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FEATURE GEARS & GEARBOXES


in February 2022, twice-as-many as in February the previous year. Meanwhile, Virta reports that 1.06million new EVs were registered in Europe in the first sixmonths of 2021, versus 413 during the first half of previous year. Registrations in China and the US rose by over 197%and 166%, respectively. Comparisons between the


IMPROVING GEAR MACHINING A


ccording to EV-Volumes, 541,780 new plug-in electric cars were registered globally


worsen the quality of the component. The after heat treatment is harder to control and traditional soft machining methods, followed by grinding processes, are very expensive. These processes also require additional oil-based machining, to benefit themachining itself and


also chip evacuation. Manufacturers therefore


need to upgrade their


environmental advantages of EVs versus internal combustion engine vehicles aren’t straightforward. According to Carbon Brief, it depends on the size of the vehicles, the accuracy of the fuel-economy estimates used, how electricity emissions are calculated, what driving patterns are assumed, and even the weather. Despite this, the report concludes that, on the whole, EVs are responsible for considerably lower emissions over than internal combustion engine vehicles.


PLANETARY GEARS For carmakers and OEMs, the above factors all underline the need to move away from traditional combustion engines. At the same time, the manufacturing of EVs will also present additional challenges, with a risk that manufacturers relying on traditional production processes will get left behind. So let’s focus on the manufacture of gear components. The ability to control the revolutions perminute


(rpm) with gears is essential for all kinds of vehicles, including EVs. All EV transmissions are so-called reduction transmissions, designed to reduce the vehicle’s speed so it can be controlled and driven economically. Because there are no combustion engine sounds in an EV, any noise fromthe transmission will be noticed. So, the main task is to avoid noises. This is where the quality of themachining setup plays a decisive role, tomake the transmission as compact, light and noiseless as possible. EV transmissions are mainly of a planetary


design, with the planetary gears and the sun gear assembled inside the peripheral ring gear with a compact and light assembly. The ring gear is themost difficult component to produce, with its thin walls and high demands on roundness. Unfortunately, traditional manufacturing processes can worsen these difficulties with several time and cost disadvantages. Traditionalmanufacturing processes typically


rely on single-purpose machines, making production lines inflexible when responding to necessary changes in component design.Moving the workpiece frommachine-to-machine can also


8 traditional manufacturing


processes. One way is by investing in multi-task machines. As mentioned, grinding equipment


commonly used in traditionalmanufacturing


can be an expensive investment. A good way to sidestep this is to divide themachining of gear components into two processes, soft- and hard- machining. Thesemethods can be implemented in a single,multi-taskingmachine setup. Multi-taskmachines can eliminatemachining


processes, their associated time and costs and also improve part quality. In addition, the process cycle times are better, or at least the same as, existing production solutions. In fact, Sandvik Coromant has seen minimum cost reductions of 30% for the end user. Manufacturers can also achieve greater


flexibility in producing future components for e-mobility. The process allows downsizing and weight reductions in transmission components. Power skiving can be applied to both internal and external gears and splines, but is especially productive when it comes to internalmachining. Themethod works particularly well inmass production, where short lead times are decisive.


POWER SKIVING Asmentioned, the ring gear is themost difficult component to produce in a planetary gear, but the concept of power skiving – which has actually been around for over a century – is emerging as the most efficient way to achieve this. Power skiving is a process that combines shaping and hobbing (a machining process for gear cutting) into a single, continuous cutting process. With power skiving, a complete component


can be machined in one multi-task machine for higher productivity and flexibility. The need for specialised machines is removed, and quality restrictions due to machine changes can be eliminated entirely. This significantly reduces total production time. Sandvik Coromant has developed its own


high-quality tools for power skiving, which are optimised to support its customers in the accuratemachining of EV transmissions. These include CoroMill 178, a solid power skiving cutter;


4 DESIGN SOLUTIONS NOVEMBER 2022


Power skiving is emerging as the


fastest-growing method for machining gears. Mats Wennmo, global


automotive transmission manager at Sandvik


Coromant, looks into its benefits


and CoroMill 180, an indexable insert cutter with railed insert seats that is designed for excellent and repeatable accuracy.


REDUCING MACHINING TIME As an example, a manufacturer or main gears in low-alloy steel wanted to replace its time- consuming shaping process, so replaced its existing processes with power skiving. The result? The customer’smachining time was reduced by 90%, with considerably increased tool life. In other instances, power skiving was shown to be two to three times faster than traditional processes.


Sandvik Coromant www.sandvik.coromant.com


A NEW SOLUTION FOR ACROW ADJUSTMENT


Having experienced the pain of using ‘acrows’ first hand on a renovation project, Grove Design’s Austin Owens challenged his colleagues to come up with a solution that would transform the time- consuming process to make it safe, quick and easy to adjust the supports using a standard impact driver. The answer involved replacing the


threaded collar with the patented J-strut gear collar, which can be wound up and down to adjust the support height using the J-strut pinion gear. Will Helme, one of the main designers


on the project, said: “J-strut removes the need for manual adjustment of the collar, avoiding the frustrations that come with repeatedly winding and adjusting… Our system enables rapid deployment by greatly reducing the time taken to spin the collar to the correct height. If a support is up against a wall and the operator can only turn the collar half a turn at a time, an adjustment that would usually take minutes to complete manually can be achieved with J-strut in a matter of seconds.”


Grove Design www.j-strut.com


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