Yarn Doubling Machine

Overview

A yarn doubling machine takes two or more single yarns and lays them together side by side into one combined package. This step is called doubling, or assembly winding. It does not put any twist into the yarn. The job is to bring the separate ends together so they run parallel and at equal length onto a single package, which then goes to a twisting machine where the ends are twisted around each other to form the finished plied yarn.

Doubling and twisting are two stages. Some plants run them on one combined machine, but on a dedicated doubler the only work is assembly: each end pays off its own supply package, runs through its own tensioner and its own break detector, and meets the other ends at a single combining point just before the winding head. The reason for the separate assembly stage is control over tension. If the ends are not held at equal tension, one will be tighter than the others in the plied package, and when that package is later twisted the loose end will loop and snarl. The whole machine is built around keeping every end at a matched, repeatable pull.

Creel and supply

The single yarns come off supply packages held in the Supply Package Creel behind the machine. Each end has its own Supply Package Holder, so a two-ply package needs two supply packages per position and a three-ply needs three. The packages pay off over their nose ends, which lets them run fast but forms an unwinding balloon that grows and shrinks as the package empties. A Balloon Control Ring ring above each package limits the balloon diameter so the tension the yarn feels does not swing as the package runs down. From there an Over-End Unwinding Guide collects the over-end yarn and leads it forward to the tensioning section.

Tensioning and combining

Each end runs through its own Per-End Tensioning Section. The core of it is a Disc Tensioner: the yarn passes between two spring-loaded discs that add a known drag. A Tension Loading Spring sets how hard the discs press, and the operator sets all the tensioners on a position to the same value so the ends arrive at the combining point under equal pull. Ahead of the discs a Pre-Tension Eyelet removes the unwinding balloon and steadies the yarn so the disc reading stays consistent.

The tensioned ends then run through the Yarn Guide & Combining Assembly. A Converging Guide for each end draws it inward so the separate yarns approach at a shallow angle and meet at the Combining Eyelet. That single eyelet is where the assembly happens: separate yarns go in and one flat doubled strand comes out. The eyelet is made of hard ceramic because the running yarn would cut a groove into soft metal within days at these speeds.

Stop-motion

A doubler has to guard against a missing end. If one of the supply packages runs out or one yarn breaks, the others keep running and the package would wind with one end short, which ruins the whole package for twisting. Every single end therefore carries its own Per-End Stop-Motion Unit. A light Drop Wire Feeler rests on the running yarn and is held up by it. When that end breaks or runs out, the wire drops, the Yarn Break Sensor reads the change, and the control stops the winding head for that position at once. A Stop Lever lifts the yarn clear and brakes the take-up package so nothing winds on until the operator has pieced the broken end back up.

Winding and take-up

The combined strand goes onto a cross-wound package at the Common Winding Head. A Grooved Winding Drum drives the package by friction and, through the crossing groove cut into its surface, traverses the strand across the package width without a separate guide on simpler heads. On heads with a positive traverse a Traverse Mechanism mechanism uses a cam barrel to move the Traverse Yarn Guide back and forth so successive layers cross at an angle and the package stays firm and stable to unwind later.

The growing package sits in the Take-Up Package Unit cradle. A Cradle Loading Spring holds it against the drum at a set contact pressure, and the cradle swings away as the package grows so the contact force and the winding density stay even from an empty tube to a full package. A Length Metering Counter counter at each position measures the length wound through a measuring roller and its encoder, and stops the head at the preset package length so every package off the machine holds the same number of metres, which the next stage needs for batch planning.

Drive and control

The winding drums turn from the Drive System system. On a line-shaft machine a single Main Line Shaft runs the length of the frame and turns every drum at one common speed through a main gearbox, which keeps the build cost low. On a servo machine each spindle has its own motor, which lets the operator stop and restart one position without touching the rest and run different package lengths across the machine. The whole creel, winding row and drive sit on a welded steel Machine Frame & Guards with guards over the running drums.

The Machine Control cabinet holds the winding recipe: speed, tension setting and package length. A touchscreen lets the operator change it and read production per position, while the controller watches every stop-motion and length counter and stops a position on a break or at the set length. Doublers run single yarns from Ne 6 up to Ne 80 in cotton, wool, polyester and their blends, and the assembled packages they produce feed directly into ring twisters and two-for-one twisters downstream.