Video: CNC Crankshaft Machining Combines Speed And Precision

Crankshafts are the core of an engine and they are possibly the most critical and stressed part of the rotating assembly. So besides needing to be strong, they need to be precision pieces. Not only do the main and rod journals need to be precision machined in size and roundness, but the location of those journals, which are offset from the axis of rotation, needs to be absolutely perfect.

If the location of a rod journal is off in one axis, you change the stroke length. If you’re off in the other axis, you are altering the timing of the piston reaching top dead center. For those of you who aren’t familiar with the use of a lathe, offset turning is no simple task, even though the machines in this video make it look like child’s play.

In addition to the journal surfaces themselves, these massive machines are responsible for all of the fillets and chamfers in some very tight spaces, shaping the counterweights in complex shapes, along with locating and drilling oil passages. With the progress in technology and hardware, these machines can also finish-polish each journal independently of the others – a job that usually requires a human’s touch.

One of the absolutely coolest things in the video, is a technology we didn’t even know existed – the induction hardening (and built in-quenching) of individual journals, as seen at 2:40 in the video. Presumably by keeping the intense heat localized to that individual journal, and the order in which individual journals and heated and quenched will minimize any distortion in the shape of the crankshaft.

Besides all of the technological marvels involved in these automated crankshaft manufacturing machines, there is just the sheer beauty of the mechanical ballet performed by the various clamps, probes, drills, and machining tools, as they turn steel into thin shavings and turn a single cast or forged hunk of metal into a precision piece of automotive equipment. So sit back and enjoy the show.

The induction heating and subsequent quenching of individual bearing journals is incredibly cool to us. As you can see, the journals are treated in a specific order, presumably to minimize any dimensional shift in the crankshaft.

About the author

Greg Acosta

Greg has spent over a decade in automotive publishing as Senior Editor of Race Pages magazine. In his free time, he is a firearms instructor and volunteer in the police armory.
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