<p>Recycled resins are widely used in injection molding to achieve net-zero carbon emissions. However, because of the distinct material properties of recycled resins, the quality of finished products often differs from that of products made using virgin materials. Therefore, to ensure uniform product quality when using recycled materials, both process parameters and machine design must be optimized. The injection screw’s design critically affects melt quality when processing recycled materials. In this study, we examined the effects of injection screw geometric design on melt quality and energy consumption in recycled resins. Using ScrewPlus software for simulation analysis and Taguchi methods for geometric optimization, we modified the screw geometry and screw tip assembly such that backflow prevention in recycled materials was enhanced. The results indicated that optimizing the screw design increased the uniformity and stability of the finished product weight when the plasticization temperature was low. In addition, modifying the design of the backflow prevention channel in the nonreturn valve (check ring) of the screw tip assembly effectively prevented melt backflow and further improved the molding stability. These geometric optimizations increased the processing performance of recycled resins and reduced energy consumption, representing an advance in sustainable practices for injection molding.</p>