https://cdn.mtdcnc.global/cnc/wp-content/uploads/2021/05/17140558/The-CERATIZIT-u-axis-system-allows-the-desired-groove-structure-to-be-produced-on-the-stem-cone-even-on-a-machining-centre-640x360.jpg
    Tooling

    Manufactured for precision fit and quality of life

    • By MTDCNC
    • May 18, 2021
    • 4 minute read

    Manufacturing artificial hip joints demands high precision, especially in the area where the hip stem and the ball joint connect. To achieve this, CERATIZIT has developed a solution based on a U-axis system and stepped reamer.

    When this process is combined with other tools, the required tolerances are met. If a hip joint is affecting quality of life by restricting movement, in most cases the only solution is an artificial replacement. More than 160,000 such operations are performed in the UK each year.

    For patients hoping for long-lasting improvements, a good surgeon and first-rate care are a necessity – but so is the need for the highest quality ‘replacement parts.’ Prosthetics usually consist of a hip stem with ball joint, a hip socket and an intermediate piece to ensure smooth movement. During manufacture, particular attention must be paid to the connection between the hip stem and the ball joint to ensure the conical surfaces fit together perfectly.

    The tools used play a crucial role when manufacturing these components. Dirk Martin, Application Manager Medical at CERATIZIT and member of Team Cutting Tools, explains: “An artificial hip joint is made from difficult-to-machine materials, which need to be economically machined within the narrowest tolerances. Ceratizit’s role is to develop suitable tool solutions for these tasks. With our huge product range and the experience of our application specialists, we are extremely well placed to provide support and develop machining strategies for applications such as where the hip stem and ball joint connect.”

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

    The cobalt-based alloy (Co-Cr-Mo) ball joint requires a conical hole that 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. Dirk Martin points out another crucial factor: “We need a solution that is suitable for mass production. This means machining must be process-secure and require as little monitoring as possible.”

    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 that can be used to machine contours or for turning. Attachment tools and indexable inserts can be used to create contours in holes and external machining. This means production times can be reduced considerably, while providing optimal surface quality.” Using the conventional process, a lathe and a milling machine would be required, adding clamping, alignment and time.

    To make the conical hole in the ball joint, CERATIZIT’s solution involves facing to provide a flat surface for the subsequent special solid carbide 180° drill. This makes a flat bottom hole. After this, an EcoCut Classic drill and turning tool is used to produce the cone with close-contour boring. Then a carbide conical reamer ensures the ideal contact pattern and tolerance. The regrinding capability also saves the user further production costs. Dirk Martin comments: “We also produced the internal contour to the required precision with a U-axis.”
    All in all, CERATIZIT’s approach enables the critical contours of the artificial hip joint to be produced process-secure and extremely economically. The contact pattern achieved and the tolerances for both machining processes are well below the specified limits. Dirk Martin is proud of this team achievement: “With this approach, we were able to position ourselves as a full-service provider for our customer, a renowned medical technology company, with the prospect of further orders.”

    https://cdn.mtdcnc.global/cnc/wp-content/uploads/2021/05/17140558/The-CERATIZIT-u-axis-system-allows-the-desired-groove-structure-to-be-produced-on-the-stem-cone-even-on-a-machining-centre-640x360.jpg

    Manufactured for precision fit and quality of life

    Manufacturing artificial hip joints demands high precision, especially in the area where the hip stem and the ball joint connect. To achieve this, CERATIZIT has developed a solution based on a U-axis system and stepped reamer.

    When this process is combined with other tools, the required tolerances are met. If a hip joint is affecting quality of life by restricting movement, in most cases the only solution is an artificial replacement. More than 160,000 such operations are performed in the UK each year.

    For patients hoping for long-lasting improvements, a good surgeon and first-rate care are a necessity – but so is the need for the highest quality ‘replacement parts.’ Prosthetics usually consist of a hip stem with ball joint, a hip socket and an intermediate piece to ensure smooth movement. During manufacture, particular attention must be paid to the connection between the hip stem and the ball joint to ensure the conical surfaces fit together perfectly.

    The tools used play a crucial role when manufacturing these components. Dirk Martin, Application Manager Medical at CERATIZIT and member of Team Cutting Tools, explains: “An artificial hip joint is made from difficult-to-machine materials, which need to be economically machined within the narrowest tolerances. Ceratizit’s role is to develop suitable tool solutions for these tasks. With our huge product range and the experience of our application specialists, we are extremely well placed to provide support and develop machining strategies for applications such as where the hip stem and ball joint connect.”

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

    The cobalt-based alloy (Co-Cr-Mo) ball joint requires a conical hole that 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. Dirk Martin points out another crucial factor: “We need a solution that is suitable for mass production. This means machining must be process-secure and require as little monitoring as possible.”

    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 that can be used to machine contours or for turning. Attachment tools and indexable inserts can be used to create contours in holes and external machining. This means production times can be reduced considerably, while providing optimal surface quality.” Using the conventional process, a lathe and a milling machine would be required, adding clamping, alignment and time.

    To make the conical hole in the ball joint, CERATIZIT’s solution involves facing to provide a flat surface for the subsequent special solid carbide 180° drill. This makes a flat bottom hole. After this, an EcoCut Classic drill and turning tool is used to produce the cone with close-contour boring. Then a carbide conical reamer ensures the ideal contact pattern and tolerance. The regrinding capability also saves the user further production costs. Dirk Martin comments: “We also produced the internal contour to the required precision with a U-axis.”
    All in all, CERATIZIT’s approach enables the critical contours of the artificial hip joint to be produced process-secure and extremely economically. The contact pattern achieved and the tolerances for both machining processes are well below the specified limits. Dirk Martin is proud of this team achievement: “With this approach, we were able to position ourselves as a full-service provider for our customer, a renowned medical technology company, with the prospect of further orders.”