1 Fundamental Operations in Weaving Dr Jimmy Lam Institute of Textiles & Clothing

2 Learning Objectives Four fundamental operations in weaving 1.Shedding 1.Tappet 2.Dobby 3.Jacquard 2.Picking 3.Beating up 4.Taking up and letting off

3 Shedding A process of raising and lowering of warp yarns by hardnesses to make an opening for the filling (weft) yarn to pass through The raised and lowered form of warp yarns is called shed

4 Shedding Three types of shedding motions (opening) are available for different type of fabrics. They are: 1.Tappet shedding 2.Dobby shedding 3.Jacquard shedding

5 Tappet shedding Tappet shedding uses tappets and cams to control the up/down movement of shafts. The bulkiness of its mechanical movement limits the loom to control up to 8 shafts (repeat not more than 8) Therefore, tappet shedding is the simplest and least versatile shedding motion. The design is restricted to plain weave, simple twill and simple sateen or satin weave. Any design more than 8 shafts requires dobby loom.

6 Dobby Shedding This is a compact, electronically guided shedding motion and capable of having up to 28 shafts. More complex and versatile shedding motion. A dobby loom, therefore, can have up to 28 shafts, and much greater weave repeat is possible. Design may be woven with two or more basic weaves and their variation. Such fabrics may be referred as dobby cloths or dobby weave, towels ususally show geometric designs when pattern is provided by dobby.

7 Jacquard Shedding To provide with unlimited design width, jacquard shedding is needed. This shedding motion has no shafts, instead, a hardness consisting of as many cords as there are ends in the warp sheet connects each end individually to the jacquard machine. Each warp could weave independently of all others. Complex and most versatile shedding motion. Biggest weave is possible with jacquard shedding as each warp yarn may be individually controlled.

8 Picking (weft insertion) Inserting filling (weft) yarn through the shed by carrier device. In shuttle loom, the weft carrier is the shuttle Whereas in the shuttleless looms, the projectile, air jet or water jet carriers the weft yarn. The weft insertion determines the production of weaving looms

9 Weaving Speeds Type of loomInsertion per minute Shuttle300 Flexible rapier950-1,300 Rigid rapier1,000-1,300 Projectile1,200 Water jet1,800-2,000 Air jet1,100-2,200 Multiphase5,400

10 Production rate (meter per 8 hours) RpmMeters/8 hours Handloom204 Ordinary loom16024 Modern auto shuttle loom Rapier loom40073 Projectile loom Air jet loom800146

11 Beating up Beating up pushes each loose filling yarn into cloth by the reed, after the shuttle has moved through the shed. The reed determines the sett (density) of the warp and weft. Beating-up gives the fabric firm and compact construction.

12 Conclusion Discuss three different types of shedding motions in weaving What are the advantages of dobby shedding over tappet shedding?