Introduction of shedding Mechanism In weaving

Object

A shedding mechanism separates the warp thread into two layer or divisions to form a tunnel known as “shed”. The shed provides passage for shuttle. A shed may be formed by means of tappet, cams, etc..

Types of shedding

• Negative tappet shedding mechanism
• Positive tappet shedding mechanism 

Negative tappet shedding

            In a tappet shedding mechanism, if the tappet control only one movement. Either an upward or downward movement of the heald shaft then the shedding is known as “negative tappet shedding”. The heald shaft are returned by some external device like springs, dead weight, roller, etc...

Positive tappet shedding

            In a tappet shedding mechanism. If the tappet controls both upward and downward movement of the heald shaft then the shedding is known as “Positive tappet shedding”.

Cam or Tappet

These are irregular metallic pieces used to produce an up and down motion in follower and lever the up and down motion is obtained by giving rotary motion to these piece. The follower and lever are required to get a continuous up and down movement.

 A cam or wiper is used. If the follower and lever are require to produce up and down movement with regular interval of rest, tappet are used. From the fig. there are specific portion in tappet correspond to “dwell” periods i.e. regular interval of rest for the major part involved in the motion.