CBN tooling expertise - Sumitomo Electric Hardmetal

Sumitomo Electric Hardmetal's €8.5 million investment in the European Design and Engineering Centre – E-DEC (pictured) – opened in May 2012, aims to develop tooling solutions in partnership with European machine tool makers and the manufacturing companies that are planning to acquire and make use of them. E-DEC is located in purpose-designed buildings adjacent to the existing Sumitomo Electric Hardmetal manufacturing plant in Laucheim, about 60 miles east of Stuttgart. And with its location in southern Germany, it is close to many German automotive companies and their suppliers, as well as much of the German machine tool industry, which is no accident either. As Makoto Abe, design and engineering centre manager, says: "Production, design and development should work together. It is a better way to create new solutions." FIRST OUTSIDE JAPAN E-DEC is the company's first engineering design centre of its type outside of Japan, with the stated purpose to establish customer support in application engineering, process design and development. It will also offer seminars and schooling for internal sales and distributors, and provide technical support, cutting tests and tooling evaluation more suited to European production methods. The company also has five 'Tech Centres' in Japan, plus further centres in China, Thailand and the USA. Currently, E-DEC is manned by four staff, with a machining facility comprising a DMG Mori DMU 80P duoBlock 5-axis machining centre and a Monforts RNC 500 Single Turn turning centre. To date, 15 research projects, pushing the boundaries in application/machining technology, have been undertaken, selected on their potential to deliver reward. Lower volume technically challenging projects are also considered, providing the future application holds promise. Sumitomo Electric Hardmetal UK's general manager, Trevor Tolley, says: "We are now introducing projects from the UK. Trials and tests can be undertaken at E-DEC, which allows those involved to spend quality time together discussing issues far better than a meeting on somebody's shopfloor allows." The E-DEC also allows new Sumitomo tooling products to be tested locally, as Mr Abe explains: "We can evaluate the best cutting data to suit Sumitomo's European requirements, which can be very different to Japanese customers and is totally independent of standardised catalogue cutting guidance figures." The tool design and development aspect is the most important element at the E-DEC, he underlines. Over 90% of Sumitomo tooling products are designed in Japan, but Europe presents more challenging, high-tech machining requirements, so working with European machine tool makers and end users is key to developing appropriate tooling solutions for Europe. "Once we have developed products, it is our expectation to export these from Sumitomo Electric Hardmetal Europe; but we are not there yet," offers Mr Abe. The focus at E-DEC is on tooling produced from SumiBoron, polycrystalline cubic boron nitride (PcBN – CBN with additional binder to give a pollycrystalline structure) and cubic boron nitride (CBN – virtually solid, with no additional binder), complemented by SumiDia, polycrystalline diamond (PCD), the latter used predominantly in the machining of non-ferrous materials. Image: SumiBoron PcBN inserts SECOND HARDEST MATERIAL CBN is the second hardest material, after diamond, with the strength of cemented tungsten carbide for machining hardened steels. PcBN hardness varies, however, depending upon binder mix, which is varied to cater to differing machining demands. Other products developed at E-DEC include PcBN-tipped ball-nose cutters for inner and outer automotive CV joint track groove milling. These are manufactured at the adjacent manufacturing facility, as are: the world's smallest boring bars with indexable PcBN insert for bores as small as 4 mm diameter; round insert CBN profiling tools; and PcBN grooving tools and inserts. In collaboration with Weisser, Sumitomo has developed a new PcBN hard turning tooling system (patent pending) that will significantly increase productivity on automotive parts made on Weisser machines and boost productivity by eliminating grinding. The reason Sumitomo Electric Hardmetal has such an association with CBN and steel hard turning can be traced back to 1977, when it first introduced its own CBN for hard turning applications (grade BN200). It was America's GE that first introduced resin bonded CBN grit as Borazon for grinding steel in 1969, however. CBN inserts for machining cast iron were subsequently introduced, in 1975. For this sintered CBN product, GE used copper or aluminium alloy as a binder, giving particular strength when milling cast iron. Meanwhile, Sumitomo developed its PcBN material with a ceramic binder that underpins the particular performance of the material, giving it its hard steel turning strength. It was also the case that Sumitomo worked with domestic Japanese automotive industry, where the turning of hard steel was an area of interest for future development. This is the root of Sumitomo's steel hard turning reputation and technology lead, but its application area is broader than this. With some 16 grades of CBN/PcBN exhibiting varying characteristics suited to differing combinations of conditions, the application range for Sumitomo CBN/PcBN materials takes in: the automotive, industrial machinery, wind energy, steel making, and die and mould sectors. SECTOR REQUIREMENTS In the automotive area, cast iron engine parts, cast iron brake discs, powder metal parts for variable valve timing, plus hardened steel components, such as transmission shafts and gears, differential housings and CV joints, are targets. In the industrial machinery sector, bearings are of prime importance, and, for the steel industry, turning of large rolls used in steel making is a key application. For the die and mould sector, ultra-precision machining of dies in high speed steel (Stavox) used in LED production is another example. Typical hardened steel part geometries that benefit from hard turning versus grinding include: bores with stepped features; spherical surfaces machined into part faces; tapered diameters; external grooving; OD profiling and facing and the facing of both sides of a part, where it is held on a mandrel (see diagram over page). This can result in fewer operations, higher productivity, shorter lead times, higher accuracy, greater flexibility, and the elimination of coolant and sludge waste (PcBN turning is a dry process). In addition, the hard turning process provides a distinct advantage, giving improved surface oil retention characteristics, compoared to grinding. And in terms of turning hard steel, there is a host of very significant opportunities to further replace grinding within, in particular, the automotive and bearing sectors, suggests Shinya Uesaka, senior general manager-technical and marketing department. Image: Reasons to apply hard turning using CBN/PcBN tooling Image: Hard steel turning is Sumitomo's core strength – SumiBoron BNC300 PcBN?inserts are in action here Reasons to apply CBN/PcBN turning and milling tooling more generally are broadly split into three areas, he explains. The first is when there is no other choice when machining hardened steel parts A second is the requirement for higher speeds and feeds than are possible with carbide tooling, giving higher productivity when tackling cast iron, powder metal, heat-resistant alloy and large steel rolls. Finally, a high precision requirement in cast iron or powder metal parts is also satisfied by CBN/PcBN in place of carbide. Recent key developments in Sumitomo Electric Hardmetal's CBN/PcBN portfolio have seen ceramic coating added in 2000, and the introduction of the SV chipbreaker technology in 2004. A softer ceramic coating on top of hard CBN/PcBN prevents any reaction with iron at elevated cutting temperatures. This can be in excess of 1,000 °C when turning. The SV chipbreaker delivers controlled machining of carburised materials and has led to further developments, including wiper geometries. Now, with E-DEC, Sumitomo is tailoring solutions more closely to European needs. It's a message the UK organisation, based in Princes Risborough, Buckinghamshire, is taking to the market. Box item Wiper-edge PcBN inserts Targeting hardened steel machining where a top-class surface finish similar to grinding is required, Sumitomo Electric Hardmetal has recently released a new range of wiper-edged PcBN inserts, developed also to extend tool life, when compared to non-wiper geometry inserts. The Sumiboron inserts are available in WG, for low feed cutting at less than 0.20 mm/rev, and WH for higher feed applications, with both insert types developed to enable high surface finishes of between 1.6 and 3.2 micron to be produced. The new inserts are also available in three grades: BNC 160, BNC 200 and BN 2000. BNC 160, with a two micron thickness layer TiAIN+TiCN coated PcBN grade, has high wear resistance on a special PcBN substrate that provides optimised free chipping from the material being machined. BNC 200, a ceramic film-coated PcBN grade, has a high resistance to damage of the insert when turning interrupted surfaces and when removing the carburised layer on hardened steels. Meanwhile, BN 2000 is a non-coated PcBN insert grade that has a tough wear- and damage-resistant cutting edge that uses a high purity ceramic binder that is also ideal for interrupted cutting cycles. In recent trials, turning 20 mm diameter shafts in 62 HRC carburised steel, the Sumiboron WG (BNC 160) insert doubled the number of parts produced per insert to 300. The insert was run at 180 m/min, with a feed of 0.1 mm/rev and 0.1 mm depth of cut. Machining dry was undertaken to achieve a surface finish of 0.8 micro metres. Further customer trials involving stepped diameters, under wet cutting conditions on a hardened pinion gear 58 to 62 HRC. This was turned to a surface finish of 3.2 micron, using a WH (BNC 200) insert. The operation was undertaken at 130 m/min with a 0.25 mm/rev feed and 0.3 mm depth of cut. Compared to existing operations without the incorporation of wiper geometry, the Sumiboron insert enabled in-cut life to be extended from 50 to 120 components. First published in Machinery, January 2014