CAD/CAM in Knitting (II)CAD/CAM in Knitting (II)Advanced development in flat bed Advanced development in flat bed

knitting machineknitting machine

Jimmy K.C. LamJimmy K.C. Lam

The Hong Kong Polytechnic UniversityThe Hong Kong Polytechnic University

Learning ObjectivesLearning Objectives

Advantages of Schedule KnittingAdvantages of Schedule Knitting Whole Garment ProductionWhole Garment Production Digital Stitch Control SystemDigital Stitch Control System

Schedule KnittingSchedule Knitting

In shaped knitting, each piece (front body, back In shaped knitting, each piece (front body, back body, and both sleeves) must be knit separately body, and both sleeves) must be knit separately and sewn together afterwards.and sewn together afterwards.

Normally, machine is programmed to knit one Normally, machine is programmed to knit one item at a time, first for body panel, back panel item at a time, first for body panel, back panel and sleeves.and sleeves.

This results in much wasted lead time for the This results in much wasted lead time for the sewing stagesewing stage

Schedule Knitting (2)Schedule Knitting (2)

Schedule knitting or sequential knitting, allows an Schedule knitting or sequential knitting, allows an entire set of fully fashion pieces to be knitted entire set of fully fashion pieces to be knitted sequentially, for one garment at a time.sequentially, for one garment at a time.

Machine is programmed to knit front, back and two Machine is programmed to knit front, back and two sleeves at the same time for one garment piece.sleeves at the same time for one garment piece.

In this way, post-knit sewing can be done immediately In this way, post-knit sewing can be done immediately after the first garment is knitted, reducing the total time after the first garment is knitted, reducing the total time taken for an entire job.taken for an entire job.

Comparison between Conventional Production and schedule knitting

Whole Garment KnittingWhole Garment Knitting

Evolutionary Process in Knitwear Evolutionary Process in Knitwear ProductionProduction

Whole Garment KnittingWhole Garment Knitting As machines improved with evolving technology, the As machines improved with evolving technology, the

knitting methods started to change to yield higher knitting methods started to change to yield higher productivity, increased efficiency, lower labour and productivity, increased efficiency, lower labour and material costs, and better consistency and quality.material costs, and better consistency and quality.

The knitting production methods, have evolved for four The knitting production methods, have evolved for four major stagesmajor stages

Stage One: Cut and SewnStage One: Cut and Sewn Stage Two: ShapingStage Two: Shaping Stage Three: Integral KnittingStage Three: Integral Knitting Stage Four: Whole Garment KnittingStage Four: Whole Garment Knitting

Stage OneStage OneCut and Sewn Panel KnittingCut and Sewn Panel Knitting

This cut & sewn production involves knitting an entire panel of knitFabric to accommodate the front body, back body and sleeve.This conventional method requires the patterns for the bodies and sleevesTo be cut out from the fabric and sewn together, involving seversalTedious post-knit operation.Up to 40% of the original fabric may go to waste as cut-loss

Stage TwoStage TwoShaping/ fully fashion knittingShaping/ fully fashion knitting

Shaping allows the front and back bodies and sleeves to be knittedAccording 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 ThreeStage ThreeIntegral KnittingIntegral 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 FourStage FourWhole Garment ProductionWhole 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 computerizedDevelopment in computerizedV-bed machine (2)V-bed machine (2)

Special needles development (compound needle and slide Special needles development (compound needle and slide needle) to facilitate pattern flexibility and production needle) to facilitate pattern flexibility and production efficiencyefficiency

Special transfer jack and stitch presser development to knit Special transfer jack and stitch presser development to knit complicated design and fabriccomplicated design and fabric

Development of new take down tension device for sequential Development of new take down tension device for sequential knittingknitting

Digital control loop length device to control fabric quality Digital control loop length device to control fabric quality (so loop length will be the same for different panel)(so loop length will be the same for different panel)

Digital Stitch Control SystemDigital Stitch Control System

Before the invention of digital system, analogue Before the invention of digital system, analogue knitting methods yielded inconsistent loop formation knitting methods yielded inconsistent loop formation which resulted in variation in fabric size (length and which resulted in variation in fabric size (length and width and fabric weight).width and fabric weight).

With digital stitch control system, tolerance is quoted With digital stitch control system, tolerance is quoted to within +/- 1% which is crucial to shaping, integral to within +/- 1% which is crucial to shaping, integral knitting and whole garment production.knitting and whole garment production.

Uniform quality is achieved among different Uniform quality is achieved among different production batches, as well as for repeat orders.production batches, as well as for repeat orders.

Digital Stitch Control System Digital Stitch Control System (DSCS) Principle(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 DeviceDigital 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 Knitting3-D Collar Knitting

4-System Computer Flat Knitting 4-System Computer Flat Knitting Universal, GermanyUniversal, Germany

Examples of Whole Garment Examples of Whole Garment KnittingKnitting

Collar Knitting

Hem KnittingSeamlessKnitting

Whole Garment Top-bottom

Variety