Piston Manufacturing: ABB Foundry Robots at Work

Piston manufacturing turns a lump of molten aluminium into a part that moves thousands of times a minute inside an engine, and the tolerances are tight. A piston has to be slightly out of round, light enough to keep the engine balanced and strong enough to survive the heat of burning fuel. This post follows the job from the first Otto engines through aluminium casting and CNC machining to the robots that now do much of the handling. It also covers a recall in September 2026 that put a single machining mistake in the news, and where ABB's foundry robots fit.

Pistons and connecting rods in a cutaway engine block. Photo: Mj-bird / Wikimedia Commons (CC BY-SA 3.0)

How pistons went from cast iron to light alloys

Nikolaus Otto's four-stroke engine of 1876 made the piston a mass-market part, and early pistons were cast iron. They were heavy, and lighter alloys were wanted for better engine balance. A foundry hand could do little to the shape beyond what the mould allowed, so each casting was finished on lathes and checked by hand. A good piston depended on the skill of the people at each stage, and that dependence is what later automation set out to reduce.

An Otto A engine on display in a museum, 2026. Photo: Tiia Monto / Wikimedia Commons (CC BY 4.0)

Lighter alloys arrived once engines began to rev faster. Piston history lists Y alloy and Hiduminium among the aluminium alloys developed specifically for pistons. Mahle, founded in Bad Cannstatt on 1 December 1920, experimented with light alloy pistons at a time when automotive pistons were generally cast iron. It introduced Germany's first controlled expansion piston in 1927 and, in 1931, an aluminium piston with a ring carrier for diesel engines. Aluminium pistons ran lighter, but they expanded more with heat, so makers had to shape them with that growth in mind.

A Tangyes of Birmingham lantern slide showing types of steam engine piston, around 1910. Photo: Wikimedia Commons (public domain)

Wartime production showed how much casting mattered. Photographs from a 1942 Rolls-Royce factory making Merlin engines show workers tipping molten metal into moulds by hand. Today, pistons are usually cast or forged from aluminium alloys, and racing pistons are often forged for fatigue life. After casting, a piston is turned and ground. It is deliberately not round: it has slight ovality and a diameter that is larger near the bottom of the skirt than at the crown. Machining that profile consistently, piston after piston, is the hard part, because the shape has to stay right as the part heats up and expands in the engine.

Workers pour molten metal into moulds at a Rolls-Royce factory making Merlin engines, 1942. Photo: Richard Stone, Imperial War Museums via Wikimedia Commons (public domain)

A September recall and the robots at the foundry

A recall this autumn showed what a small machining slip can do. In September 2026 Ford recalled 10,001 vehicles from the 2026 model year with 1.5-liter and 2.3-liter EcoBoost engines, including the Explorer, Bronco, Bronco Sport, Mustang and Ranger. According to reports, Ford traced the fault to a supplier plant in Arteaga, Mexico, where a loose lock nut on a machining tool let the tooling touch a metal insert in the piston dome and weaken its bond with the aluminium. The dome could then crack, and Ford expects the remedy in December.

A used piston from a Subaru boxer engine with damage to the crown and ring area. Photo: Phil Sangwell / Wikimedia Commons (CC BY 2.0)

Quality at that scale depends on what happens between casting and the machine tool. Castings leave the mould with gates, risers and rough edges that must be removed before precision cutting. That work is hot, dusty and repetitive, which is why foundries were early customers for robots. ABB describes its IRB 6660 as a rigid robot built for pre-machining and other post-casting work, with force control options, and its IRB 940 Tricept as a machine for cleaning and pre-machining aluminium castings. Both show how robots take over the dirty part of the process and leave exact finishing to the CNC machines.

A crankshaft being machined in a Heller machining center. Photo: HELLER / Wikimedia Commons (CC BY-SA 3.0 de)

Inside the die casting cell, ABB offers Foundry Plus 2 versions of several robots, including the IRB 1300 and the IRB 1200, sealed to cope with water, dust and heat. Photos from ABB customers show robots working beside die halves and in the steam of a Bühler casting machine. A foundry case study from ABB's library describes cells with IRB 400 foundry robots deburring engine bedplates, transmission casings and clutch housings. I found no ABB source naming a piston line, so a piston cell would be a use of existing tools rather than a documented project. The same logic is covered in robotic machining and in the post on die casting.

An ABB robot seen between the open halves of a die casting die. ABB builds protected Foundry versions of its robots for wet, dirty cells. Photo: ABB

What comes next for piston plants

Planning is where a robot pays for itself. A cell that loads blanks into a machine, deburrs the casting and passes it to a gauge can be laid out in RobotStudio before any steel is bought, with reach and cycle time checked on screen. For factories this matters more than raw speed. A programmer can also test a new piston design in simulation while the old one still runs.

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

Inspection is the next step. The Ford case shows that a piston can pass most checks and still hide a flaw, so more measuring is the obvious answer. A robot arm can present a piston to a gauge in several orientations without a person handling it, and a record of every measurement can stay with the part. The piston then travels to the engine plant, where it is fitted to its rod and cylinder, a stage covered in our earlier post on engine assembly. ABB has not announced a piston inspection product, so these remain possibilities for its existing arms.

An ABB IRB 1300 with Foundry Plus 2 protection, built to handle water and dust. Photo: ABB

Cost, safety and skills limit how fast this spreads. As more cars go electric, a plant that automates piston lines needs a plan for a shrinking market, and robot cells must be cheap enough to pay back sooner. Hot metal and spray demand strong guarding. Finding people who can program a machining cell and read its measurements is also hard. Hybrid engines and large diesels still need pistons, so the work will not vanish soon.

A white ABB foundry robot works in steam at a Bühler die casting cell. Photo: ABB

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