Raschel Knitting Machine

Overview

A raschel machine is a warp knitter built for open and heavily patterned fabric. Where a tricot machine makes a smooth closed cloth at very high speed, the raschel uses latch needles, a long needle stroke and a large number of guide bars to make lace, nets, fishing and sports netting, elastic bands, curtains, geogrids for soil reinforcement, and three-dimensional spacer fabrics. The price of that versatility is speed: the long stroke means a raschel runs slower than a tricot. The reward is that almost any open or fancy structure that warp knitting can make is made on a raschel.

The machine feeds yarn from a Warp Let-off, forms loops on a Latch Needle Bar, laps them with a large Guide Bar Set set over a Trick Plate, places fine detail through a Jacquard Patterning, runs in time from a Main Drive, draws the cloth off with a Fabric Takedown, and is run by Control Electronics.

Warp and pattern supply

Lace needs many separate yarns moving in different ways, so a raschel carries far more beams than a tricot. Large Warp Beam units carry the ground yarns that run through every course, while a stack of small Pattern Beam units carries fancy and pattern yarns that lap only where the design needs them. Each beam has its own Let-off Servo closing the loop on a Tension Sensor, because a pattern yarn that laps over four needles consumes far more length per course than a tight ground yarn. Independent let-off keeps every yarn at the right tension regardless of how it moves.

The latch needle bar

The Latch Needle Bar carries one Latch Needle per wale, grouped in Needle Block units. The latch needle suits raschel work because its pivoting latch can handle the heavy, long laps and the coarse, sometimes elastic yarns that lace and netting use. The bar rides a Bar Carrier driven by Drive Eccentric cams on the main shaft. The needle rises far enough for the old loop to clear the latch fully, which is why the stroke is long and the speed lower than a compound-needle tricot.

Guide bars and lapping

The defining feature of a raschel is the number of guide bars. A simple net machine may use four, while a high-end lace machine can stack dozens, even up to seventy or more. Each Guide Bar Beam carries a row of Guide Needle eyelets in Guide Block groups. Every course the bars swing through the needle line on the Swing Shaft and then shog sideways by their programmed amount. Combining the laps of many bars is how the machine builds an open ground, a patterned overlay and the connecting threads that hold a lace pattern together. A Fall Plate can lay inlay yarns over the needles so they are bound into the structure without being knitted into loops, which is how weft-effect stripes and heavy decorative threads are added.

Trick plate and knock-over

A raschel does not use a sinker bar the way a tricot does. Instead a Trick Plate supports each loop as the needle descends. The Trick Plate Bar is slotted so each needle passes through, a Sinker holds the fabric down between needles, and a Knock-over Bit gives the edge over which the old loop is cast off. This arrangement holds the loosely connected loops of an open fabric steady at the moment they are formed.

Jacquard patterning

For fine lace and patterned net the machine adds a Jacquard Patterning. A Jacquard Bar holds guides that can each be deflected one needle space by a Piezo Deflector, grouped on Jacquard Block units and driven by Bare PCB boards. By choosing where each guide laps a wale to the left or right, the jacquard opens or closes holes anywhere across the width, so a single machine can knit a fully figured lace pattern under software control rather than through mechanical pattern wheels.

Drive, takedown and control

The Main Drive uses a Main Motor turning a Main Shaft through a Gearbox Housing and Helical Gear Pair sets so the needle, guide and trick plate motions stay timed. The Fabric Takedown draws the delicate open fabric off with a Takedown Roller set and winds it onto a Batching Roll using a Takedown Servo at low, even tension so the holes keep their shape. The Control Electronics ties together an Microcontroller, Servo Drive amplifiers, a Power Supply and the Operator Panel panel.

Fabrics, variants and use

The same basic machine, set up with different bars and gauges, makes a remarkable range of fabric. Coarse-gauge machines with few bars make agricultural and fishing nets, packaging mesh and safety netting. Fine-gauge jacquard machines make raschel lace for apparel and home textiles. Double-needle-bar versions knit spacer fabrics with two faces joined by pile yarns for mattresses, shoes and seating, and tubular elastic bands for medical and apparel use. Technical variants make geogrids that reinforce roads and embankments. Across all of them the raschel principle is the same: many guide bars over latch needles, traded against speed, to make open and figured warp-knit fabric.