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The shift to aluminum presents a new set of problems for auto parts manufacturers conditioned to working with steel.

Sandvik

The automotive lightweighting trend has obvious utility in the present, but also carries long-view implications. In the near term, vehicle weight is one of a few key variables in the great fuel efficiency equation. Corporate Average Fuel Economy (CAFE) standards dictate that passenger cars will be surpassing 50 miles per gallon in fuel efficiency (on average) as soon as 2025. Meanwhile, pain at the pump is pushing more consumers towards vehicles with better fuel economy. These conspiring forces drive OEMs to squeeze every ounce of fuel efficiency in current and future models, and lightweighting has played a starring role in that process.

 Counterbalancing extremely heavy batteries with lightweight chassis will be a key in hybrid and electric cars’ share of the automotive market, as the global auto fleet doubles in the next 30 years. ExxonMobil expects the global personal vehicle fleet to double from more than 800 million today to more than 1.6 billion by 2040. The company sees conventional hybrids as the big winner, with “full-hybrid vehicles” making up about 40 percent of the global fleet in 2040, or more than 50 percent of new car sales in 2040. All of these will need to be partially powered by heavy batteries, so weight savings will be necessary.

There are multiple routes to weight reduction in automotive manufacture, but materials, and their more Spartan use, tend to be at the centre of the evolution. Recently, the industry has reached a tipping point – punctuated last year with the release of the new aluminum Ford F-150 – in the shift from heavier steel to lighter aluminum as the primary automotive raw material used. Consumers no longer overwhelmingly perceive aluminum as a weak, ‘tin-can’ material, and cars are getting lighter because of it. But the shift to aluminum presents a new set of problems for auto parts manufacturers conditioned to working with steel.

A departure from steel
Compared to hard and brittle steels, aluminum is a ‘sticky’, malleable material that resists clean chip breakage. It is also prone to built-up edges (BUE) in carbide cutting tools, which simultaneously shortens the cutting tool life and exposes component manufacturers to the risks of flaws and excess scrap. To compensate for the quirks of aluminum, manufacturers have turned to a cutting method that essentially takes many small ‘bites’ (low feed) from the workpiece, and do so very quickly (high speed). This technique maintains chip control and avoids problems with BUE. But when approaching edges, even the low feed/high speed cut can’t always account for a ‘pushing’ effect, in which carbide tools smudge aluminum over the component edge. This effect results in an edge burr.

Manufacturers of components like automotive cylinder heads and engine blocks, which require a high degree of precision, didn’t have to worry as much about burring when their workpieces were steel. Now that such workpieces are aluminum, many manufacturers are turning to specialty tooling to avoid burring problems. New finishing tools are being developed to address the machining challenges of aluminum cylinder heads and similar components.

BF Cutter and aluminium
Finish milling cutters typically feature an array of inserts that are all set to the same diameter, perhaps including one or two wipers. The BF Cutter from Sandvik Coromant is unique in this regard. Each insert pocket is engineered to a specific location on the tool, and there are progressive steps from location to location both radially and axially. Because each pocket is milled into the cutter body, which is engineered for a specified feed rate, each cutter is uniquely tailored for a specific application. The first insert is located at the largest diameter, the next one is at a slightly smaller diameter, and the array progresses to the final insert acting as a wiper. This staggered-cut design leaves a great surface finish, and yields higher feed rates than normal cutters when machining aluminum.

Changing the inserts is possible on the BF Cutter without having to preset. Normally, when an operator indexes or replaces inserts on a cutter, he or she would then have to preset to get the precise insert locations of each tooth. In cases that include a wiper or two in the insert array, the wipers would have to be preset slightly higher in location than the standard inserts. This equates to more set up time to optimize the axial runout. Because each BF Cutter insert is already positioned progressively, an operator can simply put a new insert in and the tool can resume cutting. This reduces set-up time and produces a faster feed rate.

Another major advantage of the BF Cutter is its capacity to cut a burr-free part. Volume automotive manufacturers previously had to worry about an exit burr or breakout on the component at edge, or exit cut. Milled across an aluminum cylinder head, the tool cuts cleanly, even at higher feeds than normal for aluminum, and doesn’t push an aluminum burr into any open spaces. If the component remains burr-free, the need for secondary operations is eliminated. Even as a specialty tool, the BF Cutter can quickly show ROI as it yields as much as a 30 percent cost reduction per part. The cost reduction stems from the 66 percent reduction in setup time realised by fewer inserts and the lack of a need to preset. If using wipers, roughing and finishing can be done on the same pass by the same tool, which eliminates an entire operation for more precise aluminum components like cylinder heads.

Keeping pace with automotive change
With the global fleet expected to double in less than three decades, the design of increasingly fuel-efficient cars will be a chief concern. Lightweighting is a strategy that will only become more commonplace. That means OEMs and their Tier-One and -Two suppliers will need to react with more proficient ways to machine aluminum or other, even lighter-weight metals in the future.  

Sandvik Coromant

Part of global industrial engineering group Sandvik, Sandvik Coromant is at the forefront of manufacturing tools, machining solutions and knowledge that drive industry standards and innovations demanded by the metalworking industry now and into the next industrial era.

Part of global industrial engineering group Sandvik, Sandvik Coromant is at the forefront of manufacturing tools, machining solutions and knowledge that drive industry standards and innovations demanded by the metalworking industry now and into the next industrial era.

Educational support, extensive R&D investment and strong customer partnerships ensure the development of machining technologies that change, lead and drive the future of manufacturing. Sandvik Coromant owns over 3100 patents worldwide, employs over 8,500 staff, and is represented in 150 countries.

For more information visit www.sandvik.coromant.com or join the conversation on social media.

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