Effect of manufacturing process on mechanical properties of polyetheretherketone (PEEK) cranial implants produced by single-point incremental forming (SPIF)

Polyetheretherketone (PEEK) is one of the most commonly used materials for cranioplasty due to its biocompatibility, relatively high strength, and light weight. Cranial implants manufactured from PEEK sheets using the same manufacturing process, e.g., single point incremental forming (SPIF), will have differing part properties based on the selected polymer forming process. Three fabrication methods for PEEK sheets were investigated: extrusion, modified hot pressing, and injection molding. Material characterization specimens were extracted for tensile, impact, and differential scanning calorimetry (DSC) experiments. The PEEK sheets were also subjected to formability tests at room temperature using SPIF. Slight differences in ultimate tensile strength and impact strength were observed, while formability was largely unaffected by the polymer manufacturing process. Therefore, the polymer manufacturing process can be selected based on equipment and material availability to speed up the custom cranial implant fabrication without impacting the ultimate material properties. This is a critical step in increasing accessibility for patients and exploring other manufacturing processes capable of producing custom cranial implants, e.g., SPIF.