Crankshafts are key parts of engines. New requirements for lightweight vehicle construction and higher efficiency in engine technology require precise crankshaft hardening within increasingly tight tolerances.

Furthermore, crankshafts must have a combination of material properties: high-precision induction hardened surfaces for low-wear operation with long service life, together with core elasticity to absorb high torque stresses. Crankshafts of various sizes are used in passenger vehicles and lorries, among other areas.


SMS Elotherm is amongst the market leaders in induction heating machines for crankshafts and has unique expertise. The patented low-warpage hardening technologies are vastly superior to conventional methods.

Specifically for induction hardening of crankshafts, SMS Elotherm has developed applications for various use cases (passenger vehicles, lorries, etc.) and crankshaft sizes, which are available to our customers worldwide. All of our hardening machines have a modular structure, allowing them to be adapted, both overall and with regard to important details, to give plant operators the greatest possible benefit.

Crankshaft hardening zones

hardening zones
Crankshaft hardening

Induction hardening – economical and gentle on the environment

Induction hardening is generally a clean process. The process sequence for hardening usually consists of heating, soaking, quenching and (if necessary) tempering. SMS Elotherm has detailed knowledge of the interactions in this process and their impact on metallurgy. Based on this expertise, we are constantly improving the efficiency of the machine technology to significantly reduce power consumption.

Energy-efficient hardening process

SMS Elotherm has continuously refined the hardening process to achieve extremely high energy efficiency. Induction hardening with induction machines from SMS Elotherm needs about 20% less energy than other comparable systems.

A decisive factor here is that with Elotherm, the converters (power generators) and the inductors (power applicators) come from the same source and are perfectly matched to each other. Elotherm therefore achieves a trend-setting energy balance, which reduces the environmental footprint as well as unit costs.

Compared to hardening processes with traditional furnace technology, induction technology needs distinctly less energy, is considerably faster and minimises distortion effects. It also eliminates the time, cost and energy expenditure of furnace preheating. When induction heating machines are not needed, they automatically switch to an economical standby mode.

Stably reproducible process results, long inductor service life, short cycle and set-up times, easy access for maintenance, optimised machine footprint, and if desired fully automatic sequences are factors for optimal customer benefits. Whether with series products or package concepts aligned to the customer’s process, we stand by our customers with all of our experience and expertise.


Short set-up times

No hydraulic components

Integrated effective power measurement

Higher productivity



Crankshaft hardening for varying geometries

For varying geometries

Surface hardening of passenger vehicle crankshafts. The machine can be configured with one or two stations. Surface hardening with one station is primarily suitable for small and medium volume production, with the focus on hardening of a variety of workpieces. With two stations, the machine is ideal for large volume production with high-throughput hardening.

SMS Elotherm has created highly effective conditions for flexible plant layout as well as flexible deployment. The machines can harden crankshafts for 2 to 6 cylinders.

Designed for versatility

Both machines can be upgraded in many ways with option packages. For example, loading and unloading in the same place is possible. Furthermore, this can be linked to a gantry loader or even equipped with a through transport system. The machine can also be equipped to adapt automatically to different workpiece lengths and different pitch dimensions.

In response to a control command, the machine automatically configures itself for different spacings between main and pin bearings.

Induction machine for crankshaft hardening
Induction machine for crankshaft hardening

120 crankshafts per hour

In continuous industrial operation, the machine can achieve cycle times under 30 s for hardening of four-cylinder passenger vehicle crankshafts. That means a profitable throughput of up to 120 crankshafts per hour, with consistently high quality within tight tolerances.


Crankshaft hardening machines with a broad deployment spectrum

To meet large demands

For hardening crankshafts with lengths up to 1500 mm, the SMS Elotherm system literally opens up a large deployment spectrum – for example, for lorries and other large vehicles as well as many stationary units. Customers can choose exactly the required performance profile to avoid overcapacity and/or excess capital expenditure.

Lorry Crankshaft hardening
Crankshaft hardening: Crankshaft bearings

Precision with very high throughput

The system can be equipped with up to 13 independent power channels, depending on cycle time requirements. A high-throughput configuration with six converters is also possible for simultaneous hardening of six bearing locations with different parameters. This results in extremely short cycle times, even with large crankshafts.

Fully automatic and flexible crankshaft hardening machine

The crankshaft hardening machines from SMS Elotherm can harden up to 40 crankshafts per hour.

Hardening of oil seal surfaces on the flange or journal end can be integrated into the machine concept. For this it is recommended to plan in a supplementary station for hardening of oil seal surfaces at the flange or journal end or a gearwheel. Integrated annealing and single-location loading/unloading by an integrated shuttle transport are possible.

Other machine features include automatic pitch adjustment and manual workpiece changing. The SMS Elotherm machines have a modular structure and allow custom stations to be integrated into the overall concept. A post-cooling station, crankshaft cleaning before hardening and integrated workpiece drying by annealing are also available from SMS Elotherm.

The machines from SMS Elotherm enable configuration with up to six transformer/inductor hangers and operation with two converters for patented hardening of split-pin crankshafts or simultaneous hardening of two bearing locations.

crankshaft hardening machine



Large-scale hardening

Hardening crankshafts with lengths up to 12000 mm and weights up to 8 tonnes – those are the breathtaking dimensions of crankshaft induction hardening machines from SMS Elotherm.

This allows enormous crankshafts to be hardened with high precision and, above all, economically. Some examples are crankshafts for marine engines or locomotives, or for the large diesel engines of generators, compressors and pumps.

Customers can choose from a basic configuration with low capital expenditure or a higher configuration level with distinctly shorter cycle times.

The hardening process can be set individually for each bearing location and is performed automatically.

Crankshaft hardening machine


Brochure - Automotive

ModuLine - Minimal distortion induction hardening of crankshafts

State-of-the-art induction technology for crankshaft hardening plants

Induction hardening versus case hardening – a comparison

Procedural aspects of induction hardening