Study on take up mechanism (Cotton Weaving).

Introduction:Take-up is to draw a fabric to the cloth roller regularly as it is woven. Texture of a fabric largely depends upon the number of ends and picks per centimeter or inch. This motion determines the number of picks of weft per inch or centimeter and contributes to the uniform texture of the fabric. It is the work of the weaver for accurately fixing the position of the fell of the cloth before starting a loom.

Objects:1.To know about the construction of the mechanism.2.To know about drive of the take-up motion.

Take up motion:The process of withdrawing fabric from weaving zone at a constant rate and then winding the woven cloth on the cloth roller with the continuous progress of weaving is called take up motion.

Main parts& Specifications:

i)Rachet, ii)Standard wheel, iii)Change pinion, iv)Stud pinion, v)Stud wheel, vi)Swing pinion and vii)Take-up roller wheel. 

Motion transfer: write according to our loom

Remarks:By this experiment we know about how to cloth is collected by take up mechanism. This is an interesting experiment too. We hope this will be very helpful in our practical life.

Study on Let-off mechanism

Introduction:Let-off is to supply warp thread in the weaving zone at a predetermined rate. Negative let-off is a mechanism for controlling the rotation of the beam on a weaving, warp knitting or other fabric forming machine where the beam is pulled round by the warp against a breaking force applied to the beam.

Fig: fig of let-off mechanism 

Main parts:1. Warp beam.2. Beam ruffle.

3. Chain.4. Machine frame.5. Weight lever.6. Pivot.7. Fulcrum.8. Weight.

Let-off mechanism:The warp beam ruffle is wrapped around by chain. The one end of the chain is fixed at . i.e. at the m/c frame whereas the other end is connected to fulcrummed device to the weight lever , which is pivoted and a dead weight is placed which can be moved along the length of the weight lever.

In this system the tension of the warp is regulated by the friction between chain and the beam ruffle. The friction is controlled by dead weight on the weight lever and the distance of deadweight from the pivot. Heavier the dead weight and longer the distance of it from the pivot lesser the let-off.

The warp beam dia gradually decreases as weaving proceeds. So it’s necessary to increase the let-off rate. If the dead weight is kept on the same place, the let-off rate will remain unchanged. So an experienced worker is required to change the dead weight gradually with the change of the warp beam dia. As a result irregular tension occurs and the rate of yarn breakage may increase.

Conclusion:Negative let-off mechanism is a very simple and manual mechanism. It is suitable for light and medium weight fabrics. It is mainly used in old looms and for weaving of plain cotton fabric.

Study on under picking mechanism.

Introduction:Picking is the second primary motion in weaving. The action of inserting weft yarn through the warp yarns is called picking. The functions of picking mechanism are:1.To deliver the shuttle along the correct flight length.2.To throw the shuttle at a predetermined speed.

Main parts:1.Picking arm 2.Picker 3.Picking cam 4.Picking bowl 5.Race board 6.Shuttle 7.Bottom shaft8.Treadle lever9.Angular lever10.Crank shaft 

Features of under picking mechanism:1.Picker arm is placed under the race board.2.Suitable for wider loom.3.Under picking works less smoothly.4.More direct action.5.Rough in action.6.More clean mechanism.7.Consumes more power.8.Used for heavy weight fabrics in silk and rayon looms.

Under picking mechanismIn under picking mechanism a race board is situated over picking arm. Under picking is controlled by picking cam which is fixed on the bottom shaft. At first the motion comes from motor and m/c pulley.

Then the motion comes in to the bottom shaft and thus picking cam. When picking cam rotates and its nose portion comes in contact with treadle lever and pushes it then the treadle lever pushes the angular lever. The picking arm gets motion from angular lever which is connected with picking arm.

A picker is placed in the picking arm which pushes the shuttle. When shuttle gets motion by picking arm then shuttle begins to move to and fro on the race board. Thus picking is done.

A spring is situated which causes the picking arm and picker to move back after the delivery of the pick. At the two end of bottom shaft, two picking tappets are fixed. By increasing nose length picking speed may be increased.

How to increase PPM:1.By increasing motor seed.2.By increasing the nose shape of picking tappet.3.By decreasing the length of picking arm.

Uses:This mechanism is used in all non-automatic cotton looms. It is also used in jute looms.

Conclusion:This picking mechanism is very important for loom. In the loom under picking is directly done by picker and picking arm. Again under picking is necessary for weft yarn insertion. So we should learn about this mechanism very carefully.

Study on beating-up mechanism .

Objects:1.To know about the construction of the mechanism.2.To know about the drive of the beating-up mechanism.

Introduction:

The beating-up is the third primary motion of weaving. It consists in driving the last pick of weft to the fell of the cloth. This is accomplished with the help of a reed fixed in the sley. The sley is given a sudden and quick movement towards the fell of the cloth by the cranks in the crankshaft. The sleywood runs from one shuttle box to another, and when at its backward movement, the shuttle travels over its race.

Main parts:1.Crankshaft 2.Crank 3.Crank arm 4.Reed cap 5.Reed6.Sley race7.Sley8.Sleysword

Description:The crankshaft gets drive from motor via motor pulley and m/c pulley. The crankshaft has two cranks. These cranks transform the rotary motion into swinging motion. The reed cap is connected by crank arm to crank of the crankshaft. Again the reed is connected between reed cap and sley. There is sleysword under the sley that is bolted to the rocking shaft. There is also shuttle box on the sley. Now the crank gives the swinging motion to the sley by crank arm. When the sley is moving towards the healdshaft at certain position the shuttle passes through warp shed. Again when the sley is coming towards the front rest at last position the reed pushes the last pick to the previous pick of cloth. This is the beating-up motion and the cloth increases in lengthwise in this way.

Conclusion:To make a woven fabric interlacement of warp and weft yarns is the main condition. That’s why beating-up mechanism is a very essential motion for weaving. Proper setting and adjustment should be taken for this motion. This practical helps me to know about beating-up motion. I think this will help me in my future career.