Biomechanica Hungarica, Évf. 12, Szám 1

Prospects in innovative manufacturing technology of UHMWPE for prostheses and comparison with medical grade UHMWPE

Ureczki Ágnes, Keszei Kitti

Absztrakt


Due to its properties like high load-bearing capacity, biocompatibility, excellent abrasion resistance and strength, ultra-high molecular weight polyethylene (UHMWPE) is widely used as a bearing material in the field of joint prostheses. Currently, UHMWPE is produced by compression molding, ram extrusion or sintering, followed by post-processing techniques, such as milling or machining to finalize the prosthesis geometry and to achieve the final tolerances. With  post-processing techniques we are wasting a high cost material, energy and time. In this paper, we collected manufacturing technologies that has have the potential to be used for creating prosthesis with one step production, minimalize material loss and with a view to providing customized manufacturing capabilities.  We compared three technologies: (i) ram extrusion (currently used technology for joint prosthesis), (ii) FDM printing and (iii) injection molding. In addition to the feasibility, we focus on the investigation of mechanical properties. Three tests were performed on the manufactured specimens: hardness measurement, tensile test and scanning electron microscope (SEM) to compare the finished parts produced by the different processing technologies.

In our work we used the L4000 (Lubmer, Mitsui Chemicals) granulate form material for the recommended alternative technologies. As a result we were able to produce specimens successfully by optimizing the machine setting parameters in the case of injection molding and FDM printing. Beyond the high processing temperatures, the challenge was the high shrinkage of the material in both cases and to achieve good adhesion between the first layers and the base plate during 3D printing.  Despite the difficult manufacturability (caused the extremely low Melt Flow Rate of UHMWPE) the SEM examination gave a favourable picture of internal fiber adhesion in the 3D printed UHMWPE. The results of the tests show that the 3D printed samples have inferior hardness, lower strength and modulus than the injection-molded samples but both alternative techniques have improved tensile strength and modulus compared to the ram extruded samples.


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