The versatility of Brother high-speed machining centres has helped Suffolk die casting specialist, RD Castings, to diversify from over-reliance on supplying the yellow goods sector, which proved volatile during the recent downturn.
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.”