The rise of electrification is happening more widely and suddenly than anyone expected, both for automobiles and other types of electric vehicles (EV). The global EV landscape is also more competitive than the automotive markets of previous decades, as more manufacturers — large and small — compete for space. How can manufacturers stay ahead of the competition while overcoming the increasing challenges posed by difficult-to-machine materials, like high-strength steel? Staffan Lundström, product manager at the metal cutting specialist Sandvik Coromant, explains why a new all-directional tooling method, combined with the next generation CoroTurn® Prime B-type insert, holds the answer.
From the mid-1930s, the “Big Three” manufacturers dominated the US automotive market: General Motors, Ford and Daimler Chrysler. This continued for the next 70-plus years. But, competition among carmakers is changing — both within the US and in the current world-leading EV markets: Asia-Pacific, followed by Europe.
As written by Matthias Holweg in The Evolution of Competition in the Automotive Industry, a chapter from the book Build To Order: The Road to the 5-Day Car: “Competition has shifted from cost-leadership during the heyday of Ford’s original mass production, to variety and choice [and then] to diversification through leadership in design, technology or manufacturing excellence.”
This also applies to the EV markets. They are shaping up to be more diverse and competitive than the automotive markets of yesteryear as larger established companies, like Porsche, compete with small, globally-expanding manufacturers, like Polestar. These companies need to catch up with China on the world stage — indeed, six of the ten best-selling plug-in electric vehicles worldwide were from Chinese brands in 2021, according to Statista.
For original equipment manufacturers (OEMs), the competitive markets are shifting the demands placed on components. EVs have fewer components that are smaller, lighter and must also withstand higher levels of torque from the electric engine. The components must support greater energy efficiency and a higher power density. This, of course, puts really high demands on the components, which has led to a shift in material technology.
Sandvik Coromant’s specialists expect this shift to include a continued increase in the use of high-strength steel from around 15% of all materials used in automotive manufacturing in 2010 to 38% in 2030. These new materials, including clean and ultra-clean steels, are made from alloying elements and are able to withstand the aforementioned challenges — like higher levels of torque from the electric engine — because they have fewer metallurgical impurities.
But how does this relate to machinability? With clean and ultra-clean steels, we see an increase in the plasticity of the material as the reduced impurities in the steels translate to machining challenges relating to chip breakability and removal. These materials have a higher yield strength that, in turn, requires higher cutting forces during machining and creates higher levels of tool wear. While high strength, clean or ultra-clean steels are more difficult to machine, the growing integration of digitalisation and computer-aided manufacturing (CAM) on production lines is setting the bar higher for manufacturing quality and efficiency.
These are the machining challenges automotive manufacturers face, and those that fail to upgrade their production processes or fall back on traditionalism risk getting left behind. But how can manufacturers stay on top of the trends? The answer lies in better machine tools and a new machining method designed to support optimised quality with improved efficiency, cycle times and cost savings — including when machining tough steels.
Better chip control
It’s well known that effective chip control contributes to productivity and reliability in machining processes and the machined surfaces’ final quality. Let’s examine chip control more closely and how it affects productivity in machining and wear on the tool itself.
If the insert machines the workpiece at a near-to-90° angle, then the thickness of the chip will be equal to the feed rate (fn) — so, at an fn of 1 millimeter per revolution (mm/rev), the chip will be 1 mm thick. If we reduce the entry angle, the smaller we go, the thinner the chip thickness will be. We can increase the fn accordingly. So, for example, if we decrease the entry angle from 90° to 25° while increasing the fn from 0.25 up to 0.6 mm/rev, the chip thickness will remain the same. The result is more productive machining with the same levels of chip control.
To support this, Sandvik Coromant has created its PrimeTurning™ methodology that includes machining with a small entry angle to give very high productivity and long tool-life. The method allows customers to do turning in all directions and, in doing so, they can achieve greater efficiency and productivity than is possible with conventional turning. PrimeTurning™ has resulted in increased productivity and longer-lasting tool life for customers.
However, the process needs specific tooling to unlock these advantages. A conventional tool won’t allow the same levels of chip control or the right clearance angles, so it will not work in practice. That is why Sandvik Coromant has developed CoroTurn® PrimeTurning™ tools, of which the latest development is the second generation CoroTurn® Prime B-type inserts. The next generation tool features double-sided negative inserts with four cutting edges designed for more cost-efficient machining, along with a new robust tip seat design and updated geometries. With these features, the tool can perform deeper cuts (mm), with higher machining (mm/rev) and fn speeds, plus improved chip control while machining high strength steels and other tough steels.
This benefits productivity, but what about tool wear? This brings us to the design of the insert itself. With a conventional insert, machining at a smaller entry angle puts most of the heat and load into the corner of the insert, which also happens to be the insert’s weakest part with the least amount of carbide to absorb. Instead, each next generation CoroTurn® Prime B-type insert has four cutting edges rather than two, with stronger corners. With more edges, more machining can be achieved with each insert, while heat and load is spread over a much bigger portion of the cutting edge.
The second generation CoroTurn® Prime B-type insert is also designed to overcome issues normally experienced when using inserts at a higher axial depth of cut (ap) and fn. That includes risks of overload and, at lower ap and fn, the risk of long chips. Machining operations can therefore be run at a much higher fn for improved chip control, stability, process security, and tool life. For manufacturers, meeting these higher standards of quality and efficiency can be met by implementing improvements at the machining stage.
The advantages of the PrimeTurningTM method are further enhanced with CoroPlus® Tool Path digital software. The software is a dedicated online tool path generator, which supplies programming numerical control (NC) codes and techniques to set up proper parameters and variables for a particular machining application. When this precise cutting data is combined with the CoroTurn® Prime cutting tools, Sandvik Coromant customers have achieved smaller entering angles, efficient edge use and no chip jamming.
Going forward, Sandvik Coromant anticipates that its second generation CoroTurn® Prime B-type inserts will achieve similar benefits for other customers in automotive — including EV manufacturers. By using these inserts within the PrimeTurningTM method, manufacturers can save time when working with difficult-to-machine materials, along with the additional tool life benefits. With these machine tools and methods in place, automotive manufacturers will be able, paraphrasing Holweg, to diversify through leadership in design, technology or manufacturing excellence.