Largely as a result of receiving new medical and aerospace contracts, MRT Castings (www.mrt-castings.co.uk) an aluminium die-casting company based in Andover — has seen its turnover increase by 70% in the last 12 months.

The tonnage of the company’s output has scarcely changed; the increase in business is nearly all derived from machining the castings, which are becoming ever more complex, and from producing sub-assemblies.

A user of Brother machining centres since the early 1990s, MRT has invested in six more machines in the last year and a half. Supplied by UK agent Whitehouse Machine Tools Ltd, Kenilworth (www.wmtcnc.com), to cope with extra demand, they bring the total number of these Japanese-built 30-taper machines on site to 18.

Moreover, the latest two — designated S1000X1 — are the first in the UK of a new model with a 1,000mm X axis, which is around one-third longer than that of the largest machine available from other manufacturers of 30-taper machining centres — including Brother until now. Despite having a 1,100 x 500mm table, the S1000X1 has a footprint of just 2.4 x 2.4m.

MRT managing director Phil Rawnson said: “Designers from Brother visited us in mid-2013 to ask what type of machine we would like them to develop next. Consulting with customers is a good sign, as it means that the machine builder is listening to what the market wants.

“As we are milling, drilling and tapping near-net-shape aluminium castings in low to medium volumes and removing typically only a couple of millimetres of material, a 30-taper spindle is suitable for our needs. We told Brother that we wanted a larger machining envelope to give us more flexibility in the way that we fixture parts. Two years later, in June this year, the two S1000X1s were on our shopfloor.”


Because a 30-taper machining centre with a 1m X-axis stroke did not previously exist, Mr Rawnson bought 40-taper machining centres to process MRT’s larger castings. There were disadvantages, however, as 40-taper machines are of unnecessarily high power for skimming off 2mm of aluminium; they also tend to cost more to buy. Furthermore, the rapid traverses and spindle acceleration/deceleration are slower, so cycle times are longer and productivity is lower.

The S1000X1 design avoids these negatives by providing a highly productive machine with 50m/min linear rapids (slightly higher for the 300mm Z axis). Tool change by the 21-station turret takes under 1sec, giving a chip-to-chip time of 1.4sec — and this is performed at the same time as both the X and Y axis movements and rotary-table indexing to reduce idle time further. This rapid cutter exchange is important, because a large mix of tooling is needed to machine MRT’s castings.

A new ISO control — the CNC C00 — provides faster processing, more functions and higher accuracy — especially in 3-D applications. Indeed, MRT’s existing programs for its 16,000rev/min Brother machines run 10% faster on the S1000X1s without any modification — sometimes even faster, depending on the type of cycle and the number of tool changes. If a program is transferred to the latest S1000X1 from an earlier 10,000rev/min-spindle Brother machine fitted with the previous control, average cycle time savings are even higher, at around 30%.


Mr Rawnson says there are four ways that MRT takes advantage of the extra working volume offered by the Brother S1000X1s.

“First, we had a 150mm column riser fitted to both machines, so that we can swing a 550mm part on a trunnion arrangement comprising a rotary table and tailstock. By using a bridge-style fixture with pockets in the fixture plate, the fourth CNC axis allows machining to be completed on four faces of a casting in a single operation. Secondly, if we need to hit the remaining faces of a component, we can carry out the secondary machining operation sequentially by fixturing parts side by side on a single fixture.

“Thirdly, we can fixture a larger number of smaller parts to fill the table; by putting more castings under the spindle at the same time, fewer tool changes are needed per component, and productivity is increased. Lastly, we can machine castings up to 1m long in three or four axes. Shoehorning larger parts onto our smaller machines is a thing of the past.”

MRT uses four pressure die-casting cells, the fastest of which can produce a casting every 40sec; and nearly all of the castings need to be machined in cycle times ranging from 2min to 20min. To keep up with the metal-cutting requirement over an extended day shift, the 18 Brother machines are of two configurations.

Eleven of them have fixed tables, while the others are equipped with automatic pallet changers with access to a total of 25 pallets — set up with rotary trunnions and dedicated fixtures to speed change-over to the next batch, which typically occurs every one or two days per machine.

The twin-pallet Brothers are generally used if cycles are short — say, less than 5min — to minimise spindle idle time during sequential op 1 and op 2 machining on six sides of a casting. Fixed-table machines are more economical if cycles are longer, as one operator can load and unload a pair of machines to complete the two operations in tandem.

The accuracies achieved are impressive, sometimes down to a couple of microns for bearing bores. For example, some electrical assemblies comprise up to 20 individual castings, and tolerance build-up can become a problem if such tight limits are not held. Other work for the electronics, defence and top-end lighting sectors also stipulates tolerances that are sometimes very tight. Mr Rawnson says that parts coming off the Brothers are not only dimensionally accurate but also highly repeatable.

In conclusion, he says: “Whitehouse Machine Tools supplies every new machine as a turn-key cell complete with tooling, through-spindle coolant, a fourth axis, mist extraction and tool and part probing. Programs, fixtures and tools are freely interchangeable between the machines, which gives us a lot of production flexibility.

“MRT Castings has been a family-run business since its formation in 1947 and has always worked in partnership with its customers, constantly evolving to meet their demands. Brother has adopted a similar partnership approach by listening to what we and other sub-contractors want and developing new machines to fit our changing requirements.”