Knitting productivity

1,367 views

Published on

an article to explain the ways to improve knitting productivity

Published in: Technology
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
1,367
On SlideShare
0
From Embeds
0
Number of Embeds
2
Actions
Shares
0
Downloads
51
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide

Knitting productivity

  1. 1. Knitting  Department  Productivity   Improvement  Techniques   Dr  Muhammad  Mushtaq  Mangat   mushtaq.mangat@gmail.com mushtaq.mangat@moderno.com.pk   Knitting is the first process in the series of the whole knitting process of converting the greige yarn into a saleable garment. In this department, yarn is converted into fabric with the help of knitting machines. This department is critical for the total productivity of knitted garments manufacturing mills. It has been observed during a survey when at the time of panel inspection in the cutting department, knitting faults accounted for more than 50% rejection of panels. Knitting department is found to be responsible for more than 20% rejection of garments. Loss can be reduced in knitting by more than 50% and its productivity can be increased through getting more production per machine, using better fabric quality, having lesser wear and tear of knitting parts and improving productivity of labor etc. This article is aimed at identifying the improvement areas in knitting and recommending measures for improving the knitting productivity. In the first part, we'll introduce the knitting technology; second part will explain the key areas of improvement and finally, the third part will suggest methods for improvements. Knitting History It is quite difficult to say when knitting actually started. Many authors and researchers have presented different views about the evolution of knitting process. However, almost all the researchers believe that the art of hand knitting is thousands of years old. It is a mystery that how ancient humans learned this art and so are the place and time of its origin. However, some researchers believe that this art originated in Persia. Others claim that it started in Israel, Jordan and Syria. Some researchers opine that mountainous areas of North Africa are the origin of this craft. Knitted socks, which were discovered in Egyptian tombs, date back from 3rd to 6th century BC. First knitting frame was invented four hundred years ago, which could knit 600 courses per minute and today, the latest machine can knit more than 15 million stitches per minute while
  2. 2. a skilled hand knitter can produce only 120-150 stitches per minute. Until 1980, most of the knitting machines were mechanically controlled. Today, most of the machines are electronically operated and controlled with the help of computer systems and the use of electronic and computer technology is increasing day by day. Jacquard knitting machines were equipped with design wheels and drums for producing a certain fabric design but today, computer is attached with machines for the design purpose. Same is the case with stripper knitting machines. Earlier, machines had manual controls for changing the yarn supply but now electronic controls have been introduced for this purpose while the whole process is managed by using computing devices.   Before the invention of knitting frame by William Lee in 1589, hand knitting was the main method of producing knitted fabrics and a skilled person could knit 120 –150 stitches per minute. Even now, some people like wearing hands knit garments and some women especially elderly women do it mainly for a pastime. Hands knit sweaters are sold in the market but its share in the total business is negligible. Knitting in Current Times Some machines can work at a speed of more than 50 RPM [revolution per minute] with gauge more than 40, diameter more than 60 inches and feeders up to 316. Now fully automatic garments knitting machines have built-in stripers and jacquards, interchangeable structures and fully computerized operations. In addition to that, people have invented machines (still not in commercial use), which process sliver (aligned fibres) into yarn. In this way, full-fledged spinning mills will not be needed in the upcoming industrial era. Furthermore, these machines produce yarn according to the requirements. Just 20 years back, maximum production from one machine was 300 Kg/day and today, we can get a productivity of 1500 Kg/day. Textile Industry of Pakistan needs to keep pace with the new technology. Unfortunately, we have old machines, which are incapable of making Pakistan competitive in the international market. Furthermore, we are still having old and outdated facilities in knitting departments. In addition, our management practices are ineffective and outdated. Pakistan needs latest technology, modern management practices and latest operating procedures for improving its knitting output.
  3. 3. Knitting Process Explanation Knitting is a process in which fabric is made by inserting loop into loop. In this process yarn loops are made with the help of needle hook and these loops are passed through previously made loops already held by the needle. From the above-mentioned definition, it is clear that knitted fabric is mainly composed of loops. These loops are formed with the help of a needle while yarn is provided through any warp sheet or through a feeding mechanism. Loops formation is the basic and fundamental differentiation of knitted fabrics from woven fabrics. All knitted fabric characteristics are based upon loop structures. Loops create elasticity and resilience in the fabric. Knitting Fabric Production Process As discussed in the first part of the chapter that knitting is the only one way of making a fabric. For this purpose, yarn is supplied to knitting machines and machines convert this yarn into fabric with the help of its various parts. There are many factors involved in the production process, which have a significant impact on the knitting productivity and output. Some of the factors are mentioned below:- 1. Controlled environment in knitting hall (moisture and temperature) 2. Machine maintenance 3. Quality of compressed air 4. Skill of workers 5. Yarn storage requirements and procedures 6. Fabric storage 7. Lubricants' quality 8. Quality of needles and sinkers
  4. 4. 9. Fluff level in the environment In this part of the article, we'll discuss different factors affecting the productivity and methods to enhance their positive impact on the total productivity. Controlled Moisture Percentage and Temperature In Pakistan, knitting industry is confined only to three major cities: Lahore, Faisalabad (Punjab) and Karachi (Sindh). There is a significant difference in climate of Punjab and Sindh. Even in Punjab, temperature varies from -2 to 50 C° while moisture levels also vary in different seasons. In rainy season, moisture content exceeds 80% and in dry season, it reduces to 20% and sometimes drops to even less than that. Cotton is very absorbing. It can absorb up to 8.5 % moisture. Tensile strength of cotton increases with the increasing moisture. Furthermore, it also gains weight after absorbing moisture, which is quite logical. To avoid problem of variation in the strength and weight, which changes with the variation in moisture and temperature, international standards of moisture and temperature have been set. As per standards, moisture content must be 65% ± 2 (Relatively Humid) and temperature must be 20C° ±1. All knitting machine manufacturers recommend controlling environment in the knitting hall. Mayer and Cie, one of the largest and most popular knitting machine manufactures recommend maintaining 20 C° temperature and 65 % RH humidity in the knitting hall. They have given their recommendations in their book, "Knitting Technology". There is a direct impact of moisture and temperature on knitting productivity. It was observed during a survey of the industry that only one mill in Lahore and one mill in Faisalabad have installed air conditioning plants. Both of them are producing better with same machines. Air conditioning system provides the required temperature and humidity along with fluff control. Air circulation system is attached to water chillers and humidifiers, which provides filtered air to the knitting hall. A production raise of 20-25% can be obtained only by installing air conditioning systems and it is evident from experts' opinions, claims of air conditioning plant manufacturers and observational surveys. In addition, 50% less faults and 50% less consumption (breakage) of needles and sinkers is expected. Above all, we'll be fulfilling our moral duty by providing a healthy environment to workers, which keeps them healthy. As per doctor’s opinion, fluff in
  5. 5. the air can cause allergies, respiratory tract infections and other respiratory disorders. Using air conditioning, we have a neat, clean, free of fluff and healthy environment, which definitely improves productivity. It is presumed that pay back period of all recommended changes and investment is less than six months. In addition, there is a 50% less consumption of needles and sinkers besides better fabric output quality and a healthy and pollution free environment for workers. Other than increase in production, a manufacturer can also enjoy the following benefits:- 1. No tripping of electronic parts, which is quite common at high temperature 2. Less breakage of needles due to low temperature 3. Clean environment with suitable temperature and humidity 4. Better knitted fabric quality, less yarn breakage and low machine stoppage frequency 5. Better health of workers 6. Less yarn wastage 7. Conducive environment for better productivity and quality output It is quite clear that air conditioning plant is one of the most important investments in a knitting mill. Based on all this discussion, it is recommended that all knitting mills should have air conditioning plants to improve their productivity. It should not be considered expensive but a viable and productive investment. Its pay back period is less than a year. Manufacturers should focus on efficient knitting workspace rather than larger spaces because air conditioning costs are high when workspaces are small but efficient. Cool and Dry Compressed Air Compressed air of 125-150 pounds per square inch pressure is used in knitting for cleaning and oiling purposes. It goes into the deeper parts of the knitting machine to remove excessive fluff from the machine. Furthermore, it is also used with oil to lubricate the inner parts of machines. It is one of the most important inputs in knitting productivity factor. When air is compressed in a vessel, its temperature increases and at the same time, moisture percentage in the compressed air also increases. Extra high temperature and high level of moisture are dangerous for the knitting process. High temperature further raises the machine's temperature, which is already too high because of mechanical movements of the machine at a high speed. High level of moisture reduces the lubrication efficiency. Since all lubricants (mainly white
  6. 6. oil) are water-soluble, moisture present in the compressed air dissolves in the oils and ultimately reduces its lubrication. It decreases efficiency of lubricants and it might result in breakage of knitting parts particularly needles and sinkers. To avoid it, all machine manufacturers recommend using compressed air, which is free of moisture and it should have low temperature (less than 20C°). In our knitting industry, manufacturers mostly use untreated compressed air despite the fact that it can increase wear and tear of machines. Many machines and equipments are available, which can reduce the moisture level and air temperature. Based on this discussion, using cool and moisture free compressed air is strongly recommended for knitting. We can have following advantages of cool, free-of-contaminants and dry air: 1. Helps reduction in needle breakage 2. No rust on machine 3. Smooth machine function 4. Reduction in accidents 5. Other than the two above-mentioned areas, knitter should focus on the following factors: • Yarn and greige fabric storage • Machine maintenance • Using lifters to move yarn and fabric in the knitting hall It is expected that by focusing on these points, a manufacturer can gain the following advantages: 1. Avoiding Mixing of yarn 2. Less yarn variation 3. Less leftover yarn 4. Less yarn wastage 5. Better machine maintenance helps in better production (A Universal Truth) After implementing all these recommendations, it is expected that knitters can improve their profitability by more than 25% as well as their image in the minds of local and overseas customers.

×