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Study of the milling strategy on the tool life and the surface quality for knee prostheses

Boujelbene M., Abellard P., Bayraktar E., Torbaty S.

Journal of Achievements in Materials and Manufacturing Engineering

2008

Vol. 31, nr 2

610-615

Purpose: The aim of this research is to make a study about the influence of the tool trajectory's generation on its tool life and the improvement of the surface quality in multi-axis milling at high speed machining of the knee prostheses. The material used for this study is the titanium alloy Ti-6Al-4V ELI (TA6V ELI) for implant. Design/methodology/approach: The methodology has consisted on proving a serie of parameters combinations with various machining configurations and various programs of the tool trajectory's generation in three and five axes (the axis of the tool is maintained normal on the machined surface by rotation around Y axis; the axis of the tool is maintained according to axis Z; the axis of the tool is tilted around the Y axis). And determined the influence of the machining strategy over of the tool life. Findings: The knee prostheses are constructed with important mechanical resistance materials with complex form, which require high performance cutting tools and high cost. The good generation's trajectory of the cutting tool in multi-axes milling permits to minimize flank wear. High speed Machining offers a considerable profit in the capacity of surface quality, duration of the machining and polishing operations and consequently in improvement productivity. But the choice of the cutting speed must be recommended by the couple tool-materials. Research limitations/implications: A possible future work would be the development of a general the phenomenal of the residual stress of various machining configurations and various programs of the tool trajectory's generation and the knee protheses life. The behaviour of the residual stress studies are planed in the future. Practical implications: The relationship found between the milling strategy on the tool life and surface quality work piece has an important practical implication since it allows selecting the best cutting condition for knee prostheses. Results are of great importance in the quality of articulation surface so the cartilage in medicine industry. Originality/value: The paper is original since the bibliographical review has allowed testing that, although works about these themes exist, none approaches the problem like it has been made in this work. This paper could be an interesting source of information for engineers and researchers who work with machining knee prostheses.

Materiały ceramiczne w węzłach ciernych protez stawów biodrowych i kolanowych

Neyman A.

Tribologia

2004

nr 3

283-292

Prace zmierzające do zwiększenia trwałości protez stawów biodrowych i kolanowych prowadzone są w trzech kierunkach: optymalizacji konstrukcji ich elementów, optymalizacji sposobu mocowania protez w kościach kończyn oraz doboru najlepszych skojarzeń materiałowych. Cztery typy skojarzeń są obecnie uważane za najlepsze: panewka z wysokocząsteczkowego polietylenu z główką ze stali nierdzewnej, stopu tytanu lub tlenku aluminium oraz zarówno panewka jak główka stawu z tlenku aluminium. W wielu ośrodkach prowadzone są obecnie badania nad zastosowaniem powłok ceramicznych w protezach. Najbardziej obiecujące wyniki uzyskiwane są w przypadku DLC i CNx.

To day used hip and knee prostheses are not sufficiently durable. Efforts to increase durability of the prostheses are undertaken in three areas: optimization of prostheses construction, optimization of prosthesis elements fixation to bones, looking for the best choice of materials for prostheses elements. Investigations to choose the best materials available are being performed from 1890. Four types of articulated materials are considered to day as the optimal choice: ultra high molecular weight polyethylene (UHMWPE) cup with stainless steel head, UHMWPE cup with titanium alloy head, UHMWPE cup with aluminum oxide head or aluminum oxide cup with aluminum oxide head. All ceramic friction elements of prostheses are of much higher costs due to expensive machining of ceramic elements. Big advantage of "all ceramic" prostheses is much lower amount of wear particles. The presence of wear particles is serious problem in prostheses with polyethylene cup as loosening of prostheses elements joints is caused by the tissue response to polyethylene wear particles. Many investigations are performed in plain tribometers and prostheses simulators to develop bulk ceramics for prostheses elements and to look for possibility to use ceramic coatings in prostheses elements. Among many investigated materials modified aluminum oxide, silicon carbide and two coatings DLC and CNx are now considered as he most promising.