Foot length is the basis of making shoe size and designing shoe last sole length, but no matter which structure and style of shoe last, its sole length must be greater than foot length. This is because the length of feet varies with the climate and intensity of labor. The change of foot length caused by climate change is generally 3-5 mm. When people are engaged in heavy physical labor or long walking, the foot length will also increase.
When they walk, their feet must have some movement space in the shoe, which is called "allowance". Generally, the allowance of men's and women's shoe last is 20mm and 16.5m respectively. At the same time, the allowance changes with the change of the last shape. Generally, the smaller the head shape (sharp, narrow) the larger the allowance; conversely, the larger the head shape (thick, wide) the smaller the allowance. The heel of the third shoe last should have proper crown (rear tolerance) to match the radian of the heel so as to make the shoes more fit. The rear tolerance of the last is about 2% of the girth. The rear tolerance of the last for men is 5 mm, and that of the last for women is 4.5 mm. Therefore, the relationship between bottom sample length and foot length is bottom sample length = foot length + allowance - post tolerance. For example, to make a pair of 250mm long men's scalp shoe last, its bottom length is 250+20-5=265mm foot girth and last girth: girth is the basis of fat and thin, and the weight of shoe last is determined by the foot girth.
The weight of shoe last is determined mainly according to the plantar circumference and tarsal circumference of the foot.
First, plantar circumference: The plantar circumference is the key part of bending when walking. If the size of last sole circumference is inappropriate, it will not only be uncomfortable to wear, but also bring early damage to the plantar circumference of shoes and affect human health. The determination of last sole circumference depends not only on the sole circumference, but also on the shoe pattern. Such as:
1. The last-plantar circumference of plain-toed and three-section-toed shoes should be 3.5mm smaller than that of sole-plantar circumference, so that the plantar circumference of the shoes is stuck in the metatarsal joint to maintain the toes from rushing forward to top the foot pain.
2. Shoes with shallow mouth and tongue style are lack of control. The last sole circumference should be 7 mm smaller than the sole circumference, so that the heel and foot can be worn after the shoes are finished.
3. Shoes with control of boots, high waist and back straps can have last-sole circumference equal to or slightly larger than the sole circumference. Especially Khmer cotton shoes need 3.5mm.
4. Children are in the developmental stage. In order to make their feet grow normally, the last plantar circumference should be larger than that of the foot plantar circumference.
2. Tarsal circumference: Tarsal circumference is generally 1 mm larger than plantar circumference in the law of foot shape. However, the last can not be made according to this ratio. The tarsal circumference of last is usually 2-6 mm larger than that of tarsal circumference of foot. At the same time, pay attention to the waist fossa stilt, the same tarsal girth length can produce different tarsal stilt, and directly affect the shape of last. Therefore, besides mastering the size of tarsal girth, we must correctly conceive tarsal stilt. Width of foot and last: Width refers to the width of all parts on the bottom of last. The width of last bottom sample is based on the width of foot. The foot has two widths, the outline and the footprint. In fact, neither of these two widths can be used as the true bottom width of last. In general, the width of the last bottom sample should be 1/2 of the point between the outline width and the footprint width of the last bottom sample except where the front and back ends (the allowance and the tolerance) need to be scaled.
The stilt of last: The stilt of last refers to the stilt of the front and back of the last. The front stilt and the back stilt of the last are in harmony. When the back stilt of last is fixed, the distance between the front end of last and the horizontal surface is called the front stilt of last. When the back stilt of last rises, the front stilt of last decreases. When the back stilt of last decreases, the front stilt of last rises, but this is not a simple leverage. According to the general rule, for every 10 mm increase in the back stilt of a female last, the front stilt decreases by about 1 mm, and for every 5 mm increase in the back stilt of a male last, the front stilt decreases by about 1 mm. Inside sole baseline of shoe last: the inner sole baseline of shoe last mainly includes heel center point accounting for 18% of foot length, waist socket point accounting for 41% of foot length, fifth metatarsal toe point accounting for 63.5% of foot length, first metatarsal toe point accounting for 72.5% of foot length, small toe protrusion point accounting for 78% of foot length, hallux protrusion point accounting for 90% of foot length.
Determine the center line and back arc call center line of last surface: first, find the middle point of head thickness convexity, tube mouth convexity, and then find the middle point in the most concave part of last back by visual inspection. The middle point of head thickness convexity and the middle point of cylinder mouth are closely attached to the desktop. Pencils lie on the desktop horizontally. The pen tip is aligned with the middle point of head thickness convexity, the middle point of the most concave part of last back and the middle point of the cylinder mouth to draw a straight line, which is called the center line of last surface. Find the middle point at the mouth of the back arc line of the cylinder mouth, the middle point at the junction of the back arc edge and the bottom edge, and then find the middle point at the point of the back arc protrusion. Connect the three points into a line, which is the center line of the back arc. The determination of last center line and back arc center line is the key to correct shoe pattern and the basis of determining the parts of upper. Without these two centerlines, there is no standard to measure whether the upper is positive or not, and the location of the upper is impossible. Determine the height of the back of the shoe: The back seam height of the full shoe is generally 1/4 (25%) of the foot length, but it is enough to take 23% of the foot length on the last when designing positioning. Because ready-made shoes already contain the thickness of materials such as inner sole, semi-inner sole, upper surface, main heel, inner part, etc., there should be a difference between ready-made shoes and positioning. The back height of tongue shoes is 25.5% - 26% of the foot length, and the design location accounts for 23% - 24% of the foot length. Because the front of the tongue is long or short, so the height of the back seam should also be different, but the tongue shoe has no shoelace adjustment control, so the back seam height must be slightly higher than the? M shoe. The back seam height of shallow shoes accounted for 26% of the foot length, and the design positioning accounted for 24% of the foot length. There is a sponge on the upper end of the back, such as leisure shoes, tourist shoes, etc. The back seam height can be increased appropriately without the above ratio. From the above proportional data, the shorter the front help, the higher the height of the back help, otherwise it will not follow. It should be noted here that the height of the back seam can not be measured according to the length of the last bottom sample. Because of the size of shoe last allowance, if the length of shoe last sample is taken as a value, the same person will wear shoes No. 25, with different back stitching height. This is obviously reasonable. To determine the total length of the front side and the location of the entrance, the length of the front side, such as Baotou, Zhongbang, the total length of the front side and the location of the entrance point, must be determined according to the percentage of the last bottom sample length.
Considering the moving parts of each joint of the foot type, the total length of the front side can not exceed 66% of the length of the last bottom. If this value is exceeded, the foot bend will be bumped when walking. The length of the entrance generally refers to the position of the opening of the shoe, such as: the tongue-shaped entrance is located under the bar, the front and the tongue of the shoe; the lace-type is located at the position where the ear and the front are connected, and the location of the entrance accounts for 38% - 44% of the last-like length (for example, the length of the entrance of women's shallow shoes should be 26% - 30%). The length of the entrance should consider the convenience of shoe wearing and last pulling. If the entrance is too long, it will press the instep of the foot. At the same time, the last pulling is too shallow, and often does not follow the foot.