All single-phase weaving machines are classified according to their weft insertion system.
Main methods in single phase weft insertion;
- They are systems with shuttles, shuttles, hooks or water jets.
CONVECTIONAL (SHUTTLE) WEAVING MACHINES
- The looms, in which shuttles are used to transport along the shed, dominated woven fabric production until the 1980s, even in countries with high wages such as the USA.
- Now it is not used, except for the weaving of several types of special fabrics.
- Despite this, a large number of automatic bobbin changing machines are still in use.
- However, they are quickly being replaced by shuttleless weaving machines.
- Shuttle-less weaving machines produce fabric with fewer errors, and fewer workers are needed for weaving and maintenance.
- Millions of hand looms still operate in Southeast Asia, protected by law.
- Fabric production on a shuttle weaving machine It is moved along the nozzle from one side of the loom to the other by the impact mechanism located on both sides of the shuttle machine that carries the bobbin on which the weft is wound.
- For each weft, the shuttle suddenly accelerates and flies over the shuttle path.
- A weft thread is deposited on the shed as the shuttle moves along the shed.
- The shuttle has to be stopped quickly when it reaches the shuttle box (home) on the other side.
- After each weft is placed in the mouthpiece, it is included in the fabric by tamping.
- The comb and shuttle path is mounted on the trolley and moved back and forth together with the trolley.
- While the shuttle is moving along the shed, it is close to the drum frames in order to allow the shuttle to pass without damaging the warp threads.
- Then, the drum is moved forward to include the weft deposited on the shed into the fabric.
- The need for an open shed during most of the weft insertion period and the weight of the reed and the weight of the drum that carries the shuttle path impose limitations on the weft insertion speed, that is, the loom cycle.
- The main weakness of shuttle weaving machines is the disproportionate mass of shuttle and bobbin compared to the small mass of weft yarn carried by the shuttle and deposited in the shed.
- Only 3% of the energy transferred to the shuttle is used for real weft insertion.
- Another limitation on the speed of the machine is the necessity of making the heavy drum move oscillating.
- Although theoretically it is possible to reach 450 m/min weft insertion speed on wide machines, only a few machines have exceeded 250 m/min weft insertion speeds in commercial use.
- In looms with non-automatic shuttle, every time the weft thread on the bobbin is about to run out, the weaver has to stop the loom and change the bobbin.
- The bobbins must be changed when there is too little thread on them to prevent the weft from ending up in the middle of the shed and thus creating a broken weft that needs to be repaired. In industrialized countries, non-automatic and semi-automatic shuttle looms are being replaced by shuttle looms where the bobbins are changed automatically.
- In automatic shuttle looms, the bobbins are changed without the intervention of the weaver without stopping the machine.
- In order for the machine to perform the bobbin replacement process when necessary, new ones are periodically placed in the magazine to replace the empty bobbins.
- Magazine fillers are interchangeable with shuttle box loaders.
- The bobbins are brought to the counter in special boxes and transferred to the changing mechanism automatically from these boxes.
- Looms where the bobbins are changed instead of the bobbins when the bobbins are empty are available for very weak yarns.
- All these methods require winding the bobbins before they are brought to the machine.
- There are practically no restrictions on the weight and width of fabrics that can be woven on shuttle looms.
- In addition to the shuttle looms, shuttle boxes and special mechanisms can be installed in order to enable more than one color or type of weft insertion according to the pattern.
- When looms with shuttle are compared with looms without shuttle, it is seen that there are looms that are more bulky and require labor compared to looms without shuttle.
SHUTTLE WEAVING MACHINES
Weaving machines with shuttles either use a single shuttle that is thrown from both sides of the machine in turn. These shuttles are then brought to the side from which the shuttle is launched with a conveyor belt or chain. An important advantage of all shuttleless weaving machines is that the weft on the conical bobbin does not have to be rewound before it is used. This eliminates a process and reduces the danger of tangling the threads. Thus, it is ensured that the weft yarn is used while it is being produced.
In shuttle looms, the weft is divided into relatively short lengths and wound on bobbins. These threads are then woven in reverse order. This can introduce long periodic faults in a yarn.
For weft insertion in a Sulzer type weaving machine, after the weft is pulled from the bobbin and passed through the weft brake and tensioner, the weft is transmitted to the shuttle feeder placed in the shuttle holder. A torsion bar system is used in weft insertion to transfer as much energy as possible to the shuttle before the shuttle leaves the impact element (picker). The torsion bar (torsion angle) can be adjusted to feed the energy needed to move the shuttle along the guides in the nozzle and deliver it to the shuttle brake on the other side. Sulzer has redesigned the scallop and shank mechanism to achieve a more powerful and faster swivel stroke allowing more time for weft insertion. 3600 mm wide machines 1300 m/min. Narrow shuttle looms can operate at 1000 m/min weft registration speeds. Weaving machine models with shuttles are available for heavy fabrics, thick and fancy yarns and weft up to 6 colors. Machines can be fitted with all kinds of shedding mechanisms and microprocessors to adjust and monitor machine performance. It is frequently preferred to weave a certain number of fabrics side by side in a wide width machine, as the weft insertion speed increases as the reed width increases and the investment cost per unit width decreases in wide shuttle weaving machines.
HOOK WEAVING MACHINES
Hooked looms can work with single or double hooks.
On single hook machines Usually hard hooks are used and it is advantageous in weaving narrow fabrics from thick yarns. Single hook wide machines remain too low speed for many applications. In single hook weaving machines, the hook moves across the width of the loom and usually grabs the weft during the return movement and deposits it into the shed. A variation of the rigid single hook is the two-sided single hook systems, also called bi-phase hooks. These systems do not use technical (industrial) fabrics. Most rapier looms use double hooks where each hook enters the shed from one side. The hooks meet in the middle and weft transfer takes place. In the Gabler system, the first weft is inserted in turn from both sides of the machine. Since the weft is cut every two revolutions, fabric edges are formed on both sides, where the weft threads are connected in a U shape.
In today's machines Gabler system place Dewas system has received. dewas In the system, the weft is thrown from one side and cut at each machine cycle.
On double hook weaving machines flexible or rigid hooks are used. Rigid hook weaving machines require more space than machines with other weft insertion systems. Fabrics woven with double hook weaving machines range from low-density geotextile fabrics to heavy conveyor belts.
Double flexible hooks are generally used in rapier weaving machines. These machines have widths up to 4600 mm and are produced for special purposes in wider widths for industrial fabrics. Standard machines have a relatively low investment cost and are used to weave a wide range of light to medium weight fabrics. Since the weft color selection mechanism of up to eight colors is simple and inexpensive, rapier weaving machines are ideal for weaving fabrics with multiple colors or types of weft and for short runs.
They are widely used with jacquard shed opening mechanisms for weaving upholstery and trendy fabrics. Hook looms are also used in the production of some industrial fabrics.
FLUID GEL WEAVING MACHINES
- Flowable gel weaving machines to carry the weft through the shed air or water used.
- This system requires a weft carrier or hook for weft insertion.
- Therefore, there is much less moving part and much less mass to move.
- Although most of the yarns can be used in air-jet looms, water-jet weaving machines are only suitable for water-repellent yarns.
water jet looms
- In order to carry the weft across the entire width of the shed, there is usually only one nozzle on the side where the weft is thrown.
- Therefore, machine widths are limited to approximately 2 meters.
- Single-level air-jet weaving machines have been commercially successful in widths up to 1700 mm, as the control of the air flow is more difficult than the control of the flow of pressurized water.
- For larger machines, reed transverse auxiliary nozzles are placed in order to ensure a smooth weft thread movement across the machine width.
- Although wide-width air-jet machines can theoretically be produced, commercially, single-width machines are more attractive and machine widths are limited to 3600-4000 mm reed widths.
- Compressed air is expensive to produce and difficult to control its flow.
- For this reason, it is necessary to limit the air flow in order to carry the weft through either the special air channel or the channel formed in the card with a special profile.
Air jet looms
- It has developed rapidly since it came into commercial use in large quantities in the 1970s.
- Today, air-jet looms can weave the vast majority of woven fabrics and dominate the mass production of relatively simple fabrics.
- Air jet weaving machines 3000 m/min. They have reached the weft speed.
- This speed is about twice the speed achieved with any single phase weft insertion system and is still in intensive development effort.
- The air-jet system is highly competitive with the investment cost per meter weft thrown.
- Air-jet weaving machines with automatic weft repair system can repair the majority of weft defects that occur between the main nozzle and the other side of the fabric.
- This unit removes the broken weft thread from the shed without damaging the warp threads and restarts the machine.
- If the machine cannot detect and correct the error, it generates a signal to warn the weaver.
- Since weft stops constitute the majority of machine stops in air-jet weaving machines, this system reduces the workload of the weaver by more than 50% in most cases.
- With this system, the quality of the woven fabric is improved and the lost time that occurs when more than one machine stops at the same time is reduced.
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