Cutting tools in action

Voith Paper, Krefeld, Germany, has reduced the time to finish 50 by 290 mm through bores to H7 accuracy from 10 minutes to one minute, a 90% per cent saving, by adopting Horn System DR reamers (01425 481800 ). DR also eliminated a problem with chatter marks that had been experienced with the arbour-mounted HSS tooling previously used for the task. Voith Paper manufactures paper-making machinery that can have working widths of 11 m and machine lengths of 800 m. The Horn tooling has been applied to precision machining a pair of bores in bearing housings made from the material EN-GJS-400-15 (GGG-40). These housings are designed to support rolls weighing approximately 30 tonnes. The 290 mm long through-bores in this component, which have to be reamed, are in turn intended for locating special bolts that perform the guidance function of a novel holding fixture for other system parts and demands a fit accuracy of H7. Image: At Voith, Horn tooling has been applied to precision machining a pair of bores in bearing housings In the initial trial, 48 housings were completely machined, including bore hole precision machining, on a FFS Werner TC 800 flexible production system. The DR reaming tool reduced machining time from 10 minutes to 1 minute and demonstrated tool life of approximately 28 mins – thereby completing the batch - with no wear to the cutting edges. Cutting data for the operation is 70 m/min, at a feed rate of 1.6 mm per revolution. A custom-made 4.3 mm thickness, straight toothed, ring-type hard metal cutting insert variant having a special coating is used, and machining is undertaken using through-tool coolant supplied at 15 bar. Chatter-free bores were produced, despite the lengthy 433 mm tool projection length. REPEATABLE CONCENTRICITY A further advantage is evident when tool exchange is made, as System DR offers 0.003 mm repeatable concentricity precision at each tool change. This and other trials convinced the company to adopt the system. From bores to shafts, and the Bencere tooling division of Mollart Engineering (01789 450132) has transformed the process of producing impeller motor shafts for a customer. Through its application development of the burnishing process with the customer, at least £40 has been saved per component by eliminating a subcontract grinding process. As a result of the application, two burnishing cycles have now been integrated into a single turning operation. Image: The Bencere tooling division of Mollart has transformed the process of producing impeller motor shafts The 316 stainless steel motor shaft had two critical ground diameters 50 by 100 mm long and 54 by 70 mm in length. Both had to be produced to 0.4 Ra surface finish. By changing the process to roller burnishing, using the Bencere multi-surface, carbide roller burnishing tool, the customer was able to pre-size the diameters to leave 0.025 mm of stock material and then, during the same programmed cycle, roller burnish the two critical diameters. Most important with the Bencere solution was that the same S2075-00 tool held in the turret of the Haas lathe was used for both surfaces. The machine was run at 800 rpm, with a 0.1 mm/rev feed. The tool was set via a sidescrew in the shank against a pre-loaded spring that accommodated bi-directional loading of 0.5 mm on each diameter, in order to take up any variation in the turned surface of the part. As a result, the customer is now producing both highly finished diameters between 0.2 and 0.3 Ra in under 130 secs. This has saved the cost of carriage to the subcontract grinding shop, packing, possible quality issues, delays in lead time while the grinding is taking place and the customer now has total control over the whole manufacturing process. The multi-surface roller burnishing tool can be used on internal and external diameters, radii, counterbores and end faces. It incorporates a carbide roll that rotates on a precision bearing to exert a surface pressure both axially and radially on the component. Tools in the Bencere series are available to process most materials up to 40 HRc from a minimum bore size in a component of 4.75 mm. MARKET LEADER Electric golf trolley-maker StandelDawman is acknowledged as a market leader and the industry benchmark. It maintained its market position by investing in cutting edge technology, the most recent being cutting tools from ITC of Tamworth (01827 304500). The company's CNC machining section produces aluminium components for its golf trolleys, as well as tooling for plastic mouldings. It was problems with machining aluminium components that led to the introduction of ITC technology, as engineering director Gary Dawes recalls: "We knew our cycle times and tool life were poor and our surface finishes could be improved, so I spoke with a friend that recommended we try ITC cutters. Their technical sales engineer visited and, two years later, we now have a consignment stock of their products, as we were that impressed." On his first visit to the 30-employee company, ITC technical sales engineer Jason Clark tackled an aluminium lighting component. He introduced ITC's 12 mm diameter 2041 Cyber Series square end carbide milling cutter and changed the machining strategy to increase speeds and feeds beyond the range capabilities of the previous tooling. Targeting the rough machining process, the 2041 Series immediately reduced the cycle time from 12 minutes to six. "The first job with an ITC cutter really opened our eyes to the capabilities and benefits of high specification tooling, especially when delivered with excellent technical support," explains Mr Dawes. "We immediately introduced the tool to alternate jobs and consequent cycle time gains led us to acquire additional cutting tools." Dedicated to the rough machining of aluminium, the first 2041 Cyber Series cutter was soon joined by 6, 8, 10 mm diameter cutters, while others with radii followed. The international supplier of golf trolley parts then acquired 6 and 10 mm diameter sizes of ITC's 2052 two-flute, ball-nosed series of ultra-wear-resistant micro-grain carbide cutters for finish machining and the processing of intricate forms. Mr Dawes highlights a direct impact on customer perception, too. "We increased the step over, and altered our speeds and feeds to purposely leave a small step-over mark on the parts. We deem this as a feature to signify quality and show the parts are precision machined, as opposed to being cast. It is great having cutting tools of such technical excellence that we can select the quality of our surface finish." Image: Machining marks – there by design to underline its products are not cast, as with other makes, says StandelDawman Success with aluminium then saw a focus on the steel machining for mould tools. With a considerable amount of P20 and H13 grade tool steel being machined, the Hanita high feed 70N7 cutter immediately made an impact, reducing roughing and semi-finishing cycle times from over two days to a couple of hours on many of the tooling components. "The Hanita high feed cutters have been a revelation to our business," says Mr Dawes. "The change of strategy to high feed and low depth of cut machining has reduced the stress on our machine tools, while bringing obvious productivity benefits. These tools have been perfectly complemented by ITC's BritCut and Hanita ball nose cutters for finish machining. NO POLISHING REQUIRED "The surface finish on our mould tools has improved to the extent that we no longer need to polish parts after machining. We used to machine, polish, etch and anodise our mould tool parts. Taking the polishing away from the process has enabled us to save additional time and move staff from this labour intensive task. "ITC has catered for all our tooling needs with high performance cutters, drills and reamers. We have benefited measurably since employing the company's carbide tooling range, with regards to productivity, tool life, surface finish and service. The company has played a considerable role in our continued success and we are delighted we chose ITC," concludes the engineering director. First published in Machinery, May 2011