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under load speed of presses .

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Dear all ,
I am about to start making a forging press and have a few questions about pressure transfer and how long pumps and systems take to build up pressure .
I have looked in the Batson book and on the pages of this forum and am left with a few questions .
I already have a working press .A mills 200tonne and it is a powerful tool but slow .It runs at just under 1/2 inch per second and slower return. It is a one way cylinder with spring return . I can happily use it to squash stuff and for a single forging action it is great. However its slow nature means that all the heat is drawn from the steel in that one operation .
I want to make a faster H frame press, however almost all the info I have seen on duel stage pumps seems to high lite to me how slow they are in the second stage high pressure phaze .
It seems all well and good having fast approach and retreat but what is a good forging speed for a press in the high pressure stage ?
another question I have is , when pressure builds up,how long does that take, by that I mean when the pump switches to high pressure from low how many seconds (or less )before the high pressure side of the system is at full pressure ?
now my assumptions around that are that length of hose and hose material must have an effect on this? my large press is a piston pump and seems to not really slow down when it engages hot steel , the motor just strains .
I want to make a press for punching and precision hot stamping and hot cutting as well as squaring damascus billets and to add context I already have power hammers, so do not need to duplicate that role .
I have accumulated various pumps /power packs rams lever valves and hose over the years and am ready to finally put something together in the new year .
so in summery :-
How fast does a press need to be during its high pressure stage in order to work for hot forging operations .
How long does perssure build up take in duel stage pumps when they switch over . are there any ways to minimise this?
would running a single stage pump and larger motor have advantages over duel stage ?
Do piston pumps have advantages over gear pumps?

thanks in antisipation .
Owen

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Dear all ,
I am about to start making a forging press and have a few questions about pressure transfer and how long pumps and systems take to build up pressure .
I have looked in the Batson book and on the pages of this forum and am left with a few questions .
I already have a working press .A mills 200tonne and it is a powerful tool but slow .It runs at just under 1/2 inch per second and slower return. It is a one way cylinder with spring return . I can happily use it to squash stuff and for a single forging action it is great. However its slow nature means that all the heat is drawn from the steel in that one operation .
I want to make a faster H frame press, however almost all the info I have seen on duel stage pumps seems to high lite to me how slow they are in the second stage high pressure phaze .
It seems all well and good having fast approach and retreat but what is a good forging speed for a press in the high pressure stage ?
another question I have is , when pressure builds up,how long does that take, by that I mean when the pump switches to high pressure from low how many seconds (or less )before the high pressure side of the system is at full pressure ?
now my assumptions around that are that length of hose and hose material must have an effect on this? my large press is a piston pump and seems to not really slow down when it engages hot steel , the motor just strains .
I want to make a press for punching and precision hot stamping and hot cutting as well as squaring damascus billets and to add context I already have power hammers, so do not need to duplicate that role .
I have accumulated various pumps /power packs rams lever valves and hose over the years and am ready to finally put something together in the new year .
so in summery :-
How fast does a press need to be during its high pressure stage in order to work for hot forging operations .
How long does perssure build up take in duel stage pumps when they switch over . are there any ways to minimise this?
would running a single stage pump and larger motor have advantages over duel stage ?
Do piston pumps have advantages over gear pumps?

thanks in antisipation .
Owen

What sort of tonage are you looking to get out of your new machine? mb

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I am looking for between 20 and 40 tonnes. and have 4" and 6" bore rams .working out the final tonnage for a given pump is not a problem. the thing I cant work out is how fast this is reached when changing from low to high pressure or in a single stage unit how fast pressure will build when the ram becomes under load.
thanks Owen

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I am looking for between 20 and 40 tonnes. and have 4" and 6" bore rams .working out the final tonnage for a given pump is not a problem. the thing I cant work out is how fast this is reached when changing from low to high pressure or in a single stage unit how fast pressure will build when the ram becomes under load.
thanks Owen

Ok,what I know may be of some use. I have a 25 ton w/ an 11 gpm vane pump @ 2500 psi, 5" cyl., 10hp single ph mtr and a prince flow regulator.The prince reg only restricts flo not psi. This setup allows fast or slow speed with no reduction in tonnage.The big 10hp mtr is needed to reach 2500 because of the large (11gpm)flo. If you already have the two stage pump then I recon you'll use that,but speed can be regulated other ways as well
Unless you have 3ph, 10hp motors are a bit spendy, especially the starter. Anyhow there's more than one way to gut a dog.Don't know if this helps, just thought I'd pass it along .......mb........Also, this type of setup works best on smaller pumps/presses 10-50 ton+- cause much larger and you get into 15hp+ motors,$$$$

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I have an H frame forging press that I am still building it has 2 5 inch bore cylinders and a 7.5hp motor I was going to use a 16gpm 2stage pump but have not bought one yet. I have similar concerns as to the 2 stage pump but I figured once you are into the metal the amount of reduction that you will get will be similar as you are not moving very far.

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Well, the reason there is no change-over time going from high-volume to high-pressure is as follows: Let's say we have a pump that puts out 11 GPM at low pressure and 3 GPM at high pressure. Inside the pump there is actually two pumps, one that puts out 3 GPM and one that puts out 8 GPM. At low pressure they are both delivering fluid for a total of 11 GPM. At the change-over pressure, line pressure simply closes a valve that cuts the 8 GPM pump out and dumps it's output. No actual lag as the 3 GPM pump is pumping all the time.

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thanks for your replies .
I managed to rig my 6 inch piston up to a milling machine power pack I have .the power pack is a bit of an unknown .I am assuming it is a single stage it has an overload bypass valve connected to the pump . its 5.5hp and 18 litres a minute ( 4 US gallon) measured at 12cc a revolution...
this gives me about 1/2 inch per second travel on my 6 inch ram .
when I put a pressure gauge inline and bottom the ram the system builds up pressure to 1500 psi this takes at least 2 seconds I think I could up the pressure by tweaking the pump bypass valve.
how can I speed this "lag " up .
my assumption is that a pump of twice the throughput would come up to pressure twice as fast ?
I am not going to use this pump however I think it has highlighted the problem I am asking about .

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Owen,
my press
5hp motor at 1725rpm to a 22gpm two stage pump..so the flow is actually 11gpm minus efficiency. A 10Hp 3600 rpm motor would run at full 22gpm.
two 5" double acting cylinders.
I run at 2800PSI for max so about 43 ton give or take.

Moves at 0.6 inches per second and maybe 0.2 per second under full load.
http://www.youtube.com/watch?v=FypNcOI96Tg
and close up
http://www.youtube.com/watch?v=QmBLvirHJCU

I do the same operation under the 3B Nazel now though.

Ric

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press speed is a subjective thing... first off not all two stage pumps are created equal. Most that are inexpensive are "log splitter" pumps that are designed to run at 4000 rpm... these pumps have a high speed stage that builds less than 500 psi. (most say they will do 650PSI but my hydraulic guy says "real world" with an electric motor one of these pumps your not actually doing any real work at the high speed or at 650PSI), at 15% load they revert to the slow speed, so with a smallish cylinder what you really have is high speed jogging... which is good if you have a lot of travel and a very universal tool station that requires lots of movement... If you have specific tooling where the ram is already very close to the work it really does not help a tremendous amount... Size of the cylinder plays a big part as well A 4" cylinder at 500 PSI makes about 3 ton, not quite enough to forge with, so it kicks to low speed, which is sloooooooooowwwwwwww...... Or you can have a bigger cylinder so you get more tonnage out of the low side, which then is slow because it takes more oil to make it move... so in this case, My feeling is your better off with a 6gpm fixed pump rather than a 16gpm/2.9gpm two stage.. More industrial two stage pumps can have higher working pressure on the high speed side, I have mine set to kick out at 800 psi, which I can do quite a bit of forging at the high speed stage (my 6.75" bore cylinder will make 10 ton at 800psi, which is enough to do 50% of the press forging I do) my system will move 20 GPM up to 800 PSI and 7 GPM there after to 3000PSI... so Its like having both a 10 ton high speed and 65 ton slow speed press in the same machine... The down side is these types of hydraulic systems are expensive and your unlikly to find one used. I built mine with a surplus motor and valve and still have over three grand into it ( just the pump, not the press)

Just for the info my Williams White 210 ton forging press which was built for Taylor Wharton Iron in Cincinnati Ohio in August of 1951 has stated specs of 67.5" per min rapid traverse down, 22.5" per min full pressure travel and a return speed of 137" per min

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thanks Ric,
I know i have used your press ......but I couldn't honestly remember any of the speeds etc
I thought it was fast enough interestingly its only just faster than my big press, but lots lots quicker on the return .........

Monstermetal, thanks I am coming to similar conclusions I already have an 11 gpm two stage pump that I bought a few months ago thinking it was going to do the job . I am now thinking that this was a mistake and that a single stage might be a better idea .
I have a couple of 7.5hp motors and a 20 ..
8gpm at 2500 psi calls for 13 hp so 2 x 7.5hp coupled together would be a good job. I will look into prices.

FE-Wood.
thanks that is a great link.
All the best Owen

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maybe this estimating template will help-
http://www.surpluscenter.com/Hydraulic.htm

The speed calculations on that link seem to be way off to me....
I prefer this one:

http://www.baumhydraulics.com/calculators/cyl_speed.htm

Ric

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thanks Ric,
I know i have used your press ......but I couldn't honestly remember any of the speeds etc
I thought it was fast enough interestingly its only just faster than my big press, but lots lots quicker on the return .........


Owen,
I sent you an email (and others) on this..guess it did not get through.

As I work stock with random/variable sizes and use drop in tooling and such I find the fast speed of the low pressure to be an advantage.
I'm building a larger press with a 12" cylinder and it will have about 40 ton on the low pressure and then kick to 160 ton with the slower high pressure action of the two stage pump....should be interesting...though nothing like the 210 ton Williams and white Monster has. The oilgear pump on that unit is $4,000 on the used market.

Ric

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Thanks rick-
That went right into my link pile... Always nice to be able to compair info....

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My feeling is your better off with a 6gpm fixed pump rather than a 16gpm/2.9gpm two stage..


Well yeah, but what about compared to a two-stage pump with the same 6gpm high-pressure side? After all, that's what determines the horsepower required. Why compare apples to kiwis?

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Well yeah, but what about compared to a two-stage pump with the same 6gpm high-pressure side? After all, that's what determines the horsepower required. Why compare apples to kiwis?


Because two apples in a row may keep the doctor away for too long?

What I wish is that they made a low cost two stage pump with more flow that the max standard of 28GPM.....unless I am just missing it out there. They make the "log splitter" pumps which we are talking about in 8,11,13,16,22 and 28 gallons per minute....the 28 requires about 15-16 horse power to run.
I'd like one with a bit more flow on a 20-30 hp motor.
As I understand it without an accumulator you can not simply tie two pumps together to get more flow.

As it is the 28GPM I will use makes about 22.4 GPM by the time all is said and done on my system (rpm of 3550,loss to efficiency etc). So in effect I will be upgrading the tonnage on the next press with no increase in speed. I am OK with that, but only because any alternative is 2-3x the money.

Ric

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Well yeah, but what about compared to a two-stage pump with the same 6gpm high-pressure side? After all, that's what determines the horsepower required. Why compare apples to kiwis?


Because in this case thats what we are doing, Its like talking about a 5HP motor on a compressor at harbor freight or the "same" 5HP on a industrial two stage IR.... They both say 5 HP but that does not mean they are created equal


In industrial pumps your right grant, but when you are talking log splitter pumps it dont think it really works like that, because you cant run a log spliter pump like it was intended with an electric motor... So your 16/3.5 GPM log spliter pump with a 3450 motor makes something like 2.8 GPM with 7.5 HP, or you can use a vane pump and get something like 4-5 GPM

But yes, thats what my system is.... mine is not a two stage, but rather a tandem pump... I actually have a single suction line and two output lines and the high output side is diverted back to tank past 800PSI system pressure


Here is a clip from a log spliter pump
log spliter PDF

You'll notice it states past 450 PSI only low stage flow is available even though it states in the chart it will make 600PSI
You'll also notice that unlike a "real" hydraulic pump chart it gives flow rates based on 250 PSI of system pressure, not very real world.... What its saying is it will move this much oil, but only if your not doing anything....

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Thanks for all your imputs . ebay has been kind and I now have some more bits to play with .10 hp motor with attatched 3500 psi 4 gpm dowty pump ($100) in old but new condition . Im going to plumb this into a 4/1/2 inch piston which is rated to 5000 psi and try running it at just under 3000 psi which is the rating of my valving. Am I rite in thinking that I will need a seperate relief valve to protect the controle valve if it is only rated to 3000 psi and the pump can give 3500 (and would with 10hp). ?

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