Structural Steel Fabrication: From Rivets to ABB Robots

Structural steel fabrication is the shop work that turns plain mill beams, columns and plates into the parts of a building or bridge: cut to length, drilled, coped, fitted with plates and clips, then welded. For most of the last century people did nearly all of it by hand. This post follows the trade from riveting gangs and hand layout to the beam punch lines and CNC drill lines of the 1970s and 1980s. Then it looks at the robotic beam assembly and welding cells being built this year, where ABB robots and RobotStudio fit in, and what still slows robots down in a steel shop.

A worker drills holes in a steel beam for the Green Line Extension viaduct near Boston, May 2019. Photo: MassDOT via Wikimedia Commons (public domain)

How rivet gangs and beam punch lines built the steel trade

In the early skyscraper years, beams were joined by hot rivets. A rivet gang needed four skilled workers: one to heat the rivet, one to catch it, one to hold it in place and one to hammer it home. High-strength bolts later replaced rivets in steel buildings, largely because two less skilled workers can install and tighten bolts. The change went so far that the 14th edition of the American Institute of Steel Construction specification no longer covers rivet installation. Inside the fabrication shop the work was just as manual. Layout, drilling, cutting and welding were all done by hand, with workers marking each hole and connection on the steel.

Three ironworkers on a steel frame high above the city, photographed by Lewis Hine. Photo: Lewis Hine via Wikimedia Commons (public domain)

Automation started with holes. According to a history in The Fabricator by Voortman's Adrian Morrall, shops first used machines like the Beatty punch, then three and five press beam punch lines. The punch lines of the 1970s punched holes in every surface of a beam in one pass, and a saw on the same line could cut the member to length. A later trick, the "pop mark", used the tip of the punch to mark centre points and the spots where plates and angles would be welded on. Machines of the late 1970s and early 1980s also had to deal with mill tolerances such as twisted beams, off-centre webs and camber.

The bridge shop of the Lackawanna Steel Company, where structural material was fabricated, 1917 to 1918. Photo: US National Archives via Wikimedia Commons (public domain)

Drilling and sawing lines came next, and Morrall writes that by the early 1980s drills were quickly replacing the punch lines, which had limits on material thickness and tonnage. Coping machines of the mid-1980s used three oxyfuel torches to prepare beam ends. By the late 1980s shops could download cut lengths, hole positions and part marks from 3D CAD in the DSTV file format, which is still in use. Moving the steel between machines was still mostly manual. Morrall estimates that a fabricator touched a beam up to 15 times at about $25 per lift, and automated loading of drill and saw lines only appeared around 1998.

A Peddinghaus punching machine in a metal workshop, 2017. Photo: Asurnipal / Wikimedia Commons (CC BY-SA 4.0)

Robotic beam assembly and welding in 2026

On 24 September 2026 The Fabricator reported that a shop which loads a beam and sends it through blasting, hole making and automated welding without a human touching it is now "not that unusual". The occasion was Voortman USA's new 110,000 sq. ft. headquarters in Monee, Illinois, with a grand opening in late September. Two days earlier the magazine profiled 1872, a Cincinnati startup that launched on 22 July 2026. It is building a fabrication plant around Path Robotics' autonomous welding, which scans a part, compares it with the 3D model and welds without a teach pendant.

A large steel tower section on turning rolls for welding in a heavy fabrication shop, 2017. Photo: Artemka / Wikimedia Commons (CC BY 4.0)

Fitting and welding the small parts onto a beam is still the hardest step to automate. A paper published on 21 September 2026 in the journal Robotics describes a planning system used in an industrial dual robot cell in Kazakhstan. An ABB IRB 6700 on a 15 m floor track picks and places the plates, while an IRB 2600 series welding robot on a second track welds them. The software simulates candidate beam setups part by part and outputs ABB RAPID code with the synchronisation between the two robots built in. In the plant's records, 92.9% of part installations and 96.4% of welds succeeded.

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

That cell uses standard ABB building blocks. Long linear tracks are handled as external axes of the robot controller, and two arms sharing one workpiece is the problem ABB's MultiMove function was built for. Most cells like this are designed and tested offline first in RobotStudio, where an engineer can check reach, collisions and torch angles before steel arrives. Smaller shops tend to start with an ABB arc welding robot on a positioner that turns the part, so the robot welds in a comfortable position instead of reaching under the beam.

An ABB arc welding robot with a positioner that turns heavy parts. Photo: Ana 2016 / Wikimedia Commons (CC BY-SA 4.0)

What comes next for robotic steel fabrication

Faster welding is the other big push. On 23 September 2026 The Fabricator reported that THG Automation has built a twin wire cold metal transfer welding system on a cobot, made with Fronius and Universal Robots and aimed at structural and heavy fabrication. It feeds two wires through one torch and deposits up to 25 kg of weld metal an hour. More cobot welding will be on show at FABTECH in Las Vegas this October. ABB's own entry point for smaller shops is the GoFa Cobot Arc Welding Package, which a welder teaches by guiding the torch by hand.

ABB's GoFa Cobot Arc Welding Package on a welding table. Photo: ABB

Over the next few years the bigger change is likely to be connecting the machines. 1872's founders noticed that Path's welding cells were often underused because cutting, handling and welding still worked as separate islands. The same thinking reaches the finishing end of the line, where an ABB IRB 6700 already grinds steel parts in Teqram's EasyGrinder cell at Ancofer. Small fabricators will see some of this too. Our post on cobot welding in job shops and garages covers that end of the market.

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

The Kazakh cell also shows what is still hard. There, parts were left unattempted in 11 of 16 assemblies. Of the welds in the CAD models, 37.9% were overhead as the beam was posed, and those welds only became possible after the beam was repositioned. Every cell also needs people who can program it and inspect its welds, which is a different skill set from fitting and welding by hand. Safety rules out letting a 235 kg class robot like the IRB 6700 work freely next to fitters, so cells use fences or monitored zones such as ABB's SafeMove.

Visitors look at an automated robotic welding facility at the Odense Steel Shipyard in Denmark, 2007. Photo: US Navy via Wikimedia Commons (public domain)

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