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Inaccurate flat pattern of cylinder

Question asked by Giorgos Karnoutsos on Apr 27, 2018
Latest reply on Apr 27, 2018 by Rick Becker

I use SW 2014 SP 5.0 and I am trying to construct a cylinder with 2mm thickness and 186mm OD. I am designing it by creating an arc and leaving a 0.5mm gap and then doing a base flange and I use a bend radius of 91mm (the radius of the ID) and a K factor of 0.5.

 

My issue is that if I cut the sheet metal according to the dimension that the flat pattern suggests (577.55mm), the cylinder I construct is larger. In order to construct the cylinder I need, I have to cut a piece that's 564.4mm.

 

Also, a curious thing that happens is that when I design a cylinder with OD of 206mm and use the same principle (bend radius 101mm and K factor 0.5) the flat pattern is almost correct. The programme calculates 640.4mm and the actual piece must be 639.8mm to construct the cylinder.

 

Any idea what's going on?

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