Modeling process for full forming sports underwear

2.1 Materials

The key dimensions of female chest morphology include chest circumference, chest point spacing, chest point to heart position, chest point to comparison position, chest height to chest base position, etc. [6]. Therefore, in the design of fully formed sports underwear, the above sizes, front, middle length, back length, and waist circumference are taken as the key dimensions of human body [7]. Figure 2a shows the key structural points of human body. Among them, breast point interval (BP₁BP₂) refers to the horizontal distance between the two breast points; chest point to heart position (BP₁C₃) refers to the arc distance from the top of the chest to the front center line; breast point to comparison (BP₁P₁) refers to the arc distance from the breast peak to the side breast; high chest to base chest (BP₁P₂) refers to the arc distance from high chest to base chest [8]. On the basis of relevant key points, combined with the drawing method of knitted full-formed clothing [9] and supplemented relevant points, the complete full-formed sports underwear prototype plate is obtained, as shown in Figure 2b, and the corresponding key parts are shown in Table 1. In the actual product development process, if there are no special requirements, Chinese national standard sizes can be used, otherwise tailoring can be carried out.

Figure 2

Structure diagram of fully formed sports underwear. (a) Key structural points of human body and (b) prototype drawing of fully formed sports underwear.

In addition, in the process of drawing, the calculation relationship between the size of the output plate and the number of knitting needles and the number of knitting lines should be taken into account [10,11], according to the formula: A = a × ρ a and B = b × ρ b .

The conversion relationship between the size of the plate and the number of knitting stitches can be obtained. In the formula, A and B, respectively, represent the number of transverse knitting needles and the number of longitudinal knitting rows in the knitted plate; a and b, respectively, represent the transverse and longitudinal dimensions of the actual plate; and ρ _a and ρ _b , respectively, represent the transverse and longitudinal density of the knitted fabric. Before calculating the number of stitches, it is necessary to test knit fabric samples in advance to determine the transverse and longitudinal density of the fabric. Finally, according to the actual situation, the braided plate is fine-tuned to make it conform to the principle of flat knitting machine [12,13].

2.2 Method

Fully formed sports underwear can be divided into three categories according to the corresponding exercise intensity: low intensity, medium intensity, and high intensity. Its style structure design [14] is divided into body part, collar part, sleeve part, and bottom circumference.

The body of sports underwear can be divided into flat type and vertical type according to whether it has darts, as shown in Figure 3a. The flat type has simple and elegant design, simple knitting process, but weak support for the chest, which is suitable for low intensity exercise. The vertical body shape design has a high fit with the human body and can provide better support for the chest, suitable for medium and high intensity exercise [15].

Figure 3

Fully formed sports underwear local style design. (a) Body, (b) neck, (c) sleeve, and (d) bottom circumference.

According to the wearing characteristics of sports underwear, the collar style should be a simple collar with only a linear collar socket but no collar seat or collar piece, as shown in Figure 3b, U-neck, square neck, and V-neck. The U-collar has the largest contact area with the skin and can provide greater support for the chest. It is generally used for high intensity exercise. Square and V-necks have better air permeability and more varied styles, which can be used for medium and low intensity exercise.

The cuff should be shaped with armhole arcs but no sleeves. As shown in Figure 3c, the rotator cuff can be divided into H, double C, and Y shapes according to the armhole arcs of the back piece [16]. Type H has the largest contact area with the back and has the best support and protection. It is suitable for high intensity exercise. The second is double C type, which is used for medium intensity exercise. The Y model is more breathable but not as supportive as the first two, so it is used in low intensity exercise.

As shown in Figure 3d, the bottom styles are divided into W type and cylinder type. W type adds a supporting part on the basis of cylinder type, which can provide better support for the chest. It is suitable for sports underwear of all strengths.

3.1 Body forming process model

The knitting process of fully formed sports underwear body is based on tube knitting, among which the flat type refers to the formation of needles directly at the side seam; vertical form is designed by darting in the body, so that the body shape fits the human body better [17]. The specific method of vertical form knitting is called two-sided braiding transfer method. The basic principle of vertical form knitting is to transfer part of the needle amount to the waist by moving the needle evenly to the left and right, so as to realize the transverse size change between the waist line and the bust line. The other part is transferred to the front and back of the center to form a straight line, which is similar to the effect of the front and back of the center of the garment plate, helping to make the chest of the sports underwear more three-dimensional.

Figure 4 shows the process model of fully formed sports underwear body. Figure 4a shows the transfer of bilateral braid with fixed number of stitches and braid rows, and the actual braid shows the twill effect. Figure 4b shows that on the basis of Figure 4a, adding a different combination of the number of stitches and the number of rows of knitting on both sides of the braid transfer, the twill curve obtained is more variable, which can better enrich the modeling effect of sports underwear.

Figure 4

Fully formed sports underwear body process model. (a) Straight twill effect; (b) Curve twill effect.

The knitting principle of the dart on both sides of the needle placement method is shown in Figure 4. The dart is taken as the center line and needles are evenly distributed to both sides. This method is divided into two parts: the preparation part and the knitting part. In the preparation part, 2x stitches are made to fill holes at the m stitches on the outer side. The purpose of the filling is to fill holes formed after the needle is moved, and the rest of the knitting continues normal pattern knitting. Next is the knitting part, the coil from the outer side of the m needle is turned over, and the coil of the m + x needle is moved to the outside of the x needle and braided. At this time, the purpose of placing the x needle to the outside is realized. Then, the coil with the size of n needle, which is far from the front center line x needle, is turned over, and the coil of n + x needle is moved inward, namely, the direction of the center line, and the x needle is braided. At this time, the purpose of transferring the needle quantity to the front and back center lines is realized, and the preparation for braiding is completed. The variable of the braided part is the number of braided rows y, and the slope of the outer side α, i.e., the slope of the twill, is determined jointly by the number of needles x and the number of braided rows y.

Slope α, the number of needles x and the number of knitting rows y are combined in the following formula: tan α = y ρ x 1 x ρ y 1 . In the formula, ρ _x1 and ρ _y1, respectively, represent the transverse and longitudinal densities of this point.

On this basis, if the number of body braiding rows is v, t times of needle placement are performed in the whole process of braiding, the number of needles each time is x, and if the angle of needle placement is α, then the following formula is satisfied: v = t ⋅ x ⋅ ρ y 1 · tan α ρ x 1 .

If the needle setting angle is divided into α and β, the two angles cycle alternately according to the law of u:w, then the following formula is satisfied: v = t ⋅ x ⋅ ρ y 1 ( u tan a + w tan β ) ( u + w ) ρ x 1 .

3.2 Collar and sleeve process model

Due to the changeable styles of the collar part and cuff in the fully formed motion, key points need to be added on the basis of the prototype. The process model is shown in Figure 5, and the corresponding supplementary key parts of the collar and cuff parts are shown in Table 2. Among them, arcs a, b, and c and arcs a', b', and c', respectively, correspond to the arcs of the front and rear collar sockets of the V-collar, U-collar, and square collar. Arcs i, ii, and iii correspond to H, double C, and Y rear armhole arcs, respectively.

Figure 5

Fully formed motion inner collar part and cuff process model.

On the basis of these points, the straight line part is called the flat roll section, such as the straight line part at the bottom of the collar, the straight line part of the armhole, etc., and the curve part is divided into four kinds according to the slope change: quick winding needle, quick releasing needle, slow winding needle, and slow releasing needle [18]. Among them, the slope of the snap-closing needle is in the interval (−1, 0), the slope of the snap-releasing needle is in the interval (0, 1), the slope of the slow-closing needle is in the interval (−∞, −1), and the slope of the slow-releasing needle is in the interval (1, +∞).

Figure 5 shows the schematic diagram of the triangular broken line segmenting method. Take a back armhole arc with a large slope change, i.e., the double C-shaped right back armhole arc, e.g., part A represents quick-closing pins. This part is divided into right triangles with different widths but the same height, whose height is the number of braided rows, and the fixed value of braided rows is generally 2–4 rows, and the width is the number of stitches. This part of the curve approximates the hypotenuse of a triangle. The curve of this part is divided into right triangles with different heights but the same width, whose width is the number of stitches each time, the fixed number of stitches is generally 1–3, and the height is the number of braided lines. Then, the curve of this part is similar to the hypotenuse of the triangle. Part C represents the buffer needle, similar to part B; Part D represents a quick release needle, similar to Part A.

If the length of the triangle is p pin, the height is q row, the angle between the horizontal direction and the curve is θ, and θ ∈ (0, Π/2), then the following formula is satisfied: sin θ ⋅ ρ y 2 q = cos θ ⋅ ρ x 2 p ,

where ρ _x2 and ρ _y2 represent the transverse and longitudinal densities, respectively.

3.3 Bottom wall forming process model

In order to improve the support of the bottom circumference of fully formed sports underwear to the chest, a supporting part can be added on the basis of the cylinder part, that is, W3–W8 can be added on the basis of the prototype of the bottom circumference as its key point, as shown in Figure 6a. Figure 6b shows the structure of the bottom circumference of the fully formed sports underwear. The front and back pieces of the cylinder part have the same shape. The front pieces of the supporting part are W-shaped and the back pieces are rectangular.

Figure 6

Forming process model of bottom circumference. (a) Bottom wall key; (b) Structural drawing of bottom wall. (c1) Efficiency knitting, (c2) Structural knitting.

In the process of braiding the bottom of the fully formed sports underwear, the cylinder part is braided by the method of cylinder braiding first, i.e., the front and back pieces are braided alternately. The supporting part is applied to the process of local braiding, which can be realized by two braiding methods, as shown in Figure 6c. In Figure 6c(1), the method of stopping the middle braiding on both sides is first used to braid the protruding part of the front piece, and then the method of stopping the middle braiding on both sides is combined with the C-shape braiding process to braid the remaining part of the front piece and the rear part. This braiding method pays more attention to the braiding efficiency, while ignoring the braiding details. In Figure 6c(2), the cylinder part is braided in the same way as that in Figure 6c(1). Then, the front piece of the supporting part is divided into three parts in turn for lead back braiding [19].

In addition, in order to make the supporting part more stable in the process of knitting, it can play a better supporting role on the chest, at the same time make the organizational structure of the body not be pulled and deformed; by adjusting the braiding degree, the density of the supporting part is relatively larger than that of the cylinder part, and the supporting part is closer to the human body. Suppose the actual width of each part is k ₁, k ₂, k ₃, and k _4, the transverse density of the cylinder part and the supporting part is ρ _x3 and ρ _x4, then the following formula is satisfied: ( k 1 + k 2 + k 3 ) ρ x 4 = k 4 ρ x 3 .

In particular, when the method of local knitting is used in different parts, if the upper and lower parts adopt different organizational structures or densities, then the following formula should be satisfied: ∑ i = 1 n k i ⋅ ρ x k = ∑ i = 1 n j i ⋅ ρ x j , where k _i and j _i, respectively, represent the actual width of local braid in the upper and lower parts, and ρ _xk and ρ _xj , respectively, represent the transverse density of these two parts [20].

4.1 Full-form sports underwear design

4.1.1 Style design

The style drawing of fully-formed sports underwear designed in this article is shown in Figure 7. Figure 7a is the front style drawing, and Figure 7b is the back style drawing. The body of the sports underwear adopts a three-dimensional design, which has a high fit to the human body and can provide better support for the chest; the front collar is a small V-neck shape, and the rear collar is a square collar shape, which has good breathability; the shoulder sleeve part is an H-shaped structure, which provides greater support for the chest; the bottom circumference is woven in a cylinder and increases the width of the bottom circumference, so that the sports underwear is not easy to shift during movement and is suitable for wearing in medium- and low-intensity movements [21].

Figure 7

Style diagram of fully formed sports underwear. (a) Front style drawing and (b) back style drawing.

4.1.2 Organization structure design

In order to ensure the overall wearing comfort of fully formed sports underwear, and that the parts have different functions, it is necessary to design the organizational structure of each part of the sports underwear [14,15,22,23].

For the body part, in order to make use of its elasticity to achieve size changes, the 2 × 2 rib-knit structure with greater elasticity and better extensibility is adopted. The knitting diagram is shown in Figure 8. Figure 8a–c shows a row of ribbing for the back piece. First, turn the coils on the back lower needle bed to the front upper needle bed according to the rule of 2 by 2, and then knit a row of ribbing together on the front upper needle bed and the back lower needle bed. Finally, turn the coils on the front upper needle bed back to the back lower needle bed to return to the starting state. Figure 8d–f shows a row of ribbing for the front piece. First, the coils on the front lower bed and the corresponding ones on the back lower bed are turned over to the back upper bed, and then a row of ribbing is knitted together on the back upper and front lower beds. Finally, the coils on the back upper bed are turned back to the front lower bed to return to the starting state.

Figure 8

Schematic diagram of 2 × 2 rib knit. (a) Step 1; (b) Step 2; (c) Step 3; (d) Step 4; (e) Step 5; (f) Step 6.

In order to provide stronger support to the chest, improve overall conformal, sports bra straps and bottom circumference choose double organization for woven [24], structure considering the limitation of four flat knitting machine needle bed, using every needle air layer organization, sectioned needle, for example, air layer organization before the knit diagram as shown in Figure 9 for the air layer outer layer of the knitting process. First, turn the coil 1 of the front lower needle bed from the front down to the back needle bed, and then knit a line of “floating thread～loop” cycle in the front lower needle bed; Figure 9c and d shows the process of knitting the inner layer of the air layer. First, knit a line of “floating thread～loop” that is misaligned with the front lower needle bed on the back upper needle bed, and then turn the coil on the back upper needle bed back to the front lower needle bed to return to the initial state. The above is to form a complete line of air layer tissue, forming a line of double-layer structure.

Figure 9

Schematic diagram of tissue knitting of air layer of septum needle. (a) Step 1; (b) Step 2; (c) Step 3; (d) Step 4.

In addition, when the chest is woven with double-layer structure, the air layer tissue of the needle is woven in the front piece, and the inner layer is copied in advance to facilitate the removal and cleaning of the chest pad.

4.2 Application of fully formed sports underwear process model

In this study, MACH2-153X four-needle bed computer flat machine with 18G needle number produced by Shima Seiki Company of Japan and its supporting SDS-ONE APPEX design system are adopted for knitting and design. Figure 10 shows the process model of a fully formed sports underwear, which is divided into four parts, S1–S4, and braided from bottom to top, sharing 7 nogs, among which nogs 1–6 are used for bulk braid, and nogs 7 are used for scrap braid.

Figure 10

Process model of fully formed sports underwear.

The S1 part represents the bottom circumference part of sports underwear, which is braided in a more efficient way in local braid. First, introduce the No. 1 yarn nozzle and weave the cylindrical part, and then, No. 2 nozzles are introduced, which braid the supporting part. In the S1 part, the actual width k ₁ = k ₃ = 8 cm, k ₂ = 12 cm, k ₄ = 30 cm, the transverse density ρ _x3 = 32 horizontal columns/5 cm of the cylinder part and the transverse density ρ _x4 = 30 horizontal columns/5 cm of the supporting part are substituted in equations ( k 1 + k 2 + k 3 ) ρ x 4 = k 4 ρ x 3 and ∑ i = 1 n k i ⋅ ρ x k = ∑ i = 1 n j i ⋅ ρ x j , and the feasibility of the process model of the S1 bottom circumference part is verified within the error range.

The S2 part represents the body of sports underwear, which adopts the No. 2 yarn tip and adopts the two-side braid transfer method to braid. The longitudinal straight lines at the position of BP point are, respectively, two reference lines, move one needle outward each time, the weaving rows are cycled in a 4:2 pattern, the transverse ρ _x1 = 35 transverse row/5 cm, longitudinal ρ _y1 = 35 longitudinal row/5 cm, substituted in the formulas tan α = y ρ x 1 x ρ y 1 , v = t ⋅ x ⋅ ρ y 1 · tan α ρ x 1 ,   and v = t ⋅ x ⋅ ρ y 1 ( u tan a + w tan β ) ( u + w ) ρ x 1 , verified the feasibility of S2 body process model within the error range.

The S3 part is the shoulder and sleeve of sports underwear, still using No. 2 yarn mouth, the overall use of local braid method in turn on the back, right chest, left chest braid, and then according to the triangle line segment method in the back and left and right chest, respectively, triangle length p = 5 needles, high q = 3 lines, horizontal direction and curve angle θ = 30.1°, the transverse ρ _x2 = 35 transverse row/5 cm and longitudinal ρ _y2 = 35 longitudinal row/5 cm were substituted in equation sin θ ⋅ ρ y 2 q = cos θ ⋅ ρ x 2 p to verify the feasibility of S3 shoulder collar process model within the error range.

The S4 part is the edge and shoulder belt of the sports underwear. The 3–6 size yarn mouth is introduced, and the front and back pieces are woven alternately. Finally, the knitting is completed.

4.3 Realization of fully formed sports underwear

Since the fully formed sports underwear keeps the state of being closely worn in the sports environment, the raw materials used must have the characteristics of skin-friendly comfort, moisture absorption, and sweat removal [25,26]. The yarn wearing configuration of the underwear is shown in Table 3. The main yarn is made of blended viscose fiber and polyester fiber [27,28], in which the viscose fiber content accounts for about 70%, with good hygroscopic property, and the polyester fiber content accounts for about 30%, with good strength and elasticity, making it fit better. In addition, in order to further improve the overall stability of it, rubber yarn is added to the bottom circumference, which can not only prevent the bottom swing of sports underwear from deformation and laxity due to repeated washing, but also provide better support for the chest structure. This example of fully formed sports underwear design object is shown in Figure 11.

Figure 11

Design object of fully formed sports underwear.