Monday, 25 January 2010

Twill Variations-1

Twill Variations:

1. Regular or continuous twills

In regular twills the diagonal lines are formed by advancing the order of interlacing in step of one in either directions.

In four threads the three orders of interlacing can be made viz. ½, 2/3 and 3/1, each can be made to incline in either direction, therefore, six different effects can be formed.

2. Zig Zag or Wavy twills

Wavy twills are those in which the direction of twill is frequently reversed. Wavy twills are normally made on point drafts. The following is an example of wavy twill:

3. Herring-Bone Twills

Unlike wavy twills, the herring-bone twill does not come to a point where it changes the direction, but instead one twill line in said to cut into the other at the point of reversal.

Construction of Herring Bone twills

We will construct a simple Herring-Bone twill. We construct it on eight ends.

Step-1 :

Construct a simple, 1/3 twill on 4 ends


Now working of 5th end will be exactly opposite to that of 4th end i.e. where crosses are replaced by blanks in 5th end and blanks by crosses i.e

Step-3 :

 Similarly working of 6th end is opposite to that of 3rd; 7th, opposite to that of 2nd and so on; so that the final herringbone twill will look like:

4. Broken twills

A large variety of effects can be produced by breaking a regular twill.

There are two ways of obtaining broken twills:

1. Break and reversal methods.

2. Entering and skipping method

1. Break and Reversal method

In this we first decide the break unit i.e after how many threads the twill will be broken. Generally it is half the number of threads in the repeat of a regular twill.

Same examples

1. 2/2 twill (break point : half the number of threads)

The regular twill is indicated as

In this case we run the twill in regular direction till half the threads, however the ends in the second half of repeat are run in reverse order:

2. 4/4 twill (Break point 2 threads)

the original twill in indicated as

There we run the twill for 2 threads, then for next 2 threads reverse it, again we run as regular twill for 2 threads and again we reverse it as shown:

2. Entering and skipping method

This method is applicable to twills that are composed of equal warp and weft floats. In this, threads in the ordinary twill are entered and skipped. Generally the number of threads to skip is one less than half the number of threads in the repeat of the twill.

Thus in a 2-and-2 twill the no of threads to skip will be 2(6/2-1) and in a 3-and-3 twill the no of threads to skip will be 3(8/2-1).

Some examples

2-and-2 twill

Step 1

Calculate the number of treads that will be taken of regular twill in order to enter and skip.

For n-and-n twill it will be (n+n) x 3

Thus for 2-and-2 twill no of threads = (2+2) x 3 = 12

Thus for 3-and-3 twill, no of threads = (3+3) x 3 = 18

Step 2

Make repeats of the no of threads calculated as above with the twill given. Thus we make 2-and-2 twill on 12 threads as:

Step 3

Now we prepare another design from this by taking 2 ends and then skipping one alternately. Thus is every 3 ends 1 end will be skipped, in 12 ends 4 ends will be skipped so design will be of 8 ends.

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