There are many factors for the error caused by last warping:
A. if the last of a shoe is selected as 8m / M and becomes 6m / m after the shoe is finished, the following errors may occur:
1. The heel is too high,
2. The sole is too thin,
3. The sole is too short,
IV. change the insertion thickness (too thick) at will,
5. The iron core is too long,
Vi. missing filling (the original setting was filled with filling),
7. The heel of the nail is displaced (moved forward),
8. Large base material retraction,
IX. poor toe leveling (upper binding position)
Note 1: the most frequent occurrence is (7), and the gesture of the nail and the operator is very important; (3) the second occurrence is (8) because the sole is too short, hard stretching and sticking to the bottom in place, and it will retract after cooling
B. if the last camber of a shoe is selected as 8m / m, and it becomes 10m / m after the shoe is finished, it may be the following error:
1. The heel is too low (including too thin skin),
2. The sole is too thick,
3. The sole is too long,
4. The midsole is too soft,
5. The village is not on the ground,
6. The iron core fails to work hard,
7. The filling is too thick,
VIII. The upper binding force is too large (the upper is too small or the pattern warpage is too large),
9. The heel and throat are too deep (deformation occurs after back nailing),
X. binding (including skewing).
Note 2: (8) if the upper binding force is too large, the depth of the shoe mouth is not right, and it can be measured and compared with a ruler. In case of (3) (4) (5), check whether the insole is fitted with a last
Note 3: if the upper material is soft leather, the warpage error is acceptable within 2mm, but it must be matched with double. If the upper material is hard leather or leather, the warpage can be high or not low
Note 4: if there is front desk shoes, the warpage can be high or not low
There are the following reasons for the askew of vamp after forming (upper binding or last entering):
A. Last part:
1. Because the angle formed by the center line and length line of the last bottom (middle bottom) is too large (generally less than 5 degrees), the last body is skewed, resulting in too large difference between the inner and outer sides of the last body, which is not easy to make the upper correct.
2. Difference between left and right middle lasts.
B. sample part:
1. The sample plate itself is obviously skewed (or the joint line is not coordinated with the last).
2. The front section and the shoe wall are prone to skew due to the template warpage error.
3. The angle and radian of the center line of the heel of the template are wrong, resulting in the deviation of the center line of the heel.
4. The inner lining and vamp pattern match incorrectly, which makes it difficult to stick the inner lining.
5. Error of joint line inside and outside. Poor generality of the sample (manual cutting, curve drawing, rigid bending, etc.)
C. surface making
1. Poor cutting and / or folding of main leather pieces.
2. Poor joint.
3. Distortion or skew caused by sticking inside.
4. Leather material selection and cutting direction is wrong.
5. No matching selection was made (the elongation of inner and outer skin pieces were different).
6. The sewing of the decorative line is not correct and the mounting trim (flower) is not correct.
D. Forming part (upper or last):
1. “Three point fixing” error or “clamp point” error before machine binding.
2. The upper and last of left and right foot are wrong (left upper with right last or right upper with left last).
3. The size of the upper is not consistent with the last.
4. The rear lining and heel are poorly shaped.
5. It is easy to correct the skew without paying attention to the correction.
6. The position of upper clamp is wrong.
Post time: Dec-13-2019