In the manufacture of biaxially‑stretched films, the stretching machine orients molecular chains via machine‑direction and transverse‑direction stretching, endowing the film with outstanding mechanical and optical properties. As a core indicator for product quality, film‑thickness uniformity directly determines the stability and finished‑product yield of downstream procedures such as printing and laminating. Relying on its independently‑owned research‑and‑development center, Nanjing sumino Precision Machinery Co., Ltd. explains how its stretching machines realize thickness‑uniformity regulation and steady‑run performance from two vital dimensions: the temperature‑control system and the clip‑chain system.

Uniform performance of the temperature‑control system underpins stretching quality. During the stretching workflow, the film needs to be heated to a proper stretching temperature in the pre‑heating zone and maintained under a constant temperature field throughout the stretching section. Uneven temperature distribution will create inconsistent draw ratios across different film zones, triggering thickness deviation or even film rupture. The stretching machines manufactured by Nanjing sumino Precision Machinery adopt a zone‑based independent temperature‑control system paired with high‑precision temperature sensors and optimized hot‑air circulation layouts. This design delivers evenly‑distributed and adjustable temperature across the full web width, effectively lowering thickness fluctuation and internal‑stress concentration brought on by temperature gaps and laying a solid foundation for consistent film thickness.

Precision of the clip‑chain and track system acts as the key to homogeneous stretching. In the transverse stretching section, film edges are clamped by chain clips that travel along designated tracks. Stable clamping force from chain clips and smooth track operation exert a direct influence on film deformation uniformity during transverse stretching. Our company applies high‑rigidity clip‑chain assemblies and precision‑fabricated tracks. Combined with servo drives and a closed‑loop control system, the equipment maintains satisfactory synchronization and dependable clamping status for high‑speed‑moving chain clips and cuts down uneven stretching caused by mechanical vibration.

The heat‑setting section serves as the final procedure for finalized film properties. Stretched‑out films undergo heat‑setting treatment to release internal stress and lock in molecular orientation. Our stretching machines are fitted with multi‑zone independently‑controlled setting sections and a rapid cooling system. They precisely modulate crystallinity and residual stress, keep the film’s heat‑shrinkage rate within target limits, and boost dimensional stability and winding flatness. Through coordinated operation of the temperature‑control system, clip‑chain mechanism and heat‑setting process, the stretching machine can steadily produce premium‑grade films with uniform thickness and reliable comprehensive performance.