Belt-type steam pre-shrinking allows fabric to relax without holding its edges. QL’s WPF-WDYS supports fabric on a net belt through overfeeding, steaming, vibration and cooling. This releases residual shrinkage before decatizing.
Where this machine sits in the line, and what comes before and after
On worsted and woollen woven routes, the belt path is WPF-WDYS pre-shrinking → WPF-ZW weft straightening → decatizing. The pin-chain alternative is WPF-ZW straightening → WPF-LTYS pre-shrinking → decatizing. Straightening changes position according to whether the edges are held during pre-shrinking.
The wool-blend knit route uses relaxed open-width pre-shrinking on WPF-WDYS and then proceeds directly to the decatizing choice. It does not include a WPF-ZW station.
What it changes in the fabric, top or yarn: handle, dimensional stability, lustre, cleanliness
WPF-WDYS allows both lengthwise and widthwise relaxation. Feed rollers overfeed fabric onto the belt, providing spare length; steam passes through the mesh from below, belt vibration assists relaxation, and suction cools the fabric before delivery.
The QL Relaxed Vibration-Steaming System connects these operations in one conveying sequence. With no pins or edge clamps, it suits relaxed treatment of wool, knitted and highly elastic fabrics. Check the result against the fabric specification: a machine setting is not the same as the finished residual shrinkage.
Why this machine is necessary: what happens without it, or with another method
Choose WPF-WDYS for free relaxation in both directions, or WPF-LTYS for pre-shrinking with the edges held at a set width. For woven fabric, compare width control, relaxation requirements and the position of straightening; the knit route uses the relaxed belt path.
WPF-WDYS has two independently operated steam chambers as standard, with a single-chamber option. After steam passes through the fabric, heating banks re-vaporise it and suction removes it to control condensation marks. The chambers can run separately or together.
Setting the parameters: temperature, tension, speed, time
The standard two-chamber version has a belt speed of 0–30 m/min, a shrinkage setting of 0–15% and a working width of 1,800 mm. Coordinate overfeed, steam-valve opening, vibration speed and belt speed. The setting range is not a promise of identical fabric shrinkage on every quality.
Give QL the composition, construction, width, elasticity and target result. Review available space and downstream connections when selecting the number of chambers.
The questions customers ask most
- Is straightening needed after belt pre-shrinking? The worsted and woollen woven routes straighten afterwards; the wool-blend knit route has no such station.
- Must both chambers run together? WPF-WDYS chambers operate independently, singly or together.
- Does pre-shrinking replace decatizing? Pre-shrinking comes first, with decatizing performing the subsequent setting operation.
Which process routes it appears on
Read the worsted top-dyed, worsted piece-dyed, woollen stock-dyed, woollen piece-dyed and wool-blend knitted fabric routes. Compare pin-chain pre-shrinking and weft straightening.