Software solves the biggest bending problems for tube fabricators

March 6th, 2017

Software solves the biggest bending problems for tube fabricators

  • Programs and apps analyze bend information, spot problematic specifications, highlight missing dimensions
  • CAD software allows engineers to work up perfect designs, and this is problematic for tube fabricators. If the engineer lacks experience with tube, they tend to develop parts that can’t be made, or can’t be made economically. Unison has introduced software to deal with this situation.

A few decades ago, manufacturers did most of their own tube bending, relying on in-house expertise. As bending knowledge spread and entrepreneurial sorts struck out on their own, jobs shops specializing in tube fabrication started to spring up more and more. The shift from OEMs to fabrication shops continues to this day.

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 specialty. The downside is that, as time goes on, tube and pipe bending knowledge gets further concentrated among specialty 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.

Desktop computers, tablets, smartphones, and the Internet, all of which assist in the spreading of information, haven’t helped to spread bending knowledge. In fact, one technology has actually made this problem much worse: Software. Specifically, computer-aided design (CAD) software. For all the good this software has done, it has been the unwitting culprit in making many fabricators’ lives difficult.

CAD allows engineers to work up 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. Most newly minted engineers would be surprised to learn that straight tube often has a bit of bow to it, round tube has a bit of ovality, and the wall thickness 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. If perfectly fabricated tubular components were to occupy a geographic location, you’d find them in one of two places: The Land of Impossibilities or The Realm of Economically Unfeasible Projects. Nobody wants to design a component, assembly, or product that ends up in one of these places.

Fabricators who accept contracts without doing a proper application review might find themselves involved in a costly and time-consuming situation, trying to make something perfect from something imperfect. Skilled tube bending applications engineers are both expensive and rare, so using the right tools to extract the data and provide detailed analysis and reports is one way of cutting the risks involved with dodgy specifications.

Where We Are Now

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:

  1. Bend radii are unnecessarily small, making the bending setup and runoff more complicated than they need to be.
  2. The specified material—alloy and wall thickness—is too strong. The workpiece has a minimum yield strength that exceeds the bender’s maximum torque.
  3. 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.
  4. Straight lengths are impractical or simply nonsensical.
  5. Parts collide with the machine that is supposed to make the part.
  6. 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, chewing up large quantities of the only irreplaceable resource (time) before manual programming begins.

These problems lead to high scrap rates, paperwork madness (reissuing work orders, issuing change notices, and ordering different material), delayed release of work packages, rework of components that don’t pass inspection, and recalls of components that have shipped by mistake.

Where We Should Be

Just as software contributed to this problem by making it easier than ever 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 these days that can alleviate these problems. Modern programs are available that extract the data, perform a detailed analysis, and generate reports that allow pipe shop fabricators to respond to the clients before they even consider bending the first tube.

Apps and software packages are available that allow users to easily extract, interpret, and manipulate tube data in CAD formats. Also, many bending machine manufacturers now offer office versions of their control software, meaning programming and simulation are available without disrupting production.

Figure 1
Modern tube bending software uses the workpiece’s diameter, wall thickness, and yield strength (left) to determine the amount of bending force (center), tooling characteristics, and bending difficulty (right).

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 (see Figure 1). The app also estimates the bend difficulty and provides other handy information to help determine if the equipment can handle the task. This allows the fabricator to respond to a bid within minutes.

Software packages such as VTube-STEP and TubeWorks (an add-in for SolidWorks) can be mastered in as little as 10 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 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 than ever before.

When a project reaches this stage, the next step is to send the bend data to a simulator, such as Unison’s bespoke simulation software Opt2Sim, to check for collisions between the part and the machine (see Figure 2). 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 isn’t successful, or if the software flags other concerns, the documentation generated by the software puts the fabricator in a strong, well-informed position to discuss the issues with the OEM and helps to suggest part revisions.

Where We Are Going

In the digital age, customers are demanding more for less. As a result, 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 isn’t far off. The process will require human input, but little more than a machine operator dropping the tools into the machine, loading a cut length, and hitting the start button.

This scenario is based on software that allows design engineers to cross-reference tooling databases and run simulations to determine which machine in the fleet is most suited to make the part as they design it, not after they design it. Such software isn’t yet available but soon will become a reality, and it will provide the designers much more control over manufacturing processes than ever before. They will be able to enhance and refine the processes by experimenting with just a few keystrokes and mouse clicks rather than using valuable shop time.

After developing a bending sequence, the designer will be able to try various tweaks to compress the cycle time, perhaps reducing a 90-second process to 60 seconds. Furthermore, a warning about the bend difficulty will allow the design engineer an opportunity to make the operators’ lives easier. Trying various combinations of material, wall thickness, and centerline bending radius based on a tool set that is easy to install, will allow the designer to reduce the likelihood of wrinkles and splits while keeping setup time to a minimum.

As bending simulators become even more sophisticated, the simulated cycle times will be accurate enough to use in the shop’s production schedule and in customer quotations. In turn, these capabilities mean that the fabrication shop’s production manager can release the work package to the production team knowing that the shop has the machines, tooling, and time to get the job done right, the first time, on time.


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