Essential Weaving Operations in loom

-->

Essential Weaving Operations

On the conventional loom or weaving machine, the warp beam is mounted at the back and the warp yarns are conveyed to a cylinder called the cloth roll, which is at the front of the loom and on which the fabric is rolled as it is constructed. Supported on the weaving machine frame between these two cylinders (the warp beam and the cloth beam), the warp yarns are ready to be interlaced by the filling yarns that run in the width of the cloth, thus producing the woven fabric. 

Textile yarn that is to be used for the filling must be packaged in some form that allows it to be unwound easily for transport through the shed. In shuttle looms the device that carries the yarn across the shed is called a shuttle and is made up of a wooden carrier into which a quill, or prim, is placed. The filling yarn is wound onto the quills from larger packages of yarn. For shuttle-less looms this step of winding quills is unnecessary because filling yarn is drawn directly from large packages carIn any type of weaving, four operations are fundamental. They are performed in sequence and are constantly repeated: 

• Shedding –raising specific warp yarns by means of the harness or heddle frame. The shed is formed by raising the harnesses to form an open area between the sets of warps. The formation of the shed is known as shedding. 

• Picking –inserting filling yarns through the shed. While the shed is open, the yarn is transported across the opening, laying a filling yarn across the width of the loom. The insertion of the filling is known as picking. A single filling yarn is known as a pick. Speed of weaving machines is generally expressed as the number of picks per minute, yards or meters of filling inserted per minute, or yards or meters of fabric per hour. Speed obviously is related to the width of the loom. Wider looms, weaving wider fabrics, would require more time for one filling insertion. 

• Beating Up (Battening)–pushing filling yarns firmly in place by means of the reed 

• aking up and letting off–winding the finished fabric on the cloth beam and releasing more of the warp from the warp beam. 

• Monitoring Yarn Breakage - There is always the danger that a warp or filling yarn may break during weaving, causing a flaw in the cloth. Warp yarns are threaded through drop wires, small metal plates with holes, which are drawn down when a yarn breaks or they may be monitored by electronic scanners that indicate when a yarn is broken. Through signals resulting from either the drop wires or a break in the electronic contact, the loom is shut off, allowing the broken yarn to be repaired 

YARN TRANSPORT METHODS 

The carrier used for transporting the filling yarn may differ from one kind of loom to another. The different devices used form the basis for classifying different types of looms. Within the industry many people refer to newer equipment as weaving machines rather than looms. Weaving machines vary from older, shuttle looms to modern shuttle-less machines with sophisticated electronic controls.

-->

Weaving Machine motion | Control of Loom Motions

-->

Weaving machine or loom is a essential part of fabric manufacturing technology. The weaving technology and mechanism is developing day by day. At past we used only hand loom which was powered by human strength. It was developing day by day. New we got the most powerful weaving machine and modern loom which can automatically produce the fabric according to the instruction. But in this article I will just describe about the essential loom or weaving machine motion control device. Although it is entry lave concept but you can get a clear concept about the topic. 

The essential motions in loom operation are the motion of the harnesses to form the shed and the activation of devices for carrying the filling through the shed. 

Cam Loom 

All types of motion of weaving machine is controlled by mechanical cam. The weaving machine is in the past the motions in most simple weaves were controlled by mechanical devices called cams. The shape or profile of the cam is followed by a device called the cam follower, and the irregularities in the cam shape are translated by the cam follower into the motions of the loom. In this way simple repeat patterns can be created. Repeats are limited to six or fewer picks, but this includes a substantial majority of the most commonly used fabrics. More complex designs require dobby or jacquard looms. Such looms are rapidly being replaced by more modern machines with electronic control of motions. 

Dobby Loom 

All types of motion of weaving machine are controlled by mechanical dobby. This dobby loom is faster than cam loom. The dobby loom is a conventional loom with a somewhat enlarged dobby “head.” The traditional dobby mechanism uses a pattern chain on which there are pegs. Needles or feelers contact the pegs in the pattern chain and are positioned by the pegs. The feelers cause hooks within the dobby head to be connected or disconnected, and the motion of the hooks is translated to the harnesses that move from up to down or to in-between positions as dictated by the pattern. 

From twenty-four to thirty shedding combinations are controlled in this way, so that the repeats are limited to about thirty rows in size. A machine called the double cylinder dobby loom has been developed that approximately doubles the size of the repeat that can be made. The fabrics woven on this loom are less complex than are jacquard patterns and usually consist of small fancy or geometrical figures or designs. Plain terry towels are also woven on dobby looms. With the development of electronic jacquard looms that can make both 

Jacquard Loom 

All types of motion of weaving machine are controlled by mechanical jaquard. It is faster than dobby loom. The jacquard loom is the descendant of an oriental loom, the draw loom, which was used to weave complex patterned fabrics. Operation of the draw loom required two workers: the weaver who threw the shuttle and operated the batten and a draw boy who raised and lowered a series of cords that controlled the pattern. The draw boy had to work from a platform above the loom while the weaver sat below. 

Since the draw boy could make mistakes in the selection of cords, later modifications of the loom structure introduced a mechanical device for raising and lowering the cords. In 1805 Joseph Jacquard, a Frenchman, perfected the principle of the mechanical draw loom. To this day, this same type of loom used in weaving complex patterns is known as the jacquard loom and the weave is known as the jacquard weave.

-->