hammerforged Posted October 30, 2011 Report Share Posted October 30, 2011 I know this is not directly hunting related but it is related to making my life easier in making knives. I have built a 20 ton air over hydraulic forging press to aid in the forging of Damascus billets. My question is what type and size air compressor would anyone recommend to run the press. The press utilizes a 20 ton air over hydraulic bottle jack like you can find at Harbor Freight with a recommended operating pressure of 110 to 120 psi. I know that this press will not be as quick on the cycle as a full hydraulic press but I was able to build this for the cost of the bottle jack. I have a small 20 gallon 3.5 hp air compressor rated at 125 max psi that barely gets the job done. Would I be better off with a gas powered aircompressor or go with a higher hp larger storage capacity electric? Wish I knew more about air compressors but hopefully someone on here who works construction can educate me. Quote Link to comment Share on other sites More sharing options...
redkneck Posted October 31, 2011 Report Share Posted October 31, 2011 Not sure why your compressor isnt getting the job done. Im very familiar with air over oil set-ups but glancing at the one at harbor freight im not really sure how it works, doesnt look like enough displacement on the air side unless the little ccylinder strokes back and forth to pump. Quote Link to comment Share on other sites More sharing options...
hammerforged Posted October 31, 2011 Author Report Share Posted October 31, 2011 Like I said - I don't know a whole lot about air compressors. When the little lever is depressed the intake of the air from the compressor raises the ram on the bottle jack and then a T-handle must be turned to lower the ram and the process repeated for each "Squeeze" of the press. with the compressor I have I can only get at best 4 squeezes per heat, which as the billet is drawn out becomes problematic causing more re-heats of the billet and leading to carbon loss due to subsequent heats. Just wondering if a compressor with a larger storage capacity and higher hp would give me better performance from my press. Here is a pic of the press I built. Beer is just a size reference. Quote Link to comment Share on other sites More sharing options...
OJR Posted October 31, 2011 Report Share Posted October 31, 2011 I would think you need a bigger tank for more volume of air. Also it would help to go to 220V for the motor. This might help, but I am not sure! Quote Link to comment Share on other sites More sharing options...
fladawg Posted October 31, 2011 Report Share Posted October 31, 2011 (edited) I work with a compressor on my werk truck,it has a 13 horse briggs n stratton on it with bout a 40-45 gallon tank.I use all kind's of tool's with it with no prob,course not a press.I think you need one that will go up to 150 psi,or even higher.You can alway's regulate it to desired pressure.Bigger HP and Tank Volume is what i think you need... Edited October 31, 2011 by fladawg misspelled volume Quote Link to comment Share on other sites More sharing options...
wtnhunt Posted October 31, 2011 Report Share Posted October 31, 2011 Is the compressor pressure not keeping up with the press Ross? If your pressure gauge drops and you find the compressor running and unable to keep up with the press while you are cycling it then a bigger compressor would probably help. If it were me for a shop, I might look at industrial 220 models. Quote Link to comment Share on other sites More sharing options...
redkneck Posted October 31, 2011 Report Share Posted October 31, 2011 (edited) Ross, I could be way off on this, but I think the problem is the volume of displacement in your pneumatic cylinder on the jack. Air/oil presses work by taking the force of the air on a piston and multiplying it by displacing a much smaller volume of oil. That's the reason you are able to move so much with such a small amount of air pressure. For instance if you have a 2" piston on your air cylinder then you have 3.14 square inches of piston area. Multiply that times 100(100psi) and you are generating 314 pounds of force..... Still very little force, however on the opposite side of the piston you may be pushing a plunger rod of only .5" which is forcing hyd oil into the jack. A 1/2" dia rod will displace 0.19625 square inches. A very small area, but when divided into your 314lbs of force, you now have 1600 psi coming off the bottom side of the boost cyl. Feed that into a jack cylinder with a 3" dia cylinder (7.065" area) and you now generate over 11,000 lbs of force using only 100PSI of air. You can multiply the force quickly, but looking at the pic of the jack you have, the air cylinder looks pretty stubby, meaning you have to keep stroking it to achieve the stroke to get your billet done, costing you time and heat. In comparison, the air/oil presses I use at work have air cylinders that are about 10" diameter by about 20" in length, and those are on the small side for that type of press. Like any mechanical advantage, what you gain in force is given up by more distance. In essence to get that big jack to move 3" of stroke, you need a much longer stroke on the air cylinder, otherwise you have to make multiple strokes to achieve the end result, which it seems like what you're doing from what I read. Edited October 31, 2011 by redkneck Quote Link to comment Share on other sites More sharing options...
Leo Posted October 31, 2011 Report Share Posted October 31, 2011 Like the folks above are saying Your compressor volume capacity and horsepower is the problem. Especially when you are using compressed air to run tooling (in your case a press) the CFM (Cubic feet per minute) of air the compressor can produce becomes very important. Being able to produce a high enough operating pressure is only part of the equation. Unfortunately it's not as simple as selecting a compressor with a high enough pressure rating and high enough CFM rate. The reason is compressors produce their highest pressures at their minimum CFM. At the highest CFM rate they are producing minimum pressure. An accumulation tank will allow you to send air at the highest pressure at a higher CFM rate. Depending on how big that tank is and what the demands are on it will determine how many full strength cycles you will get on the press before the compressor struggles to recharge the tank. A larger tank will get you more cycles before it looses power but it will take much longer to recharge the tank. If you only need a few more cycles and have plenty of time for a recharge that might be the best solution. Otherwise a higher horsepower compressor and larger tank will probably be needed. Quote Link to comment Share on other sites More sharing options...
redkneck Posted October 31, 2011 Report Share Posted October 31, 2011 Looking at the product manual for the jack, I see it is an air motor, not a "one stroke" type booster, so you can disregard some of what I posted. That being said, a 3.5hp 20gal compressor is more than enough I would think to do what you are doing I would think. It could be that the operation is taking more tonage than you think. Just plug a gage into the inlet and see what type of pressure drop you get when in operation. You would need a lot of consumption to get much drop on that 20 gallon tank for a short stroke like that. If you can't seem to work it out, I do have a force gage I could let you borrow and you can actually read how many tons it takes to do the job while you're pressing. Quote Link to comment Share on other sites More sharing options...
Leo Posted October 31, 2011 Report Share Posted October 31, 2011 The air motor driving that jack is a reciprocating type cylinder motor. It won't chew through as much CFM as a vane type air motor. Minimize the stroke of the jack as much as possible to reduce the air volume requirement. Quote Link to comment Share on other sites More sharing options...
hammerforged Posted October 31, 2011 Author Report Share Posted October 31, 2011 Thanks everyone - it sounds like I need a larger capacity air compressor with a higher hp. I don't have 220 out to the shop - what about a gas powered air compressor, would one of these have a faster cycle rate over an electric one? Leo - I will take a look at shortening the stroke for the press to alleviate cycle time between squeezes. Quote Link to comment Share on other sites More sharing options...
TBow Posted November 1, 2011 Report Share Posted November 1, 2011 I believe that the power source driving your compressor is only relevant when you increase the actual size of the air compressor. If 120 VAC is currently running the motor to your compressor without tripping the breaker at the electrical distribution panel, or tripping the AC motor's thermal cut-out, then all should be well in that respect. Increasing the voltage supply from 120 VAC to 240 VAC will still only run the motor at the rated rpm (at either 120 vac or 240 vac), but will reduce the electrical load to half the current when run at 240 vac. It merely reduces the stress (electrically and thermally) on the wiring and motor at 240 vac. It will not increase the air volume or pressure of the actual compressor. You need to increase your SCFM (or CFM) which requires a larger compressor with a greater sized piston(s) to increase the volume of air in order to sustain the operation of equipment that is run at a high cycle rate or else continuously. Most pneumatic equipment is rated at SCFM or CFM @ a particular PSI. Knowing that info is critical in sizing the correct compressor to maintain the operation of the equipment you want to run. Most compressors will have ratings listed on them showing the SCFM or CFM @ 40 PSI and 90 PSI. I recently bought a 20 gallon / 5hp compressor with a rating of 5.2 SCFM @ 90 psi. That means my compressor will maintain a constant flow of 5.2 Standard Cubic Feet per Minute (at a particular temperature) of air flow at 90 pounds per square inch. Higher capacity compressors typically are run by heavier HP motors which will draw higher AC currents. Hence the use of 240 VAC single phase or else 3 phase motors to reduce the electrcal stress on the system. Lower rated compressors are usually "oil less" and are usually geared towards the hobbyist or part time back yard mechanic. Higher rated compressors are typically "oil" systems with higher ratings for continuous operation. TBow Quote Link to comment Share on other sites More sharing options...
redkneck Posted November 1, 2011 Report Share Posted November 1, 2011 (edited) Unless you are having significant pressure drop (down below 80psi) at the tank, you are wasting your money Ross. That jack should not have much consumption. It may be that your process is simply requiring more force than you are able to provide with your set-up. Edited November 1, 2011 by redkneck Quote Link to comment Share on other sites More sharing options...
hammerforged Posted November 1, 2011 Author Report Share Posted November 1, 2011 Made some operating adjustment this morning. Shortened the travel on the ram and made a longer "T" handle for the cutoff on the ram which enabled me to have a quicker response on the process. All told it increased the functionality 3 fold of the press. Thanks everyone for your input - it looks like the compressor I have will work just fine. Quote Link to comment Share on other sites More sharing options...
hungry hunter Posted November 5, 2011 Report Share Posted November 5, 2011 Looks like somebody slep at a Holiday Inn recently. lamo Quote Link to comment Share on other sites More sharing options...
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