Technical Articles

Each year thousands of air-jet looms are increased and installed over the world, with various speed, width, and weaving species. The better understanding and knowledge of the technical features about heddles and heald frames will help companies to make the right choice, purchase suitable heddles and heddle frames, and ensure the performance of their loom and quality of fabrics.

1. Feature of Air-Jet Loom
a) The proportion of air-jet weaving machines is getting higher and higher, occupying 80% of total number shuttleless looms.

b) The speed of the air-jet loom is continuously increasing. The average running speed of 190cm width loom is 700-800r/min, maximum reaching 1100r/min, while in the 1990s lower than 600rpm.

c) Wide width air-jet looms are becoming more and more popular. 340cm and 360cm air-jet looms are widely used, some factories even use 380cm.

d) Variety adaptability is becoming wider. The sum of warp density and weft density has reached 144picks/cm.

All these have brought the forward higher requirement for weaving heddles and heald frames.

2. Heddle for Weaving
Six points need to consider while choosing weaving heddle: type of connection, simplex or duplex, total length X width X thickness, length X width of heddle eye, normal heddle eye, or special heddle eye, and heddle material.

2.1 Type of connection between heddles and heald frame
There are three types of connection between heddle and heald frame, O type (closed type), C type, and J type (open type). O type weaving heddles are mainly used in old shuttleless looms, and air-jet looms and water-jet looms with negative shedding; while C type heddles are mainly used in shuttleless looms with positive shedding.

2.2 Simplex and duplex heddle
In the weaving of coarse yarn, simplex heddles are used; and in the weaving of fine count yarn, duplex heddles are used.

2.3 Size and specification of weaving heddles
O type heddles heald loop distance mainly are 260mm, 280mm, 302mm, 330mm, etc; C type and J type heddles heald loop distance are mostly 280mm, 306mm, 331mm, 382mm, etc.
Width of heddle is normally 5.5mm, and thickness 0.3mm.

2.4 Size and specification of heddle eye
Heddle eye with length 5.5mm and width 1.2mm, are mostly used in weaving fine count yarn; while heddle eye with length 6.5mm and width 1.8mm, are mostly used in coarse count yarn; other special sizes are used in fewer occasions.

2.5 Heddles with special heddle eye
In previous weaving of high-density fabric with fine count yarn, normal duplex heddles are applied, but now duplex heddles cannot meet the technical requirements of increasing warp density. Heddles with the special eye are developed to meet the new demand, with a 32% increase of heald density over normal weaving heddle, and 1%~3% increase of weaving efficiency.

2.6 Material for heddles
The general material used in the production of weaving heddles are stainless steel, nickel-plated carbon steel, and galvanized carbon steel. Due to heavy pollution to the environment from electroplating, Groz-Beckert and Steel no longer manufacture carbon steel heddles.

3. Heald Frame
The requirement of the heald frame mainly refers to the width, the way of connection with the heddle, the way of connection with the shedding mechanism, cross beam height, corner joint, central support, etc.

3.1 Width of the heald frame
Width of the heald frame is consistent with loom reed width; however, the absolute width differs in different model weaving looms, different ways of connection with heddle. Same width heald frames from different loom models or with different ways of connection with heddle cannot reciprocate each other.

3.2 The way of connection with the heddle
Heald frames to be fitted with O type heddles have clamp, and with C type and J type not have a clamp. Heddle frames should match weaving heddles specifications.

3.3 The way of connection with the shedding mechanism
Heddle frame has various ways of connecting with shedding mechanism, listed below are the commonly used positive connection ways,


DRC1 or DRC10 are mainly used in Tsudakoma and Toyota from Japan; DRC2, DRC3, or DRC30 are mainly used in Picanol rapier and air-jet looms; DV is mainly used in rapier and air-jet from Somet and Smit.

3.4 Cross beam height

In the old days, in positive shedding mechanism, cross beam height of heddle frame is 120mm; as the loom speed increases, strengthened heddle frames have been released to the market, with a cross beam height exceeding 150mm. Here is theoretical weaving speed (loom width 190cm) while using heddle frames with different cross beam height;

a) Cross beam height is 120mm, maximum weaving speed 650rpm

b) Cross beam height is 140mm, maximum weaving speed 750rpm

c) Cross beam height is 150mm, maximum weaving speed 850rpm

The neglect of cross beam height influence to loom speed may result in loom working in a critical state, causing damage to cross beam and side stay.

3.5 Corner joint

The corner joints play an extremely important role as all force goes to four corners. Corner joints have two types, rigid connection, and flexible connection.