A Novel Standard for Footwear Industrial Machineries - IEEE Xplore

IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS, VOL. 7, NO. 4, NOVEMBER 2011

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A Novel Standard for Footwear Industrial Machineries Giovanni Danese, Member, IEEE, Sergio Dulio, Mauro Giachero, Francesco Leporati, Member, IEEE, and Nelson Nazzicari

Abstract—Economic globalization has scattered industrial production, promoting manufacturing models able to chase the most favorable conditions in the widened international scenario. Interorganizational communication becomes thus a critical element for production streamline, being the bridge that creates continuity among industrial districts. However, many sectors still lack proper communication standards, thus slowing the production and increasing its costs. The footwear manufacturing industry especially suffers from this condition, having chronically promoted a plethora of similar-but-incompatible dialects to supply partial data exchange. To regulate and rationalize part of the footwear industry interorganizational communication, in this paper, we present the Shoe PRocess INTeroperability Standard (SPRINTS), conceived and carried out within an industrial district, ranging from shoe design to mass production. SPRINTS is based on the XML standard language to define a data exchange protocol among systems and machines of the footwear production field. SPRINTS describes both “vertical” transfers (i.e., between different steps of the design/production chain), and “horizontal” transfers (e.g., to allow data exchange between CADs from different vendors). Moreover, it allows a smooth transaction from existing standards, and it has been tested in real-world scenarios. SPRINTS is designed in collaboration with ASSOMAC, an association of shoe machineries manufacturers, comprising the worldwide majority of footwear manufacturing companies (http://info.assomac.com). The standard has been validated and already adopted by a few companies, that contributed to its development. In this paper, we present the standard and a tool able to validate and graphically render a SPRINTS file. Index Terms—Footwear manufacturing, industrial districts, interoperability, XML data exchange standard.

I. INTRODUCTION: THE NEED FOR A COMMON DATA STANDARD

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N the last decades, intelligent automation led to a dramatic improvement in the manufacturing process in terms of costs, quality, safety and affordability with respect a pure craft-made production [2]–[4]. The advent of the economic globalization introduced a diversification: low/medium quality products are made in countries Manuscript received March 31, 2011; revised June 22, 2011; accepted July 03, 2011. Date of publication September 06, 2011; date of current version November 09, 2011. Paper no. TII-11-187. G. Danese and F. Leporati are with the Department of Informatica and Sistemistica, University of Pavia, Pavia, I-27100 Italy (e-mail: [email protected]; [email protected]). M. Giachero is with 7pixel S.r.l., via Copernico 2, I-20082 Binasco, Milano, Italy (e-mail: [email protected]). N. Nazzicari is with CSIS, Computer Science Department, George Mason University, Fairfax, VA 22030 USA (e-mail: [email protected]). S. Dulio is with Dulio Consultants and Assomac [1], I-27029 Vigevano, Italy (e-mail: [email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TII.2011.2166789

offering low-cost labor, and high-quality products are still made in historical districts, where, however, a wider industrialization and automation should be introduced to reduce the too expensive craft-made contribute. The footwear sector is a good example of this trend [5], [6]. The growing relevance of Inter-Organizational Systems (IOS), especially in the case of industrial districts, has raised much attention both in the academic literature and business practice. IOS could be defined as comprehensive logic and technological architectures that integrate interorganizational processes through shared data and knowledge flows [7], [8]. The aim is to satisfy interfirm coordination needs also including electronic data interchanges and standards for digital communication, supply chain management, electronic funds transfer, interfirm knowledge management tools, shared databases, and so on. Features of the industrial district model—especially the emerging ones—fit very well with functionalities and opportunities offered by IOS and coordination technologies in general. Since the middle of 1990s, probably Electronic Data Integration (EDI) is the most known kind of digital interface. Compared with the past, the notions of open standards and modularity characterize the modern era of IOS. Current interfaces—i.e., XML, WSDL, SOAP, APIs, and “ad hoc” solutions—permit to logically decomposing district value chain into many discrete functions/capabilities and easily resembling it, in absence of a high dependence on a specific node. A digital communication standard, with its own specific industry-based data dictionary, allows a fluent direct electronic data transfer between information systems/technologies. It provides a common set of business terms, definitions, and digital forms. If inconsistencies or inefficiencies are detected, then the district architecture could be rapidly reengineered without unreasonable investments. API technology applies the modular connectivity approach also to the level of different “pieces of software” that perform specific functions. The benefits of this approach, especially in the district framework, are evident. The main problem is the effective adoption and sustained diffusion of the standards [9]. Indeed, technological interface shows its potentials only if a large number of network nodes adopt that common digital language. Compatibility, switching costs and relative advantages are some of the most frequently considered determinants towards interface diffusion. However, the very critical issue in the district framework is probably the firm perception about “relative advantage” of technological standard. It means the extent to which a potential adopting firm views the new digital interface as offering competitive and cost reduction benefits, benefits over previous ways of performing the same tasks. In terms of technological interface, another critical point concerns the choice about property communications standards

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versus open systems. The former leads to a competitive advantage based on ambiguity and inimitability, while the latter support the development of competitive advantage based on the so called “first mover” advantage, on sustained diffusion and on dynamicity over time, also in the case of small and medium enterprises [10]. The industrial district of Vigevano, located in the north-western Italy, is known worldwide for the high quality of its production of machineries and industrial equipments for shoe, leather and tan industries. However, from the beginning of this century, the footwear machinery industry has been increasingly confronted by a fierce competition. Although recent years showed a moderate economic resumption of this district and a partial retrenchment of the emerging economies impressive expansion, local small enterprises recognize the need for a radical strategic repositioning, especially towards: • intercompany networking initiatives, in order to create flexibility among local Small and Medium Enterprises (SMEs); • innovation projects, as a response to the rapid growth of environmental turbulence and dramatic cost reduction stemming from emerging competitive economies; • better exploitation/exploration of ICT technologies, in order to amplify benefits and highlight new opportunities about the first two points. These interoperability and efficiency requirements highlight the need of a unique and universally accepted communication standard. A lot of data description formats are available (DXF, IGES, STEP, VRML among the most popular and used). However, they are often hard to be managed and interpreted. Moreover, they are linked to specific implementations, and adopted by isolated producers independently. Interoperability is thus hardly achieved. Close to them, several proprietary formats survive, often used as a defense for application domain or markets, instead of a real support to the interoperability of the customer systems. On the other hand, shoe producers notice more and more the need of exchanging data within the same firm or among the chain companies and could gain considerable benefits from the availability of a standard, complete and adopted by the most important market players. Since the footwear industrial field is highly specialized, a universal data exchange protocol would be very useful, allowing a compatible data exchange among machineries charged with several production phases. At the present time, a similar standard protocol does not exist and shoe design is made through CAD programs. However, different software manage geometrical data in a substantially different way. Typically, nongeometric information, intrinsic of shoe manufacturing process, are squeezed in CAD files through ad hoc customizations. Moreover, since a lot of unofficial dialects are present, often companies are forced to produce case-specific filters to adapt and translate files between formats. This confusion makes the process slow and expensive. Human contribution is still critical whenever a data transfer is needed between different softwares. This scenario forces all companies to control and adapt the information coming from CADs (typically in DXF format [11]) or from other machineries (typically in HPGL or ISO format).

In this paper, the Shoe PRocess INTeroperability Standard (SPRINTS) is presented, a XML-based standard that covers most of the information transfers needed in the shoe manufacturing field, from shoe design to production control. SPRINTS was conceived and carried out within an industrial district, and copes with the real-world necessities of the partner companies. The proposed standard focus on the generalization of the data structure and hierarchy, and is as technology independent as possible. SPRINTS can describe both vertical transfers (i.e., between different steps of the design/production chain), and horizontal transfers (i.e., to allow data exchange between CADs from different vendors). SPRINTS was created by means of an incremental and iterative approach. Industrial partners provided information and objectives to the development team, which responded with a prototype. The prototype was then analyzed and checked by the companies, providing suggestions on fine-tuning arrangements, and sent back to us. The process went through several iteration up to the point where all functionalities were satisfactory for all partners involved. In the following, the technical requirements are described suggesting the design and the adoption of a XML standard for data description (Section II), together with the different phases characterizing the manufacturing shoe process (Section III) and the limits of the previous projects that tried to propose a unified “language” for footwear machineries (Section IV, “state-of-theart”). Sections V and VI depict the “structure” of the developed standard, whileSection VII illustrates a viewer tool which allow to easily open and visualize a SPRINTS file, while verifying its compliance to the format. The benefits assured by SPRINTS adoption and the feedback of the companies involved in the project are highlighted in Sections VIII and IX. Considerations about the work still necessary to spread the standard diffusion conclude this paper (Section X).

II. THE PROBLEM Modern production contexts need wider and wider interoperability among software applications with different nature and origin. Indeed, this is relevant especially when passing from the design to production, exploiting strong automation and integration among processes and inside them. At the same time, interoperability is needed at the shop-floor level when machineries with strong automation should communicate among themselves (synchronization signals or process data) or with computer systems controlling production lines or their single cells. There are examples in literature of standards defining process data developed in several but different sectors to reach these targets [12]–[18] and of papers providing a survey about them [19]. However, the features of the footwear field led us to a completely innovative and application specific proposal. We distinguish three types of data that need to be exchanged (Fig. 1): • geometrical data, produced during the 3D Computer Aided Design (CAD) design process and relative to the last, to the upper together with its components, and to the other main

DANESE et al.: A NOVEL STANDARD FOR FOOTWEAR INDUSTRIAL MACHINERIES

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Fig. 2. Shoe design and its components. Fig. 1. Data exchange directions in footwear manufacturing.

III. THE MODERN FOOTWEAR INDUSTRY constitutive elements like the bottom (leather or plastic) and heels; • technological data, integrating the geometrical ones with information related to the specific process producing each designed shoe’s component and depending on its nature and on the correspondent cycle phase (i.e., which cutting tool should be used or its action range); • process data, specifying the machinery to be used in the particular production phase (i.e., rotation velocity in a roughing head or the number of passes of a rotary brush for glue). These data feature proper characteristics and description needs and can be exchanged horizontally (i.e., among software applications or machineries of different manufacturers and with heterogeneous characteristics and even among different subjects operating in the same die during same designing or production phases) or vertically among different phases (i.e., between design and production or between the process control level and the single machineries, also in this case considering different subjects operating in the same chain [20]). Finally, the efficient management of these processes requires describing relevant data regarding nature, function, source and destination, in a universal understandable way and to transport/ transmit those data in a safe and affordable way among different applications and phases. These ideas motivated the design of the SPRINTS standard format (intellectual property of ASSOMAC) describing geometric, technological and process data related both to machineries and to their driving applications. At first, it has been conceived, starting from a reconnaissance of what until now was adopted by the different companies, which brought to a first definition incorporating all the benefits of the proposed solutions. Then, a first group of pilot companies began to introduce the standard to spread its utilization throughout the shoes machineries sector. The presence of companies leading this manufacturing area helps in establishing SPRINTS as a de facto standard for machinery data exchange.

In the following, we give some fundamentals about shoe components and their different manufacturing phases. People familiar with these topics can skip this description and continue with Section IV. A. Shoe Components The basic components of a shoe are (Fig. 2): upper, insole, sole, and heel; others optional parts can be added such as laces, buckles, buttonholes, etc. The upper is the topmost part of the shoe, attached to the insole and the sole through stitching and/or glue. It can be realized from different materials such as leather, fabric or other less valuable materials. In the classic shoe kind, it is divided into vamp, which covers the foremost part of the foot, and quarter. Often uppers are reinforced with a reinforcement tip and counter (on the back). The insole is the base the shoe is built on; it is the most critical bottom component from a functional point of view, since this is where the foot plant lays and is the junction element between upper and sole. In most cases, it is made of fiber paperboard (covered with a thin leather layer on the inner shoe side at the end of the manufacturing), while only seldom leather or other materials are used. The sole is the part laying on the ground and is made of leather, rubber, plastic or even wood. It is attached to the upper with nails, glue or stitching. The heel is a support made of leather, wood, rubber or other materials, applied to the back part of the sole in the heel area; its height ranges from a few millimeters to several centimeters. Aside from sustaining the body weight, it gives the shoe its particular appearance, and this is the reason why there are so many variants. B. Shoe Design Up to a few decades ago, shoe design and construction could be considered a fruit of engineering, architectural and stylistic

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experience, surely a great demonstration of manual skills. Almost everything was left to shoe designer’s fancy, interpretative ability and experience. The dependence on the skills of a single person and the time required by the design (often requiring repeated trial-and-error steps) induced companies to spend energies on the automation and simplification of the whole process. This change is still happening, and the current production mixes up technology and handcrafting skills. The CAD and Computer Aided Manufacturing (CAM) technologies were introduced in the footwear sector only in the 1980s. Developing these new technologies became important when the fashion induced a much wider selection of different shoe models. There are two main footwear CADs: • 3D CADs which allow the designer to interact with 3D entities such as the last, heel, upper, and sole in a way similar to the traditional manual process; • 2D CADs which only allow to manage the upper after it has been flattened. C. Manufacturing Phases Manufacturing a shoe requires a great deal of workmanship and personal experience, even though most of the manual work is assisted by more or less sophisticated machines. There are three main philosophies on which machines for footwear production are built: manual, semiautomatic, or automatic machines. Depending on the amount of automation present in the factory, there can be even the three types of machines all together, spread over the whole manufacturing chain. The shoe assembly process (also named lasting or making) can be split in six main steps: • last and upper preparation; • assembling of the upper on the last; • heat treatment; • bottom and sole preparation; • sole fastening; • last removal and finishing. The number and type of processes required to make a shoe depend heavily on several factors such as the type of shoe, the desired quality of the finished product, production time constraints, and final cost. Here is a list of the most general manufacturing rules, even though every shoe factory follows its own rules. 1) Last and Upper Preparation: The last: the shoe assembling phase is done on a last to give the shoe its right shape. The upper, initially flat, is forced to assume the last shape with pincers and other grabbing devices, which are part of some machines (such as the toe lasting machine and the seat and side lasting machine). This central role in the production process gives the last a great importance, since errors in the last design or production can lead to problems in later manufacturing phases or in the shoe usage. The upper: the initial upper design is performed by a shoe designer directly on the last or on a standard shape (the flattened upper) following the fashion designer drawings. This work is done for a single size, it is flattened (if done on the 3D last) and

scaled to generate all the shoe sizes usually available. A testing phase, during which a small set of shoes is produced, is usually done to detect and fix possible errors. The next step is the component (pieces) production. The leather cutting can be done manually for small productions, or automatically for medium and large-scale productions. Cutting machines can have or not have socket punch, thus actually changing the operations needed to obtain a single piece. Cutting with a socket punch is fast but requires the production of templates (a time-consuming process) which are pressed on the leather. Cutting without socket punch can be either hand-done (using a cutter and a paperboard reference) or automatically using cutting machines which are somewhat similar to plotters with several cutting heads. The pieces to be cut are coded in a file and projected on the leather so that the operator can place them in the best (less space waste) way. There are many technologies for this kind of machines (oscillating blade, ultrasonic, laser, water-jet, etc.). Cutting without a socket punch is very economic and flexible and (obviously) removes the time penalty of building the template itself. It is the preferred technology for prototyping and, with the most advanced software, even less experienced personnel can obtain good results. Nevertheless, for large productions of identical shoes, it is slower than using a socket punch, so there is market for both technologies and indeed some footwear factories have both of them. The leather usually requires the splitting phase to ensure uniform width on the whole area, and a skiving and folding phase to have better-looking edges. Some additional operations can be required, for example to realize ornaments. Once all shoe pieces are available, they are stitched together. As usual, several means and materials are available to achieve different cost/quality compromises. Once the upper is complete, the outside counter performing is done. In this phase, the heel area is thermally shaped and the counter is placed. The insole: the next step is to temporarily fasten the insole to the last, through paper tape or a nail, and its trimming. These operations are usually either manual or performed with semiautomatic machines. 2) Assembling the Upper on the Last: The shoe assembling is usually done with two semiautomatic machines, the tack lasting machine (for the fore part) and the waist lasting machine (for the lateral and back parts). The upper is fastened with glue and/or nails. A peening phase ensures good coupling between glued components. 3) Heat Treatment: The assembled shoe must remain on the last for some time to permanently assume the proper shape. To shorten this time, the shoe is subjected to relatively strong thermal shocks. 4) Bottom and Insole Preparation: The next steps are roughing (used to remove the leather superficial layer whose finishing treatments are somewhat glue repellent) and gluing of the bottom preparing it to the sole fastening. These phases are usually performed through semiautomatic machines, and sometimes the same machine performs both operations. 5) Sole Fastening: In this phase, the sole and the upper-insole (still on the last) are joined. To guarantee perfect coupling


Fig. 3. The manufacturing shoe process.

a sole-press is used. Doing this operation with great care is extremely important for the quality of the finished product. 6) Last Removal and Finishing: Once the shoe is completed the last is removed. It is now possible to fasten the heel and the final operations (like polishing) are performed. After some quality checks, the finished shoe is confectioned. Fig. 3 summarizes the previous considerations onto the shoe manufacturing steps. IV. THE STATE-OF-THE-ART Other standards have been proposed to solve the communication problems of shoe manufacturing process. However, those attempts were seldom adopted by companies and never saw real-world implementations. The CWA15043 [21] project, proposed (July 2004) as part of the EFNET 3 project [22] does not count significant implementations. Some of these projects were too poor to allow a complete description of the process and others were too much specific resulting in a freedom limitation for the machine producers. EFNET3, in particular, was the most recent step of the enterprise promoted by the European Confederation of the Footwear Industry (CEC, [23]) to define a European data description standard (SHOEML), at first related to commercial transactions (EFNET1 and EFNET2), and then to design issues (EFNET 3). In this last case, however, the focus is only centered on the horizontal geometrical data exchange between CAD/CAM systems, touching on our project aims only marginally and in a not complete way. SPRINTS, on the contrary, is the first standard project that starts from the real necessities of both users and producers and that has real possibilities of implementation and adoption. Moreover, SPRINTS is not an isolated project: all along the shoe manufacturing sector a technology innovation is developing. Machinery is a high technology product, but production

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method and production organization yet follow a traditional and old approach and there is no much room for further improvements. However, the necessity of being competitive on new markets requires to optimize also those parts of the process, leading more and more toward a nearly complete automation. In the past, some EU projects aimed at preserving production activities that are bound to shoe manufacturing through the development of advanced production systems. Few projects worked on distributed control system for optimization of materials passing from one machine to another [24] or to apply well known international standards (IEC-61499) to shoes plant automation [25]. Another very innovative high technology project (EUROSHOE) was about the attempt of obtain personalized shoes at prices comparable to those of mass production, developing custom made models as were normal before industrialization [26]. It is not only about the aspect of the shoe but also to adapt it to the real shape of the foot. The target is to have a more comfortable shoe that can be also adjusted to anatomical imperfections. The SHOENET project was strictly related to footwear sector but it was more oriented towards issues related to the Supply Chain and the definition of business documents [27]. The CEC-made-shoe EU project continued the previously cited projects with a definition of a Strategic Collaborative Network able to coordinate production and transmission of business documents and workflow oriented activities (the extremes of the chain) [28]. In [29], more details about these projects can be found, but they unfortunately never reached complete acceptance by the footwear industries so as to be implemented on their machineries. In other sectors close to shoe manufacturing, the standardization already happened, such as in the textile one. However, all analysis made show that in the shoes production, there are several more problems related to the variety and the number of processes involved and SPRINTS features inputs and implementations coming straight from the companies belonging to the field. V. THE GENERAL CONCEPTS OF THE STANDARD DESIGN The process bringing from the idea for a new shoe model to the complete shoe production is compound by many phases, during which the problem arises of describing data in a way that is usable by all process members, supporting communications: • from 2D CADs and cutting machines; • from 3D CADs and last woodturning machines; • from 3D CADs and assembling machines; • involving material variants and production orders. Among these, the most felt issue is the first one, and to compensate for the absence of a standard technology, producers adopted many DXF dialects, incompatible with each other. Nevertheless, they suffer the limitations induced by a format conceived for different uses. SPRINTS introduces a proposal for a data format that: • represents the 2D geometric data without suffering the DXF limitations, and in particular enabling vector and semantic descriptions where appropriate;

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• describes 3D geometric data in a way usable by both CADs and machinery; • describes stitching; • describes material combinations and production orders; • provides a uniform communication language between CADs and machines, and, with minor emphasis, between different CADs. One of the standard objectives is also to be completely independent from adopted technologies and implementation details of any product.

VI. DATA DESIGN SUMMARY AND STRUCTURE OF A FILE The shoe design phase defines the geometries of every shoe component which is associated to a specific manufacturing phase. These geometries are repeated many times, in properly sized versions depending on the shoe model and fit. For what relates to bidimensional processes, two data families can be distinguished, related respectively to shapes and automatic placement. Shape data includes borders and internal paths, with actions associated, text, either printed on the piece or on a sheet accompanying it, notches of various kind. Data related to automatic placement include piece directionality (to account leather anisotropy) and quality areas (hidden areas admit lower quality). About the 3D context, the significant data relate to last geometry, working areas and paths, elements about the insole and heel geometry. Other significant data include assembly directives, material specifications, and production orders. To achieve a suitable file structure while keeping it easy to manage, it was decided to distribute it in different XML files related to different topics; XML is a well known technology indicated by the literature to support interorganizational systems and industrial standards for data exchange [30], [31], and to put all of these and their pertinence in a single ZIP archive. XML, in fact, is not conceived for a specific data set like DXF, but for generically structured definitions explicitly devoted to communicate information of different nature. This defines XML as a “markup meta-language,” since the elements and attributes significance can be customized through a suitable scheme for a specific application field. What follows describes the content of the archived XML files. A. Introduction to the Data Format Only manifest.xml (declaration of the file type) and general.xml (general information about the project) are mandatory: the combination of some or all of the other files available determine the meaning of the archive. The main purpose of manifest.xml is to redefine information concerning the type of file, while preserving the compatibility with previous standard version in the case it should evolve. General.xml, on the contrary, contains information related to the project itself. This currently includes descriptions about the model described, the authors and more generally textual information that are not elaborated.

B. 2D-Geometries Bidimensional geometries description (2d.xml) starts with a series of tags, containing size-independent information and processing data related to specific piece. A unique identifier allows referencing from the size-dependent sections. The component properties list is followed by geometric detag). Components are treated scriptions ( as a set of paths, each divided in a sequence of tracts. To achieve the required flexibility, each tract can be described using several different approaches (sampling, vector-based, semantic), even at the same time. This, together with proper restrictions aimed to ease the format adoption and the development of low-cost solutions, enables several production-time optimizations which are, at the present time, either handmade or completely driven by heuristics. Paths can identify the component perimeter, an internal open or closed working path or an area. To each path is associated an action, describing what has to be done with respect to it. Available actions include cutting, etching and marking (printing on the component surface, usually to ease assembling), as well as operator reference lines and quality information usable by automatic placement algorithms. C. Assemblies This file (assembly.xml) describes stitching paths, grouped by geometry (size). Stitches are defined either using the path abstraction and then specifying some attributes, like back-tacking and point-to-point distance, as well as a set of arbitrary points. This approach simplifies CAD export features and allows the description of decorative stitches (such as company logos). D. 3D-Geometries Three-dimension domain information (3d.xml) are about: • last geometry: it must be defined with different precision levels so it can be used for last turning and for shoe design, moreover surface decomposition must also be easy to do; • workpath definition, allowing automatic tool driving and specifying the action to be performed; • insole and heel basic definition, allowing automatic heel nailing. The last geometry is defined through a sampling process whose rates are organized in accordance to the following rules: • the description uses a certain number of closed lines placed around the last; every line has the same number of points and every point has a unique identifier, that is always the same in different lines; • the final mesh has triangular faces; • the resulting structure is based on rings that share the same number of points. It is possible to specify the interpolation error and for each point the specific surface (top, bottom, upper) to which it belongs. It is also possible to have different sampling (with different distances), but they need to share the same reference system. Concerning the workpaths, geometric features of a lot of manufacturing processes can be defined using one-dimension lines in 3D space (i.e., pulling over—lasting machines, heel-seat lasting machines, or machines for direct injection


onto uppers). Workpaths belonging to the same process can be grouped and it is also possible to specify materials combinations for which the set of workpath is valid. Heel fixing is different from the processes already discussed, so they have their own data structure. Insole and heel base are supposed plane to simplify their representation. Heel volume is approximated by a set of circular frustums. Both in the planar part or in the solid one, it is possible to specify where nails are allowed and were forbidden. It is also possible to specify heel fixing method: nailing, gluing or both. . Specific nuAll information are grouped by size meric identifiers associate 3D information with 2D information contained in other files. For every geometry, it is possible to specify one or more custom coordinate transformation matrices. It is possible to add the meaning of the specified transformation (e.g., one roto-translation could move the last so that one specific point is in the axis origin). E. Materials and Production Order The file is divided in two parts: the first one describes every material usable in the project, specifying its name, thickness, and an unique id. The second part lists material combinations allowed in the project. specifies how many shoes must The file be produced, if some extra copies of a single component are needed, and if the production of other components must be stopped. F. Add-On To improve the data exchange, SPRINTS considers information not managed by the previously used DXF format. Up to now, this information was added through additional files with respect to those provided by the CAD output. An example of this concerns cutting machines with automatic placing for which the orientation of the leather piece with respect a reference direction is required together with the admitted tolerance. These data are not represented in the DXF format, while others have been more conveniently redefined in SPRINTS. A significant example is in the management of the sizes, for which DXF uses the stratagem of tally marks that, however, makes the machines job very dull. In SPRINTS, this problem is solved by simply adding more fields for the requested sizes. VII. THE VIEWER As a part of the development process, we have also implemented a Viewer, i.e., a software able to help suitable standard adoption (Fig. 4), to check the syntax correctness of the data contained in SPRINTS files and to draw those relative to the 2D part, allowing different levels of introspection. The employed software technology exploits Xerces C++library for reading XML files and Qt4 for advanced graphics and for managing the data structures, in a portable way [32]. This last set of libraries is fully used with a rich set of high-level data structures (hash tables, database, meshes, vector graphics) and advanced functions for 2D design. Qt4 allows

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Fig. 4. A typical snapshot of the Viewer.

multithreading and communication among objects through the signal (transmit) and slot (receive) flexible mechanism, intensively employed during the data-tree structure identification [33]. The overall design has been conceived and developed using ArgoUML [34]. At first, a parser has been carried out, which reads the SPRINTS XML file through the SAX interface (exploiting the plug-in Xerces library) returning a tree-structure of the document: we preferred SAX to DOM, since it builds the structure in an incremental, and thus less heavy way. The control check is performed through XSD files (schemas) containing particular keywords that indicate the right content of every file contained in the SPRINTS archive. The internal data representation is a tree-structure that reflects the scheme of the 2d.xml file providing an easy way to access the contained data. On the other hand, the internal structure of the Viewer to manage and visualize the files is complex but enough flexible to allow, in the future, adding further sections. The implemented paradigm was the Model-View-Controller, which provides a separation among data and related graphic interface, together with more Views linked to the same Model, each one upgraded when data are modified. Each component, for example, can be developed in more sizes and each version can be showed with the relative single parts. Moreover, the internal structure of the Viewer is modular, thus easily allowing future development and implementation of new features. Since data contained in the standard file are structured on many levels, it was very important to easily select and explore them: it is possible for the end users to move up and down the data tree, easily showing, hiding or highlighting different elements, executing zooms and pans and customizing the appearance of drawn data selecting different rendering options. Nevertheless, users can also visualize data in text format to manage single elements details and to modify their organization. The Viewer exploits the following technical features: • multiplatform: it is compatible with Microsoft Windows (from 98 to Vista), Mac OS X (from 10.3), Linux, Solaris and other operating systems, supporting both 32 and 64 bit; • it uses hardware acceleration and of the video card when possible; • it is not bound to any specific XML-parsing library, that can be changed dynamically through a plug-in approach; • it provides multilanguage support.

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VIII. THE STANDARD BENEFITS The SPRINTS standard aims to limit or, when possible, to eliminate data passing problems during different steps of shoe manufacturing process. That would be possible only if every actor involved will implement correctly the standard. Here, a brief list is presented of practical advantages coming from standard adoption for the machineries customer side: • no translations needed any more: this will allow more automation, that brings time and cost reductions; moreover, no more translation errors will happen; • it will be possible to receive orders from every customer; • no more binding to specific machinery producers; • elimination (or at least a strong limitation) of on-board machinery programming: that procedure consumes time and slows the production down, on the other hand, the standard adoption supports more efficient offline programming; • it will be possible to get, in every manufacturing step, information from other steps, allowing process optimization and less constraints in designing. Also machinery producers benefit from standard adoption: • leader producers will gain a standard method to describe machine functions, allowing them to concentrate on specific features that characterize their products; • new and growing producers will not need to project new communication solutions and could concentrate on machinery quality; • every producer could reach higher technology levels thanks to an easier way of sharing data. The standard will also help to move production to higher quality levels, that is useful to face towards new and growing markets. Designers will gain new expression freedom, that will help to create strong brands and styles, thanks to a more accurate manufacturing process. Closed standards led to no communication between different companies: the proposed standard could bring to new dynamism and aid new ideas to spread. Concerning its adoption, the standard foresees three gradual integration levels. At first, we need to write down translation programs from old closed standards to the new one (and vice versa). This is the quickest and cheapest method because machineries are not modified so allowing to use old machines that cannot be upgraded anymore. However, this approach adds new steps to existing process and translation can be a very challenging task. The second integration level is useful to computer guided machines: a software update could add the new standard as one of the direct input supported and provides an internal translation. In this case, the standard adoption will be completely transparent to end users. At the maximum level of integration, all machinery is compliant to the standard format and no more translations are needed: a specific driver transforms standard data to electric/mechanical commands. This is clearly the hardest step but also the one that can lead to best results. IX. REAL EXPERIENCE, FEEDBACK, AND LIMITS The analysis and definition work of the standard involved several proof-of-concept tests under the responsibility of a selected

group of companies, which participated in the definition activities of the standard itself. These tests focused, in particular, to the most relevant “use cases” as identified by the testing group and according to market priorities. CAD to cutting machines was agreed to be the most relevant and demanding case to be explored, being this the typical situation in which data are to be transferred between software applications and machinery provided by different vendors in normal productive environments. In the scope of this activity, three cutting machine producers and a CAD developer implemented specific converters in their suite of software applications to write and read data in the SPRINTS format. The tests were run by generating a complete set of data for a normal cutting job in the system of one vendor and importing them in the machine controller of another and proofing both the integrity and completeness of the data transfer as well as the efficacy of the operation. This allowed to demonstrate the compliance of the standard to its initial specifications and its capability to fulfill the industry demands that drove its development. This group of early implementers are currently offering SPRINTS as the recommended data exchange format to their clients. The successful case of the CAD to cutting machine transfer was not followed by similar adoptions for other cases of CAD to machine exchanges, in particular, in the domain of transfers of 3D data to process machines in the shoe assembly phase and the CAD to CAD exchange scenarios. There are several factors that can explain that. The most relevant one is the low market diffusion of highly integrated and automated footwear production systems which, on the one hand, necessarily require a solid and effective data exchange framework such as SPRINTS is thought to provide and, on the other hand, are the ideal vehicle for its diffusion. As long as this technological evolution in the footwear sector is not fully accomplished there will be no strong market drivers for the widespread adoption of the standard and hence its diffusion will be limited to the few implementation cases mentioned above. SPRINTS, nonetheless, represents a powerful enabler for such technological growth of the sector. Its adoption is currently under evaluation as part of a research project dedicated to the study of new shoe manufacturing solution based on a wide usage of robots for various processing steps and whose programming is done via CAD data. In parallel to that ASSOMAC [1] (the association of shoe machinery producers which fostered its development) is intending to continue with its development and to actively promote its adoption by its associated companies.

X. CONCLUSIONS AND FUTURE WORKS Within the footwear manufacturing, the lack of coded or standardized directives and operations forces additional work and leads to the same continuous difficulties recurring every time a specific production phase is going on. Thus, a common effort of the involved industries (although competitors) is needed to define a precise data standardization and to minimize possible incompatibilities: that was the lesson of our case study passing over the considered industrial district.


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REFERENCES

Fig. 5. The SPRINTS stand at SIMAC exhibition

Currently, the standard has been tested and run on a few machineries of the firms involved and presented to the main companies of the sector. Moreover, the design/development of the standard is in its maturity stage. It seems that critical issues concern an expected focus on both business and technological dimensions: • technological issues: due to dynamic innovation of the footwear sector the standard could be in a permanent prototyping; • business issues: standard management (international strategy, closedness versus openness, brand development,…). Several future developments can be conceived at this point in the work, in order to improve the standard and to extend its use: one of the most important, for example, deals with the CADs interoperability; however, we feel that some managerial activities will be critical in order to support the implementation/diffusion phase: • fluent negotiation among firm partners about standard specifications/rules; the aim is to assure a good equilibrium between costs and benefits, between technological upgrade and exploitation of each machinery peculiarity; • communication and marketing, in order to create a critical mass of standard adoption; if only few suppliers accept this language, then the value added for costumers is poor; • openness degree of the standard (is it better to open its definition spreading its diffusion or to make it close defending the achieved production quality?); • certification of the effective adoption of the standard; this is probably one of the critical success factors of SPRINTS: (self-certification? Official body for formal certification? Self-certification and committee for the control of effective/fully adoption? Does Market self- regulate this dynamics?…). A few firms belonging to the industrial considered district introduced SPRINTS in the new version of their machineries. Moreover, the new standard has been officially announced and presented at SIMAC (the International Exhibition of Machines and Technologies for Footwear and Leather Goods Industries) which was held in Bologna on October 2009 (Fig. 5).

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Giovanni Danese (M’01) received the Ph.D. degree in electronics and computer engineering from the University of Pavia, Pavia Italy. He is Full Professor of Computer Programming and Computer Architecture with the Faculty of Engineering, University of Pavia. His current research interests include parallel computing, special-purpose computers, and signal and image processing.

Sergio Dulio has strong experience as a consultant and manager in the technical assessment and performance evaluation of complex automated systems. He led a research consortium with partners in the shoe machinery field and research institutions (Italian National Research Council). He has been active in the analysis and implementation of innovative production processes for shoe manufacturing since 1996 (SINTESI). He was also Director of the Consortium of Italian Shoe Machinery Companies.

Mauro Giachero received the Ph.D. degree and Laurea degree (First Class With Honors) in computer engineering from the Faculty of Engineering, University of Pavia, Pavia, Italy. His current research interests include computer and microprocessor architectures, compilation techniques, and resource-constrained computing.

Francesco Leporati (M’96) received the Ph.D. degree in electronics and computer engineering from the University of Pavia, Pavia, Italy. He is Associate Professor of Industrial Informatics and Industrial Electronics in the engineering faculty at the University of Pavia. His current research interests include automotive applications, FPGA and application-specific processors, embedded real-time systems, and computational physics. Prof. Leporati is a member of the Euromicro Society.

Nelson Nazzicari received the Ph.D. and a 1st class Laurea degree (Hons) in computer engineering from the Engineering faculty, University of Pavia, Pavia, Italy. He is an Electronic and Computer Engineer currently working on joint research projects between the Microcomputer Laboratory, University of Pavia, Pavia, Italy, and the Centre for Secure Information System, George Mason University Fairfax, VA. He is mainly focusing on creating embedded, low-power high-performing hardware for pervasive computing and security related applications.