Jimmy K.C. Lam The Hong Kong Polytechnic University CAD/CAM in Knitting (II) Advanced development in flat bed knitting machine Jimmy K.C. Lam The Hong Kong Polytechnic University

Learning Objectives Advantages of Schedule Knitting Whole Garment Production Digital Stitch Control System

Schedule Knitting In shaped knitting, each piece (front body, back body, and both sleeves) must be knit separately and sewn together afterwards. Normally, machine is programmed to knit one item at a time, first for body panel, back panel and sleeves. This results in much wasted lead time for the sewing stage

Schedule Knitting (2) Schedule knitting or sequential knitting, allows an entire set of fully fashion pieces to be knitted sequentially, for one garment at a time. Machine is programmed to knit front, back and two sleeves at the same time for one garment piece. In this way, post-knit sewing can be done immediately after the first garment is knitted, reducing the total time taken for an entire job.

Comparison between Conventional Production and schedule knitting

Whole Garment Knitting Evolutionary Process in Knitwear Production

Whole Garment Knitting As machines improved with evolving technology, the knitting methods started to change to yield higher productivity, increased efficiency, lower labour and material costs, and better consistency and quality. The knitting production methods, have evolved for four major stages Stage One: Cut and Sewn Stage Two: Shaping Stage Three: Integral Knitting Stage Four: Whole Garment Knitting

Stage One Cut and Sewn Panel Knitting This cut & sewn production involves knitting an entire panel of knit Fabric to accommodate the front body, back body and sleeve. This conventional method requires the patterns for the bodies and sleeves To be cut out from the fabric and sewn together, involving seversal Tedious post-knit operation. Up to 40% of the original fabric may go to waste as cut-loss

Stage Two Shaping/ fully fashion knitting Shaping allows the front and back bodies and sleeves to be knitted According to specific pattern shapes for each piece. Each pattern is shaped using only the amount of yarn necessary to knit that piece and seam allowances, so cut-loss is eliminated. Trimmings and pockets still must be knit separately and post-knit linking and sewing are required

Stage Three Integral Knitting Integral knitting uses shaping technology to knit pattern-shaped piece. It improves shaping by “integrating” trimming, pockets and other accessories such as buttonhole to avoid sewing together these items. Great saving can be had in post-knit processing.

Stage Four Whole Garment Production Whole garment or “complete garment” production is an entire garment is knit on the machine without any linking or sewing. Incredible cost-savings can be had as a result of eliminating all post-knit labour. On demand knitting capability shrinks production lead time considerably.

Development in computerized V-bed machine (2) Special needles development (compound needle and slide needle) to facilitate pattern flexibility and production efficiency Special transfer jack and stitch presser development to knit complicated design and fabric Development of new take down tension device for sequential knitting Digital control loop length device to control fabric quality (so loop length will be the same for different panel)

Digital Stitch Control System Before the invention of digital system, analogue knitting methods yielded inconsistent loop formation which resulted in variation in fabric size (length and width and fabric weight). With digital stitch control system, tolerance is quoted to within +/- 1% which is crucial to shaping, integral knitting and whole garment production. Uniform quality is achieved among different production batches, as well as for repeat orders.

Digital Stitch Control System (DSCS) Principle As shown in the figure, the DSCS-equipped machine is programmed with the desired loop length, it monitors yarn consumption continuously and adjust yarn feed and tension through each course to yield consistency throughout the fabric.

Digital Stitch Control Device It is located on both the RHS and LHS of V-bed machine. The yarn consumption is monitored continuously so that any variation in loop length and knitting tension can be adjusted immediately.

3-D Collar Knitting

4-System Computer Flat Knitting Universal, Germany

Examples of Whole Garment Knitting

Collar Knitting Seamless Knitting Hem Knitting

Whole Garment Top-bottom Variety