A post-bend specification controlling wall thinning which sets the minimum wall thickness allowed for the finished part. In rotary-draw tube-bending wall thinning is unavoidable in the extrados, which see, but it can be mitigated by proper placement of the mandrel nose relative to the line of tangency, using the least direct pressure the application requires, and using assist pressure to feed material from the trailing tangent into the extrados.
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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.