TPT May 2007

T ube B ending, H ydroforming & E nd- Fo rming

Set-up secrets for mandrel bending

Forming and bending equipment for the US market KGK International Corp, USA, was established in 1981 to import quality machine tools from Japan to the US and Canadian markets. In addition to the Okuma range of machine tools, KGK International supplies Nissin’s precision 3D tube bending machine and Nihon Spindle spinforming and flowforming machines. The Nissin 3D tube bender ensures highly improved productivity with a bending radius of over 360º. Available in three models, the machine offers large radius bending from 5 / 16 " to 2 3 / 8 " diameter. The machine is operated by placing a tube through the die without a special mold or die change. Radius and bending directions can easily be input on the user-friendly controller. The bending section is securely guided by the die so that accurate roundness can be obtained on the cross section.

Bend Tooling Inc, USA, is a manufacturer of die sets, mandrels, and wipers for rotary- drawing tube-bending. The draw bending method produces high-quality tube bends and, unlike compression or ram bending, the draw method fixes the line of tangency in space. This allows tooling to be fixtured at the point of bend where the tubing material becomes plasticised as it is drawn through the line of tangency. The mandrel is of central importance in controlling the flow of this plasticised material before it sets into a bend. In fact, the draw method is so closely associated fi Tooling is fixed at the point of bend where the tubing material becomes plasticised

with the use of a mandrel, it is often called ‘mandrel bending’. The key to maximising the performance of the mandrel is the ‘forward-mandrel’ set-up. The three factors to consider are the diameter of the mandrel nose (n), the radius of the nose (m), and the position of the nose relative to the line of tangency (S). These values are calculated using a formula comprising of mandrel nose diameter {n = t – (w x 2.21)}, mandrel nose radius {if F<50 then m = n x 0.1, else m = n x 0.02, where F = t / w}, and set-up position of mandrel nose {S = sqrt ((r + (t / 2) – w) 2 – (r + (n / 2)) 2 ) + m}. Bend Tooling’s website features a ‘Four- step setup procedure’ section, with further information on how to optimise mandrel setup. The website also features ‘The bend tooling encyclopedia’, with definitions of the terms used in this article.

Bend Tooling Inc – USA Fax : +1 616 454 9958

KGK International Corp – USA Fax : +1 847 465 0181 Email : tdonnowitz@kgki.com Website : www.kgki.com

Email : info@bendtooling.com Website : www.bendtooling.com

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M ay /J une 2007