Machining Medical Implants In Just One Process

Annual sales generated by the medical device sector have exceeded $200 billion for more than 2 years. A variety of sources anticipate an annual global growth rate of 6-8% for the market. In focusing on the sectors that comprise the entire market, however, it is apparent that anticipated growth rates may differ from one to another.

For example, orthopaedic products that comprise clearly defined sectors such as traumatology, spine (surgery on the spinal column) and instrumentation have enjoyed an average growth of 15 to 20% over the past few years.

The cardio-vascular field that requires the use of extremely small, highprecision parts -- such as components used in pacemakers and defibrillators - shows growth between 10 to 20% each year, depending on application and market.

Instrumentation and measuring devices (analysis instruments, pumps, metering devices, etc.) with their variety of work-pieces and precision turned parts made from different materials are also showing a marked upward trend.

The dental sector, with its implants, devices and instruments required for surgical interventions has also witnessed growth of between 10 and 15%.

In general business, activities in the medical and dental sectors have led to the highest and fastest rates of industrial growth in the world. This trend is stimulated by various contributory factors, such as:

• An ageing population (greater life expectancy).
• A better quality of life.
• Aestheticism (dental in particular).
• Medical insurance (repayment of costs).
• Early detection of illnesses and faster treatment.
• Development of new products thanks to technological progress and modern technology.
• Emerging markets such as Asia and the Pacific region with considerable demand from the Chinese market in particular.

No doubt, the volume of medical device parts being machined is constantly growing, especially in the spinal sector. In order to keep pace with global market demands, manufacturers (and designers) require an efficient network of sub-contractors capable of machining parts according to stringent quality requirements.

Looking at peripherals adapted to meet demands of the medical and dental sectors, TORNOS has gained valuable experience by providing these sectors with turnkey machining solutions through innovative product development.

TORNOS is the first manufacturer to develop and adapt loose tail stock lathes to perform highly specific machining processes for certain medical and dental implants. This includes external and internal thread whirling in operating and back-operating modes which may include a high-pressure spray deep-drilling system as well as many other special machining operations.

From among the many innovations produced by TORNOS, machining hip screws on the DECO 20a without reworking, ranks as one of its most valuable developments.

Every year in Europe, nearly 700,000 people suffer hip fractures, which are frequently linked to osteoporosis. With the number of medical facilities currently available, rapid surgical intervention can be conducted to reduce the fracture by applying plates and retaining screws, allowing patients to quickly regain their mobility and pursue their activities.

The hip screws used for surgery are highly complex parts requiring numerous machining operations involving swarf evacuation. Highly resistant materials such as stainless steel and titanium used in these implants often call for several rough-working, finishing and deburring operations.

Without doubt, the best solution in terms of productivity and feasibility is to proceed with the complete machining of the parts in a single chucking operation, using just one machining unit. Thanks to a line of products - the DECO 20a, in this case - it is now possible to machine specific parts within six to nine minutes.

The DECO production tool greatly simplifies allocation of the various machining operations from the bar (main spindle) and for back operations (counter-spindle).

Kinematics of the DECO include 12 numerically controlled axes all with simultaneous interpolation and allow up to four tools to be used simultaneously to execute back-operations 100% in hidden time.

The lathe tool system and various devices developed to date, especially rotating tools, offer numerous facilities for different types of machining operations, using only one production tool.

Specific tooling/operations required to machine hip screws:

• Turning.
• Centering/drilling/reaming.
• High pressure drilling - 120 bar (1).
• Tapping.
• Hexagon broaching/swaging (2).
• External hexagon milling (3).
• External thread whirling in backoperation mode (4).
• Deburring operations.
• Part support (5).
• More than 20 tools.

The DECO 20a loose tail stock lathe lends itself particularly well to hip screws because of its dimensional geometry, chucking facility, re-chucking for back-operation and facility to change between main operations and back operations.

What are the main technical reasons behind further improvement to the overall machining process for these difficult materials?

Phillippe Charles is Technical Sales Manager and Senior Product Manager, Single Spindle Products, for TORNOS, Switzerland. He holds a degree in Micromechanics / Watchindustry as well as a Mechanical Engineering degree from the Swiss Technical University.

TORNOS Technologies U.S. Corp.
Brookfield, CT
tornosusa.com