QC Common Sense in Shoe Industry

There are many factors causing the error of last warping.

A. If the warp of the last of a shoe is selected as 8m/m and becomes 6m/m after the shoe is finished, the following mistakes may be made:
First, the heel is too high.
2. The soles are too thin.
3. Shoe soles are too short.
4. Change the thickness of insertion at will (too thick).
Fifth, the core is too long.
6. Leakage filling (originally designed for filling the abdomen)
Seventh, the heel displacement after nailing (moving forward).
8. Large base material shrinkage.
9. Bad leveling of toe head (joint position)

Note 1: The nail heel operator’s gesture is very important for the occurrence of (7); (3) Secondly, the occurrence of (8) the situation is that the sole is too short, the hard elongation is in place, and the sole will retract after cooling.

B. If the last warp of a shoe is selected as 8m/m and becomes 10m/m after the shoe is finished, the following mistakes may occur:

1. The heel is too low (with too thin skins).
Second, the sole is too thick.
Thirdly, the soles are too long.
4. The midsole is too soft.
Fifth, Chuanzhuang has not landed.
6. The core is not exerted.
7. Abdominal filling is too thick.
8. Too much pulling force (too small upper or too warped sample).
9. Too deep heel throat (deformed after turning back nail).
10. Gang formation (inclusive of skew).

Note 2: (8) If the tie-up force is too large, the depth of the shoe mouth will not be right, and the measurement can be compared. For (3), (4), (5) case, it is necessary to check whether the midsole sticks to the last.

Note 3: If the lining material is soft leather, the warping error is acceptable within 2 mm, but must be matched. If the lining material is hard leather or leather, the warping can be high or not low.

Note 4: If you have front shoes, the warp can not be lower.

There are the following reasons for the deflection of the shoe upper after shaping (lining or last insertion):
A. Shoe last part:
1. Because the center line and the length line of the last bottom (midsole) are too large (generally less than 5 degrees) to form an angle each other, the last body tilts, resulting in too large difference in the inner and outer surface area of the last, and it is not easy to make the lining correct.
2. Difference between left and right last.

B. Model section:
1. The pattern itself is obviously skewed (or the splicing lines are not in harmony with the shoe last).
2. The wrong warping of the model is easy to cause the deflection of the front section and the shoe wall.
3. The angle and radian of the heel center line of the model are wrong, which causes the heel center line to be skewed.
4. The incorrect matching of inner-lining pattern and upper pattern makes it difficult to paste inside.
5. Internal and lateral joint line errors. Poor generality of the model (manual cutting, line drawing arc, etc.)

C. Facial parts
1. Poor cutting and/or folding of major leather pieces.
2. Poor jointing and sewing.
3. The inside of the sticker is distorted or skewed.
4. The direction of material selection is wrong.
5. Unmatched selection (different elongation of inner and outer skin).
6. Incorrect sewing of decorative thread and incorrect assembling ornaments (flowers).

D. Shaping part (knot or last):

1. Error of “three-point fixing” or error of “clamping point” before machine joining.
2. The upper and last of left and right foot are wrong (left upper with right last or right upper with left last).
3. Upper shoe size (SIZE) does not match last.
4. Poor placing of back lining and heel.
5. Skew that can be easily corrected without attention to correction.
6. The position of the forceps is wrong.


Post time: Sep-09-2019
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