Renthal is famous for manufacturing aluminium alloy handlebars for the aftermarket and they are also fitted as OEM components on Honda, Kawasaki, Suzuki and KTM motocross bikes. Rear chainwheels are also core products and it was to these in particular that Renthal turned its attention in 2011.

Rear chainwheel blanks, which are made from aluminium, have their outside diameter in the range 150 to 280 mm plasma-cut from sheet of 6, 7 or 9 mm thickness. They are transferred to a gear planer to have their teeth machined around the periphery and chamfered.

 These preparatory operations were and still are performed. However, from here on the new process route differs markedly, with the remainder of operations completed in a single operation on both pallets of the two Brother TC-R2B 3-axis, moving-column, turret-type machining centres.

 With the established method of manufacture, which currently is still in operation alongside the new cell, wheels are machined in four stacks of six on a different make of machining centre so that an indexable-insert drill can quickly produce around three dozen holes to lighten the components and fix them to motorcycles. From here on, countersinking, deburring and other jobs are done as individual operations.

 This finishing of the many millions of holes produced at Manchester was time consuming and expensive. Minimum batch size was 24-off and production time was 5 to 6 minutes per component. The new method of manufacture being phased in is based on single piece CNC production. As each hole is profiled individually, very fast machines were needed to minimise idle times and maximise metal removal in-cut, hence the choice of the Brother TC-R2Bs.

 Of nominally third-metre-cube capacity, the machines have 16,000 rpm maximum spindle speed, a fast, servo-driven, 14-position tool turret, chip-to-chip time of 1.7 seconds including deceleration from and acceleration back to maximum rpm, and 50 m/min rapids. Unusually, pallet change in less than three seconds can take place at the same time as rotary table movement, tool change and linear axis movements. This pares even more from overall idle time and greatly speeds the start of metal removal from the next workpiece.

 After machining, the holes are chamfered by plunging or interpolation and the component is fixtured to allow a dovetail cutter to pass through the holes and perform similar on the reverse. Even the part number that was formerly hand-stamped is CNC engraved. Cycle time is from 3.5 to 4 minutes, a reduction of around one-third compared with the traditional method of manufacture.

 Production Engineering Supervisor at the Manchester factory, Steve Grainger, commented, “The new production route is not only more economical in terms of time and labour, but has also freed up an enormous amount of space for other projects.

 “We have gained another level of accuracy in rear chainwheel production by doing away with repeated handling and refixturing as well as variable hand finishing.

 “We used to have to machine them 24 at a time and hold a large number of chainwheels in stock, which was expensive and took up a lot of space, whereas now we can make them quickly and economically to order.”

 Renthal’s first experience with Brother dates back to 2007, when it bought a TC-R2A. Mr Grainger said that the machine has not been down for a single day since it was installed. The company’s production engineering manager, Adam Kirby, added, “We were drawn to Brother because at the time it was the only twin-pallet machining centre in its class on the market on which the pallet simply rotates without lifting.

 “It means that there is virtually no possibility of swarf becoming trapped underneath, avoiding the repeated pallet alarms we can get with other makes of machining centre.

 “It proved to be as reliable as predicted, which gave us confidence in the machine builder, all of whose models use the same method of pallet exchange.

 “So two years ago, when we embarked on a big push to expand in-house CNC production, we decided to standardise on this supplier for prismatic machining equipment.”

Next to be installed was a Brother TC-R2B and a TC-324 in 2010. The machines are taking over production of most new core work as well as sharing machining of non-core products with existing machining centres on the shop floor. Such components include motorcycle handlebar levers and, more recently, parts for top-end cross country and downhill bicycles.

 The sixth Brother addition, in 2011, was a TC-S2D-0 with a 700 mm rather than the standard 500 mm X-axis. It was bought specifically for research and development, a function that until then tied up production machines. A Nikken 2-axis tilting rotary table was supplied so that the machine can simulate manufacture on all previously installed Brother equipment as well as the latest, seventh machine installed in March 2012, which has 4- and 5-axis capability.

Designated TC-32BN-QT, it is the manufacturer’s top model with 70 m/min rapids, 40-tool ATC, 1,000 psi high-pressure through-tool coolant and a comprehensive FSE swarf management system with back-flushing rotary drum filtering to less than 50 microns. On one pallet is a Kitagawa 2-axis table that gives 5-axis functionality, while on the other pallet, a Kitagawa trunnion provides one additional CNC axis.

 The machine currently produces 10 types of handlebar lever from aluminium billet in three operations instead of the previous six. The plan is to machine other components as well, including Renthal’s new Duo Stem for performance mountain bikes. The two-piece design presently needs 14 machining operations, which will be halved on the TC-32BN-QT. Production costs will be lower, not least through the use of fewer fixtures, which are all designed and manufactured in-house.

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Tried and tested designs and components used by leading global machine tool manufacturers have been selected by Averex Automation, Taichung (www.averexcnc.com), to produce the Akari HS-450i horizontal-spindle machining centre (HMC). By selecting only the best constituents and coupling them with a lower cost manufacturing base in Taiwan, the company is able to build a very high precision machine at a competitive price.

The twin-pallet, 4-axis HMC was originally aimed specifically to fulfil a requirement in the American market. Over 100 have been sold in the US as well as in European countries including France, Italy and Germany, but none yet in the UK. To address this, Whitehouse Machine Tools has been appointed sole UK sales and service agent under an agreement signed shortly before MACH 2012.

A novel design feature is the machine’s ability to be expanded retrospectively in the field, easily and affordably, from two to six pallets and from 80 through 120 to 220 tools in about one day.

The result is a highly flexible manufacturing centre that can grow with a user’s business to allow extended periods of high-efficiency, unmanned machining. Large batches, small-lot multiple-part runs, and even ones and twos may all be produced cost effectively. Unusually, both 400 and 500 mm pallets can be used at the same time, offering additional flexibility for oversized parts and fixtures.

Of extremely high quality and precision, the 12-tonne HMC is built to exacting standards and includes thermal control of ballscrew nuts, thrust bearings, Y-axis servo mounting and spindle cartridge by means of recirculating, chilled oil. The machine also boasts hand scraped surfaces for mounting the ballscrew bearing blocks and roller bearing slideways, plus a host of other top end features.

An air/oil mist system delivers precise, pressurised lubrication to the ballscrews, roller guideways and spindle bearings, reducing thermal growth and allowing cutting accuracies of 2.5 microns and repeatability of 2 microns to be maintained. Circularity and roundness are quoted as 3.6 and 2.1 microns respectively if the machine is installed in a temperature controlled environment.

Only top quality components are used, such as the single-piece FCD600 castings for the spindle and pallets, Tsubaki ballscrews, THK heavy duty roller guideways, Tsudakoma rotary table which provides a full fourth axis, BIG Plus 40-taper spindle with face-and-taper contact coupling, Kosmek tapered cones on the automatic pallet changer which also has high pressure air clean, and Fanuc 31i NANO control.

The machine is also fast. It has a 15,000rpm / 22 kW direct drive spindle and one-second servo-driven tool change, extending to three seconds when probes, special boring bars or heavy tools are being exchanged. 1g linear acceleration to 60 m/min cutting feed rate around the 640 x 610 x 680 mm working volume ensure minimal idle times. Maximum workpiece size is 750 mm diameter by one metre high.

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Whereas the company used only to machine its own zinc and aluminium high-pressure die castings, during the second half of 2009 it started a subcontract milling and turning service, producing components in a variety of materials for a much wider spread of industry sectors.

Since the mid 90s, six Brother machining centres have been supplied by Whitehouse Machine Tools to R D Castings’ Mildenhall factory. They systematically took over from manual milling, drilling and tapping, which was labour intensive and subject to quality variation due to human involvement. All of the Brothers are fitted with twin APC (automatic pallet change) and some are equipped with a Nikken rotary indexer to provide a fourth CNC axis.

According to R D Castings’ Sales and Marketing Director, Anthony Pateman, the production centres are ideally designed for machining castings. In particular he cites fast feeds rates and tapping speeds as well as sub-second tool change time as central to the ability of these high-speed machines to generate profit. Floor-to-floor times, he says, are twice as fast when machining centres without APC are used.

Latest to be installed at Mildenhall was a Brother TC-32BN QT 4-axis machining centre with 16,000 rpm spindle, 40-station BT30 tool magazine, 8,000 rpm rigid tapping, 70 m/min rapids, 20 m/min cutting feed rate and acceleration up to 1.5g. Such a specification makes it one of the quickest machines on the market and underlines why R D Castings has continued to invest in this Japanese manufacturer’s equipment.

Cycle time can be as short as 20 seconds, although at the other end of the scale, a complex gearbox casting recently took 10 minutes to machine on all six faces. It required the use of 26 tools to produce a complex sequence of milled features including numerous undercuts and circlip grooves. Very tight tolerances were held in respect of squareness, concentricity and roundness.

When machining its aluminium and zinc high-pressure and gravity die castings, minimum run is typically 1,000-off but when providing subcontract services, batch runs on the APC machining centres are often as low as 200-off. General tolerances are ± 0.10 mm, reducing to ± 0.01 mm for some bore diameters and flatness features.

Continued Mr Pateman, “The Brother machines have pushed the boundaries regarding the cutting tool technology we use; no longer is carbide tooling sufficient.

“We are now fully committed to the use of polycrystalline diamond (PCD) inserts, which are clamped in dynamically balanced tool holders to achieve speeds and feeds that are not possible by conventional machining.

“Coupled with the benefit of high-pressure, through-tool coolant fitted to the Brother machines, the new tooling allows a level of productivity that a few years ago was beyond our imagination.”

In 1995, when researching the market for its first machining centre, R D Castings’ directors were looking for a fast, compact machine with APC and programming software that was intuitive and easy to use. Mr Pateman says that the Brother TC-32 met all of these requirements and was much faster than anything else on the market for general production applications.

He added that a competitive price, ready availability of spares and good service back-up were also important. In the latter respect, he described Whitehouse Machine Tools’ support as “first class”.

Machine reliability is also crucial to an operation like R D Castings’ and Mr Pateman commented, “I can count on one hand the breakdowns across all our Brother machines over the last 16 years.

“Their reliability and speed combined with the high level of support from Whitehouse has been an unbeatable package for us.”

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