The Design of a Piston Extruder for the Production of Gelatin Filaments Available for Hydroxyapatite Biocomposite 3D Printing

Abstract

Hydroxyapatite is naturally found in bone tissue. Tissue engineering often utilizes synthetic hydroxyapatite biocomposite for bone alloplastic grafting. The bone graft shape and size accuracy can be realized using three dimensions (3D) printing technology. The most important part of the 3D printer is an extruder producing printable filament of the material. This work presents a design of the extruder employed to create a gelatine filament. The gelatin will be used as the matrix of a hydroxyapatite biocomposite in the future. The main components of the extruder are a 10 mL acrylic syringe and a non-captive stepper motor. Three parameters, i.e., extrusion speed, material viscosity, and nozzle size, are examined to find the optimum filament production. The extrusion speed was controlled by programming the frequency step of the motor, and the viscosity was controlled by varying the composition of the aquadest-gelatine mixture. The results showed that the stable operation and the best filament were obtained with a motor speed of 0.17 mm/s, the aquadest-gelatine composition of 10 mL aquadest and 3 grams of gelatine powder, and a nozzle diameter of 0.3 mm.