In fabric structure; it is important to know, how much yarn is in length wise and width wise. To know the number of yarn in a specific fabric a measurement is done for this. For this yarn in inch is measured by the magnifying glass setting multiplier. It is a off line quality assurance system.
In knit fabric yarn is measure in course and Wales direction. CPI means yarn is in course per inch and WPI means Wales per inch.
Measure the CPI & WPI with the magnifying glass setting multiplier:
- Take the fabric & marking 1 inch with the ball pen according to the Course & Wales wise of a knitted fabric.
- Then set the marking point with the multiplier scale & counting the CPI & WPI of knitted fabric in 1inch.
- Wales per inch and course per inch is counted by the magnifying counting glass.
In woven fabric EPI and PPI is measured to the number of yarn in a fabric. EPI means ends per inch and PPI means picks per inch. Number of yarn in warp direction is measured by EPI and number of Weft yarn in fabric is measured by PPI. In weaving beam is prepared by analyzing the fabric by magnifying glass setting multiplier.
Measure the EPI & PPI with the magnifying glass setting multiplier:
- Take the woven fabric & marking 1 inch with the ball pen according to the warp & Weft wise of the woven fabric.
- Then set the marking point with the multiplier scale & counting the EPI & PPI of woven fabric in 1 inch.
- Ends per inch and Picks per inch are counted by the magnifying counting glass.
So, calculate CPI and WPI for knitted fabrics and EPI and PPI for woven fabrics.
The inspection and grading of fabric quality is one of the important functions of Quality Control in the grey or finished state, the grading of fabric is a difficult task, taking two primary considerations: as the frequency of effects and the seriousness of defects.
The grading has two primary functions: First, to classify the fabrics according to standard qualities based on the end-use and costumer demands and second, to supply information as to the qualities actually being produced.
The Knitted fabric can be classified into three levels of quality, each one have a number of points for defects as follows.
The First quality level : 40 points per 100 Linear Yards.
The Second quality level : (40 – 80) points per 100 Linear Yards.
The Third quality level : 80 points or more per 100 Linear Yards.
General Instructions for the final inspection: Before sending the grey knit fabrics to the dyeing floor, following inspection is done in batching section.
- All pieces will be graded on the base of 40 points per 100 linear yards Mapping will be done on each piece to insure proper grading. Do not count more than 4 points per one yard.
- All defects must be recorded and marked in final inspection and an accurate account of points made to insure proper grading.
- All fabric must meet specifications.
- At the end of each piece of fabric, the inspector will add up total points and decide whether the piece can be shipped as first quality or not, reworked, placed in lower quality, or cut and upgraded for shipment. Fifteen yards or more can be shipped as first quality.
- The quality control supervisor must approve the grading of all quality levels and check the lower quality.
- Major or unsightly defects in the first and last yard of a roll or piece will be cut. All defects of one yard length or more will be cut out of the piece. Defects within the first 2 inches or the last 2 inches of a piece will not be cut out or counted in the grading.
- Open defects on the back of fabric such as drops, runs and hanging picks are to be included in the grading of fabric.
- Pieces can be connected together, once each piece must be the same shade.
- All defects such as runs that extend more than a yard in length will be cut out.
- Fabric up to 70 inches will be allowed a bow of not more than 1 inch and a Bias of not more than 2 inches.
- Defects within one inch of the fabric edge will not be counted except on tubular fabrics. All defects will be counted in tubular goods.
Grading Procedure: During inspection, following points are considered.
- All open defects or major defects counted with 4 points per defect.
- Surface defects over 9 inch length counted with 4 points per defect.
- Surface defects 6 to 9 inches length counted with 3 points per defect.
- Surface defects 3 to 6 inches length counted with 2 points per defect.
- Surface defects up to 3 inches length counted with one point per defect.
- Running defects, such as tucks, needle lines, barre, crack marks, are judgment defects
Batching is the process to get ready the fabrics which should be dyed and processed for a particular lot of a particular order.
In knit fabric inspection system; most of the companies follow four point systems for measuring the quality of the knit fabric. There are various methods for measuring quality of the knit fabric but among all of the methods four point systems is preferable to the inspector of the quality.
After knitting; knitted fabrics are gathered in front of the checking table and the quality inspector inspect the quality of the knit fabric and listed the faults found in the knit fabric and mark it in the knit fabric.
Most of the knit fabric manufacturing companies maintain the ISO: 9001:2000 standards in case of quality. Therefore, the four point systems are followed to inspect the body & rib fabric. The defects found and points given against are recorded in the inspection sheet. Following table shows the four point grading system followed by inspection at different knitting mills.
Four (4) – Point system for knitting fault inspection: During inspection, if the inspector found any knitting faults then he marks it in the fabric and counts it in the sheet. During inspection, following points are considered.
|Needle breakage(up to 10)
|Thick, Thin, Dirt, Oil spot, Contamination up to 3″ in length
|Thick, Thin, Dirt, Oil spot, Contamination up to 6″ in length
|Thick, Thin, Dirt, Oil spot, Contamination up to 9″ in length
|Thick, Thin, Dirt, Oil spot, Contamination above 9″ in length
Quality (points per 100 square meter) = (Total point X GSM)/ (Roll weightX10)
Quality Classification: After calculation of the quality of the knit fabrics, decision is delivered according to the following way.
||20 – 30
So, when we will check the quality of the knit fabric, we should follow the four point systems.