Different drawing methods pankaj kumar das
- 1. Different Drawing Methods Submitted by: Pankaj Kumar Das B.Tech Polymer science (1308023)
- 2. Drawing • It is defined as a process of stretching spun fiber on a roller at a specific draw ratio to significantly align the fiber molecules result in a higher degree of crystalinity and enhance physical properties.
- 3. Why do we need “Drawing”? • To develop the fiber strength, polymer molecules in both the crystalline and the non-crystalline regions are further oriented by elongating the fiber between two rolls at different speeds. • Higher draw ratio generally leads to higher molecular orientation and thus higher fiber strength. • Mostly, increasing the drawing speed (higher elongation rate), drawing at a temperature lower than appropriate, or increasing the orientation of the feeder yarn from the spinning process decreases the fiber uniformity and quality. • Therefore, spinning and drawing are best operated as an integral process to control the fiber morphology, physical properties, and end-uses.
- 4. Drawing machine • Drawing is carried out by simply stretching the filament yarn between two sets of rollers. • The drawing occurs between feed rollers and take-up rollers (Draw rollers) at room temperature or at an elevated temperature by providing a heater plate. • The drawn material is given a small twist and is wound on a bobbin. • The path of the yarn undergoing drawing is regulated by proving guide pins or alternately placing the feed and take-up (drawing) rollers perpendicular to each other. • An idler roller at an angle is provided with each roller set (i.e. feed or draw) to allow the yarn to be wound in multiple loops separately on each on these rollers. This gives a better grip to the yarn and the yarn does not slip easily under drawing tension.
- 6. PROCESS INTEGRATION • To increase process efficiency and reduce production costs, an industrial effort has succeeded in integrating the spinning and drawing processes. • Therefore, there are now three different types of spinning process arrangements. Each of these processes gives a different set of yarn properties and morphology. I. Separate spinning and drawing: a two-step process II. Stack-draw process: a one-step process III. Spin-draw process: a one-step process
- 7. Separate spinning and drawing • This method is most widely used for the production of various yarn types. • The take-up speed is generally around 1000m/min to make ‘‘undrawn’’ yarn of low orientation. • The undrawn yarn is ‘‘lagged’’ in storage for 4–12 h and then drawn at about 3:1 draw ratio to develop the fiber strength. • The process of this type, yields a fully drawn yarn (FDY). • Additional twisting step to provide the filament bundle cohesiveness is generally followed in the same process. • Thus, the process is also called a draw-twist process.
- 8. Stack-draw process • The take-up speed of this one-step process is greater than 3000m/min. • The product is known as the partially oriented yarn (POY). • The combination of drawing and textile finishing seems suited particularly for the production of POY at high spinning speeds.
- 10. Spin-draw process • The take-up speed of this process ranges from 600 to 3000m/min, coupled with immediate drawing on the panel. • The resulting product is a fully drawn yarn.
- 12. Draw-Twisting • Polyamide filaments produced in high-speed operations that do not combine spinning and drawing processes must be subjected to a subsequent draw-twisting process to develop more useful properties. • Since this process is performed in the solid state, the resulting orientation is mainly controlled by the draw (deformation) ratio and is less affected by relaxation factors (molecular motions). • Thus the drawing rate and temperature in the draw- twisting process are of less importance than they are in the spin-draw process.
- 13. Spinning–Drawing–Texturing • A one-step spinning–drawing–texturing process for carpet and other applications. • In this process, the yarn is generally spun at a take-up speed of about 2000m/min, immediately drawn on panel at a draw ratio from 1.1 to 2.5, and passed through a texturing device to develop a crimped fiber. • The crimped fiber will continue onto a perforated drum to be cooled before it is wound up on a package. • Alternatively, an undrawn yarn spun earlier can be used as a feeder yarn to be drawn and textured as above.