Cam Construction of Tappet Shedding

CAM CONSTRUCTION 

Follow Step

• First create two circle as shown in figure

• Here create cam for plain weave ( 1 up 1 down) so divided in two part of circle because only two pick per repeat. either as different design calculate the total no. of pick per repeat and divided into circle total no. of pick per repeat. example like a 4 up 4 down weave so in case circle divided into 8 part.
  

Total circle degree is 360. here divided two part in circle so each part is 180 degree. one part for up movement and second part is for down movement of heald shaft. 

• after divided in two part of circle. each part divide in 1/3 as shown in figure. that 1/3 part is dwell period of shed.(that is standard for plain power loom) and other part in movement of heald shaft.
  

Here 1/3 part is 60  degree. that is dwell. and 2/3 part is 120 degree that in part  movement of heald shaft.

• next process is draw the line as par require a pick par repeat. so here we start form up part in dwell part. how draw the line that is shown in figure (STEP 4)
  

That red line is dwell of up movement of heald shaft. that is draw on NPC circle because that is for up movement

• after dwell draw line for movement for heald shaft for going to down potion that is shown in figure (STEP 4.1)
  
   

That draw red line is movement of heald shaft for down position.

• After the movement of heald shaft they stationary for some time for pick insertion (passing shuttle one shuttle box to anther shuttle) that is a Dwell period of heald shaft or shed.
• So Here, after the down movement of heald shaft require to remain stationary for some so draw the line for dwell time that is shown figure.(STEP 5)
  

This draw red line is dwell period of down movement of heald shaft.

• After the remain stationary heald shaft goes to movment. here helad shaft going to up position. that line draw in figure (STEP 6)
  

In last draw red line is movement of heald shaft for going to up postion.

• after the movement they remain stationary that is dwell. here figure in also show the dwell of down potion 
• This is one cam in plain weave that type two cam use and both are mounted on bottom shaft but 180 degree opposite to each other. as that shown in figure.