Tube Bending Robot: Sand-Filled Pipes to ABB Cells

Bent tubes are everywhere once you start looking: brake and fuel lines under a car, the exhaust behind it, the frame of an office chair, a bicycle handlebar, a handrail. Each one starts as a straight length of steel, aluminium or copper. For most of the last century people bent them by hand or fed them into a bender one at a time. A tube bending robot takes over part of that work, either by loading and unloading a CNC bender or by carrying the bending head itself. This post follows the craft from sand-filled pipes to CNC machines and robot cells, and shows where ABB robots such as the IRB 4600 fit.

A fabricator flares the end of a tube with a ram end tool on a bending machine, 2008. Photo: Chris Yarzab / Wikimedia Commons (CC BY 2.0)

How tubes were bent before robots

A tube bent carelessly flattens or kinks on the inside of the curve. Early metalworkers solved this by filling the tube before bending. Sand packing, heated for thick tubes, kept the wall round, and pitch was used the same way in the past. Plumbers still slip a bending spring inside thin copper pipe for the same reason. Tubes themselves got stronger when Reinhard and Max Mannesmann developed their method for rolling seamless steel tube in the 1880s. In wartime factories such as the K-25 plant at Oak Ridge, workers still shaped pipe on bench benders by hand.

Pipe bending in the prefabrication shop of the K-25 plant at Oak Ridge, Tennessee, February 1945. Photo: Ed Westcott, U.S. Department of Energy via Wikimedia Commons (public domain)

Bent tube also reached the home. At the Bauhaus in 1925 and 1926 Marcel Breuer designed the club chair later called the Wassily chair, from bent tubular steel, and tubular furniture soon became a factory product. Machines took over the bending itself. Pines Engineering, founded in 1943 by Byron Bower, whom the company credits with inventing the mandrel bending machine, says it built the first fully automatic three axis CNC bender in 1962 and the first microprocessor controlled bender in 1976. Eaton Leonard, founded in 1973, made its name measuring bent tubes so that bending programs could be corrected.

Wassily chairs by Marcel Breuer, designed in 1925 and 1926 from bent tubular steel, in the Bauhaus building in Dessau. Photo: Kai 'Oswald' Seidler / Wikimedia Commons (CC BY 2.0)

A CNC bender could repeat a part with dozens of bends, but someone still had to load straight tubes, unload bent ones and check them. Robots took over that handling first, because bent tubes are awkward three dimensional shapes that are tiring to lift all shift. Later machine builders turned the idea around. The German company transfluid put the bending machine in the robot's hand: a bending head with clockwise and counterclockwise tools mounted on the arm. In its cells two synchronised robots can bend tubes up to 6,000 mm long at both ends. WAFIOS built its TWISTER system, in which a KUKA robot feeds the tube during bending.

Workers at CNC tube benders in a Rohr Industries aircraft parts plant, 1981. Photo: San Diego Air and Space Museum Archives via Wikimedia Commons (public domain)

Tube bending robots at FABTECH 2026

The next big look at tube bending comes at FABTECH 2026, which returns to Las Vegas on 21 to 23 October for the first time since 2016, with more than 1,400 exhibitors expected. In previews published by Canadian Metalworking in late September, BLM GROUP USA announced Plug & Bend, a plug in tooling system for its ETURN and ELECT electric benders that replaces manual tooling adjustments. BLM also described the PRO-RUNNER 28, which bends tube straight from the coil up to 28 mm in diameter, with a mobile orbital cutter that cuts while bending goes on.

A Vietz pipe bending machine with a large coated pipe after bending. Photo: Alf van Beem / Wikimedia Commons (CC0)

Electric benders like these are designed to run in automated cells. A typical cell today has a robot that picks straight tubes from a magazine, puts them into the bender, takes the bent part out and passes it to end forming, cutting, a measuring station or a rack. Car makers and their suppliers use such cells for brake lines, fuel lines and exhaust parts. Furniture makers use them for chair frames and table legs, where the same shape is bent thousands of times. Long tubes swing as they come off the bender, and a robot can be programmed to move them without hitting the machine.

An operator teaches an ABB robot with the FlexPendant in a metal fabrication cell, from ABB's 2007 metal fabrication brochure. Photo: ABB

We found no ABB robot named in the FABTECH tube bending previews, so the ABB part of this story is about fit, which is a possibility. The IRB 4600 is a compact arm with payloads from 20 to 60 kg, small enough to sit close to a bender and quick at loading and unloading. For a robot held bending head, or for heavy tube bundles, a larger IRB 6700 would be the candidate. ABB robots already tend sheet metal bending machines, which we covered in our post on robotic press brake cells.

An ABB IRB 4600 in the Orora Fresh Packaging cell that stacks produce trays in Kingsville, Canada. Photo: ABB

Where tube bending robots go next

Tube bending cells will keep moving toward small batches. Electric benders, plug in tooling and robot held bending heads all aim to change from one part to the next in minutes, so a shop can bend a few hundred chair frames and then switch to handrails or bicycle parts. Bending from coil cuts waste in short brake and fuel lines. Measuring will move inside the cell, with cameras or laser scanners checking every part and sending corrections back to the bender without stopping production.

An ABB IRB 6700 grinding a steel part in Teqram's EasyGrinder cell at Ancofer. Photo: ABB

For homes the effect will mostly show up in what people buy: more custom furniture, railings, bike frames and car parts made in short runs, because changeovers cost less. Small fabrication shops will want cells that fit the floor space they already have. In factories that build cars, buses and appliances, robots will handle the longest and heaviest tubes. Two arms working together on one part, as in transfluid's cells, can be coordinated on one ABB controller with MultiMove.

An orange ABB robot in Foundry finish holds a sheet at a Trumpf TrumaBend V230 press brake, 2005. Photo: Borowski / Wikimedia Commons (public domain)

Springback is the first hard problem. Every batch of tube springs back a little differently, so the cell has to measure each part and correct the next bend. A robot that carries the bending head needs a path that avoids its own cables and the tube's free end, which is easy to get wrong. Engineers usually plan and check cells like this in RobotStudio before the first tube is bent. Cost remains a barrier for small shops, and they also need staff who understand both bending and robot programming.

An engineer programs a robot cell in RobotStudio next to an ABB industrial robot. Photo: ABB

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