bottles Posted June 5, 2014 Share Posted June 5, 2014 Hi quick question on power (psi) versus speed of ram (or pump)? I have a 3 phase 2.2kw (3hp) motor run via a vfd. It has a 4cc (0.25"?) pump running at 1400 rpm. It will easily hit 3000psi at 50hz. My ram is 4" and moves around 1/2 per second at 3000psi. I have a pressure regulator before a solenoid block. The solenoid diverts to tank when not engaged. When the ram moves and contacts hot metal it takes about half a second to reach 3000psi during which time the dies suck out the heat. It does move a reasonable amount of metal. BUT if I increase frequency to 100hz this would give 3 gpm increase the ram speed and dropped the max pressure to 2000psi am I likely to see any real difference? As most of the work seems to happen at the initial contact of the dies especially when screaming hot. Andrew Quote Link to comment Share on other sites More sharing options...
Frosty Posted June 7, 2014 Share Posted June 7, 2014 I'm no expert on presses but have some experience with hydraulic systems. If you start thinking of hydraulic systems usiing simple gearing or belt gearing as a model it's actually easier. For instance, thinking of GPM as rpm or horsepower and psi as torque is a valid model. What you're doing by changing the GPM of your pump is spending torque (pressure under the dies) for horsepower, ram speed. I'd have to search out and read through conversion tables to interpret herz. watts, etc. into terms I'm used to. Anyway, one easy trick I used fairly often on the drill rigs to speed things up without sacrificing power was t oversize supply lines and fittings. The down side for a small system is increasing the supply volumes means more fluid to move but if it's modest it's not a significant factor. Just be very careful if you decide to chase and retap the ports for fittings, you're dealing with 3,000psi and that's a significant risk. Sure it isn't going to explode but a pinhole leak can slice flesh like the sharpest knife you've ever imagined and even if it doesn't slice you it can inject hydraulic fluid into you. This is a BAD thing. And that's about all I have to say without more specifics from you without launching into a long rambly post. <grin> Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Frozenforge Posted June 8, 2014 Share Posted June 8, 2014 Like Frosty said increase volume of fluid equals increase of ram speed, a quick boost of pressure could be supplied by an accumulator. Of course theres no substitute for more horsepower and a bigger pump! Quote Link to comment Share on other sites More sharing options...
Jim Posted June 8, 2014 Share Posted June 8, 2014 What you will want to find is a two stage hydraulic pump with about 15 g.p.m. for fast approach to your work then about 5 g.p.m. for pressing at pressure this should yielid 2" a second ram speed for 6" bore hydraulic cylinder at 3000 psi. The low pressure is @650 psi and 15 g.p.m.. Also get a copy of Dr. James Batson book on build a hydraulic forging press will answer a lot of question, Blue Moon Books has his book for sale ask for Judy. Jim :rolleyes: Quote Link to comment Share on other sites More sharing options...
macbruce Posted June 8, 2014 Share Posted June 8, 2014 Higher gpm (faster ram speed) at the same psi requires more horsepower. My 25 ton is a single stage is powererd by a 10 hp mtr with an 11 gpm pump @2500 psi. 11 gpm drives the 5'' cyl fast enough to eliminate the ''suck'' factor unless the piece is just too massive to forge under 25 ton anyway. Two stage pumps slow down when they make contact with the work piece so that contrubutes to the suck factor imo. They each have advantages and disadvantages...... Quote Link to comment Share on other sites More sharing options...
bottles Posted June 8, 2014 Author Share Posted June 8, 2014 I have a copy of Batson's and keep looking at various parts to understand everything. Still trying to work out how to calculate safety factors as this isn't covered very well especially for the h frame. I am restricted in the size of motor available and pump. I went for a single stage as the easy option and some here suggest that a single stage pump can be better. Haven't had a chance to play with pressure and motor speed yet. I suspect there won't be any noticable difference. Andrew Quote Link to comment Share on other sites More sharing options...
basher Posted June 9, 2014 Share Posted June 9, 2014 As far as the psi vs pump volume goes it kind of depends upon what you want to do with the press. I changed my press from a 2500 psi press to a 1500 and increased the ram speed accordingly it punches a lot better and moves hot steel better but does not have the same grunt as before. For my use it was an improvement. I also feel a lot better about working a home made press at lower pressure. Quote Link to comment Share on other sites More sharing options...
Kevin K Posted February 13, 2017 Share Posted February 13, 2017 Macbruce: How did you figure your numbers? When I use the formula in Batson's book, I get 18 HP required for 11 GPM @ 2500 psi. Thanks, Kevin Quote Link to comment Share on other sites More sharing options...
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