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the frequent changeovers for producing batches as low as 10-off are much faster when there is one machine to set rather than four.
“The advantages of one-hit machining are significant, both for us and our customers,” says Mr Thornton. “For a start, we achieve the required accuracies easily without tolerance build-up between ops. We regularly hold the position of a cross hole to a shoulder, for instance, to within 25μm total.
“The rigidity of the Stars and the absence of play in the axis movements allow very fine features to be machined accurately – we currently have a job going through that needs a 0.19mm hole drilled. Labour savings are considerable due to the reduction in set- ups, so we are able to hold down prices and there is no work-in-progress to manage. Material savings are also evident,” he continues. “Whereas to produce a batch of 50 we often lost 10-20% in the process, now every part is good.” Mr Thornton went on to say that with batch runs normally in tens rather than 1,000s there is a tendency to think that sliding head bar automatics are not the way to go. He and his co- director, Tim Buckley thought differently, however.
Star GB took their interest seriously during initial discussions and helped to formulate ideas on the savings that would be possible. The approach was in contrast to that of other potential lathe suppliers and is the reason Kirkstall Precision chose Star. Originally established in 1988, the ISO 9000 registered subcontractor provides a full service to its customers, from problem solving consultancy and computer aided design through prototyping and batch manufacture. Within its 8,000ft² facility is a wide variety of CNC production plant for milling, turning, wire eroding and grinding, underpinned by laser marking, finishing, heat treatment and both CMM and conventional inspection in a temperature controlled QA department.
A turnkey solution proposed by Mills CNC that included an investment in a new Doosan TT 1800SY (twin turret/twin spindle) turning centre, has delivered excellent productivity and performance benefits to a leading precision manufacturer. The machine was installed at precision air motor
manufacturing specialist, Briggs Brothers’ facility in Redditch in December 2010 and was supplied as the machine tool element of a total, integrated turnkey package designed, managed and implemented by Mills in partnership with Briggs. The actual TT 1800SY machine purchased was supplied with an automatic bar feeder and driven tools and operates as an autonomous manufacturing cell. The machine is being used exclusively to manufacture complex, high precision air motor parts such as front plates, rear plates,
rotors and cylinder housings for Briggs Brothers’ principal customer Norbar Torque Tools, specifically for its Pneutorque PTM series of handheld, air operated torque multipliers. The PTM series has steadily increased in volume over time with production now triple the original requirement per annum. Richard Clark, Briggs’ managing director explains: “These parts were originally manufactured on our two CNC lathes and two machining centres which necessitated transferring parts between machines and cleaning and loading fixtures in between machining operations. This was very time consuming and created bottlenecks and backlogs whilst waiting for machines to become available.” It was this lack of free capacity that led Briggs to initially consider strengthening its existing manufacturing process by adding another machining centre to the
mix and duplicating fixturing. “We approached a number of machine tool suppliers with the intention of investing in another machining centre,” continues Mr Clark. “However, once we had explained what we wanted to achieve to Mills CNC’s pre-sales and applications – their response was very different from the other companies we had approached.” The mainstay element of Mills’ recommended turnkey solution was the TT 1800SY twin turret/ twin spindle turning centre and not a machining centre. The TT 1800SY is a high performance, flexible and productive machine featuring two 15/22kW, 5,000rpm (208Nm torque) spindles, two non-lift servo-type 12 position turrets (24 index positions) with 5.5kW, 5,000rpm driven tool capability. It also has a maximum turning diameter of 230mm on both upper and lower turrets and 240mm maximum workpiece length on both left hand and right hand spindles. Furthermore Mills proposed – and went on to demonstrate – that all PTM series parts could be manufactured solely on the TT machine, thereby negating the need for an additional machining centre and freeing-up all the capacity on the existing CNC lathes and machining centres. PTM series parts are now machined in single set-ups and cycle times have been significantly reduced. Owing to the elimination of transferring parts between machines,
part accuracies have been improved, productivity has increased and the company now has a more reliable and repeatable machining process. In addition to the TT
machine, Mills also supplied the workholding, tooling, bar feeder and CNC part programmes required. And, as part of the turnkey solution, Mills verified the manufacturing process and passed off the machine and all equipment at its own facility and at Briggs Brothers, once installation had occurred. Training was also provided by Mills via the CNC Training Academy.
Mr Clark adds: “The investment was larger than we originally intended but the results have been exceptional. Furthermore, because all PTM series parts are now machined on the TT machine, we have significant turning and milling capacity that we use to manufacture precision air motor parts for a number of different customers operating in the automotive, medical, aerospace and mining sectors. “Mills took the time to understand our business and the issues we were confronting. They recommended a bespoke solution that has paid dividends and delivered the goods.”
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