Crankshaft Manufacturing: From Forge to ABB Robots

Crankshaft manufacturing turns a rough steel forging into the part that carries every piston's push into a spinning shaft. It has to be straight, balanced and ground to very fine tolerances, because it turns thousands of times a minute for years. This post follows the crankshaft from early cranks and hammered Model T forgings to grinding lines and robot loaders. It also looks at what recent engine failures say about quality control, and where ABB robots could fit in a crankshaft plant today.

A crankshaft lying in an open engine block. Photo: Seedlesslime / Wikimedia Commons (CC BY-SA 4.0)

From hammered forgings to ground journals

The crank is old. Researchers point to a crank and connecting rod at a Roman sawmill in Hierapolis from the 3rd century AD, and the engineer al-Jazari described a crankshaft in his twin-cylinder water pump in 1206. Engines later asked far more of the part. Ford's Model T used a forged crankshaft in vanadium steel, an alloy that Ford engineer Charlie Sorensen credited with making the car possible. A stronger steel meant a thinner, lighter shaft that could still take the load, and the photo shows the four-cylinder engine of a 1909 car.

The four-cylinder engine of a 1909 Ford Model T at the Henry Ford Museum. Photo: F. D. Richards / Wikimedia Commons (CC BY-SA 2.0)

A crankshaft can be forged from a steel bar or cast in ductile iron. Forging squeezes hot metal between dies, which gives a dense, tough blank. A photograph from 1938 in the Powerhouse Museum collection shows a man standing beside a huge forged crankshaft in a workshop, and the overhead crane tells you how the shaft got there. Whatever the metal, the blank is only a rough shape with extra material left all over it, and most of the real precision still has to be cut or ground in afterwards.

A man stands beside a large crankshaft forging in a workshop in 1938. Photo: Powerhouse Museum via Wikimedia Commons (public domain)

Machining turns that blank into something exact. Photographs from the United States in 1917 and 1918 show crankshafts going through grinding departments, and one is titled micrometer control of final crankshaft grinding. The main bearings and crankpins must be round and parallel to very fine limits, then balanced and polished. In those days a person lifted each shaft into the machine, clamped it and measured it, shift after shift. Heavy, repeated lifting of identical parts is the work that automatic loaders were later built to take over.

A worker at a crankshaft grinding machine during the First World War, 1917 to 1918. Photo: U.S. National Archives via Wikimedia Commons (public domain)

What crankshaft plants look like now

Today a crankshaft line is a chain of CNC machines: turning, milling, drilling oil holes, grinding, polishing, then washing and gauging. The photo shows a crankshaft being machined on a HELLER machine tool. Grinding cells are built for speed. One patent describes a three-station crankshaft grinding line with a 60 second cycle that includes 9 seconds for loading and unloading. Every second spent moving a shaft is a second the wheel is not cutting, so loading is worth automating, and a robot is the obvious tool when the shafts are heavy.

A crankshaft being machined on a HELLER machine tool. Photo: HELLER / Wikimedia Commons (CC BY-SA 3.0 DE)

Quality problems show how little room there is. General Motors' July 2025 recall of its 6.2 liter L87 V8 covers 597,571 vehicles. GM blamed sediment on connecting rods and in crankshaft oil galleries, plus crankshafts whose dimensions and surface finish did not meet specifications, and it pointed to a third party supplier. In October 2026 the trade press was still reporting owner complaints after the repair and a regulator follow-up. The story is a reminder that a crankshaft is checked for size, finish and cleanliness, and that a miss anywhere can wear out a bearing in service.

An ABB robot handles a glowing crankshaft forging at a press, from ABB's 2003 forging robots datasheet. Photo: ABB

ABB robots already work at both ends of the line. A 2003 ABB forging datasheet shows a robot lifting a glowing crankshaft forging at a press. On the machining side, the IRB 6700 is a large industrial robot with payload variants up to 300 kg, and one is shown grinding a steel part in Teqram's EasyGrinder cell at Ancofer. I could not find an ABB project for crankshaft grinding specifically, so loading a grinder with an IRB 6700 or an IRB 4600 is a possibility built on these existing uses. Cells like this are usually programmed and tested first in RobotStudio.

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

Where crankshaft production is heading

Inspection looks like the next big change. A coordinate measuring machine such as the cylindrical one in the photo checks journals, strokes and runout, but the shaft still has to be carried to it. A robot holding a gauge or scanner could measure shafts beside the grinder and send the numbers straight back to correct the next cut. One supplier sells a deburring cell for crankshafts up to 1,200 mm long and 150 kg, loaded by hand or automatically through a roof hatch, which shows how much automation already surrounds these parts.

A cylindrical coordinate measuring machine with a crankshaft mounted for inspection. Photo: Turbonut / Wikimedia Commons (CC BY-SA 4.0)

ABB sells a 3D Quality Inspection cell that scans metal parts, and the photograph shows one in use. I have not seen it applied to crankshafts, so that is an open question for any plant that wants to try it. The hard part is accuracy: journals are measured to very fine limits, and shop vibration and scanner tolerances make that difficult. Safety matters too. Shafts weighing tens of kilograms need guarded cells, and a cell changed over for a new engine needs robot programming skills that many small plants lack.

ABB's 3D Quality Inspection (3DQI) cell scanning a metal part. Photo: ABB

Electric cars change the demand but do not end it. Hybrids and range extenders still use engines, and in September 2026 HD Hyundai Heavy Industries announced more than 1 trillion won of investment in power engines. The photograph shows four shafts at different stages of finishing, the range a robot cell has to handle. For most drivers the part stays invisible, but a recall like GM's shows how much depends on it. Cost, safety and programming skills will decide how many plants add robot cells over the next few years.

Four crankshafts laid side by side at different stages of finishing. Photo: Olaf / Wikimedia Commons (public domain)

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