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Thursday, 23 July 2020

Construction of Tappet Shedding Cam

Emdadul Haq
Lecturer, Department of Textile Engineering, Primeasia University; Bangladesh

Construction of Tappet Shedding Cam for Plain weave (1/1) using the following parameters:
1. Weave design of the fabric: Plain (1/1)
2. The minimum distance between Cam and Follower or Treadle bowl centre = 3 inch
3. The diameter of Follower or Treadle bowl = 2 inch
4. Lift of the Tappet = 5 inch
5. Dwell Period = 1/3 of a pick
6. Movement pattern during rising and fall: Simple Harmonic Motion (SHM)


Tappet Shedding Cam Construction for Plain Weave | Texpedia
Tappet Shedding Cam Construction for Plain Weave



Calculation:
    Formula Number: (1/1) Plain
    Repeat Size: 2 x 2
That means, the 360° rotation of the bottom shaft, two picks are inserted; i.e.-
         Degree/ two Pick = 360°
Degree/ Pick = (360°)/2=180°
Dwell Period/ Pick = 1/3  x 180°=60°
        So, Dwell-1/ Pick = 60° [After the formation of the first shed, one pick inserted according to weave design]

         Dwell-2/ Pick = 60° [Then the formation of the second shed, also one pick inserted according to weave design]

Total Dwell Period = 60°+60° = 120° 
Total Working = 360° – 120° = 240°

Working-1 = 120°

Working-2 = 120°

Tappet Shedding Cam for Plain weave | Texpedia
Simple Harmonic Motion movement pattern for plain weave

    0° – 120°            =     Working-1 (Rise)
    120° – 180°        =     Dwell-1 (Heald Lowered)
    180° – 300°        =     Working-2 (Fall)
    240° – 360°        =     Dwell-2 ( Heald Raised)

Steps for drawing a Tappet Shedding Cam for Plain weave:
1. Drawing a circle having its centre O and radius, OA = Minimum distance between Cam and Follower/ Treadle bowl centre = 3 inch

2. Then draw two another circle with radius,

        OB = OA + Radius of Follower/ Treadle bowl = 3 + 1 = 4 inch
        OC = OB + Lift of the Tappet = 4 + 5 = 9 inch

3. Now, divide the circle into four segments of 120°, 60°, 120° and 60° for Working-1, Dwell-1, Working-2 and Dwell-2 respectively.

4. Then, divide  ∠COD into six equal parts by the radius of OP1, OQ1, OR1, OS1 and OT1. Similarly divide ∠EOF into six equal parts by the radius of OP2, OQ2, OR2, OS2, and OT2.

5. Draw a semi-circular on BC having its centre M and divide this semi-circle into six equal segments in which each segment is 30°.

        i.e. ∠BMM1 = ∠M1MM2 = ∠M2MM3 = ∠M3MM4 = ∠M4MM5 = ∠M5MC = 30°


6. Draw a perpendicular on the diameter of BC from the points of M1, M2, M3, M4, and M5.


7. Take OM1', OM2', OM, OM4' and OM5' as a radius and draw arcs which cut the radii OT1 & OT2 at  2, OS1 & OS2  at 3, OR1 & OR2 at 4, OQ1 & OQ2 at 5 and OP1 & OP2 at 6 respectively.


8. Draw circles having a radius of AB = 1 inch which representing the follower/ treadle bowl at the centre of 1, 2, 3, 4, 5, 6 and 7 (Total 14 centres).

9. Join the inner surface of these 14 circles with a smooth curved line to get the Tappet Shedding Cam.

We can easily draw any Tappet Shedding Cam by following this calculation:


1. (2/1) Plain:

    Repeat Size: 3 x 3; that means, the 360° rotation of the bottom shaft, three picks are inserted; i.e.-
     Degree/ three Pick = 360°

     Degree/ Pick = (360°)/3=120°

     Dwell Period/ Pick = 1/3  x 120°=40°  [Dwell Period =1/3 of a pick]


So, Dwell-1/ Two Pick = 120°+40°=160°            
[After formation of first shed, two pick are inserted according to weave design]
    Dwell-2/ Pick = 40° 
[Then formation of second shed, one pick inserted according to weave design]
Total Dwell Period = 160° + 40° = 200°

Total Working = 360° – 200° = 160°

    Working-1 = 80°

    Working-2 = 80°


2. (2/2) Twill:
    Repeat Size: 4 x 4
That means, the 360° rotation of the bottom shaft, four picks are inserted; i.e.-
     Degree/ four Pick = 360°

     Degree/ Pick = (360°)/4= 90°
     Dwell Period/ Pick = 1/3  x 90°=30°  [Dwell Period =1/3 of a pick]

    So, Dwell-1/ Two Pick = 90°+30°=120°            

[After formation of first shed, two picks are inserted according to weave design]

Dwell-2/ Two Pick = 90°+30°=120° 

[Then formation of second shed, also two picks inserted according to weave design]
Total Dwell Period = 120° + 120° = 240° 
Total Working = 360° – 240° = 120°

    Working-1 = 60°

    Working-2 = 60°


3. (3/2) Twill:
    Repeat Size: 5 x 5
That means, the 360° rotation of the bottom shaft, five picks are inserted; i.e.-
     Degree/ five Pick = 360°

     Degree/ Pick = (360°)/5= 72°
     Dwell Period/ Pick = 1/3  x 72°=24°  [Dwell Period =1/3 of a pick]

So, Dwell-1/ Three Pick = 72°+72°+24°=168°            

[After formation of first shed, three picks are inserted according to weave design]

Dwell-2/ Two Pick = 72°+24°=96° 

[Then formation of second shed, two picks are inserted according to weave design]
Total Dwell Period = 168° + 96° = 264° 
Total Working = 360° – 264° = 96°

    Working-1 = 48°

    Working-2 = 48°


Now, we can easily draw the tappet shedding cam above three weave design by using necessary parameters and calculated data of Working-1, Dwell-1, Working-2 and Dwell-2 as following the “steps for drawing a Tappet Shedding Cam for Plain weave”.

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