TPT November 2008

Before Bend

After Bend

 Figure 6

Theoretical tube length The theoretical tube length is the sum of the three main components: clamping stock, component(s) stock, and collet stock: Theoretical tube length formula : Clamping stock + Component(s) stock + Collet stock From the sample data : Theoretical tube length (with boost) = 96.63 + 509.27 + 106.41 Theoretical tube length (with boost) = 712.31mm Theoretical tube length (without boost) = 96.63 + 509.27 + 30.41 Theoretical tube length (with boost) = 636.31mm Conclusion As process consultants, AddisonMckee is often asked to advise clients on the amount of material required to bend a component or series of components. To aid in a smooth ramp-up to production, AddisonMckee typically calculates the numbers in accordance with a ‘play-safe’ policy. It is vital that a client is not left with twenty bundles of tubes that are an inch too short. However, it is often the case that the initial tube length is accepted and never re-evaluated. In these circumstances, the opportunities for efficiency improvements are tangible and easily achievable. For this reason, it is essential that material length and potential wastage is properly observed and evaluated. This approach holds the key to efficiency improvements and possibly the success or failure of a business.

Without boost (collet will release the tube during the last bend): When bending without boost, the pressure die length is not a consideration. As seen in figure 6, the pressure die can be ‘backed’ out of the way while the tube is positioned for the last bend. As the tube is positioned, the wiper die becomes the only point of interference. Once the tube is in position and clamped, the collet is retracted and the pressure die is advanced. • WL = Wiper die length • CD = Collet depth • SLx = Straight length (where x is the last straight) • CF = Clearance factor (5mm) • ALy = Length along the arc (where y is the last bend) • LL = Limiter length (distance from tangent at which the collet housing will encounter interference) Arc length formula : ALy = ( Π * CLR / 180 * degree of last bend) Limiter length formula : LL = WL (Pressure die length is not considered) Collet stock formula :

LL + CF + CD – SLx – ALy Using the sample data : • LL = 100mm • CD = 30.15mm • SLx = 48.45mm

• ALy = ( Π * CLR / 180 * 50.79) = 56.29 Collet Stock = LL + CF + CD – SLx– ALy Collet Stock = 100 + 5 + 30.15 – 48.45 – 56.29 Collet stock without boost = 30.41mm

AddisonMckee – USA Fax : +1 513 228 7226

Email : info@addisonmckee.com Website : www.addisonmckee.com AddisonMckee Ltd – UK Fax : +44 1772 323227 Email : sales@addisonmckee.co.uk

Note: If the calculated Collet Stock is a negative number and the last straight is less than 2D, then only add enough material to make the last straight 2D. If the calculated collet stock is a negative number and the last straight is greater or equal to 2D, then no additional collet stock material is required.

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N ovember 2008

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