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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Folding sheet metal
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David R Brooks wrote: My project involves folding 1.5mm and 2mm aluminium sheet (think tube amplifieers CAD packages such as Solid Edge will compute sheetmetal bending allowance, etc., for a specified "bend radius". This of course works fine if you are bending in a press, with V-dies formed to the radius in question. I am bending using a brake (the machine with a hinged "wing" that swings up to make the bend.) The only adjustments I have a 1. Set the scribed bend-line forward of the edge of the clamping bar. 2. Set the "wing" to swing a little in front of that bend line. Who made the brake you have? My DiAcro finger brake has two settings -- but different from your description of yours: 1) Adjustment for thickness of metal to be clamped -- moves the "fingers" up and down so the clamping is just over-center for maximum grip. 2) At the back -- an adjustment to move the edge of the fingers back relative to the joint between the "wing" (apron is more what I would have called it) and the stationary part. 3) Actually -- there is also a third setting -- the stop pins which determine just how far you can bend before the apron comes to a stop. These pins can be moved to various holes appropriate for different desired angles. Is there a convenient rule for converting thickness & bend-radius into those settings? The design has 2 U-folded pieces fitting within each other (simplifying somewhat): I want them to fit with minimal clearance (obviously, not negative clearance!), so my bending needs to be accurate. I would consider the bend radius to be a function of how far back the edge of the fingers is behind the line joining the apron and the base. I think that you will have to try with some scrap of the same type and thickness of metal to get it really right. But -- for the most simple state -- when the fingers are exactly one metal thickness behind the join line between the apron and the base, you will get a zero radius at the inside of the bend, and a radius equal to the metal thickness at the outside of the bend. (But if it is too hard an alloy, you will also get a crack along the bend.) If you are measuring the bend radius at the inside of the bend, I think that a reasonable approximation would be the setback of the fingers minus the thickness of the metal. There are three reasonable places to make the radius measurement -- the inside of the bend, the outside of the bend, and the center line between those -- and I don't know which is the standard one to which your software is working. I just set up with some scrap to get the feel of the settings -- but I also don't use a CAD program for doing the layout. Perhaps someone else will respond with more experience in this field. But at the moment, I see no other followups. Good Luck, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
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David R Brooks wrote: My project involves folding 1.5mm and 2mm aluminium sheet (think tube amplifieers Cool, Iv'e built a few of these myself. snip I am bending using a brake (the machine with a hinged "wing" that swings up to make the bend.) The only adjustments I have a 1. Set the scribed bend-line forward of the edge of the clamping bar. 2. Set the "wing" to swing a little in front of that bend line. Is there a convenient rule for converting thickness & bend-radius into those settings? The design has 2 U-folded pieces fitting within each other (simplifying somewhat): I want them to fit with minimal clearance (obviously, not negative clearance!), so my bending needs to be accurate. Look he http://www.engineersedge.com/dist_bend_line.htm http://www.engineersedge.com/bend_allow_calc.htm I haven't done this in 40 years, but these look correct. -- Gary A. Gorgen | "From ideas to PRODUCTS" | Tunxis Design Inc. | Cupertino, Ca. 95014 |
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