LINE SEWING. THEORETICAL AND PRACTICAL ASPECTS

1. Theoretical aspects


Fig 1. Loop tensile diagram


Fig 2. Loop equilibrium

The above formula needs to be improved as follows:
1) Consider the resistance of the thread is twice, due to the upper and lower thread.
2) The zigzag stitch consists of two types:
Traction stitches (drawn in red) work when the loop tend to slide.
Complementary stitches only work adding friction force.
Consequently. The formula can be improved, according to the following expression:

N=F / (4·T·(((sin (alpha) ) + (2·mu·cos (alpha)))


Fig 3. Example of calculus

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Fig 4. Real examples in 1.2 mm and 1.9 mm lines

2. Practical aspects


Fig 5. Example 1 and 1.8 mm


Fig 6. Examples 1.2 mm


Fig 7. How to measure and cut loop


Fig 8. Special foot


Fig 9. Couper et brûler truc