Overlock Serger

Overview

An overlock serger trims a fabric edge and wraps it with thread in a single pass, producing the finished overedge seam used on knits and the inside of most garments. Twin needles, an upper looper and a lower looper interloop their threads around the cut edge while a knife trims the fabric just ahead of the stitch, so cutting and sewing happen together at high speed. This is a four-thread industrial machine running up to 7,000 stitches per minute on a direct-drive servo.

Power comes from the Servo Drive Motor, an energy-saving servo that turns the handwheel pulley and the Main Drive Shaft, whose timing gears drive the needle, looper and feed mechanisms in phase.

How it works

The Needle Mechanism reciprocates two needles through the fabric while the Looper Mechanism swings an upper and lower looper, driven by eccentric cams and links off the main shaft, to carry thread around the edge and interloop with the needle threads. Just ahead of the needles, the Trimming Knife Mechanism trims the fabric to a clean edge: a moving upper knife shears against a fixed lower knife so the overedge stitch always wraps a freshly cut line.

Fabric is advanced by the Differential Feed Mechanism, a differential feed with independent main and differential feed dogs. Setting one dog to move faster than the other gathers or stretches the fabric as it sews, which is how knit seams are kept flat without waving or puckering. Thread runs from the Thread Path, a four-cone stand feeding through tension discs and the threading tree.

Running clean at speed depends on the Lubrication System sump pump, which oils the high-speed shaft and looper drive, and the Control System system, where a board reads the foot pedal and a needle-position sensor to govern speed and stop the needle up or down.