Hydraulic Die Forming Discussion Group
Starting Sheet Shape vs. Micro-fan Shape

Jack Berry
berry2000@prodigy.net

I had a very interesting problem posed to me by a gal who saw me demo in Tuscon and has been doing microfolding. She designed a classically shaped fan-fold as part of a piece for a client. The client didn't like the "hole" which forms at the apex of the fan and wanted it "fixed". Since a price had already been set, she didn't want to add a lot more work (soldering steps, etc.)and asked me if I could help. First I looked at the ratio of the 2 axes of a rectangle which would give a fan of about 180 degrees. The first figure holds the length constant at 3.0" and varies the width. The second piece gave a desirable shape using 3.0" x 0.75" but with the "hole". My first attempt was to increase the width of the rectangle by 3/16" at the center of the side with a straight taper to the original 0.75" at the top and bottom edges. The second figure shows the interesting "double scallop" result (along with the second attempt). I then tried the same 3/16" increase at the mid point but cut the edge back to 0.75" with a curve rather than a straight line. The third figure shows the folded and cut sheet (this gives perfect symmetry), the microfolded sheet, and the resulting fan. Voila!! Notice that any alternation like this also causes other subtle changes. The "tip to tip" length of the fan has increased somewhat. What a fun project this was!!.....Jack the Metal Sleuth

[ This message was edited on Mon Mar 25 by the author ]

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