An architectural term borrowed by tube-bending to describe the geometry of material flow. The extrados is that section of the tube which is undergoing elongation during the bend forming process; that part of the tube of which the wall thins. Roughly, the extrados corresponds to outboard half of the tube bend, but in fact includes a significant portion of the tangents and some of the tube inboard of the centerline radius. The extrados is separated from the intrados by the neutral axis.
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A complete guide to the principles of the 4-Step set-up for tube-bending tools
This is a printable handbook showing how to implement in four standardized steps the “forward mandrel” set-up for rotary-draw tube-bending machines and establish process control over the so-called black art. The procedure is based upon the guiding principle that the tools make the bend and takes advantage of the inserted design of modern mandrel tooling.