The medical sector is big business. The NHS alone spends around £90 billion each year, rising to £110 billion in 2010, while the UK medical technology sector specifically has an estimated £500 million trade surplus in a sector worth about
The machining companies benefiting most from this spend are those combining the latest machine tool and manufacturing technologies with established expertise. A case in point is Wickford, Essex-based Dixons Surgical Instruments, which is celebrating its 60th anniversary. Technical director Jay Dixon, grandson of the company's founder Frank Dixon, suggests that the art of surgical instrument making today revolves around combining modern machining techniques with the traditional crafts of hand-working and polishing.
It was back in the early 1990s that Jay's father, John Dixon, recognised that many of the parts then being produced would lend themselves to CNC machining prior to hand finishing.
"Today, we have a catalogue of 5,000 individual instruments and items," says Jay Dixon. "Our batch sizes tend to be around 20-off, which means offsetting the programming and setting time against the actual cycle time, with three or more operations required to finish most components. To finish parts in a single set-up, we recently acknowledged that investing in a high specification turning centre was the way forward."
Image: One-hit machining is now being employed at Dixons Surgical Instruments
SETTING TIME SLASHED
The result was the installation of a Mazak QuickTurn Nexus 200-II MSY by Yamazaki Mazak (01905 755755). "One of our biggest problems has been machine setting time, so the first criteria that we had for the new machine was the control system," he continues. "Of particular interest with the Mazak control is its conversational language, which makes programming much simpler. You don't need to worry about tool approaches and retractions, or correct spindle rotation: the control takes care of all that. The outcome is that setting times have been reduced greatly."
It is well documented that certain types of machine tools lend themselves to the production of specific surgical instruments. For instance, drilling and sawing procedures during small bone surgery require highly accurate components to avoid vibration and noise. Furthermore, there is a trend in this area towards smaller, more compact instruments of greater complexity.
Tewkesbury-based sub-contract machinist Bushell & Meadows has solved the problem by transferring much of its turned parts production from fixed-head lathes to two new SV-32 sliding headstock lathes supplied by Star Micronics (01332 864455).
"None of our fixed-head turning machines has a counter-spindle, unlike both of the Stars," says Mike Attwood, operations manager. "It means we can produce components in two or three operations that previously needed six or seven. The savings in machining time alone are considerable, around 20 per cent on average, as tool movements are quicker on sliding-head lathes. Faster spindle speed, overlapping machining operations and simultaneous front and rear-working also contribute to cutting idle times."
Another sub-contractor using recently installed turning technology to great effect is Unicut Precision of Welwyn Garden City, where the company's growing expertise in the medical sector is really paying dividends. Following some three years of extensive prototype development with a customer on needle-less drug administration technology, Unicut has been awarded a contract from a Dutch company to produce an initial 10,000 sets of the 12-part assembly worth more than £230,000.
Within the machining cycle on one complex component, Unicut has to ensure the positioning of thread pitch line starts, which have to be relative to slots at the other end of the component within 0.5° in order to enable the user to precisely set the dosage of insulin. There is also a highly accurate milled cam profile that has to be machined within the single cycle operation in order to 'fire' the drug through skin pores.
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"With the capability of our Citizen (01923 691500) sliding-head lathes and Miyano (01384 489500) fixed-head turn-mill centres, we are able to machine each part in a single cycle," explains joint managing director Jason Nicholson. "Furthermore, we have been able to eliminate any need for grinding."
Successful diversification into the medical sector is far from impossible, as High Wycombe-based Erode-All, a sub-contractor known for its motorsport expertise, has proved. Much of the company's recent success in the medical sector is credit to its investment in a series of DMG (01582 570661) and Mikron (GF AgieCharmilles 024 7653 8666) 5-axis machining centres, along with hyperMILL V9.7 CADCAM software from Open Mind Technologies (01865 338026).
Erode-All now produces prosthetic feet and knee joints, as well as tooling, moulds, pistons, valves and valve seats for the respective limbs. In 2008, the company produced 18 different prosthetic feet types and sizes that are currently undergoing testing.
"The 30Mb STEP files have a huge amount of detail and, when using our previous CADCAM package, it would take over 2.5 days to process the information and produce an aluminium limb," says company partner Glen Tavender. "The processing speed of hyperMill now means we can manufacture the same parts in 1.5 days."
Another medical sector manufacturer, Hospital Metalcraft of Blandford Forum in Dorset, has also turned to the latest CADCAM software to help produce its Bristol Maid range of hospital equipment, which includes trolleys, cabinets, bins, stands, carts and shelving systems.
None of the many products is manufactured for stock, as the company is working towards single-piece workflow, with lean manufacturing principles applied across all of its production cells. With everything made to order, achieving a lead time of just three weeks requires automated production technology, with software support provided by Radan (Planit Software, 01225 721330).
Production engineer Ben Spicer, explains: "When we invested in a Trumpf TC5000R CNC punch press, equipped with an auto sheet loader and parts un-loader, we also invested in Radan CADCAM to help us maximise its potential."
Using Radan to program parts, he applies the punch tooling and also decides where the best automated pick- up point will be for the part in horizontal or vertical orientations, so that Radan can nest for the best fit on the sheet and still efficiently unload the cut part.
"Radan software exercises a great deal of control over most eventualities. Additionally, programs can be proved in a single run, with any modifications completed quickly and easily," reports
The company also uses Radan CADCAM software to support its recently acquired Trumpf 3530 laser profiling centre.
Speed, accuracy and reproducibility' were the watchwords employed by Acrobot for the development of the groundbreaking new 'Acrobot Navigator computer-assisted surgery system
, currently in use by health facilities, including Charing Cross Hospital and the London Clinic. They are also the qualities the company looked for when selecting partners for the product's development.
Acrobot Navigator is an innovative surgical navigation system that uses mechanical tracking of surgical instruments relative to the patient to achieve high surgical accuracy – enabling accurate bone preparation and implant positioning by the surgeon. The system features a computer together with two tracking arms, all mounted within a trolley that is rolled to the side of the operating table.
To create the final product, Acrobot worked closely with designers Kinneir Dufort and precision toolmakers Midas (01234 358394), a specialist in the production and supply of polyurethane RIM mouldings and PUR castings, which manufactured the trolley enclosure panels.
Midas and Kinneir Dufort worked closely as a team to create a solution that combined both metal castings and large PUR mouldings to produce a strong and robust machine, while retaining the aesthetic vision.
First published in Machinery July 2009