TPT July 2018

T E CHNOLOG Y

Software helps to solve bending problems A FEW decades ago manufacturers performed most of their own tube bending, relying on in-house expertise. As bending knowledge spread, job shops specialising in tube fabrication started to spring up. This shift from OEMs to fabrication shops has continued. • The specified material – alloy and wall thickness – is too strong. The workpiece has a minimum yield strength that exceeds the bender’s maximum torque.

• Bend radii fluctuate throughout the part. A closely related problem concerns bend radii that have no bearing on the tools that the fabricator has on the shelf. • Straight lengths are impractical or simply nonsensical. • Parts collide with the machine that is supposed to make the part. • Part drawings are dimensioned in such a way that they provide no meaningful information to the fabricator. Head-scratching ensues, followed by substantial time spent on calculations, using up large quantities of the only irreplaceable resource (time) before manual programming begins. Just as software contributed to this problem by making it easier for an engineer to design the impossible, or at least the very difficult and very costly, software is coming full circle. Programs and apps are available that can alleviate these problems. Modern tube bending software uses the workpiece’s diameter, wall thickness, and yield strength to determine the amount of bending force, tooling characteristics and bending difficulty. Apps such as ‘Tube Bending Tooling Calculator Pro’ (available for free from the Apple app store) need a couple of inputs, such as material and bend radius, to generate information about the required torque, tool setup and bending difficulty. Software packages such as VTube- STEP and TubeWorks (an add-on for SolidWorks) can be mastered in as little as ten minutes and allow fabricators to: • Extract tube specifications from imported tube models (round, square, rectangle, flat-sided oval and standard oval) to find the outside diameter, wall thickness and bend radii automatically. • Build accurate XYZ/YBC/LRA data in just a few clicks. • Check bend radii against the tooling database. • Change bend radii to use existing tooling without altering overall part shape. • Create technical drawings and reports to assist the production and quality departments. • Flatten part shapes to understand cut lengths and other features within a part. • Create CNC bend data outputs in

This arrangement frees OEMs to do what they do best – designing and assembling their products – and allows fabricators to concentrate on refining and expanding the knowledge of their speciality. The downside is that, as time goes on, tube and pipe bending knowledge gets further concentrated among speciality job shops and becomes increasingly rare among OEMs. The result is a tendency for design engineers at OEMs to develop components and assemblies that cannot be manufactured, at least not economically. CAD has introduced some problems as it allows engineers to create perfect designs. Common – but unreasonable – specifications include too-precise bend angles, end point locations with extraordinarily tight tolerances, and zero ovality in the bend zone. Some newly qualified engineers may be surprised to learn that a straight tube often has a bit of bow to it, round tube has some ovality, and the wall thickness often varies. As the saying goes, “Round tube isn’t round, and the hole isn’t in the middle.” Imperfect inputs lead to imperfect outputs, and this is what fabricators deal with every day. Unaware that tube normally has dimensional shortcomings, designers and engineers press on, designing perfect parts. A scarcity of practical metal fabrication knowledge is accompanied by an abundance of poor part designs. Often the part shape has no consideration for the equipment or tools that tube fabricators actually have at their disposal. Six problems come up repeatedly: • Bend radii are unnecessarily small, making the bending setup and run-off more complicated than they need to be.

industry-standard formats that can be read by most bending machine software. These Windows ® -based applications are easy to use, reduce development time and help fabricators respond to enquiries faster. When a project reaches this stage, the next step is to send the bend data to a simulator to check for collisions between the part and the machine. Many simulators either are derived from CAD or are reverse-engineered representations of the machine, leaving little doubt about the simulation’s accuracy. If the simulation is successful, the fabricator can accept the contract with confidence. However, if the simulation is not successful, or if the software flags other concerns, the documentation generated by the software puts the fabricator in a strong position. In the digital age, tube and pipe shops must streamline their working practices and eliminate rework to remain competitive while maintaining reasonable profit margins. The day when a fabricator can go from CAD to production more or less immediately is not far off.

Unison Ltd – UK Website: www.unisonltd.com

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JULY 2018