Paul Cobb — managing director of Nottingham-based Hemlock Engineering — says it appears that a seminal moment has arrived in British manufacturing, as use of the latest ultra-high-speed machine tools allows UK sub-contractors to rival their competitors in low-wage countries and still make a profit.

He has calculated that the average 8sec chip-to-chip time on his 40-taper vertical machining centres (VMCs), of which he has 20, costs his company £400,000 per year in idle time for tool changes alone, whereas the 1.4sec chip-to-chip time offered by his 30-taper Brother Speedios from Whitehouse Machine Tools Ltd, Kenilworth (www.wmtcnc.com), would save Hemlock nearly £330,000 annually if he operated 20 of them.

The received wisdom in UK manufacturing is that lower-volume higher-complexity work has tended to stay on these shores, while higher-volume production of simpler components has largely disappeared abroad, notably to the Far East — and more recently to countries in eastern Europe. Mr Cobb says: “Half of the parts we make are exported, and most of the remainder end up abroad via our UK customers. OEMs are global and can have their components made anywhere in the world.

“Two or three of our contracts for annual quantities of 10,000 or more are under attack every year from competitors outside Europe. OEMs are always looking for lower prices. Sub-contractors in the UK — and presumably other countries in western Europe — often don’t get an opportunity to pitch for business, as their rates are expected to be too high.

"It is true that we would lose money doing this type of work using our 40-taper machining centres, even at the lowest hourly rate feasible. However, our Brother Speedios are so incredibly fast that they give us an edge, typically halving production times and knocking 25% off the cost of manufacturing a part.”

Saving an operation

He also says that with a fourth-axis indexer fitted, one operation can frequently be saved compared with using a three-axis machine, reducing floor-to-floor time by up to two thirds and cutting costs even more. Instead of being 10 or 15% too costly, Hemlock can be a similar margin under the competition when quoting, allowing it to take on high-volume work and still make a profit.

Mr Cobb cites the example of the initial job put on his first Brother Speedio — an S500X1 four-axis machine with a Kitagawa high-speed CNC indexer. The application involved producing a pair of left- and right-hand plates for a printer — 380mm square x 12mm thick — from solid aluminium. For many years, Hemlock had been machining the plates two pairs at a time in two operations per plate on a three-axis 40-taper VMC in a cycle time of just over 48min — 24min for two components. This included 5min to re-fixture them to drill holes in the opposing sides of each plate. Manual deburring of sharp edges took extra time, so in practice only four plates per hour were produced.

On the four-axis 30-taper S500X1, which has a working volume of 500 x 400 x 300mm, a single pair of plates is machined in a 12min cycle that includes deburring with a milling cutter. The parts are ready for delivery as soon as they leave the machine, and the production rate is 10 plates per hour. If the through-spindle-coolant option on the Speedio had been chosen, the cycle time would have been just 8min, equating to 15 plates per hour — nearly four-times the original production rate.

Machine replacement

The increase in productivity provided by the first machine (installed in August this year) was so great that Mr Cobb decided to immediately replace three more 40-taper machines with Brother Speedios — two identical models and an S700X1 with 700mm of travel in the X axis. All four were delivered in the space of one month. The larger machine is fitted with through-spindle coolant and a faster Yukiwa CNC indexer, which rotates at 200rev/min — double the speed of the Kitagawa indexers.

“All the indexers fitted by Whitehouse are not only fast but also very rigid during machining; this is because they are clamped hydraulically at both ends, rather than being held by the servo motor. This configuration allows us to take heavy milling cuts without vibration, maximising productivity and prolonging the life of the cutters. In addition, their speed of rotation enables us to ‘spin’ swarf off the components and fixtures after each cycle, so we save a few more seconds by not having to blow the chips away with an air gun.”

Rather than having a standard 10,000rev/min spindle or the 27,000 rev/min option, all of Hemlock’s Speedio VMCs are fitted with a 7.4kW 16,000rev/min spindle, which Mr Cobb considers optimal for machining the various grades of aluminium that account for around 95% of production. He believes that higher-speed spindles lack torque and require unnecessarily costly balanced tooling, while lower speeds are not enough for the productive machining of light alloys.

Rapid spindle deceleration to zero for tool exchange and acceleration to full speed, as well as quick indexing of the 21-station turret, combine to bring the chip-to-chip time down to 1.4sec, cutting out a lot of idle time. Tapping at 6,000rev/min also promotes high productivity, as do 50m/min rapids in the linear axes, cutting feed rates up to 30m/min and axis accelerations up to 2.2g.

In-cut times

An analysis of the cutting data from Hemlock’s standard VMCs and its new Speedios shows that, on average, the former are in-cut for 45% of a cycle, whereas the Brother machines are cutting for 66% of the time. Another facet of the machines that Mr Cobb appreciates is the power of the latest Brother CNC system. It has faster processing and a 200-block look-ahead, allowing higher-accuracy machining, especially when working in 3-D. It also has many standard features that are costly extras on other controls.

In conclusion, Mr Cobb said: “Our new Speedios will give any of our competitors a run for their money, whether they are in Budapest, Beijing or anywhere else in the world. We plan to replace two of our standard 40-taper VMCs with two Speedios every year for the foreseeable future in a bid to halve production times right across our shopfloor.

"We have around 2,000 job numbers here. It takes time to swap jobs from our existing machines to the new platform because we rewrite each program, rather than just edit and transfer it. Only in that way do we gain maximum productivity advantage from the Speedios.”

Most cycles, which invariably involve interpolation in up to three axes as well as indexer positioning, are created off-line using HyperMill and Mastercam. Further advantages of the new Brother machines are their low power consumption, which reduces electricity bills, and their accuracy (Hemlock routinely holds a positional tolerance of 10µm).