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

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?

Closed-loop Control Model PROCESS INPUT OUTPUT CONTROL

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

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

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

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

Coefficient of Variance

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.

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

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

Yarn count & Needle hook

Knitting Performance and Yarn Count

Yarn Count and Machine Gauge

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”

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

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

Effect of Yarn Friction

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 ?

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