How a pre-shrinking machine works

Damp-Heat Pre-shrinking machine Primarily used for pre-shrinking fabrics made from cellulosic fibers such as cotton, linen, silk, and viscose. These fabrics are highly absorbent, causing the fibers to swell easily—resulting in a reduction of fiber length and subsequently affecting the dimensional stability of both the fabric itself and any blended textiles derived from it. The basic process of a wet-heat pre-shrinker involves wet spraying, compression, and drying. Depending on the type of coating material used, the equipment can be categorized into two main types: rubber blanket pre-shrinkers and felt pre-shrinkers. Both operate based on the principle of "bending, deforming, and compressing."

Pre-shrunk fabric has the following features:

(1) Stabilizing the fabric's shrinkage rate;

(2) Further enhance fabric quality and dimensional stability;

(3) Enhance the fabric's physical properties or protect its surface quality, such as improving hand feel and visual appeal, colorfastness, eliminating creases, boosting fullness, achieving smoother surfaces, and ensuring uniformity in both warp and weft densities as well as weft slant.

(4) Setting treatment for synthetic fiber fabrics;

(5) Enhance sewing performance;

(6) Enhance fabrics to boost the added value of apparel products.

There are several methods for fabric pre-shrinking: wet-heat shrinking, rubber blanket shrinking, steam shrinking, and hot-air setting shrinking. It’s worth noting that the most commonly used pre-shrinking machine in garment factories is the steam shrinker.

The working principle of a steam pre-shrinker is based on the thermal shrinkage properties of fibers. According to the shrinkage mechanism of wool fibers, which are highly hygroscopic, their scales align in a specific direction. Under certain conditions—such as temperature, humidity, and pressure—the wool fibers undergo felting. However, excessively high temperatures or pressure can lead to severe, irreversible shrinkage. This is why using rubber blankets or wool blankets for pre-shrinking wool fabrics is impractical. Instead, the so-called "zero-tension pre-shrinking" condition must be carefully maintained throughout the process of pre-shrinking wool textiles.