machinery
new ways of machining transmissions brings manufacturers cost savings
However, whatever their circumstances, cost-cutting remains a priority. Take the machining of gears.
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Manufacturers want more flexibility in gear machining, but achieving this while reducing costs is not straightforward. Traditionally, projects that involved machining gears would depend on special machines and processes, especially in mass production. This means limitations — and often higher costs — in the production process. Three new ways of machining
transmissions make getting beyond these limitations possible. Moreover, these advantages go beyond automotive into areas like general engineering, wind power, aerospace and even robotics.
Power Skiving Power skiving is a rotary cutting technique where the tool meshes with the gear being made. The continuous cutting process enables all machining to be carried out in one single set-up. In essence, it combines hobbing and shaping, and the intersecting angle between tool and gear axis and the revolution speed is decisive for productivity. Power skiving has been around for more than
30 years — so, why am I talking about it in an article on new ways of machining transmissions? Because, the machining landscape is changing in ways that will effect a variety of sectors — including manufacturing transmissions for electric vehicles (EVs). Let me explain.
eleCtriC veHiCleS The received wisdom used to be that EVs do not need multiple gears or transmissions. But this view has changed, and the likes of Tesla and Porsche are rolling-out multi-gear EVs. Electric motors achieve much higher revs per minute (rpm) than conventional cars — 20,000 rpm in electric motors versus just 4,000 to 6,000 rpm in conventional combustion engines. So, a reduction gearbox is needed to reduce these rpms to a manageable level. These EV transmissions also must be hard-
wearing to withstand higher rpms, and are tougher to machine as a result. Less obvious is that, when producing these parts, manufacturers must focus on the metal removal rate, which expresses the speed of the machining of the workpiece.
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Here, Harish Maniyoor, global product manager for Automotive at machine tooling specialist, Sandvik Coromant, explains how three new ways of machining transmissions can help manufacturers do more with a less. Another major demand for EV transmissions
achine shops have faced variable high and low-demand scenarios during the COVID-19 pandemic.
is lower noise from the gearbox, since there is no noise from engine. This means producing components with tighter tolerances and entails more challenging machining. So, the question for machine shops should
be: is it fast productivity you are looking for, or something else? Such agility cannot depend on traditional transmission manufacturing processes. Instead, power skiving makes it possible to machine the complete component in a multi-task machine or machining centre, in a single set-up. This shortens production time, improves
quality and reduces handling and logistics costs. The advantages of power skiving were
shown when Sandvik Coromant was asked by a large automotive customer in Sweden to supply a component machining solutions. Working with the customer’s automotive
development team, the project proved that power skiving is possible with two 5-axis machines, using Sandvik Coromant’s own CoroMill 180 indexable power skiving cutter. The CoroMill 180 is designed for high-output gear and spline production. The customer achieved a better-than-
expected cycle time. The customer had demanded it be within 14 minutes-per- component and achieved a cycle time of less than one minute-per-component.
AeroSPACe The advantages of power skiving are not limited to automotive, but stretch into other sectors, including general engineering, wind turbines, aerospace and robotics. Aerospace in particular, is prioritising cost
reduction. The effects of the COVID-19 pandemic on the industry have reported extensively with Airbus reporting that its aircraft production rates have dropped by 30 per cent.. Like EVs, older aerospace engines are being
upgraded for better performance and efficiency, so well see an evolution in their production. The flexibility of power skiving has much to offer here, such as in its capability to machine close to shoulders, allowing greater freedom in component design. As aerospace components are made from tougher materials, this can require tougher inserts. This includes launching a pair of new ISO P-
turning carbide insert grades for steel turning, GC4415 and GC4425 to its range. Their names apply to the ISO P15 and P25 application area, which refers to the demands that different
Summer 2021 UKManufacturing
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