Needle Penetration Depth

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Machine variables: Needle punch density. Needle penetration. Entry and exit speed. Machine design parameters: Needle density on board. Pattern arrangement of needles in the needle board. Type of needle/needle shape, size, number of barbs. Single or both sided needling. Pre-needling/finish needling. Straight/inclined punching/elliptical needling. Except the shape and size of a needle, all the above factors affect needle punching density. The fiber carrying capacity and finishing of felt structure of a needle is decided by the shape and size of the needle. Needle Punch Density: The product of machine strokes per centimeter of web advance and the number of needles per centimeter of working width will give the specific number of punches per…show more content…
The penetration depth affects the fabric stretch during the needling process. During the needling process, the fabric gets stretched. This stretch is directly proportional to the amount of needle penetration. The needle penetration not only determines the amount of fibers being taken up by the needle barbs but also decides the extent of' the movement of fibers. The following structural changes occur during the punching process. i) higher needle penetration causes greater stretch, which in turn causes fabric breakage ii) high needle penetration causes decrease in fabric thickness, which is due to the reorientation of fibers and the greater pressure exerted on fibers that remain in the horizontal plane. These fibers are held by Fibrous arcs between adjacent tufts as they are pulled further into the web. This causes web compression and a consequent increase in density. iv) With lower needle penetration, the punched loops do not protrude from the bottom surface of…show more content…
The number of fibers in a vertical unit increases with an increase in depth of needle penetration and leads to better entanglement and consolidation of the structure. After certain levels of needle penetration, there is a decrease in tenacity that is due to the occurrence of fibre breakage, which tarnishes the fabric structure. Higher needling density restricts fibre mobility during bending and this in turn, results in higher bending length. An excessive needle depth and/or needling density results in severe fibre breakage, which leads to poor stiffness. An increase in amount of needling decreases the fabric weight produced from a particular web weight per square unit. The decrease in fabric weight/square unit is due to the drafting and spreading of fibers during punching, which increases as needling is increased. As the number of needle penetrations are increased, increased fiber locking causes a decrease in thickness. So when the needle is withdrawn, it resists the fibres to bounce back to their original

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