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Artificial Hip Joint Manufactured For Precision Fit

Artificial Hip Joint Manufactured For Precision Fit

Artificial hip joints must be manufactured with high precision, especially in the area where the hip stem and the ball joint connect. CERATIZIT has developed an economical production solution for precise interface between hip stem and ball joint.

If a hip joint is affecting quality of life by restricting movement and causing chronic pain, and if conservative treatment methods are no longer helping, the only option is to have an artificial replacement joint implanted – over 200,000 such operations are performed in Germany-alone each year. Those who take this route are hoping for long-lasting improvements. In order to make this hope a reality, as well as a good surgeon and first-rate care, the highest quality ‘spare parts’ are needed.

Prosthetics like this usually consist of a hip stem with ball joint, a hip socket and an intermediate piece to ensure movement is as smooth as possible. Particular attention must be paid to the connection between the hip stem and the ball joint. For the conical surfaces to fit together perfectly, they need to be produced with the highest precision and surface quality. Therefore, the tools used play a crucial role when manufacturing these components. 

“An artificial hip joint consists of difficult-to-machine materials, which not only need to be machined within the narrowest tolerances but also as economically as possible. Ultimately, an artificial hip replacement should be affordable for as many people as possible. We work with great dedication to find suitable tool solutions for these tasks,” explained Dirk Martin, Application Manager Medical at CERATIZIT and member of Team Cutting Tools. 

Meeting Machining Requirements

CERATIZIT is a full-range provider in the machining sector that has a wide range of standard and specially-made tools as well as in-depth machining expertise at its disposal. “With our huge product range and the expertise of our application specialists, we are extremely well equipped for tasks like machining the area where the hip stem and joint ball connect,” stresses Martin. “With our range of tools, we can test all manner of approaches to ultimately find the optimal solution.”

In the case of the artificial hip joint, the customer has particularly demanding and varied requirements. For the hip stem, made from high-strength titanium alloy Ti6Al4V, an angle tolerance of just +/-5‘ must be achieved in the conical connection area. Other tolerances are 3 µm for straightness, 8 µm for roundness and 60 µm for the diameter. It is also important that the specified contact ratio for the cone is achieved and a precisely defined groove profile produced.

The ball joint is made from a cobalt-based alloy (Co-Cr-Mo). Its conical hole must have the same shape, angle and dimension tolerances, as well as the specified contact ratio. However, there must be no marks, ridges or grooves made during machining. Martin mentions another crucial factor: “We need a production solution that is suitable for mass production. This means the machining must be process-secure and require as little monitoring as possible.”

Flexible u-Axis and Special Conical Reamer

To produce the conical outside profile, CERATIZIT’s application specialists opted for pre-machining with a solid carbide conical milling cutter. The subsequent roughing and finishing are then completed using a CERATIZIT u-axis system. 

“This is an interchangeable, freely programmable NC axis for machining centres, which can be used to machine contours or for turning.” explains Martin. 

“Attachment tools and indexable inserts can be used to create contours in holes and external machining work. This usually means that production times can be reduced considerably, while providing optimal surface quality and higher shape accuracy than usual,” he continued.  

This means the desired groove structure can be produced on the stem cone even on a machining centre. This has the benefit that all machining processes can be done on a single machine. Using the conventional process, a lathe and a milling machine would be required, which means additional clamping, aligning, time and money.

To make the conical hole in the ball joint, CERATIZIT’s solution involved the following steps being carried out on a lathe: First, the part is faced to provide a flat surface for the subsequent special solid carbide 180 deg drill with four cutting edges. This is then used to make a hole with a flat bottom. After this an EcoCut Classic drill and turning tool is used to produce the cone with close-contour boring, while a special solid carbide conical reamer ensures the ideal contact pattern and perfect surface quality and tolerance is achieved. The regrinding capability also saves the user further production costs. 

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3D Printing And Titanium — A Life-Changing Combination

3D printing And Titanium — A Life-Changing Combination

3D printing is delivering customisation options that make it possible to create almost any shape using additive manufacturing (AM) technology. In fact, the possibilities of 3D printing are so game-changing, it is even possible to create carbon copies of our own skulls. Sandvik’s additive manufacturing and metal powder specialists are exploring the potential of AM in the medical field, and are preparing for the future of medical implants.

Life-threatening accidents, vertebral damage, chronic osteopathic conditions and side-effects from medical treatment can all cause irreparable damage to patients. The consequences can be painful, debilitating and even fatal, so we must develop solutions to help the human body overcome challenges, enhance the healing process and improve patient prognosis. Medical implant technology has developed vastly over the years, and one of manufacturing’s most disruptive technologies is set to transform the way we treat patients.

Medical implant developers require a manufacturing technology that delivers speed, individualisation and the ability to produce complex designs. 3D printing, paired with bio-compatible materials like titanium, is demonstrating its evident potential as the medical industry’s manufacturing technology of choice for life-changing solutions.

In the past, surgeons used metal mesh to replace areas of the body such as skull bones, which tended to be weak and lacked precision. 3D printing eliminates these flaws because it uses medical imaging to create a customised implant, shaped exactly according to the individual’s anatomical data. This means that the patient can be fitted with an exact match to replace the lost or damaged area of the skull.

In Sandviken, Sweden, lies one of the world’s most cutting-edge titanium powder plants. At the plant, Sandvik’s experts are unlocking the potential of 3D printed titanium devices for the medical industry. “Titanium, 3D printing and the medical sector are the perfect match,” explains Harald Kissel, R&D Manager at Sandvik Additive Manufacturing.

“Titanium has excellent properties and is one of few metals accepted by the human body, while 3D printing can rapidly deliver bespoke results for an industry where acting quickly could be the difference between life and death.”

In addition to titanium’s material benefits, AM can help overcome some of the challenges when producing medical implants and prosthetics. Typically, the process of being fit for a prosthesis involves several visits to create a device that fits a patient and their needs. As a result, the time between a patient’s life-changing surgery and them receiving their device can be painstakingly slow.

“If a patient undergoes a serious accident, one that destroys areas such as the skull or spine beyond repair, they simply do not have time to spare to ensure their reconstructive devices fit correctly. Instead, they’re given solutions that work, but aren’t tailored to their bodies,” Kissel explained.

“Long waiting times and a lack of customisation can really impact how a patient feels after they’ve undergone a life-changing event or procedure. Even in 2020, there are still prosthetic patients using devices that do not move, or are simply just hooks.”

“Using computer tomography, it is now possible to optimise designs that simply cannot be produced using other manufacturing methods. What’s more, we can make our designs lighter, with less material waste and in shorter lead times. Patients could receive a perfectly matching device, in less time and using a high-performing, lightweight material.”

In summer 2020, Sandvik’s specialist powder plant was awarded the ISO 13485:2016 medical certification for its Osprey titanium powders, positioning its highly automated production process at the forefront of medical device development. As AM disrupts many areas of manufacturing, it’s clear that its potential in the medical sector will be life changing.

Sandvik is also part of one of the most ground-breaking research projects within the medical segment to date, contributing with its extensive material expertise. The Swiss M4M Center in Switzerland is a public-private partnership initiated by the Swiss government, aiming to evolve medical 3D printing to a level where patient-specific, innovative implants can be developed and manufactured quickly and cost-effectively.

“The Swiss M4M Center is intended to build up and certify a complete end-to-end production line for medical applications, like implants. Being able to facilitate this initiative through the unique material knowledge that is found within Sandvik is an empowering experience. Joining forces with an array of experts to reinvent the future of medical devices as well as the lives of thousands of people — is an experience out of the ordinary.”

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A Remedy To Uncertain Times

A Remedy To Uncertain Times

Medical manufacturing company Straits Orthopaedic delivers on diverse medical applications with their flexible ANCA CNC grinding machines. Article by Duncan Thompson, ANCA.

If manufacturers have learned anything over the recent months, it is that you can take nothing for granted. Circumstances can change quickly and how you are set up to respond can be the difference between your business flourishing or folding. Recognising this, Straits Orthopaedic has been investing in ANCA machines as part of their strategy to be a flexible manufacturer in the medical tooling and component market. 

The events of COVID-19 this year are perhaps the most extreme example of rapid market change and resulting uncertainty. But, even after more normal circumstances return, manufacturers need to be constantly vigilant, watching and responding to changes in the market that provide new opportunities or necessitate a pivot in their business. 

ANCA CNC grinding machines have long been recognised in the industry for their flexibility. It is this kind of flexibility that allows ANCA users to produce parts for diverse applications, so they are not limited to just one customer or one application. Powerful software allows users to create programs for a broad range of cutting tools and components. While modular machine design means features can be easily configured to suit the varying needs of different applications. 

The medical industry offers exceptional and diverse opportunities for manufacturers, with ANCA grinding machines supporting international markets in the production of complex bone rasps, long rotary reamers and tiny dental drills and burrs, just to name a few. 

Straits Orthopaedics, based out of Malaysia, is a case-in-point of a company taking advantage of ANCA’s diverse capabilities. Already well established for contract manufacture of medical components, Straits Orthopaedics’ first tool grinder was an ANCA FX5.

Senior Process Development Engineer Vidyadhiraj Vidyadharan comments, “Custom made tools have become a significant part of our growth in the medical tool market. We need the ability to make special tools to varying customer requirements and to be able to do it quickly. ANCA’s FX5 with its flexible tool programming software has certainly allowed us to meet this need. Demand for our diverse range of medical drills, reamers and planers easily justified our second FX5.”

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