Tube bending, step by step: from straight stick to finished part

It starts as a straight length. The tube laser cuts it to size and, in the same setup, adds any holes, slots or cope where it’ll meet another part later — so the bent tube comes off ready to assemble, not needing a second machine to notch it. Getting the length right here matters: a bend eats a predictable amount of material, and we allow for it now.

The tube is loaded onto the rotary-draw bender and clamped against a die shaped to its exact diameter. For thin walls or tight radii, a mandrel goes inside to support the tube from within — without it, the tube would flatten or wrinkle on the bend. The die and mandrel are tooling matched to the tube, which is why sticking to common sizes keeps a job cheap.

The die rotates and draws the tube around itself to the programmed angle. The outside of the bend stretches, the inside compresses, and the mandrel keeps the section round through it all. On a part with several bends, the machine indexes the tube — rotating and feeding it between bends — so all of them come out in the right plane relative to each other.

Metal is elastic before it’s permanent — so the moment the die lets go, the tube relaxes and opens up a few degrees. That’s springback, and it’s consistent for a given tube and radius, so we measure it once and over-bend by exactly that much. Bend to 88° to land on 90°. The customer sees the finished angle; the machine did the arithmetic.

The first part off a run is checked against the drawing — angles, the rotation between bends, overall length — usually on a fixture that either fits or doesn’t. Once it’s right, the setup is locked and the rest of the batch follows it. What leaves is a tube that drops straight into your assembly, coped, drilled and bent to land.