Feature Production machinery
Milling machines help model engine maker expand business
Not a day passes without Kontax Engineering, a small precision engineering business based in Maidenhead, Berkshire, receiving pre-paid orders from customers around the world for its Sterling model engines. These are now produced with the help of two XYZ Mini Mill VMCs
that Chris was saying we needed to invest in some new higher performance CNC machine tools. The one that stood out at the time, and I haven’t been tempted elsewhere since, was an XYZ compact VMC with Siemens ShopMill conversational control.”
A
lthough Kontax Engineering con- tinues to provide a sub-contract milling and turning service, its step change to international status as a manufacturer actually began some 10 years ago. This was when Chris Guise responded to a situations vacant advertisement posted by Steve Leversuch, Kontax Engineering’s owner and managing director. An experienced CNC operator and pro- grammer, Chris Guise’s involvement prompted the first step into CNC milling and the company’s eventual emergence as the world’s largest manu- facturer of the world’s smallest com- mercially available Stirling engines (typically around 15cm high). “It was during one of the slacker peri- ods in our sub-contracting activities that we began making these small model engines almost as a hobby,” recalls Leversuch. “However, we found we could sell them relatively easily, espe- cially if they could be priced so that enthusiasts would be buying from their ‘back pocket money’. We began without a comprehensive business plan, but we were soon introducing new models and the demand from as far afield as the USA, Australia and Japan became such
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Steve Leversuch (right) and Chris Guise of Kontax Engineering have transformed an interest in model Stirling engines into a thriving interna- tional business
IINSET: A Kontax low-temperature differential model Stirling engine – the emphasis is on visual appearance as well as performance
XYZ Machine Tools T: 01823 674200 www.xyzmachine
tools.com Enter 317
Ideally suited to the type of work and batch sizes typically undertaken by Kontax Engineering, the XYZ Mini Mill 560 vertical machining centre is capable of machining a wide range of components within a 560mm (X) by 400mm (Y) by 500mm (Z) working envelope contained within a 2,000mm (width) by 2,060mm (depth) footprint. The sturdy Meehanite ribbed cast iron construction ensures that full use can be made of the 15hp (11kW)/8000 rev/min dynamically balanced BT40 spindle, with induction hardened and ground Turcite-coated box ways ensur- ing smooth operation at axis travels up to 20m/min. A 12-station toolchanger holds tools up to 100mm diameter. The ease with which the Siemens control can be programmed both on- and off-line was a deciding factor, in part because Leversuch is not a for- mally trained engineer. In fact, he was working as a sales representative for what was at the time the UK’s largest steel stockholder when he became increasingly curious about what hap- pened to the steel bar after he had taken the order. “So I started working in an auto shop on Saturday mornings, learning how to make things and how it was all done,” he says. “I became more and more interested in the engi- neering side and less and less inter- ested in selling. Anyway, some 30 years ago I was talking to one of my steel customers who offered to put work my way if I bought a small engi- neering business from him. To cut a long story short I decided to take the gamble, although it took five years of doing the day job and working evenings and weekends before I was
able to complete the purchase… and it’s been an interesting ride ever since.” Kontax Engineering now has two XYZ Mini Mill 560 VMCs, which machine the majority of the steel, alu- minium and brass components needed for each model engine in batches up to 200-off. Several of the components require custom-made fixturing as well as the use of rotary indexers, and all have to be machined to tight toler- ances with an emphasis on visual appearance as well as performance. The manufacture of flywheel spoke discs, for example, begins with the supply of pre-cut 8cm diameter sheet metal discs that are turned to the required close tolerance OD size before being loaded, polished face down, into custom machined collets held in a hydraulic fixture secured to the table of the XYZ Mini Mill 560. The first machining operation is the precision countersinking and then drilling of irregularly spaced PCD holes (to ensure the correct orientation of the flywheel during assembly of the engine) for the securing screws that will attach the completed flywheel assembly, polished face to the front, to the rear face of the axle boss. This is followed by drilling and reaming of the centre hole that will house the axle bearing. The final opera- tion is milling of the spoke profiles, designed to be aesthetically pleasing, with one of the five segments of the cir- cumference being slightly wider, so as to act as a counterbalance to the inher- ently out-of-balance front boss. Other components are machined on fixtures held in a rotary indexer located along- side the hydraulic fixturing. Kontax Engineering’s model Stirling engines are available fully assembled or, an increasingly popular alternative, as a kit of parts taking a couple of hours to assemble. This do-it-yourself option explains the care taken at the design stage to avoid any possibility of incorrect assembly.
MARCH 2011 Factory Equipment
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