ELECTRONIC CONTROL OF RAPIER LOOM:-

ELECTRONIC CONTROL OF RAPIER LOOM:-

Rapier loom is controlled almost exclusively by electro-mechanical,means through push buttons. If electronic control is used, as applied on one model, it works on the same principle as on shuttle weaving machines. Electronics are used on rapier machines primarily for weft monitoring. Exception are those weavning machines operation on the Gabler system (loop insertion) on these machines, weft monitoring by piezoelectric weft detector is not advisable as the thread draw-off speed in the second half of the weft insertion operation in which monitoring is needed is zero.

For rapier weavning machines operation on the Dewas system (tip transfer) the piezoelectric system is preferred. The weft thread without any additional tensioning is passed at low angle over the sensing unit.

 The start and duration of monitoring are determined by the control system (trigger). With the loop system this consist of a stationary coil and a switching quadrant rotating with the weaving machine crank-shaft.

A signal is thus produced by induction. Eltex uses a light cell for control, which operates in conjunction with a marker on the crank shaft as an electronic switch. On electronic weft detectors for rapier weaving machines , the required minimum speeds for the positive functioning of the device on the Dewas weft insertion system is dependent on the following criteria.

1. The warp-round angle of the weft thread.

2. The thread material.

3. The yarn count.

4. The potentiometer setting.

It was demonstrated that certain “pressure” must be exerted on the thread guide eye or the warp-round pin for the weft detector to be able to registering thread movement. The following advantages of electronic compared with mechnical weft yarn detectors may be quoted:

(a) . Monitoring of weft yarn of all types over the full working width.

(b) .No moveable sensing parts.

(c) .Simple mounting , adjustment and maintenance.

(d) . Monitoring of single, double and multiple weft insertion.

(e) .Low thread tension and no weft thread breaks in the center of the cloth.

Development in Rapier loom:-

Rapier loom has been making in roads to heavy fabrics (900 gms) and also shedding off known draw back of higher weft waste. The design improvement in rapier gripper permits handling a wide range of yarns without any need for changes .

The machine owes its speed, flexibility and low energy consumption to a combination of high technology and economic design. Style changes can be executed “exceptionally rapidity”. Having independent motor drives , this yielded fewer moving parts , fewer gear, fewer oil seals and no timing belts i.e. there are fewer elements to influence fabric quality, less need for resetting and reduced maintenance. There are no toothed belts, which are prone to wear, and breakage.

fig of electronic let-off & take-up ref by www.onlinetextileacademy.com

Following devices are used in the development of a rapier loom:-

1. Sumo Motor.

2. P F L,(Programme filling Lamellar).

3. E L S Y (False Selvedge Device).

4. Electronic take-up and let-off motion.

5. F D E I (Filling Detection at the End of Insertion).

The features and benefits of the above given part's in rapier looms are described as below.

Sumo motors:-

(1) Saving on energy consumption of more than 10% in comparison with conventional clutch and brake configuration.

(2) Machine speed setting is done accurately and completely electronically, via the key board of microprocessor. This reduces the setting to zero.

(3) Speed setting is easy to copy to other machine either with electronic set card or with Production computer with bi-directional communication.

(4) Automatic pick finding becomes faster , which significantly reduces the down times for filling and reparing warp breakages.

(5) The machine can always work at optimum weaving speed on function of quality of the yarn, the number of frames and fabrics construction.

P F L (Programme Filling Lamellae):-

It controls the filling brake ensuring consistent yarn tension at any time during insertion cycle. The PFL can be installed for each channel between the Pre-winder and entry of fixed main nozzle. It has been designed to slow down the filling at the end of insertion. The PFL thus significantly reduces the peak tension of the pick at the end of the insertion and decreases the tendency of pick to bounce back in the shed. As a result of which the filling tip is stretched correctly.

FEATURES:-

1. Lower peak tension in filling yarn.

2. Reduced tendency of filling to bounce back .

3. Inserted pick can be stretched more easily.

4. Adjustment are done by means of machine key board and display.

5. The setting can be adopted for each filling yarn.

BENEFITS:-

1. Fewer filling breaks.

2. Fewer machine stops.

3. Better fabric quality.

4. Higher productivity of machine and staff

5. Weaker filling yarn can be used.

6. Correct setting of filling waste length and consequently less waste .

E L S Y (False Selvedge Device):-

The unique ELSY full Leno false selvedge motion is electronically driven by individual stepper motor. They are maintained in front of harness so all harness remains available for fabrics pattern (design). This only rapier machine that allows selvedge crossing to be programmed on microprocessor independently of shed crossing even while machine is in operation. So result of resetting can be checked immediately. The easiest position of rethreading can be set by a simple push button. When machine starts the selvedge system automatically comes to its original position.

Electronic Take-up and Let-off motion:-

It plays important role . Required pick density can be programmed on microprocessor keyboard. No pick wheel required. The accuracy of setting makes it easy to adjust pick density of fabrics with optimum fabric weight and minimum yarn consumptions. By ETU (electronic take-up) make possible to weave fabrics having various pick densities. The electronic link between let-off and take-up is an additional tool to manage then fabric marks. Warp beam driven by electric let-off through separate drive wheel that stays on loom ensures trouble-free operation of let-off system and improves fabric quality.

F D E I (Filling Detection at the End of the Insertion).

When weaving “ lively" yarn,! used F D E I system. It checks the presence of filling at the end of insertion. The system detects short picks , rebouncing fillings and prevent faults in fabrics at right end. At filling breaks, the machine stops and only the harness are moved automatically to free the broken pick for removal of weaver. This is outstanding since automatic pick finder is not driven by separate motor but mounted by hydraulic system. In this way a two speed slow motion becomes a standard luxury to the weaver. The transfer position of filling yarn on center of fabric is always correct even after changing the cloth for new style.

Ref:-https://www.textilelearner.net