ram/die. Is this correct?

velocity of the ram x the 3.68 lever arm ratio= velocity of the cylinder (607 IPM)

velocity of the cylinder x specific gravity of the oil x area of the bore (on the push side)= mass volume required (6554 in^3/min)

I am on the right track here? 6554 cubic in per min seems like I made a mistake. If you wish to provide some "oversight" I can provide you with the excell spread sheet with all my calculations and data so far. I appreciate the help, I am in dark waters here.
 

dana gear

Hot Rolled
Joined
Feb 27, 2013
Location
Northern califorina, usa
The rod end of the hydraulic cylinder will travel faster then the piston end due to the fact the rod within the cylinder will decrease the volume of oil within the cylinder (less oil needed to travel the same distance). that is with all things the same pressure/volume and the same load on the ram both ways.
I would strongly advise that you install a standard flow divider on the pressure output side of your hydraulic pump, sized correctly you can control your rams travel speed by simply adjusting the bleed of the divider. it's dirt simple, pressure in and out with a 3rd line that dumps divided oil back to sump/tank.
 

muckalee

Cast Iron
Joined
Jul 17, 2011
Location
Americus, Georgia
6554 cubic in. divided by 231 cubic in. equals 28.37 gallons. A 3 inch cylinder extends @ 32 IPM with 1 GPM oil flow, retracts @43 IPM.
A cylinder yielding 80,000 pounds of force @ 1000PSI would be 10 inched in diameter.

A system requiring 30 GPM @ 1000 PSI, requires 20 HP.
 
Joined
Jan 15, 2005
Location
The Netherlands
A flow devider is not enough on a press brake
Not working properly if bending on the side
Eighter done mecanicly With levers on both sides connected to a torsion tube Or a rack with pinion on both sides with a torsiontube connecting the 2 pinions Hydraulicly by one big cilinder where the return oil goes to a smaller cilinder on the other side making displacement both sides the same
Or nowadays electronicly controling the valve or valves

Peter
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
Since my Chicago Dreis Krump 131-36 clutch press brake, broke, and almost took of my hand in the process it is getting an UPGRADE. I saw that Baileigh has a 3142, 31" wide 42 ton press brake. A "cute" little item, but with a 22,000 price tag. I like the size, despise the company, hate the price tag. I am going to step the game up and go from a 12 ton mechanical press brake to a 40 ton hydraulic press brake. I am going to have to dig into my stash of 1" plate that I have been hoarding for a whiles now for the new strengthening members. I have the mechanical aspects all worked out, reinforce that, weld this, strengthen that, large pin here, big bolt there, voila! I am in need of my hand being held with regard to the hydraulic system, as I never had to design a hydraulic system from scratch before I naturally have some questions.
I am trying to mimic a Piranha 6' 45ton press brake for ram velocity and such, the Piranha lists a work velocity of 19 IPM and a retract velocity of 165 IPM. I have no idea what type of pump they are running, but it seems as if it is a variable displacement pump in order to get the ram velocities mentioned, 5hp is specified for the motor.

On my monstrosity:
-The upper die will have a travel of just over 4"
-The upper die will be driven by a lever arm with a ratio of 3.68:1, that will give me plenty of safety room to hit the 40ton mark.
-The cylinders are 4x18x1.5" diam rod.
-The motor is a 10HP 3 phase motor 1750 RPM for the power
-I am going to build a baffled tank with about 25-30 gallon capacity with all the proper fluid management built into it.



Now the requested help, the pressure calculations show that I can run 1000psi from the pump in order to achieve the 40 ton target force. The pump I bought is a Eaton/Cessna gear pump but it is only a 0.6 in^3/rev displacement (originally I had planned for a 3x6 cylinder), but the pump is bought already. From what I calculated the max velocity that pump will allow for is 29 IPM at the ram/die. Is this correct?

velocity of the ram x the 3.68 lever arm ratio= velocity of the cylinder (607 IPM)

velocity of the cylinder x specific gravity of the oil x area of the bore (on the push side)= mass volume required (6554 in^3/min)

I am on the right track here? 6554 cubic in per min seems like I made a mistake. If you wish to provide some "oversight" I can provide you with the excell spread sheet with all my calculations and data so far. I appreciate the help, I am in dark waters here.

A flow devider is not enough on a press brake
Not working properly if bending on the side
Eighter done mecanicly With levers on both sides connected to a torsion tube Or a rack with pinion on both sides with a torsiontube connecting the 2 pinions Hydraulicly by one big cilinder where the return oil goes to a smaller cilinder on the other side making displacement both sides the same
Or nowadays electronicly controling the valve or valves

Peter
Peter nailed it.

Try this:

Homemade 48" Press Brake - HomemadeTools.net

or this:
GRK ENTERPRISES - RANDY KECK [email][email protected][/email] FAIRVIEW,OKLAHOMA - (580) 227-7050 580-227-0732 - Home
 

BT Fabrication

Hot Rolled
Joined
Nov 3, 2019
6554 cubic in. divided by 231 cubic in. equals 28.37 gallons. A 3 inch cylinder extends @ 32 IPM with 1 GPM oil flow, retracts @43 IPM.
A cylinder yielding 80,000 pounds of force @ 1000PSI would be 10 inched in diameter.

A system requiring 30 GPM @ 1000 PSI, requires 20 HP.

looks like he is trying to build a press brake same idea with a long lever and 18" of travel on the cylinder, sure the leverage will help the press brake numbers, but I think working in a push stroke it wont quite multiply the tonnage like he is thinking.
4" cylinder is most likely 3.5ID bore. = 9.62 Sq. inches of area at 1000psi is only 9620 lbs. or about 5 tons. the lever arm would need to be like 4 ft. long I would guess and about 3 x multiplication on gets 15 tons max if set up correctly.
to hit past 40 tons, you would need to be about 3000PSI.

the pump can move 1050 Cu3 of oil max at what PSI? most have pressure curves that reduce substantially as pressure builds.
cylinder bore would be about 173.16 CU in fully extended, give or take. so at 0 psi it would take 1/5 of a minute to extend and more time as pressure builds. so 12 seconds + give or take.
 

SShep71

Cast Iron
Joined
Sep 17, 2014
Location
San Diego, Ca
I attached a screenshot from the Baileigh 3142 manual to better show the design that I am running with. I intend on using a pressure compensated flow divider on both the compression and retract sides. There will be two 4" bore 18" stroke cylinders in parallel that will drive the lever arm assy, the arms are welded to the 3 1/2" .375 wall center tube, as the arms are welded solid and the flow divider is inline I was under the impression that the system would balance as the flow divider would work in unison with the arm assy to compensate for any variance with travel differences.

This is the way I came up with the force per cylinder: With a 5/18.375 lever arm 21769lb force one one side of the center pivot generates 80000 lb force on the opposite 5" length arm. I would only need each cylinder to generate 11tons to generate the desired force of 80000lb. Levers

To control the speed of the cylinder I was going to use a single spool hydraulic valve with the notches in the spools to allow for small movement or full movement with full throw. Similar to the spool valves that forklifts use to allow inching of the mast vs full force on the mast.

Baileigh 2142.JPGBaileigh 2142 2.JPG
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
6554 cubic in. divided by 231 cubic in. equals 28.37 gallons. A 3 inch cylinder extends @ 32 IPM with 1 GPM oil flow, retracts @43 IPM.
A cylinder yielding 80,000 pounds of force @ 1000PSI would be 10 inched in diameter.

A system requiring 30 GPM @ 1000 PSI, requires 20 HP.

I attached a screenshot from the Baileigh 3142 manual to better show the design that I am running with. I intend on using a pressure compensated flow divider on both the compression and retract sides. There will be two 4" bore 18" stroke cylinders in parallel that will drive the lever arm assy, the arms are welded to the 3 1/2" .375 wall center tube, as the arms are welded solid and the flow divider is inline I was under the impression that the system would balance as the flow divider would work in unison with the arm assy to compensate for any variance with travel differences.

This is the way I came up with the force per cylinder: With a 5/18.375 lever arm 21769lb force one one side of the center pivot generates 80000 lb force on the opposite 5" length arm. I would only need each cylinder to generate 11tons to generate the desired force of 80000lb. Levers

To control the speed of the cylinder I was going to use a single spool hydraulic valve with the notches in the spools to allow for small movement or full movement with full throw. Similar to the spool valves that forklifts use to allow inching of the mast vs full force on the mast.

View attachment 327822View attachment 327823

So they are copying an accupress.

But how to bias one side or the other ? You need adjustment on one ram.
 

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
To get a very high unloaded ram speed the trick is to port the fluid leaving one side of the cylinder back into the pressure side. That's how they make production hydraulics "Holy fuck fast". Multi stage pumps help too.
 

SShep71

Cast Iron
Joined
Sep 17, 2014
Location
San Diego, Ca
@digger doug: I am going to have adjustment through screws on the connection between the upper die and the first "knuckle" I just haven't finished my drawing sheet sets yet to be able to post a picture up.

@Garwood: I kind of figured that there were either multi stage or multi displacement pumps for the ultra fast press brakes for production, where I would like to have a fast machine I don't need those servo or multi stage pump levels of fast. My attempt to use the Piranha was just a basis for a starting point for design as it is twice as wide as my press but the tonnage would be the same.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
You need a variable displacement axial piston pump ,doubled.......two axial units on the one driveshaft.....Lucas Fluid Power used to make a basic one for the Clark Bobcats,with manual controll of the swash plates ,each pump driving one side of the Bobcat......More expensive you go to Sundstrand ,more again,the Linde line of either swash plate or bent axis.........incidentally ,with variable displacement pumps,you dont use any valves ......all fluid controll is by pump displacement,as is reversing of fluid flow.
 
Joined
Jan 15, 2005
Location
The Netherlands
This design has the linkage to keep the upper and lower die parralel
You can go for higher speed on the stokes but that makes things much more complicated
Easy way I think is to put a VFD on the pump motor
Am I assuming right that pos 147 in pic 1 is a mecanical way to adjust the position of the stroke and that you go to end of the hydraulic stroke with every bend Adjusting the actual depth with pos 147??

Peter
 

Strostkovy

Stainless
Joined
Oct 29, 2017
I actually specced out everything for a press brake and bought most of the stuff a while ago. We bought a brake so I'm repurposing the stuff.

I used rotary flow dividers, and leadscrews to adjust stroke.

I had two pumps I could gang up or bypass one for two speed pressing and I combined the rod side and piston side of the cylinders for excessive speed on return.
 

SShep71

Cast Iron
Joined
Sep 17, 2014
Location
San Diego, Ca
@john.k: Way to throw a wrench in things, I forgot all about axial piston pumps. I haven't touched one in a long time. That is a much better design than just using a fixed volume gear pump like the one I went with, although cheap, the benefits may outweigh the costs. To Ebay!

@Peter from Holland: From what I gather from the part break down, the threaded portion at the bottom of POS 153 is used to control the point of travel of the ram through the gears at POS 147 being rotated to reduce or increase the stroke. The gears are controlled via the handwheels at the operator interface. I am not sure if the gears at POS 147 are designed to be rotated independently, as I have never seen one of these presses in person or operate (the drawbacks of pricing these machines at going unicorn rate). I am going to have independent adjustment of each side when my design is finished, I am getting there with my drawings.

@Strostkovy: I had considered buying a machine, but when I looked all the machines in the small size that I am looking for are 20-30 ton, or are just way out of the ballpark for me to even hope and dream. I had to resort to making what I have work, which is why I am at the point I am at. I also looked at rotary flow dividers for my application, but I was under the impression that the efficiency was very low, I will have to revisit that idea. I am not exactly sure what you meant by combining the rod side and piston side of the cylinders.
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
I really think your overcompicting this, with no gain in ram accuracy.

Your making linkages, and adjustments, but still need matching hydraulics (flow divider et all)

The single long cylinder design I linked to is used by several OEM press brake manufs.
You'll still need some linkages, and one adjustment screw, but no special hydraulics.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
With simple readout scale application on each guide ,the attitude of the blade can be controlled to 001 if needed.......computer control of pump output is quite standard ....if fact manual controll is the odd one out now ,pumps having either a hydraulic analogue system ,or full electronic pump connection .....all standard off the shelf parts.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Funny story about a big press.....was at an auction where one lot was the double axial pump and extras from a press rebuild ...new never used ......anyway ,sale dragged on and on ,and finally up to lot 1,532 or whatever.....,there was another guy I knew waiting for the pump to,so I put a big coldsaw blade on top of it .......and I got the lot for $100.......about ten lots on the guy starts squawking to the auctioneer that the pump hasnt come up....Auctioneer says ,yes it has ,you were yapping and missed it ......John here got it......yap-yap says where is it then?......auctioneer says .....you re standing on it.....Everyone pissed themselves laughing .....anyhoo ,sold the pump to yap yap for $500,and got the 6ft dia coldsaw blade free.
 

SShep71

Cast Iron
Joined
Sep 17, 2014
Location
San Diego, Ca
I abandoned the press brake I was going to retrofit, I found a CNC press brake local to me that needed a bunch of work for the same cost as the materials needed to complete the retrofit.
 

dana gear

Hot Rolled
Joined
Feb 27, 2013
Location
Northern califorina, usa
I was simply suggesting a flow divider to control ram travel speed, certainly not to control ram balance.
One of my press brakes a 700 ton unit has a Oilgear drive unit with "ready for this a Flow divider" with divided oil going to the servos that control balance.
 








 
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