Preliminary assessment on the effects of line width, layer height and orientation on strength and print time for FDM printing of total contact casts for the treatment of diabetic foot ulcers

Abstract

The application of 3D Printing (3DP) for use in fracture casts and orthopaedic splints has been explored in several studies. The challenge of 3D printed casts is their size and relatively long production time compared to traditional/fibreglass casts. This preliminary study aims to determine the effects of three specific parameters specifically in the context of manufacturing Total Contact Casts (TCCs) for the treatment of diabetic foot ulcers. The effects of printing parameters have been evaluated previously in the literature. However, there are little data in single experiments on layer height ratio dependent on line width; typically, lower values of layer height have been assessed that remain constant with all line widths. The combination of line width, layer height and print orientation have been evaluated here, with a focus on achieving quickest possible print time without sacrificing part strength in the context of 3D printed TCCs. Flexural testing was conducted on FDM-printed PLA test specimens with 36 different treatments, adjusting the above parameters. The relationship between part strength (flexural modulus and maximum flexural stress) and print time was investigated. It was determined that a low layer height could be paired with a high line width to achieve optimal part strength, considering also print time. The specific application, and associated direction of forces/loads is an important consideration when selecting a print orientation to optimise mechanical performance. A case example applied to the printing of a TCC is also presented.