Int J Adv Manuf Technol (2010) 46:11–19 DOI 10.1007/s00170-009-2087-7
ORIGINAL ARTICLE
A computer-aided design system for foot-feature-based shoe last customization Shuping Xiong & Jianhui Zhao & Zuhua Jiang & Ming Dong
Received: 3 December 2008 / Accepted: 30 April 2009 / Published online: 14 May 2009 # Springer-Verlag London Limited 2009
Abstract There has been a growing trend among shoe manufacturers to introduce customized shoes to satisfy varying customer style, fit, and comfort needs, thus to increase the product’s added value. This study presents a computer-aided design (CAD) system for designing a customized shoe last based on the chosen shoe style and customer’s foot features. The CAD system first automatically extracts 18 important foot features from a laserscanned customer’s foot. Then, it applies a global grading with a local deformation approach that can deform the base shoe last with the customer’s chosen style to the customized shoe last based on the extracted foot features while maintaining the customer’s chosen style. Finally, the system evaluates the final foot shoe last fit and represents the fit in a contoured figure. The experimental results show that the proposed CAD system can be adopted by shoe manufacturers to make customized shoes with the customer’s chosen style and foot size and shape. Keywords Customized shoe . Computer-aided design . Shoe last . Foot feature . Grading . Fit
S. Xiong (*) : Z. Jiang : M. Dong Department of Industrial Engineering and Management, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China e-mail:
[email protected] S. Xiong Shanghai Key Laboratory of Advanced Manufacturing Environment, Shanghai 200240, China J. Zhao School of Computer, Wuhan University, Wuhan, Hubei 430072, China
1 Introduction The foot is regarded as the second heart of human beings in traditional Chinese medicine, transmitting and attenuating the impact forces between the ground and the human skeletal system. Serving as an interface between the foot and the ground, footwear is expected to be designed to protect the foot from undesirable pressure stimulus and facilitate it to perform its daily functions [1, 2]. However, the induced foot deformations from ill-fitting footwear have been reported to be the major causes for discomfort, pain, and even foot problems such as calluses, corns, hallux valguses, plantar ulcers, and pressure sores [1, 2]. Therefore, a pair of shoes designed and manufactured with a good fit is very important for foot comfort and health. The market surveys in Hong Kong [3] and Europe [4] also showed that next to the shoe fashion and style, the good fit and comfort are the second important determinant in the purchase of footwear [5]. However, in the traditional shoemaking, the shoe is categorized by the length only (sometimes the length and width) for the customer to select, even though both the shoe and foot are complex 3D objects [6]. Since different people have different foot shapes (wide vs. narrow, slim vs. fat, high-arched vs. low-arched), even though they may have the same foot length [7, 8], the customers need to learn how to adapt their own feet to the standardized shoes to fit their own needs. For example, the use of different lacing methods in shoes, off-the-shelf insoles, and arch supports to change or adapt a shoe based on their own personal needs [6, 9]. In this procedure, the customer’s specific needs are not considered. Often, a customized shoe is needed for the person whose foot shape is not normal or whose feet are very sensitive. Increasingly, there is a trend among the shoe manufacturers to advance the shoe customization so that the customers’ satisfaction level and the
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manufacturer’s competitive power can be improved [10, 11]. Therefore, there is a need of an automated system which can make customized shoes. The most important component of the shoemaking is a shoe last, a solid 3D mold around which a shoe is made. Figure 1 shows the close relationship between a shoe, a shoe last, and the foot. A shoe last is closely related to the foot and its design is based on many factors such as the foot shape/size, comfort parameters, shoe fashion/style, type of construction, etc. [12]. It has been regarded as the “heart” of shoemaking since it mainly determines the shoe shape, fashion, fit, and comfort qualities [13, 14]. The back part of the shoe last is for fit and comfort, while the toe part (pointed toe, rounded toe, squared toe, etc.) is mainly for fashion and style [14, 15]. Once the shoe last has been made, other shoe components (shoe upper, outsole, insole, midsole, the heel, etc.) can be made afterwards. Using traditional shoemaking methods, making a customized shoe last is expensive, time-consuming, and complicated to manufacture due to constraints imposed by the manual measuring of several foot dimensions and manual crafting of a shoe last to fit the specific foot dimensions through a trial-and-error approach [7, 8]. In recent years, with the rapid development of computer technology and advanced design and manufacturing technologies such as computer-aided design (CAD) and computer-aided manufacturing (CAM) [7, 8, 16–26], to automate the process of manufacturing, the customized shoe lasts become possible. The published approaches can be summarized into two categories: (1) to retrieve the best fitting shoe last from the available shoe last library or database based on the 3D foot scan of the customer through geometric similarity comparison [16–18] and (2) to deform an existing shoe last into the customized one that matches with the scanned foot data through free-form deformation
Int J Adv Manuf Technol (2010) 46:11–19
[19], amendment of distance map [7, 8], or some other methods [20]. However, most of the proposed methods do not have the ability to allow the customer to freely select shoe fashion/style and then design the shoe lasts with both the customer’s chosen style and unique foot size and shape. Consequently, the primary objective of this paper was to describe a CAD system which can be used for designing customized shoe last tailor-made for the customer’s foot and the chosen style. The rest of paper is organized as follows. The system design of the CAD system is presented in Section 2. Section 3 describes the detailed design of the CAD system and each module. The experimental results for assessing the effectiveness of the CAD system are presented in Section 4. Section 5 discusses the proposed CAD system and concludes the paper.
2 System design The input into CAD system begins with the customer’s selection of the style (toe style, color and shoe material combinations, heel height, etc.) from shoe digital database. Then, the customer’s feet will be laser-scanned through a YETI™ foot scanner; this process takes approximately 10 s [10]. The customer can then leave the store and the customized shoes will be delivered to the customer’s mail address within a few weeks. Based on aforementioned two inputs, the CAD system will design the customized shoe last through the procedure shown in Fig. 2. Visual C++ and OpenGL have been used for the system development, and the system consists of three main modules (Fig. 2): (1) automatic extraction of 18 important foot features from a laser scan of the customer’s foot; (2) a global grading together with a local deformation approach that can deform the base shoe last of the customer’s chosen style to the customized shoe last based on the extracted foot features without altering the style of the base shoe last; and (3) a color-coded map for the final evaluation of the fit/match between the reconstructed customized shoe last and the customer’s foot.
3 Detailed design of each module 3.1 Module 1: automatic extraction of foot features
Fig. 1 Foot shoe last triangle
After the customer has selected the shoe style from a digital shoe database, the base shoe last has been determined. However, the base shoe last probably does not fit the customer’s foot in terms of both size and shape; thus, the base shoe last should be modified/reconstructed to match the customer’s foot. In order to do this, the key features of that foot should be first extracted from the laser-scanned data, which
Int J Adv Manuf Technol (2010) 46:11–19
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Fig. 3 Laser scan of the foot: the points are arranged in several parallel slices spacing by 1 mm
Fig. 2 Proposed procedure for foot-feature-based shoe last customization
consists of approximately 90,000 3D points distributed on the surface of an average foot (Chinese size 40) shown in Fig. 3. In this study, 18 key foot parameters (five lengths, four widths, three heights, six girths) have been identified from the design requirements for a customized shoe last [27, 28]; their definitions are given in Table 1. The 18 foot dimensions are primarily needed for characterizing the particular foot and reconstructing the customized shoe last later (Section 3.2). 3.1.1 Foot scan data alignment Since the automatic calculation of lengths, widths, and heights depends on the measuring axis, which can be affected by the customer’s foot orientation during scanning, an automatic alignment is first applied on the scanned data to adjust the foot orientation to ensure consistency. This is done by letting the foot heel centerline be consistent with the scanner longitudinal axis (X-axis, Fig. 4) through an alignment process similar to that used in Feng [12]; the process is described as follows (Fig. 4): Step 1. Select all scanned points no more than 25 mm above the bottom of the foot (XY plane, Fig. 3) and project them on to the XY plane.
Step 2. Pick all projected points satisfying X 2 Xmin; 20% ðXmax Xmin Þ. Note that (Xmax − Xmin) is approximately foot length; hence, 20% × (Xmax − Xmin) corresponds to approximate 20% of the foot length from rear and thus can be considered as the foot heel region. Step 3. Divide the aforementioned heel region into K (round to integer) sections; each section has a thickness of 1.1 mm, since the interval between each scanned slice from the laser scanner is around 1.0 mm (Fig. 3). Step 4. For each section i (=1,2…K), find the two boundary points (point with minimum Y coordinate and point with maximum Y coordinate) and then determine the midpoint Ci. Step 5. For the jth iteration, fit a least-square line Y ¼ aj þ tan qj X from K midpoints Ci; the fitted line is considered as the temporary heel centerline. Step 6. If qj 0:00175 (corresponding to 0.1°), go to step 8; else, rotate all the projected points by θj in a clockwise direction (if θj ≥0) or by −θj in an anticlockwise direction (if θj
