Precision Micro develops new process route for sagittal/oscillating orthopaedic saw blades

Traditionally, such sharp-toothed blades have been manufactured using laser technology, followed by precision grinding, in order to achieve the required tooth off-set. By combining its Laser Evolved Etch Process (LEEP) technology with advanced wire EDM techniques, Precision Micro claims to improve part quality in a more economic and efficient manner. Tooth off-set and blade topography is achieved using the depth etch technique, with dissimilar patterns on each side of the blade. An etch resist is applied to both surfaces and a pattern is exposed on each side simultaneously, using Laser Direct Imaging. This guarantees top/bottom pattern alignment. The exposed plate is then developed, revealing the metal to be etched away. The depth etch process erodes the metal from both sides simultaneously, generating the required topography, but leaving the blade securely within the overall metal sheet. "Depending on the part and the material type, photo etching can become a little uneconomical above 1.5 mm thick, due to the amount of time involved in the chemistry," explains Mark Jarvis, toolroom manager at Precision Micro. "So we profile these blades using advanced wire EDM. Even though it means a second operation, it's a far more cost-effective solution for the customer." Sheets are stacked and machined to produce hundreds of blades in a single cycle. The process can achieve tolerances of <±5 µm that cannot be achieved using other metal cutting techniques. A feature of the advanced wire EDM process is its ability to generate parallel sidewalls with accuracy more than sufficient to create the ultra-sharp tooth profile required. Rigorous process validation, from the design stage through to commercial production, has shown this process route to be capable of consistently delivering quality product. The blades are manufactured from a hardened, Sandvik martensitic stainless steel, characterised by its very good corrosion resistance, high toughness and excellent fatigue strength. Being an ambient temperature process, the blades are not subject to thermal stress and all the original material properties are maintained. This Precision Micro process combination utilises all-digital tooling, making it economical to manufacture the numerous versions of bone saw blades that have been optimised for each specific procedure. The same process route is used to produce prototypes and volume parts, an essential requirement when seeking medical device classification and certification.