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View Full Version : Adding more "feel" to a hydraulic press



Dawai
04-19-2008, 07:21 PM
I got this three phase 5hp hydraulic press, it puts out by calculator about 50 tons.. I can't press bearing races in with it cause if they hang, the aluminum casting explodes. that just seems too expensive to risk.

OK, how to tone it down? is there a pressure regulator that is pretty cheap? easily adjusted for job at hand?

I have been putting off buying a small hand press like a 12 ton or so.. this big un scares me anyways.. I got it rewired and running again today *moved the 3ph generator to make room for another handy lift.

jacampb2
04-19-2008, 07:41 PM
How about a VFD for pump speed control, or perhaps an adjustable relief valve?

wierdscience
04-19-2008, 07:51 PM
Circuit selector valve and a adjustable relief valve.Allows you to keep the punch and speed you have for grunt work,but switch over to a lower relief setting for touchy work.

Alternate idea is a hand pump between your current valve and cylinder so you can use the motor to run it down until contact,then shut it off and finish it by hand.

lwbates
04-19-2008, 07:58 PM
Much cheaper and just as reliable- Just add an appropriatly spec'ed pressure guage to the pump and keep an eye on how the pressure is building as you work. If you need to, add ton marks to the face.
lwbates

Dawai
04-19-2008, 09:15 PM
There is a flow control handle on the pump.. the pump, made onto a 5 gallon bucket.. motor is kinda wierd, it will build the same pressure forward or reverse. Not sure what kinda pump it is, it is sunken in the bucket.

I tried just now playing with the handle, not much difference there. It don't bang bottom like it did, but still way too fast and the pressure will jump to 2500psi in just a split second.

I am going to put a steel plate over the cylinder.. How thick? I have 14 ga.. about 1/8" or so.. will that be enough to handle the cylinder shrapnel if it explodes? It also has schedule 40 pipe fittings on the return lines.. I know.. but there is another press series with the return loop.
With it cranked open, it rattles the shop foundation and the house about 100feet away when it hits bottom. THE limit stops it, but.. inertia carries it on.. I was breaking 1/2" metal in the break on it.. I did a 1/2" x 24" wide piece by two breaks.. Like I said, this thing scares me. It sure is handy tho.

SO? I am looking for a back pressure regulator bleed off.. preferably one with a guage? The pump has a guage on it.

Northerntool? any more sources?

jacampb2
04-19-2008, 10:01 PM
surpluscenter.com has all sorts of hydro and pneumatic stuff at very reasonable prices. Typically fairly fast shipping as well.

davidh
04-19-2008, 10:13 PM
i think a manual controlled presure relief valve is in order. or as was said in another post, pipe a 10,000 lb chepo portapower pump in the line and do the final press by hand. . .

Holycross
04-20-2008, 12:43 AM
Dave,

Think you should be able to just plumb a pressure gauge in parrall with the cylinder. Then watch the pressure as you operate the press. If you know what pressure you want to limit for a sprecific job just release the handle if the pressure rises too much.

Or use an adjustable pressure release valve to limit max pressure.

Mark.

dp
04-20-2008, 02:52 AM
You need a waste gate adjustable valve to by-pass the pressure line back to the tank. It will need to handle full pump pressure without exploding.

macona
04-20-2008, 03:39 AM
A standard gear type pump is no good for a small press. Look for a enerpac type pump. They work good and are controllable.

The GPM rating on the pump is just too high. You can either get a bigger cylinder or smaller pump. Dump valve might help.

The cylinder will not explode. Oil dosnt have the stored energy compressed gas has and thats what makes shrapnel.
You are using a real hydraulic cylinder, right?

Dawai
04-20-2008, 04:06 AM
http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200339411_200339411

This is the one I am looking at
https://www.northerntool.com/images/product/images/202518_lg.gif
100-1000psi... which will keep everything okay. It was $89 if I remember.

http://img.photobucket.com/albums/v85/ibewgypsie/50_ton_press_001.jpg
The press, made from H-beam, linear bearings on each side. I've welded the paintline trolley track to it and tied it off to the Ibeam in the ceiling in the next room to stabilize it, put a swivel crane on it to load things on the mill.lathe. AND tooling I was making a harley fender stamp.. kept ending up with wrinkles so??? THE whole frame flexes under the full load of the pump.. acts like it was going to take a step, the hoses tighten, the lights dim.

ANYWAYS< I'll do the math and see if that is the right relief, it does have a hand knob on it. This rig is home made-at a place I bought it from. Guys' it jumps to 2500psi so fast it is uncontrollable. NO watching a guage and shutting it down.

It was cnc'ed. NOW it's manual again. Even the encoder was robbed for a midnight robotics job. A mouse ate my schematic, I stripped it down to about a dozen wires. (really) it made a bed with the paper. Where's a good snake when you need one?

ptjw7uk
04-20-2008, 08:47 AM
David
Years ago at work we had a mass spectrometer that had valves to shut the various parts of the high vacuum system and that used a 0 - 2000 psi pump to operate the valves. If my memory serves right it was operated by valves which opened to the rams and you operated the bypass valve to get the fluid to the rams. So could you not do this it would certainly make it more responsive and controlable. The bypass was set to bypass on start up and close to power the rams.
Peter

jimmstruk
04-20-2008, 01:33 PM
David, Look in Northern Tools at item #20111. That valve might do what you need. Using that type of valve you should be able to "feather" the speed of the cylinder or open it up wide open. JIM

macona
04-20-2008, 03:10 PM
That cylinder is really a bit small.

The pressure is not the problem. It is the flow rate. You WANT the pressure. You basically built this like a log splitter, not a press. You want short stroke cylinders with large rods with a big bore. If you put full pressure to this cylinder you could tweak the rod. Also it lacks stiffness due to the small diameter of the rod vs. diameter.

A manual hand pump would be better for setting in a bearing. Much more control.

Dawai
04-20-2008, 06:38 PM
http://www.youtube.com/watch?v=mrVqI_9QkOc

This one is running Siamese with it. On the same hydraulic pressure, in the return valve flow from the other side.

Yeah, I put that long stroke cylinder on there about two years back or so.. did not build it. THE larger cylinder has a much shorter stroke.

I'll look at the flow valve listed here in a bit.

CCWKen
04-21-2008, 10:38 PM
I don't think you're getting anywhere near 50t. with that cylinder and pressure. If the bearings and/or races are cocking, use your lathe and make some press guides. A lot cheaper than hydraulic gizmos. ;)

Dawai
04-22-2008, 12:06 AM
No, I am no longer getting 50 tons, there is substantial impact speed and force tho. THE smaller diameter cylinder goes much faster.

It is square inches cylinder x pressure.. the pressure guage used to slam all the way to 4500, but I think the guage was bad.. it does not move at all now.. I changed the fluid to a less vicious one. I'll get another guage.. small leaks also here and there.. I noticed the rousselle press is dripping from the rod.

Ever see the MSDS on hydraulic fluid? it'll cause cancer and cure warts.

I plan on taking the old large diameter cylinder and building a hole punch you can hang on a chain to punch plate and Ibeam.

macona
04-22-2008, 01:13 AM
You need a damper on the gauge so you dont destroy them:

http://www.flowfitonline.com/acatalog/Online_Catalogue_FT291_90__ANGLE_GAUGE_ISOLATOR_NE EDLE_VALVES_65.html

digger_doug
04-22-2008, 09:07 AM
David,
Yes a gear pump will work, oil is oil. Having said that, you could
tee in parallel a hand pump for seating bearings, and use the gear
(or whatever motorized pump) for bending, broaching and such.

Niagara used to make a 135 ton press that did it all, was sold as
a maintanance type press. It has feel, the valve looks custom.

Best I can figure, you could use a standard spool valve, a very small
bore cylinder coupled in parallel with your cylinder, that pushes back
on the spool handle as the pressure build up. Yes it's kind of
hillbilly engineering, but you would have to push harder on the spool
valve's lever, as the pressure built up.

Sound like what is needed is like a truck air brake treadle, only to
handle 2000 psi oil. Look up "mico". They build truck brake controls
for hydraulic brakes (off highway).

Forrest Addy
04-22-2008, 11:28 AM
I suggest a hand operated relief valve. Your hand treis to close it against pump pressure thus giving you a direct analog sense of what's happening via "seat of t he pants" Vs what's going on with eyes alone. It could be as simple as a manual piston pump with the check valves removed whose pressure port is connected to the press pressure and a return line ports from the side of the hand pump cylinder. The hand pump piston opposes pump pressure and the the pressure can (if the hand effort allows it) force the piston up to uncover the port. Recular spool valves will not work unless there is an actuator that opposes hand effort.

I saw a powered press in a small shop arranged this way. There was a valve to block the pressure line to the hand relief valve for brute force jobs. When the valve is opened he manual force control was in effect.

One thing, the flow capacity of the hand relief valve and the lines service it have to be sized to minimize back pressure otherwise there will be some inescapable downward force in the ram from flow restriction.

Dawai
04-22-2008, 11:57 AM
{exerpt}Northman Fluid Power In-Line Hydraulic Relief Valve 50 GPM, 1001000 PSI Adjustable, 3550 PSI, 3/4in. NPT Ports, Model# RFT061

This Northman adjustable relief valve is designed to limit the operating pressure in a hydraulic system to a maximum set pressure. The valve may be connected into the pressure line so that system pressure flows through, or it may be teed off the pressure line with one of the pressure ports plugged. When the system reaches the maximum desired setting, the internal piston moves to smoothly relieve pressure to tank, maintaining stable pressure control and repeatability. Ports are also provided for a gauge and for remote pressure control.
{/exerpt}

Remote pressure control port.. meaning I could use a air regulator? possibly?

CCW, this press has two linear bearings, (high dollar) on it. It runs true. I make the race press guides on the lathe, I made a knocker a month or so back and left enough meat on it for press work. I dislike knocking races in.

PaulF
04-22-2008, 11:58 AM
Hi,
I built a hydrostatic test tank to test underwater equipment.
We used a spring adjustable pressure relief valve in the tank.

We would set it to the depth of the test and it would not let the pressure go above that limit. The excess water was sent to a drain , however you could just dump it in the Oil reservoir.

Like everything else in the world they have them at McMaster Carr for $ 35.00
and deliver shortly after you think about it!
PaulF

Alistair Hosie
04-22-2008, 01:53 PM
couldn't you do what we used to do in Dentistry David when taking an x ray set up everything so you can control it from another room with cctv just kiddin.:D I do know you are smart to be cautious though thos buggers will tear you up if they explode so I too would put a metal skirt round it and stand well clear. good luck Alistair ps wish I had a big press to take the wrinkles oputah mah kilt boyoh.:DAlistair