Press brake math

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Hey guys, been lurking around the forums for a few years never had a question I couldn't find or had anything educational to add.Looking for some help from a experienced fabricator involving creating a curve with a press brake. I have been building my welding bed off and on between jobs and life and I still need to complete a curve for my fender wells. I've attempted measuring the length and using whatever calculator on line to solve what little math I understood but ended up with no luck. My brake will do .25" up to 8', how would a experienced person go about properly measuring a curve and getting if anything within ball park of the desired product.Thank you, just trying to become better at stuff I have the abiltiy to do but lack the capabilities
Reply:Are you looking for little bends or are you trying to get a smooth curve? If you are going to make small actual bends every half inch or so, you just set the depth of the knife to give you a bend with a certain degree. To get that degree you have to figure out how many bends you can make without overlapping. If you want to make a smooth curve, a piece of rubber and a pipe welded to a piece of flat stock to attach it to your break ram. That requires some test pieces but it is pretty forgiving and easy. I have even used wood because I had no rubber. Sincerely, William McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:Hello Texasbr, if you are only doing a half-round or something close to that you need to utilize the "centerline diameter". Consider the ID and OD of the end view of a rolled/formed round, add one metal thickness to the ID or subtract one metal thickness from the OD. This will give you the centerline diameter. Multiply this diameter by PIE(3.1416), the answer to this equation would give you the length if you "unrolled" a rolled/formed round(the circumference). To find the length you need for a partial-diameter round fender use the number that represents this "circumference", divide this number by 360(this will give you the length by degree) and then multiply this product by the number of degrees of the round that you require for your fender. Example: if you were going to make a half-round for a fender you would use the single degree length determined by dividing the circumference by 360 and then you would multiply this number by 180. The resulting length would be correct for 180 degrees of the correct diameter of formed material.As to the actual forming process: if you are using your press brake and once you have determined the length of the material needed, you will need to add some additional material to each end of the piece to allow for "bridging" the span of your bottom die in order for the radius to be even all the way to the end of the piece. You will need to divide the part you are going to form with lines every 1/2" or so(closer together, smoother radius, further apart, more "kinks"), additionally, you will cut off the excess that you added to the part in order to achieve a radius all the way to the end after the part has been formed. You will also need a "radius checker", this is a piece of metal or other material that matches the inside radius of the part you are bending and can be placed on the inside of the part while you are forming it to be sure that there is enough bend but not too much bend as you proceed to form your part(it should fit the bending without seeing daylight as the forming proceeds(it will rock on the inside of your part if it has too little bend, it will show daylight on it's edge if the part is formed too much). If the part is 180 degrees you will need to form from the outside edge to the center and then turn the part around to form from the other outer edge to the center. If you simply try to form from one outer edge to the other you will experience interference problems between the part and the press brake. Good luck and I hope that I have included something that can be of help. Best regards, Allanaevald


Reply:Welcome to the forum Texasbr.Lincoln A/C 225Everlast P/A 200
Reply:Thank for the long explanation. After reading this I figured out I was close on getting the right measurments but going about it in the wrong way. I'll sit down write some numbers down and do another piece and see how it goes. Oh and yes I'm doing a partial curve, the piece I'm doing is only 30" long and the curve is about the size of 48" pipe if my memory holds true
Reply:i thought all the curved fender wells of pipeliner welding beds were just cut out sections of pipe?https://s-media-cache-ak0.pinimg.com...95b242dd84.jpghttp://www.customweldingbeds.com/image/105413180.jpghttp://tinyurl.com/zhko73kLast edited by Jimmy_pop; 03-19-2016 at 12:54 AM.
Reply:

Originally Posted by aevald

Hello Texasbr, if you are only doing a half-round or something close to that you need to utilize the "centerline diameter". Consider the ID and OD of the end view of a rolled/formed round, add one metal thickness to the ID or subtract one metal thickness from the OD. This will give you the centerline diameter. Multiply this diameter by PIE(3.1416), the answer to this equation would give you the length if you "unrolled" a rolled/formed round(the circumference). To find the length you need for a partial-diameter round fender use the number that represents this "circumference", divide this number by 360(this will give you the length by degree) and then multiply this product by the number of degrees of the round that you require for your fender. Example: if you were going to make a half-round for a fender you would use the single degree length determined by dividing the circumference by 360 and then you would multiply this number by 180. The resulting length would be correct for 180 degrees of the correct diameter of formed material.As to the actual forming process: if you are using your press brake and once you have determined the length of the material needed, you will need to add some additional material to each end of the piece to allow for "bridging" the span of your bottom die in order for the radius to be even all the way to the end of the piece. You will need to divide the part you are going to form with lines every 1/2" or so(closer together, smoother radius, further apart, more "kinks"), additionally, you will cut off the excess that you added to the part in order to achieve a radius all the way to the end after the part has been formed. You will also need a "radius checker", this is a piece of metal or other material that matches the inside radius of the part you are bending and can be placed on the inside of the part while you are forming it to be sure that there is enough bend but not too much bend as you proceed to form your part(it should fit the bending without seeing daylight as the forming proceeds(it will rock on the inside of your part if it has too little bend, it will show daylight on it's edge if the part is formed too much). If the part is 180 degrees you will need to form from the outside edge to the center and then turn the part around to form from the other outer edge to the center. If you simply try to form from one outer edge to the other you will experience interference problems between the part and the press brake. Good luck and I hope that I have included something that can be of help. Best regards, Allan
Reply:I saw the picture of the truck and I am pretty sure they just made a couple of bends to create the round. I used to do that sort of thing truck bodies and dump bodies, and that is what we would do. Even though we had a power roller. If you are going to use a break you need about 9.5" of material to create a 90 degree round with an approximate 6" inside radius, that has about 12 small bends in it about 3/4" apart. You just chalk out twelve lines about 3/4" apart. You need 90 degrees so 90 divided by 12 means each bend has to be 7.5 degrees. A lot of iron shops do not have a small "V" block unless they make treads. Most sheet metal shops do.

Those three measurements on each side show the inner wall the imaginary center line and the outer wall, arc length. In decimals on the left and fractions on the right. If I was rolling something like that, something that is not that critical, I usually just add a 1/16" to the inside radius and it comes out nicely. And you can always grind a little if you have to. Sincerely, William McCormickLast edited by William McCormick; 03-19-2016 at 10:36 AM.If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:It also helps if you have a round knife, most people do not. Sincerely, William McCormickIf I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.
Reply:

Originally Posted by Texasbr

Thank for the long explanation. After reading this I figured out I was close on getting the right measurments but going about it in the wrong way. I'll sit down write some numbers down and do another piece and see how it goes. Oh and yes I'm doing a partial curve, the piece I'm doing is only 30" long and the curve is about the size of 48" pipe if my memory holds true
Reply:

Originally Posted by Texasbr

Thank for the long explanation. After reading this I figured out I was close on getting the right measurments but going about it in the wrong way. I'll sit down write some numbers down and do another piece and see how it goes. Oh and yes I'm doing a partial curve, the piece I'm doing is only 30" long and the curve is about the size of 48" pipe if my memory holds true
Reply:

Originally Posted by Jimmy_pop

i thought all the curved fender wells of pipeliner welding beds were just cut out sections of pipe?https://s-media-cache-ak0.pinimg.com...95b242dd84.jpghttp://www.customweldingbeds.com/image/105413180.jpghttp://tinyurl.com/zhko73k
Reply:ive seen these alot. amazing. I probably dont want to know how much bondo is in thosehttps://i.ytimg.com/vi/y877YgPXm3Y/maxresdefault.jpg
Reply:Jimmy pop are the Picts of those trucks out of San Antonio ?    There a shop there that builds very similar rigs.  Sent from my iPhone using TapatalkMiller BobcatHarris cutting outfitMiller spectrum 625 plasmaVariety of shopmade tools