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17th Sep 2020, 11:05 PM #1Most Valued Member
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Workshop press build - hydraulic questions
I need to upgrade my old 6T Supercrap press to something of a larger physical size and force.
I've already decided on a rough design and have some of the material collected, including a used ~130mm diameter double acting cylinder.
Should give me a solid 25T at 3000psi.
I've thought about going to the high pressure 10,000psi cylinders but just feel that its a whole lot more stress on all the hydraulic components, and if I stick to 3000psi then hoses and fittings etc are easy and relatively cheap to buy.
I'm reasonably comfortable with hydraulics in general having done a fair bit in a past life with aircraft maintenance, but I have no experience with industrial pumps so hoping for some guidance from those who do.
What type and size of pump should I be looking for?
The 130x400 cylinder is approx 5.3L, so I figure that something of at least 20L/min would be reasonable- ie full stroke in ~15secs.
I definitely don't want huge flow as a fast moving ram in a press would be deadly.
I'm thinking a pump like the 2-stage ones they use for wood splitters might be suitable. Low pressure/high volume for moving to position and then the high pressure side for the actual pressing. They would seem to be similar sized rams and speed to what I'm thinking.
Perhaps one of the all-in-one vehicle hoist pump/motor/reservoir units might be the easiest way to go?
Any ideas?
Steve
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17th Sep 2020, 11:11 PM #2Most Valued Member
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As good as a powered press is. I really like having a hand pump option for careful work so I'd plumb one in as a backup.
Sent from my SM-G973F using Tapatalk
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17th Sep 2020, 11:16 PM #3Most Valued Member
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18th Sep 2020, 01:09 AM #4Most Valued Member
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Before you go too far, consider the power it will take to run a press at the performance level that you choose. A hydraulic pump providing 20 LPM @ 3000 PSI will take a shade over 10 Horsepower to drive it, which is solid 3 phase electric or internal combustion engine territory. Bearing that in mind, either a 10000 PSI air over hydraulic pump or a 2 stage rotary pump become viable options. If going the 10000 PSI air pump route, then buying a complete press becomes an interesting option, $900 +/- buys a 30 tonne air over hydraulic press with pressure gauge and $1600 =/- takes you into 45 tonne territory. It won't take too much to run up those sort of numbers buying pumps, control valves and hoses if building from scratch.
The integral pump, reservoir and control valve units from car hoists are typically single acting units which will mean that you need to use return springs (less than ideal, but possible nonetheless) if you choose to use one of those units. They will fall a long way short of 20LPM @ 3000 PSI though.
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18th Sep 2020, 08:05 AM #5Most Valued Member
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Thanks Karl - the power requirement was going to be my next bit of research!
I've got 32A single phase so practically limited to about 5HP. In saying that, I really only want the higher flow at low pressure for positioning.
I poked a few values into one of the online calculators and 2HP gives about 4 LPM @ 3000psi.
That's about 300mm ram travel per min if I've got my calcs right, so 5mm/sec. That feels like a reasonable rate for a bit of press bending etc.
FWIW, in regards to the rest of the design:
Force I'm working on bending a 500mm length of 6mm mild steel - which is around 30T.
The frame itself will be approx 1m opening, 100x20 flat uprights and 250x90 channel so likely good for about 100T. I got lucky at the scrappy and picked up a some suitable sized offcuts of brand new channel for 88c/kg
Uprights will be 1.5m long (so I get 4 out of a 6m length) but will make some feet/legs for the bottom to get the total height to around 2m. Hydraulics all mounted up the top out of the way.
Haven't decided on table height adjustment yet, but likely either cable winch or rack and pinion.
Pins probably single 30mm each side under the beams, but may as well make another hole in the beam web while I'm drilling..
Steve
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18th Sep 2020, 09:19 AM #6Senior Member
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20 l/m to me is to fast for a press. Good for long travel but a bit hairy for fine adjustments.
My electric pump does 4 l/m (1.5hp) to 5000psi and I thought that was to fast when trying to set somethings up.
I have fitted a hand pump which is ideal for setting things up with a bit of pre-load then hitting it with the other pump.
Tony
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18th Sep 2020, 10:19 AM #7Most Valued Member
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Thanks Tony. Great to have some real world feedback.
What size ram are you running?
How is the hand pump connected - just via a check valve or some form of selector valve to choose either hand or electric as the supply?
Steve
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18th Sep 2020, 12:59 PM #8then buying a complete press becomes an interesting option, $900 +/- buys a 30 tonne air over hydraulic press with pressure gauge
Sure my shop at work is a bit more than the average backyard setup, but personally I put any spare time into what I cant buy easily for reasonable cost, or for that matter to suit the gear I already have -- just my 2 bobs.Frisky wife, happy life. Then I woke up. Oh well it was fun while it lasted.From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".
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18th Sep 2020, 02:04 PM #9Most Valued Member
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I'm hearing you, and completely agree about putting time into what you can't buy for a reasonable cost.
Yes, $900 gets me a 30T chinese pretzel, but I'm looking at building what will be the equivalent of a ~$4000 press if I was to buy one. Roughly equivalent to the Hafco HPM50 footprint albeit with less power.
Overkill for what I need - probably. Will I outgrow it - unlikely. Will I enjoy building and using it - hell yeah!
Steve
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18th Sep 2020, 04:19 PM #10Most Valued Member
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If you want decent bending capabilities then you will really need to work on having fine control of either ram speed, ram travel or preferably both - .1mm makes quite a difference to your bend angle. At 500mm bend width, you will also be at the point where a mechanism to ensure parallel travel should be considered.
It sounds like 2 stage pump could be the go along with an adjustable stopping mechanism.
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18th Sep 2020, 05:52 PM #11Most Valued Member
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My press gets 12 to 15 ton with a car power steering pump, it has a relief valve. The control valve gives excellent speed/pressure control.
Operating a foot pump will get it to 40 ton but i cant remember the last time i used it.
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18th Sep 2020, 06:29 PM #12Most Valued Member
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Thanks Shed. I've got a couple of PS pumps lying around I could play with...
What are you using for the control valve?
Steve
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18th Sep 2020, 07:02 PM #13Most Valued Member
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18th Sep 2020, 07:07 PM #14Diamond Member
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The 60T press at work has an adjustable relief valve, and a flow control valve, really handy additions for when you are trying to press bushes out of flimsy parts.
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19th Sep 2020, 11:09 AM #15Member: Blue and white apron brigade
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I have a small hand pumped press with the pump cylinder oriented vertically. It's been slowly dribbling oil for about a year and probably needs topping up. How does one know how much to put in?
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