regrind

Regrind refers to material that has already been processed and ground into smaller particles and is reused in subsequent production steps. In manufacturing, it commonly denotes scrap or failed parts that are reprocessed to recover material and reduce waste, often blended back into the feedstock for molding, extrusion, or similar processes. The term can also describe a finishing operation in machining where a previously machined surface is ground again to meet final tolerances and surface quality.

In plastics and rubbers, regrind is typically produced from trim waste, runner systems, and defective parts. The material is sized to a specific range and may be dried before reuse, as moisture and contaminants can affect processability and final properties. Regrind is commonly blended with virgin resin in defined proportions; the ratio depends on resin type, color, and performance requirements. While it lowers material costs and reduces waste, regrind can introduce impurities, color shifts, or property variability if not properly sorted and processed.

In metalworking, regrinding describes a secondary grinding operation to restore flatness, surface finish, or dimensional accuracy after rough machining. It is used for precision parts such as gears, shafts, and other components where tight tolerances must be maintained.

Key considerations for regrind include material compatibility, moisture and contamination control, particle size distribution, and the impact on mechanical or thermal properties. Effective sorting, cleaning, and quality control are essential to maximize reuse while maintaining product performance and regulatory compliance.