Clean bill of health – medical engineering review

At the Billingshurst facility of Delta Tooling, the VISI suite of CADCAM applications from Vero Software (01189 756084) has been instrumental in helping to develop the world's most advanced myoelectric prosthetic hand. Delta Tooling was approached around two years ago by prosthetics specialist RSL Steeper to assist in the manufacture of the bebionic3 prosthetic hand, which is transforming the lives of amputees worldwide. The bebionic3 utilises leading-edge technology to trigger a total of 14 programmable grips. So versatile is its functionality, that it allows users to perform everyday tasks, such as using a computer keyboard, chopping vegetables and even tying shoelaces. Delta Tooling manufactures five parts for the hand, including the aluminium knuckle, the plastic sub-section it connects to and a complex thumb bracket that allows the opposable thumb to rotate and move back and forth. MAXIMISING ON VISI "The initial concept of casting or moulding the components, followed by finish machining operations, gradually evolved into fully machined parts to improve quality and maintain consistency," says Delta Tooling director Gary Childs. "Maximising our use of VISI Machining, we developed strategies that not only machined the parts from solid billets, but produced them in highly competitive cycle times." The company recently invested in a Mikron UCP 800 Duro from Agie Charmilles (02476 538666) and updated its machining software to the latest 5-axis release of VISI 20. "This gives a better quality finish on the product, thereby reducing the number of set-ups and producing cost-effective production runs," says Mr Childs. "First, we carry out various checks on the file to ensure its integrity. Then we'll assess the part's machineability, using VISI Machining's collision control and kinematic simulation." A new feature in VISI 20, which Mr Childs says represents "a huge step forward", is the dynamic incremental stock (DIS) command that creates the stock model automatically from the uncut material of previous toolpaths, to be used as reference data for subsequent milling operations. It also trims the toolpath automatically to remove unnecessary movements and fresh air cuts. "This allows us to rough machine from one side of the component," he explains. "When we turn it over, we have a new machining cycle that allows us to rough again, but we're not cutting fresh air. This reduces machine cycle time further, making us even more efficient." Elsewhere, at the Birmingham headquarters of Salts Techstep, the requirement is quite different. Here, CADCAM software from Delcam (0121 766 5544) has helped, increase the volume of custom orthotic insoles from around 50 up to 1,000 pairs each month. Other benefits from the change include a reduction in delivery time, from a minimum of 72 hours using previous manual methods to as little as an hour using the digital approach. Phil Wells, technical support manager at Salts Techstep, was an early advocate of the use of CADCAM in the orthotics business. He started out by customising Delcam's standard engineering software, PowerShape for design and PowerMill for machining. Away from conventional metal removal processes, the medical sector is one of the major beneficiaries of additive manufacturing (AM) technologies, such as 3D printing. For instance, pioneering surgery that could lead to a revolution in orthopaedic adult re-constructive knee operations is about to be performed by Professor Justin Cobb, who holds chair in orthopaedic surgery in the Department of Surgery and Cancer at the Imperial College Healthcare NHS Trust-based in Charing Cross Hospital, London. The process revolves around the use of 3D printing technology for creating technically complex, bespoke solutions for the patient through pre-operative modelling. Professor Cobb opted to install an Objet Eden 250 3D printer from OPS (01283 585933). His goal was to develop a 'patient-matched' process of conserving as much of the original functional and healthy joint tissue as possible, while lowering the need for ligament reconstruction to help speed recovery. As a result, the new surgical process helps to realign the leg by using pre-operative 3D modelling, followed by modelling the fixation plate and a series of cutting guides to accurately and more quickly reconfigure damaged areas of bone. The Objet 3D printer has also created models for the customisation of the fixation plates used across the periphery of the joint. The custom knee implants, which are designed and produced by specialist Stanmore Implants of Elstree, are then inserted by robot into the patient. Not only should the new process speed recovery, especially in young, otherwise healthy, limbs, it also reduces operating theatre times, from around 40 to 30 minutes, and costs, due to a need for only one tray of sterilised surgical instruments versus the previous five. FIXTURES FOR BRAIN SURGERY Over in the USA, AM technology from EOS (01926 623107) is helping surgical equipment manufacturer FHC Inc produce more precisely, quickly and economically the electrode insertion guide frames needed for deep brain stimulation. Here, patients are saved a gruelling conventional procedure, whereby stereo-tactic frames fix to the patient's head for many hours of MRI and CT scanning. Instead, to prevent head movement during these critical procedures, a bespoke platform is fixed directly to three or four anchor points on the patient's skull. This provides a unique mounting interface that allows the selected target and trajectory of the electrodes to be built directly into the geometry of the fixture. The so-called STarFix customised stereo-tactic fixtures are manufactured from PA 2201 polyamide powder in an EOS Formiga P100 machine. From receipt of a patient's file, turnaround time to supply a fixture is around 24 hours in the USA, 72 hours in Europe. In comparison with previous AM approaches taken by the company, STarFix CEO Ron Franklin says: "The Formiga machine is smaller, lighter and more accurate than what we were using before, added to which we have been able to include new functionality into the platform, while reducing the cost of materials and processing. "We are able to build more parts into the platform and include additional features that simplify the mounting of various devices, so it is more precise and assembly time in the operating theatre is reduced." At Oxford-based Adlens, the success of instant-prescription, variable-focus glasses, modelled on the iconic look of rock 'n' roll legend John Lennon, have been aided by the use of a SmartScope ZIP 250 metrology platform from OGP UK (01283 585933). With the capability of each individual lens to be adjusted at the turn of a dial, the eye's natural dynamic behaviour can be modelled quickly and the quality of vision restored. Critical in the decision to install the SmartScope ZIP 250 (pictured) was its versatility to incorporate multiple measuring techniques, switching from one to another as a seamless operation in a single setting. The OGP machine, according to Adlens quality manager and test engineer Johannes Prins, can be used with one setting for touch-probing, non-contact scanning of solid and transparent materials and surfaces, and non-contact data capture in any plane, due to the 5-axis positioning of the part. In addition, the high resolution video camera, with 5:1 zoom optics and automatic calibration, make detailed examination of the glasses frame a simple twist of the control. Mr Prins says: "Without the SmartScope, we would have had great difficulty in gathering realistic measurements that were consistent. Furthermore, we would have struggled with the lead time required to launch the product, which could have resulted in the possibility of the business being challenged." He concludes: "We also needed to understand what was happening in the early life-cycle of the product-track: the results of design changes; fine-tuning and alterations to tooling; and most importantly, keep a detailed history in-house. This would have been very difficult using different types of measuring equipment and having to reset for different measurements. Also, we would never have had everything under our control, if we had to use outside sources." Box item 1 of 1 Midas touch at Randox Polyurethane mould and toolmaker Midas Pattern Company (01234 358394) is celebrating its achievement in providing customer Randox with no less than 26 reaction injection moulding (RIM) tools in 10 weeks. The fast-turnaround tooling project was critical to the scheduled launch of the new Randox Evidence Evolution, claimed to be the world's first fully automated, random access biochip testing platform, which is anticipated to transform current diagnostic testing practice. The debut of this new technology called for the development of a visually stunning instrument casing, incorporating a range of colours and finishes. This was quite a challenge, as the largest moulding stands at 1668 by 1191 by 403 mm, and all parts were specified to be cast in flame-retardant material to allow for internal shipping and the obtaining of necessary approvals. Altogether, the equipment casing incorporated a total of 26 RIM components, as well as numerous smaller injection moulded parts – and naturally the budget needed to be managed carefully, too. All tools were delivered on time and no modifications were required to any of the 26 parts produced – clear evidence of really effective design for manufacture processes. First published in Machinery, March 2013