Wednesday, April 1, 2020

TESTING OF DRAPE COEFFICIENT OF FABRIC BY CUSICK DRAPE TESTER


TESTING OF DRAPE COEFFICIENT OF THE FABRIC CUSICK DRAPE TESTER:


Drape coefficient of the fabric:  

It is a very important characteristic of the fabric. It prescribes the fabric deformation by gravity when it is allowed to hang under its own weight. "The drape coefficient is the ratio of the difference between the area of the draped sample and supporting disk to the difference between the area of the specimen and the supporting disk". it is also expressed in term of percentage. Its value becomes always less than one. The low value of the drape coefficient shows good draping properties of the fabric or low % the drape coefficient means fabric has good draping ability.

This characteristic also contributes to the aesthetic appeal in the garment. There are many factors which influence the draping characteristic of the fabric. The some of factors influencing the drape coefficient are : fabric GSM, material used and weave of the fabric.

Testing principle of drape coefficient of the fabric:

We have already stated above about the drape coefficient of the fabric.  The area of fabric specimen is find and it is suspended over the a supporting disc. The area of draped specimen is find. Finally, the drape coefficient is calculated according to the formula.

Apparatus used:

The apparatuses to being used in fabric drape test are given below:

1 - Cusick drape tester

2 - weighing scale.

3 - scissor

4 - measuring scale

5 - fabric

6 - paper card having little stiffness.

7 - marker pen

8 - flat table

9 - compass

10 - a carbon pencil

11 - Calculator



Testing procedure:

The whole testing of drape coefficient of the fabric gets completed in below steps:

Preparation of fabric specimen:

There are three types of templates supplied with Cusick drape tester.

Large template diameter - 36 CMS.

Medium template diameter - 30 Cms .

Small template diameter - 24 CMS .

In this picture, the templates have been illustrated as "G".

The supporting disc has diameter of 18 CMS .

Total four specimens are prepared in this test. The two specimens are tested by placing them face side up over the supporting disc. The remaining two test specimens are tested by placing them back side up over the supporting disc. All the four specimens are tested separately.

The specimen cutting template is selected according to the stiffness of the fabric. The small diameter template is used to test the fabric having low stiffness .

The large diameter template is used to test the fabric having high stiffness.

The medium diameter template is used to test the fabric having medium stiffness.

The template should be selected in such a way that it could be draped when it is being suspended over supporting disc. The supporting disc diameter remains fixed.

The fabric is spread over the flat surface ( table). An appropriate template is placed over the fabric. The out line marking is done along the edges of the template with the help of marker pen.



Now the test specimen is cut along the marked out lines with the help of scissor. A very small hole ( pin hole) in the middle of the specimen is made.

The remaining thee test specimens are prepared by following above described method.

Paper rings preparation:

Total four paper rings are prepared in this test. One paper ring gets used for testing of drape coefficient of  one test specimen. The outer diameter of each paper ring is kept equal to the diameter of the test specimen. You see below figure.



After cutting a circle of paper card, it is placed over table. The centre point of the paper disc is found. A circle of 18 cms. diameter ( equal to supporting disc) is drawn with the help of a compass and carbon pencil in the centre of the paper card disc. The point of the needle of the compass should be placed just in the centre of the paper card disc. Now the paper ring is cut with the help of scissor along the circle drawn on the paper disc.

Loading the specimen over supporting disc:

When all the specimens get prepared and paper rings get also prepared, the test specimen is placed over the supporting disc of Cusick drape tester. The specimens are tested one by one. When the full testing of one specimen gets completed, the next specimen is processed. You can see below picture:


The technician brings the lid of the drape tester as shown in above figure. The centre hole of the specimen is placed just in the pin mounted in the centre of the specimen asupporting disc. Now specimen is pressed gently by hand. The centre of the specimen gets touched to the centre of the supporting disc. The specimen is spread over the supporting disc and glass surface. The should be no wrinkles at the specimen surface. Now, the tester's lid brings in closed position.

Marking of the outlines just over draping pattern shadow:

The paper ring is weighed before mounting over the supporting disc. The weight of paper ring is recorded . The paper ring is mounted over the supporting disc as shown in the future:


Now the drape tester is connected to a appropriate power supply. The supply point is switched on. A halogen bulb us mounted inside the tester. A parabolic mirror is are fitted inside the drape tester. When the light drops over parabolic mirror, it gets reflected in upward direction. The upward reflecting light penetrats to the paper ring. The area covered by specimen makes a shadow ( draping pattern) over the paper ring. Now the technician draws the outline along the shadow of draping pattern with the help of marking pen. Now the traced paper ring is taken out. The outlined shadow of draping pattern is cut carefully with the help of scissor. The outside cuttings of the paper rings is thrown in the dustbin. The cut draping pattern of paper ring is weighed property.
Now, the same procedure is repeated for remaining three specimens.

Drape coefficient Calculation:


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