Optimization of bar soap extrusion process parameters through numerical modelling

Mechanical soap plodders refine, homogenize, and compact soap. Processing pressure, screen mesh size, and L/D affect plodder capacity and soap quality. Grittiness, air bubbles, and poor surface finish hinder soap production. This study optimised soap plodder machine screw length, speed, and density to maximise pressure at low-temperature. Soap plodder FEM was made with ANSYS Polyflow software. The rheological and thermal properties of soap paste were measured with a rotational viscometer and transient hot wire. Viscosity, thermal conductivity, and heat capacity were 900 cps, 0.0449 W/m-K, and 17.29 J/Kg-K. A L9 Taguchi DOE was used for three screw speeds (20, 35, and 50 RPM), screw lengths (300, 550, and 800 mm), and soap product densities in FEM simulation. ANOVA and Taguchi optimization modelling were adopted for analysis. The ANOVA showed a positive correlation between extrudate pressure, screw length, speed, and density. Temperature was mostly density-dependent. Ideal conditions were 800 mm screw length, 50 RPM screw speed, and 900 kg/m³ material density. Response pressure was 4.3604 bar, temperature 315 K. The observed responses would optimize soap plodder pressure, improving refining, homogenization, and soap processing with small mesh screens. The low temperature eliminates the need for a cooling jacket, reducing construction and operating costs.