Typical of Key Precision’s drive to reduce the cost per part produced in its sub-contract precision-turning business is the machining of complex lock components that previously required as many as six individual operations but are now being turned, milled and drilled in a single cycle on sliding-head turn-mill centres in under a minute.
Neil Dawson, managing director of the Cannock-based firm, says that his working life — along with that of his brother Adam — changed in 2004 when the two of them phoned their father to tell him they were driving home having just bought a new Citizen L32 CNC sliding-head lathe from Bushey-based Citizen Machinery UK Ltd (Tel: 01923 691500 – www.citizen-miyano.co.uk) and were going to install it in their shed.
In reality, the two graduate mechanical engineers were following in their father’s footsteps. He had a business manufacturing bearings in the West Midlands; and though now proud of his sons’ achievements, he was a little concerned at the time — especially as the budding entrepreneurs had no work to put on their new purchase.
He had no reason to worry, as the brothers had soon won an important two-year order. The contract was the result of their re-design of connector components (made from welding-grade aluminium); these formed part of an oil cooler assembly that was installed in a range of popular vans. For the previous supplier, these components proved very troublesome to make, as they were produced from 1in square bar. Key Precision’s solution was to offer a redesign for certain areas of the parts, so they could be machined on the Citizen using round material (with the flats milled in the same cycle). This approach not only achieved an appreciable reduction in cost but also gave a problem-free and consistent production cycle.
Steady growth
Such was the brothers’ enthusiasm that, over the first few years, the company doubled its sales each year. It achieved a turnover of £1.6 million in 2010 and £1.9 million in 2011. This year, the target is to achieve £2.4 million.
Key Precision is still a family business, but it is now housed in three units totalling over 10,000ft2 on two sites. The company employs 24 people and has 10 CNC machines: six are Citizen CNC sliding-head turn-mill centres, two are other makes of sliding-head machines, and two are Miyano fixed-head turn-mill centres (an ABX-64SY and BNX-42SY). Generally, the machines run ‘round the clock’. Last year, Mr Dawson senior’s machine shop was transferred into the third unit (about half a mile away), adding a high-volume production capability with 15 Wickman and Davenport multi-spindle autos. This factory unit is also running ‘flat out’, with five people producing some 400,000 parts a week (just three part types make up three quarters of the output).
Adam Dawson, technical director, says the fast set-up capability of the Citizen sliding-head machines allows the company to produce pre-production samples and prototypes, as well as provide ramp-up and ramp-down production prior to transferring component manufacture to the multi-spindle autos as quantities build up. Materials machined in the CNC operations include titanium, stainless steels, brass, phosphor bronze, copper, high-tensile steel and mild steel. Typical cycle times range from 10sec to 4min.
The six Citizens are primarily engaged in producing batch sizes that start at around 50 parts. Installations that followed the original Citizen L32 were two Citizen K16-Vlls, a top-of-the-range Citizen M32-V (which features two Y-axis cross feeds) and two Citizen L20-Vlls. Neil Dawson says: “When we compared their specifications against other machines available, the Citizens were a far better solution for us due to their easy and quick resetting. We also specified each machine with high-pressure coolant, an off-feed conveyor and paid attention to swarf removal. We even invested in Citizen’s call-out system, in case the machines stopped at night when running unmanned.”
Overlapped operations
The fixed-head Miyano ABX-64SY, which has a 64mm bar capacity, has proved to be a real workhorse; and with a bulging order book, the brothers supplemented this machine with a Miyano BNX-42SY from Citizen Machinery UK, to relieve capacity on the larger machine. What surprised Adam Dawson when he transferred a 35mm-diameter bar component from the ABX to the BNX was the immediate saving of over 20% on cycle time. This, he says, was largely due to the configuration of the machine and the ‘overlapping capability’ of the Citizen control.
The Miyano ABX has a 15kW main spindle and a 7.5kW secondary spindle; both have C-axis positioning and a top speed of 5,000rev/min. There are two 12-station in- dependent turrets that can access both spindles. The top turret has four axes (including a Y-axis cross feed) and supports compound machining, while the lower turret has three axes of movement. Both turrets have all-driven positions (via 4.5kW 6,000rev/min motors). To increase the capacity to accommodate billets up to 125mm in diameter, Key Precision has recently added a chucking option to the machine.
Neil Dawson says: “Such is the level of flexibility and change-over on the ABX that we often run one long-running job in the day and change over late afternoon to run a different part through the night. We have quick-change collets, so there is never any hold-up to accommodate different bar sizes. There are ample turret positions for tools, and to change the program takes a few seconds.”
Typical of the single-operation work run on the ABX are plastic Polypipe cutters used by gas companies to cut holes in pipes — in-situ — for connectors. Made from mild steel, processes involve turning, milling, thread chasing and broaching a 12mm A/F hexagon. The component incorporates a machined cutting edge that has a maximum flat width of 0.5mm for cutting the plastic material. These cutters are produced complete in a single cycle in regular batches of 4,000 — and in a cycle time of under 2min.
For Key Precision, the latest Miyano BNX — a machine with a 42mm bar capacity — offers a particular advantage, as it incorporates (for the first time) a Citizen-developed control. This system has won praise from the Dawson brothers for its operator interface and quick setting capabilities. The BNX has an 11kW 6,000rev/min main spindle delivering 6,000rev/min and a 5.5kW 5,000rev/min second spindle; both are accessed by a single 12-station all-driven turret with ±40mm of Y-axis cross feed.
Two years ago, Key Precision won AS 9100:2003 accreditation; early last year, it received the Black Country Supplier of The Year award. These are opening new doors for the firm in the aerospace and defence sectors, adding to its existing customer base in the electronics, automotive and plumbing industries.
Neil Dawson says: “Everything is coming together. We have funded an apprentice through Aston University who gained a 2:1 in Mechanical Engineering, our CNC machines are running at 98% efficiency in the day and 85% overnight, and we are now looking to develop our own product.”