The £210,000 contract originated from a visit to Mollart’s stand at the 2013 China International Machine Tool Exhibition in Beijing. The customer had previously heard of Mollart’s reputation and the success of four previous Mollart gundrill installations in China on similar components within the country’s medical industry.
Says managing director Guy Mollart: “While America is the largest medical market, this sector in China is the fastest growing. Worldwide, Mollart is well established having already delivered over 30 machines for work of this type plus we are providing a subcontract production service at the Chessington headquarters which adds to our level of expertise.”
Surgical grade titanium is difficult to machine and trauma related components such as femoral nails for the Chinese customer, where hole depth-to-diameter ratios up to 40:1 are required, swarf control can be a major problem. Also as titanium is a very poor conductor, this means it is slow to dissipate heat generated in the cutting process which can cause edge welding and failure with conventional drills. In addition, its low modulus of elasticity means slender workpieces can deflect and are especially vulnerable when thin wall sections are involved around the hole.
It was Mollart’s proven development of process solutions to these issues against competitor machine suppliers that contributed to the UK order. Says sales director Ian Petitt: “Critical in the order was our ability to better 0.2 mm TIR between the drilled hole and the outside diameter of the component over part lengths of 400 mm.Also, our in-house development and manufacture of special high precision hydraulic chucks that aid the achievement of geometric tolerances was a key factor. In addition, our own high pressure 70 bar coolant and filtration systems built at our fabrication facility in Resolven, South Wales, means each installation can be precisely tailored to the application.”
The femoral nails involved in the contract range up to 16 mm diameter by 400 mm long with through holes drilled between 5.17 mm and 8 mm diameter. On the smaller holes, for instance, spindle speeds are 2,650 rpm and penetration rates of 30 mm/min can be achieved.
