Investigation of hole geometry and surface integrity in abrasive water jet drilling of UHMWPE for orthopedic knee implant applications

Ultra-high molecular weight polyethylene (UHMWPE), a thermoplastic, is commonly used as the primary material for plastic spacers in complete knee artificial implants in the biomedical sector. However, holes are required for screwing the plastic spacers to the femoral and tibial components. This material frequently presents problems during conventional drilling, such as burr formation, rapid tool wear, and poor surface finish, resulting in inadequate hole quality. Due to constraints in conventional processes, alternative machining techniques for UHMWPE are being examined. In this work, a full-factorial design was used to drill 10 mm holes into the work material to determine the characteristics of holes produced by abrasive water jet drilling (AWJD). The following process variables: traverse rate (v) (150, 300, 450, and 600 mm/min), abrasive mass flow rate (m a ) (250, 300, 350, and 400 g/min), and abrasive water jet pressure (p) (210, 260, 310, and 360 MPa) are considered. Also, a detailed analysis of the geometric characteristics of the drilled holes was conducted, including surface roughness (R a ), roundness errors, and roundness of the entrance and exit diameters. The testing results show that the parameters p and v primarily influence roundness and R a features. It was found that the higher v of 600 mm/min and p of 360 MPa result in the lowest degree of inaccuracy. Scanning electron microscopy (SEM) examines the roundness deviation in the drilled holes. It was revealed that more abrasives were deposited on the drilled-hole surfaces at 360 MPa, especially at higher magnifications.