Sizing Machine

A sizing machine applies a protective coating to warp yarns before weaving, a process that can increase yarn strength by 15–50%, reduce hairiness, improve abrasion resistance, and dramatically reduce warp breakage during weaving. The size—typically starch for natural fibers, PVA (polyvinyl alcohol) for synthetics, or blended formulations—penetrates the yarn structure and forms a film that protects individual fibers from the mechanical stresses of shedding, beating, and weft insertion.

The sizing process passes warp yarns through a size box where squeeze rollers control the amount of size applied, typically achieving 5–15% size pick-up by weight. Steam-heated drying cylinders then remove moisture while the tension control system maintains consistent yarn stretch. Operating speeds range from 20 to 150 meters per minute depending on yarn type and size formulation, with working widths of 180–360 cm.

Three sizing approaches serve different production scenarios. Single-end sizing treats individual yarns and is used for specialty applications. Beam sizing processes multiple warp beams together on a conventional sizing machine. Slasher sizing combines multiple beams, sizing, and drying in one high-speed continuous operation—the dominant method for high-volume production. Sizing is essential for staple fiber yarns and becomes increasingly critical as weaving speeds increase, particularly on high-speed air jet looms. The sized warp then proceeds to a drawing-in machine for threading through heddles and reed.