Innovation in the blood

Some companies just have innovation in their blood. Such a company is investment caster and machinist Micro Metalsmiths, North Yorkshire, which has two sites – Kirbymoorside and nearby Pickering, both a few miles north east of York. The company was a keen user of advanced automated technology in the 80s – Matchmaker FMS 3 multi-pallet horizontal machining centres, with 300 mm square pallets, for those with a memory of such machines; was an early and prolific adopter of Renishaw touch trigger probe technology, and paid much attention to combating machine errors through the use of external geometric and temperature compensation software, developed by Huddersfield University. Fast forward a quarter of a century and the company is again adopting innovative machining techniques and once more anticipates minimising machine tool errors through external error correction software, again working with Huddersfield University. This time the investment, at its Pickering site, has been in nine 21-tool Fanuc Alpha T21i Fb Robodrills, featuring 24,000 rpm spindles(600 UK, 01924 415000), while a new development from Huddersfield is in the process of being finalised. Established by managing director Christopher Shaw in 1964, Micro Metalsmiths is a specialist in the design and manufacture of microwave guides, with which it generates about half of its turnover; the other half comes from investment casting and machining. Exports represent half of turnover, although, for the microwave products, they constitute 90 per cent of production – half to the US and half to Europe, according to John McGreevy, director. The company boasts some 500 different microwave designs, and it also makes all its own mould tools, manufacturing 130 this year, he adds. Image: One of nine Fanuc Robodrills installed at Micro Metalsmiths CASTING CREDENTIALS Micro Metalsmiths' speciality on the investment casting side is its use of a special plaster-based mould body, developed in-house, plus the use of wax blends that support the production of the "exceptionally fine surface finishes and close tolerances" that are demanded by castings for microwave applications – the company is reluctant to make openly public the figures. The use of soluble wax cores also allows for complete flexibility of internal geometry, from which the special plaster material is washed out with high pressure water jets. The company claims that other investment casters often refer customers to Micro Metalsmiths when they are unable to meet specifications themselves. Castings produced by the company weigh from one gram up to 9 kg, for aluminium parts, and from 1.5 grams up to 20 kg when brass is the material – the plaster block process does not support steel casting. As standard, parts fall within a volume of 200 by 220 by 110 mm, or 300 by 150 by 200 mm, in the case of large items. In comparison to die casting, while a die-cast tool will last for 80,000 parts, a mould tool to produce waxes for the plaster block process "will last for ever" and will cost 20 to 70 per cent less to make, says Liam Todd, one of Micro Metalsmiths' most experienced casting engineers. Part runs of up to 500,000 have been undertaken by the company, he offers, and, while it is commonly thought that investment casting offers a slower production rate, that is not always the case; it depends on the tooling, says Mr Shaw. As an example, he examples that one microwave part was tooled up to produce one part every four seconds, while a commercial part was produced in a 16-impression mould that cycled every 15 seconds. Image: The Pickering site is laid out in a neat, organised fashion, underlining the drive for efficiency Micro Metalsmiths' list of customers attests to its level of quality and service – the European Space Agency; Rolls-Royce; Rutherford Laboratories; Bentley, Dutch car maker Spyker; McLaren F1 (indirect); and Renault F1 (indirect); Alstom, railway industry; and Balfour Beatty, trams. Other areas to which the company has supplied parts include paint spray gun heads, fall arrester mechanisms, ATM parts, shopping trolley items, coin mechanisms, musical instruments and hang glider frame fitments. Indeed, there are very few sectors where the company is not active. The credentials of the company underline its unusual, almost one-off status as a plaster block investment caster and machinist of precision parts to very high standards of finish, function and dimension. So, when it came to investing in new machining technology, essentially to improve on the Matchmaker FMS machines it had installed all those years ago – some of which are still operating at the Kirbymoorside factory – Mr Shaw took a typically scientific and analytical approach in selecting the equipment, and then supported that with a robust technology implementation plan, with the result showcased at an Open House event on 27 May at its Pickering site. NEED FOR CHANGE The need to change, explains the company, was because the equipment currently in use, predominantly CNC milling machines, varied in age from 10 to 25 years and operated at maximum spindle speeds of 10,000 rpm. In spite of high quality maintenance and the use of dynamic temperature compensation in some cases, the market place required higher degrees of accuracy than the installed equipment was able to produce, without exceptional measures. Married to that was an aim to operate one manned shift and two unmanned nightshifts to drive down cost. The current machines could not reliably support that, because of the occurrence of tool breakage with the small diameter cutters, down to 1.5 mm, that are increasingly needed for modern high-frequency microwave designs and where cycle times of 8 hours or more per component are common. The company decided to combine the two main machining areas and to look for a machine tool that would suit both the short-run requirements to finish off castings and the long-run requirements of the latest, sophisticated microwave devices, machined from solid material, which were requiring cycle times of up to 20 hours on the older equipment. Image: Microwave products, such as these, present a challenge to unmanned machining – the small tools employed demanding the very best machine rigidity and dynamics to avoid tool breakage: a problem with the company's older machines The managing director goes straight to the heart of the matter when describing the Fanuc machines' qualities. "These machines are the only ones outside Japan that are fitted with the Fanuc 31i A5 control. The interoperability between machine and control was a high selling point. And the machines' ability to work with very small diameter cutters is amazing," he enthuses, adding: "I hadn't realised how advanced these machine had become." As an example, he instances the use of 2 mm diameter cutters, machining four aluminium microwave parts over an 8-hour unmanned cycle, one component placed on each face of a fourth axis rotary table. Rego-Fix balanced toolholders (PCM Tooling, 01424 753174) are also part of the equipment equation, as are Renishaw (01453 524524) tool breakage and tool measurement technology: the former to catch any tool breakages, the other to compensate for any Z-axis thermal growth. The company has used Renishaw spindle probes for more than 25 years to obtain initial datums when machining castings, so the added functions were readily accepted as part of standard procedure. An additional benefit of the Fanucs is the fact that machines require no special foundations. They don't "walk around", even at the very high acc/dec rates of which they are capable – "We've saved a fortune on concrete," says the company. The level of technical detail that Mr Shaw is in the habit of discussing is underlined by the fact that the head of Fanuc Robomachine Europe, Minoru Fujita, also attended the Open House for further discussion about CNC and motion control details, while, in addition, Dr Andrew Longstaff of Huddersfield University was there to discuss compensation software integration. ATTENTION TO DETAIL But the managing director's attention to detail is also demonstrated by the installation and application details. The initial order for new equipment was for six machines, ordered in early 2008. These were divided among the three machining areas then in existence within the company. One machine was fitted with a 5-axis system for use by toolmakers; one was fitted with a fourth axis indexer having a 5° resolution for handling certain microwave machining problems; and the remaining four were fitted with full fourth axis systems – two being dedicated for use in machining castings and two for microwave components. These machines were used mainly for process development, for training and for new part production until this year; three more machines were ordered in late 2008, one of which remains to be delivered. "Thorough training and familiarisation is vital," says Mr Shaw. "I always allow a year for the process." And the results? Compared with its earlier equipment, Micro Metalsmiths has cut the times for making tooling down by between 50 and 75 per cent; casting machining cycles have been reduced by more than half and long-run machining for microwave components by two thirds. These cycle times will continue to be improved, it is added. In addition, the company has begun to eliminate several separate tapping processes, because the new machines can handle sub-2 mm threads, which its previous equipment could not manage. A substantial reduction in deburring times via careful programming is also anticipated. Accuracy is "greatly improved" and this is seen directly in reduced 'tuning' times for complex microwave components. Tuning is needed simply to overcome tolerance spreads and, whereas its most complex devices had required eight-hour 'tuning' times employing highly skilled individuals, these have already reduced to three hours. They will be reduced further as the company introduces procedures to cope with the inevitable changes in dimensions that temperature changes provoke, with the company likely to continue its partnership with Huddersfield University, in this respect. First published in Machinery August 2009