Better machining

Producing a diverse range of bench top CNC lathes, machining centres, routers and manual lathes for the education market, Boxford's machine shop was coming under pressure. But the decision was whether to invest in new technology or sub-contract machining overseas. "In the end, the choice was simple, as we wanted to maintain production here in Halifax and avoid becoming an assembly plant," says director Paul Barraclough. Having made that decision, he set about finding the best solution to his manufacturing problem. Along with manufacturing manager, Steve Randerson, he visited the UK manufacturing facility of Yamazaki Mazak in Worcester. Impressed with what they had seen, a coach trip was organised for the entire company to visit Mazak's Open House to see what Mr Barraclough describes as "what a successful manufacturing plant should look like." Initially, Boxford was looking to purchase an Integrex multi-tasking machine, but, after talking it through with Mazak, the company opted for a Worcester-built VTC 300C-II vertical machining centre, as this would deliver immediate benefits to production. The decision was also taken to have this 18.5 kW, 12 000 rpm spindle machine fitted with a partition on its 2,000 mm table, a feature that has virtually eliminated set-up times at Boxford. In addition, it invested in Mazak's CPC tool management software, as well as laser tool probing, to allow precise tool monitoring and management. REDUCE DOWNTIME "Our criteria were to reduce downtime and increase productivity, especially on the small batches that we are called on to machine," says Mr Randerson. "The VTC 300C-II has helped us to achieve these aims, with the ability to set one job while another is being machined, eliminating all of our set-up time, a situation helped by the 48-position tool carousel, which is monitored and controlled, along with the sister tools, by the CPC software." Boxford has 'retired' two 10-year-old vertical machining centres, while at the same time made substantial increases in productivity and improvements in overall component quality. It has subsequently also installed an Intregrex 200-IV ST, which, in addition to the standard twin spindles (22 kW and 18.5 kW) and 18.5 kW/12 000 rpm milling spindle, is also equipped with a 120-position automatic tool change, bar feed and workpiece conveyor. This machine was delivered in December 2008 and is used to machine a wide variety of components and operate lights out on batches as small as one-offs. "Our plan is to use a single diameter of bar stock to produce a number of components when we run the machine unmanned. While this will result in some wasted material, the cost savings of being able to run lights-out will far outweigh this expense," adds Mr Randerson. Any components machined overnight will be straightforward chucking jobs that do not require any second spindle working. During the manned day shift, Boxford will make full use of the Integrex. The arrival of the Integrex saw a further seven machines taken out of commission, including every manual machine in the factory, with the two Mazak machines now providing the bulk of the company's machining capacity for the short to medium term. Image: Boxford kept machining in-house and in the UK through investment in Mazak technology Bedfordshire sub-contractor, Anotronic specialises in machining exotic materials, such as titanium alloys, nickel alloys and CPM10V, a 9.75 per cent vanadium tool steel that is four times tougher than D2. To reap the benefits of 5-axis machining in these difficult applications, the company's production director, Martin White, installed a Hurco VM10U vertical machining centre in November last year. He said that it is not unusual to produce in three operations on the 5-axis machine components that previously needed nine separate set-ups. Cumulative tolerance errors are all but eliminated, and the potential for damaging the part through handling and reclamping is much lower. Scrap rates are drastically reduced and so, too, are labour costs. In the first three months of operation, the VM10U was used to machine 10 different components, including a particularly problematic 17-4PH stainless steel part. It was previously produced on any of the company's four other Hurco VMCs, all 4-axis models, which are consequently freed to tackle more jobs of a simpler nature. Says Mr White: "The only downside of using a 5-axis machine is that you are only producing one component at a time, whereas with 3- and 4-axis machining, several parts are often fixtured and completed in one cycle. NO HESITATION "Nevertheless, the benefits of 5-axis strategies using 3-axis cutting while positioning and clamping the other two axes are so great that we have no hesitation in machining the more complex jobs that way. "We are already looking to retool other jobs for 5-axis machining, especially longer runs of parts requiring multiple operations to high accuracy where tight tolerances are tied up to one another."Our intention is to install further 5-axis capacity as soon as possible and on some jobs to progress to fully interpolative machining, using all axes simultaneously." Elsewhere, the introduction by Kalstan Engineering of a Dugard Eagle 1000 vertical machining centre (VMC) has not only solved a series of aggravating downtime problems with existing VMCs, caused by poor swarf clearance and inadequate CNC machining program capacity, but the machine is also enabling the company to stake a claim in the machining of larger workpieces. "All around us, turned parts and components requiring milling are increasingly being sourced abroad, but now, with the new machine installed, we have created lots more opportunities to build the business," says managing director Stephen Kalmar. "Having witnessed the trend for turned parts and, increasingly, smaller prismatic work being sourced overseas of late, predominantly from China, we knew we had to invest in larger milling capacity, if we were to remain in business as a precision sub-contract operation. But to avoid the continual hiccups we are encountering on our three smaller VMCs, I was very careful in my choice of machine and supplier. "In particular, I had to ensure that it would be 'fit for purpose' in terms of being able to cope with the amounts of swarf that are particularly evident when machining aluminium, and be able to handle the size of program required by larger and more complex workpieces. "By making the decision in favour of the Dugard Eagle 1000, with its 1,200 by 540 mm table, integrated coolant flushing system, augers and swarf conveyor, and PCM card for programs, the machine had all the main attributes I was looking for," he adds. "In addition, its 12,000 rpm spindle, chiller and powerful coolant pump added to an impressive specification that includes a positional accuracy of four microns and a repeatability of ± 0.002 mm." Maintains Mr Kalmar: "In addition to being of larger capacity and a higher specification than any of our existing VMCs, the Dugard Eagle also cost less! It's just what we needed to satisfy the demand for larger workpieces from existing customers at home and abroad." To which he includes blue-chip names such as ABB, British Gas and Volvo. Image: Parts machined on the Dugard machine.