2. QC in Knitted Production Part 1: Material Control Jimmy Lam Institute of Textiles & Clothing

3. Learning Objectives n What is material control in knitting? n What are the variables in material control? n Amongst all the variables found in material control, which one is most important and why? n Discussion –Requirement for knitted yarn and woven yarn –Why material control is the most important control in knitting process?

4. Closed-loop Control Model PROCESS INPUT OUTPUT CONTROL

5. Closed-loop Control Model Quality Control Process KNITTING YARN FABRIC INSPECTION

6. Which one is the most important ? n Yarn Control ? n Knitting Process Control ? n Fabric Control ? n Final Inspection Control ?

7. MATERIAL CONTROL n YARN APPERAANCE –Yarn cleaniness; –Trash Impurities –Hairness –Yarn Faults The yarn appearance directly affecting the fabric appearance which cannot be improved after knitting Only the BEST yarn should be used for knitting

8. Yarn Evenness n Regularity of yarn expressed in CV% n eg. Carded yarn or worsted yarn n It affects both the fabric quality and knitting performance

9. Coefficient of Variance

10. Yarn Colour n Same source of yarn with different shade. n This will affect dye absorption on different fibers n Once there is mistake in colour, no correction can be made.

11. Fibre Composition n Ramile/Cotton n Acrylic/Wool n Test by burning test, staining test and solubility test

12. Yarn Count n It will affect the following –Fabric weight, thickness, material cost –Fabric dimensional stability –Knitting performance

13. Yarn count & Needle hook

14. Knitting Performance and Yarn Count

15. Yarn Count and Machine Gauge

16. Yarn Elasticity n Elastic yarn is easier to knit, less trouble in drop stitches n However, different filament with different elastic property will show “row of horizontal stripes” known as “yarn barrie”

17. Yarn Twist n Amount of twist will affect yarn property on: –strength; –elasticity; –light reflection; –dye absorption; –softness; –abrasion resistance

18. Yarn Friction n Yarn to yarn friction n Yarn to knitting elements –Results: holes; press off and shorter needle life; bad selvedges; and high knitting cost

19. Effect of Yarn Friction

20. Discussion (1) n Amongst all the yarn variables, which one is the most important ? –Yarn colour ? –Yarn strength ? –Yarn elasticity ? –Yarn twist ? –Yarn friction ? –Yarn appearance ?

21. Discussion (II) n Compare the knitted yarn and woven yarn, which one requires higher quality and why ?