As the metal cutting industry becomes more and more competitive, machine shops are continually looking for ways to deliver market differentiation. In combination with stricter environmental requirements, machining operations are becoming increasingly automated to ensure energy efficiency and streamlined production with a minimum of waste, interruptions and late deliveries.
The automotive industry is not just at the forefront when it comes to automated manufacturing processes, but leads with its willingness to communicate the amount of energy required to produce each vehicle. Cutting force in component machining operations is just one part of that equation, while recycling, scrap and number of inserts used, are other parameters that have to be included.
Maximising Output
The objective for tooling suppliers is to design premium cutting tools that can handle ever greater speeds, feeds and depths of cut, in order to maximise output. However, production planning today is far more holistic than it has been historically. In fact, increasing the cutting data by 30 percent in a certain operation is no longer sufficient. As a result, demands for sustainable manufacturing along with automated, unmanned production call for a completely new understanding of productivity.
Productivity throughout the large and varied P25 area is to some extent an individual measure, depending upon the type of production. But generally it is a combination of machining efficiency, often measured in metal removal rate, and machine tool utilisation, in pieces machined per hour. For the cutting edge, this comes down to the good old values of cutting data and tool life.
Market surveys indicate that the majority of machine shops place process security and the potential to run unmanned at the top of their wish lists, followed closely by higher metal removal rates. In truth, the ultimate aim is to combine all three ambitions.
Steel turning in the ISO P25 material classification is the backbone of operations at machine shops around the world, which makes it a good focus area for the purposes of this article. The P25 category covers the whole range, from unalloyed to high alloy steels, from soft and sticky to hard and abrasive, and from low specification to high. Of course, machinability differs considerably from steel type to steel type, particularly as the material comes in workpiece variants that include forgings, castings, bar, tube, rolled, drawn, untreated, hardened, tempered and pre-machined.
Factors To Consider
To maximise output, the selected insert for each type of steel must balance a number of factors. These include durable and predictable tool life, which will lead to fewer stops for insert changes, as well as high reliability for limited or unmanned supervision, guaranteed surface quality throughout the life of the insert, and a broad application area. The latter entails sourcing an insert that can deliver excellent performance in continuous and interrupted machining, and from finishing to roughing, in a wide variety of steels. In turn, this will reduce tooling inventory, handling and storage costs.
The ability to machine a multitude steel with different hardness properties is also vital. With this in mind, the condition of the edge-line is particularly important as it can help achieve the highest possible process security and repeatability, reduce the need for supervision and thus boost the potential to run unmanned. In short, the edge-line must possess the necessary hardness to resist any plastic deformation induced by extreme temperatures in the cutting zone.
Furthermore, although it might sound obvious, the insert coating must adhere tightly to the substrate. If the coating fails to stick, the exposed substrate deteriorates rapidly. A chipped or broken insert can result in production stoppages and unacceptable scrap.
Throughout the years, leading cutting tool suppliers have strived continuously to offer insert coating properties that offer ever-greater levels of adhesion, toughness and wear properties, predominantly by optimising the microstructure and post-treatment processes. Among the most significant breakthrough in recent years is Inveio, from Sandvik Coromant, which uses advanced material science to align the direction of crystals in the coating.
In conventional CVD coatings, the direction of crystal growth is random, but this latest breakthrough manages to control the crystals so that every one is lined-up in the same direction, towards the top surface. Controlled crystals give a substantially stronger edge line that endures high temperatures and intermittent conditions, for longer. Most importantly for manufacturers, machining processes and tool life become predictable, while as an additional benefit, the technology ensures a high proportion of recycled carbide material is utilised.
Proven Technology
Many are already experiencing the advantages of aligned crystals, including Bajaj Motors of Agra, India, a supply chain partner to major automotive OEMs that include Tata, Suzuki, Nissan and Renault. Customers of Bajaj require excellent quality at the lowest possible cost and just in time delivery. Due to the high volume of components, it’s impossible to measure and check every one. As a result, the tools and suppliers selected by the company are evaluated carefully prior to adoption.
So, what does a new coating have to do with a more holistic way of evaluating productivity? From what is known now, quite a lot. At Bajaj, which is producing steel components in their millions every year to customers that require outstanding quality at low prices, the pressure is on.
High machine utilisation is crucial and the company needs to trust that every component will meet close tolerance demands. Exploiting the aforementioned benefits of coated inserts featuring crystal orientation technology, Bajaj Motors is finding it can improve productivity and reduce its cost per component substantially.
