Product design and engineering

This paper describes the results of an experience carried out in the field of systematic innovation. Its main goal has been to verify the validity of evolutionary laws introduced by TRIZ theory applying them to a complex industrial product. The product considered is a washing machine and particular attention has been focused on two sub-systems, the tub and the soap dispenser. The paper, first, describes the patent search activity carried out for both the whole washing machine and the specific subsystems; then their evolutions have been single out and compared with the evolution patterns coming from the formulation proposed by Savransky.

Keywords: Intellectual property management , Trend of evolutions , TRIZ

In this paper, we describe a framework which helps designers visualize and verify the results of robotic work cell simulation in a Virtual Environment (VE). The system aims at significantly reducing production costs and error sources during manufacturing processes. The means to achieve these goals are the development of a prototypical VE for the support of robots planning tasks, reuse of animation events, and the implementation of customization tools for animation elements and their behavior. By using advanced Virtual Reality (VR) techniques, the system is also able to direct the focus of the observer to interesting events, objects and time-frames during robotic simulations in order to highlight the Human Robot Interaction within the manufacturing systems. © The Eurographics Association 2007.

Benign Paroxyrnal Positional Vertigo and variants, collectively called "vestibular lithiasis", designate a common disorder caused by a malfunction of the inner ear. These pathologies are connected with the presence of dense particles within the semicircular canals which interfere with the sensing capabilities of angular velocity in the patient, causing nystagmus and vertigo. Some of these conditions can be treated by repositioning maneuvers physically done by the doctor that moves the head of the patient along different poses in space. Despite the fact that the treatment shows a success rate up to 80-90%, the failure rate remains highly significant and it is proven that precision repeatability and unlimited 360° manoeuvrability can improve diagnostic and treatment potential for overcoming this kind of vertigo. In this paper the kinematic design of a serial robot that will execute repositioning maneuvers automatically is performed through a simplified task based kinematic design technique. The aim of the method is to find the minimum number of degrees of freedom to carry out a set of given tasks as well as the manipulator's topology and the Denavit-Hartenberg parameters. The proposed procedure firstly minimizes the number of degrees of freedom only and then a cost function connected to the total link length. © 2007 IEEE.

Keywords: BPPV , Data structure , Discrete optimization techniques , Genetic algorithm , Inverse kinematic , Task based design

Range maps registration still represents one of the most time consuming phases in the digitization of 3D shapes due to the high user intervention required. The traditional approaches are, in fact, based on manual rough alignments, followed by ICP refining techniques. On the other hand, existing unattended methodologies, based on the automatic searching for correspondent morphological singularities on adjacent point clouds, do not seem to guarantee sufficient robustness and flexibility in the fast reconstruction of target objects. This paper presents a methodology to acquire free-form shapes by combining a 3D stereo vision system and a fully automatic range maps registration process. The automatic alignment is carried out without any assumptions about the initial positions of the point clouds and is based on the automatic detection of fiducial markers, located on the surface object, by processing grey intensity images. © 2008 Taylor & Francis Group.

This paper describes an approach for comparative evaluation of manufacturing cost in the early stage of the design process of products and assemblies. The methodological approach used here refers to Design For Manufacturing and Assembly technique (DFMA) and is addressed towards the development of optimized design solutions.

This paper describes an approach for comparative evaluation of the response of a system in different domains in the early stage of the design process. The solution proposed here is based on the following ideas: feature based product representation, which serves as a 'shared product description'; estimation of the response of the system in a set of points (training points) through automatic simulation; categorization of the system response; generalization to other design regions through classification trees; evaluation of reliability. The result is an approximated 'model' of the system we are investigating. The level of detail of the model can be modified by changing the number of classes used to categorize the response.

Keywords: Classification trees , Cost estimation , Design-by-feature , Product design

Mandibular distraction osteogenesis is a clinical procedure used for modifying the mandibular geometry when problems of dental overcrowding and arch shrinkage occur. The objective of this study is to use a computational model of tissue differentiation to examine the influence of the rate of distraction on bone re-growth within the fracture callus of a human mandible submitted to symphyseal distraction osteogenesis. A 3D model of the mandible is reconstructed from CT scan data and meshed into finite elements. Two different mastication loadings have been investigated: a 'full' mastication load and a 'reduced' mastication load where the action of each muscle was reduced by 70%. Four different distraction rates were analyzed: 0.6, 1.2, 2, and 3 mm/day, allowing a total displacement of 6 mm. In the early stages of the distraction process it is predicted that there is a decrease in the amount of bone tissue forming within the center of the fracture gap for all distraction rates. After the initial phases of expansion, the bone tissue within the callus increases for the slower rate of distraction or continues to decrease at the faster rates of distraction. At the end of the simulated maturation period, 47% of the distracted callus was predicted to consist of bone tissue for a distraction rate of 0.6 mm/day, decreasing to 22% for a distraction rate of 3 mm/day. Significantly higher amounts of bone formation were predicted for all distraction rates for the case of reduced mastication loading. Disparities between the model predictions and what is observed in vivo were found. For instance, during the latency period, the distraction period and beyond, the model is predicting larger than expected amounts of cartilage tissue formation within the callus. This and other limitations of the proposed model are discussed and possible specific explanations for these disparities are provided in the paper. The model predicts a distraction rate of around 1.2 mm/day to be optimal as higher rates produce less bone tissue while the risk of a premature bone union is greater at slower rates of distraction because in the latter stages of the distraction process bone tissue is predicted to form between the left and right side of the bone callus. © 2007 Biomedical Engineering Society.

Keywords: Finite element analysis , Mandibular distraction osteogenesis , Mechanobiology , Osteotomized human mandible , Tissue differentiation

Cosmic rays, mostly composed of high energy muons, continuously hit the Earth's surface (at sea level the rate is about 10 000 m-2 min -1). Various technologies are adopted for their detection and are widespread in the field of particle and nuclear physics. In this paper, cosmic ray muon detection techniques are assessed for measurement applications in engineering, where these methods could be suitable for several applications, with specific reference to situations where environmental conditions are weakly controlled and/or where the parts to be measured are hardly accessible. Since cosmic ray showering phenomena show statistical nature, the Monte Carlo technique has been adopted to numerically simulate a particular application, where a set of muon detectors are employed for alignment measurements on an industrial press. An analysis has been performed to estimate the expected measurement uncertainty and system resolution, which result to be strongly dependent on the dimensions and geometry of the set-up, on the presence of materials interposed between detectors and, ultimately, on the elapsed time available for the data taking. © 2007 IOP Publishing Ltd.

Keywords: Cosmic ray muons , Elementary particle detectors , Mechanical alignment monitoring , Monte Carlo simulations , Multiple scattering , Position measurements

Reverse Engineering and Rapid Prototyping are consolidated practices in the industrial product design process. In any case, best practices should be set up according to the type of product and of objectives. This paper presents the results of a product re-engineering application in the field of high quality stainless steel cutlery. This activity included a re-modeling of a basis-shape that reproduces at best the original shape of a cutlery set designed in the Thirties for Alessi, which is still considered to be very fashionable. The shape of the manufactured physical pieces of cutlery has changed in time in respect to the original design, mainly because of some problems related to their manufacturing, which has been transferred from the central plant to other branches. We have obtained the digital model of the pieces of cutlery on the basis of the analysis of the available original 2D drawings, and of the laser scanning and subsequent re-engineering design of the available manufactured objects. Particularly complex activity was the removal of the shapes deviations due to the different forming techniques used in the various production factories. At the end of the reconstruction activity, physical prototypes of the new models were produced by means of a sintering process in order to evaluate and compare them to the original ones. © The Eurographics Association 2007.

This paper presents the results of a research project aimed at developing haptic tools for virtual shape modelling resembling real tools like rakes and sandpaper used by modelers and designers in the real workshop. The developed system consists of a CAD (computer aided design) system enhanced with intuitive designer-oriented interaction tools and modalities. The system requirements have been defined on the basis of the observation of designers during their daily work, and translating the way they model shapes using hands and craft tools into specifications for the modelling system based on haptic tools. © Springer-Verlag 2007.

Keywords: 3D interaction techniques , Haptic interfaces , Haptic modelling , Virtual shape modelling

The field of computer graphics is greatly increasing its overall performance enabling consequently the implementation of most of the product design process phases into virtual environments. The deriving benefits of using virtual practices in product development have been proved intrinsically highly valuable, since they foster the reduction of time to market, process uncertainty, and the translation of most prototyping activities into the virtual environment. In this paper we present the developed platform in mixed environment for ergonomic validation. Specifically we defined a methodology for testing both aspects related to design and ergonomic validation by allowing the tester to interact visually and physically with the car dashboard control devices and related interface by the mean of a rotatory haptic device. By experimental session it has been highlighted that it is possible gathering qualitative data about the design, and finding typical occlusion problems, but also quantitative data can be collected by testing the infotainment interface and the consequent users' distraction during the device use. © Springer-Verlag Berlin Heidelberg 2007.

Keywords: Ergonomic analysis , Mixed environments , Tactons

This paper presents some results of a research project aiming at developing haptic tools for virtual shape modeling resembling the real tools like rakes and sandpaper used by modelers and designers in the real workshop. The developed system consists of a CAS (Computer Aided Styling) system enhanced with intuitive designer-oriented interaction tools and modalities. The system requirements have been defined on the basis of the observation of designers during their daily work and translating the way they model shapes using hands and craft tools into specifications for the modeling system based on haptic tools. The haptic tool and the interaction modality developed for exploring and sanding a surface is presented in the paper. © Springer-Verlag Berlin Heidelberg 2007.

Keywords: 3D interaction techniques , Designer-centered user interface , Haptic interfaces , Shape modeling

Defining a procedure for the characterization of the crankshaft and entire engine unit, based on CAD-FEM multi-body methodology, would provide an analysis tool which avoids the simplified hypotheses usually accepted when designing these components. The methodology is based on the Craig-Bampton method, i.e. on the theory of component mode synthesis. According to the Craig-Bampton theory, the deformation of a flexible crankshaft interfacing with the rest of the engine is obtained through static and normal modes, considering the discretized model with a large number of degrees of freedom and using modal truncation. It is based on the separation of interface and internal d.o.f. Using modal stress analysis has the advantage of reducing the d.o.f. of the FEA model. The multi-body model includes the elasticity of the camshaft and the reduced inertia of the gearbox and timing system. Comparing simulations performed at different engine speeds, the crankshaft evidenced the angular oscillations of generic sections of the axis and shaft, without separating the bending and torsional d.o.f. At higher engine speeds, the vibrational response showed how the harmonics with greater amplitude correspond to the crankshaft's first natural modes and are excited by some harmonics present in the engine moment.

This paper presents a computer-aided design (CAD) module able to analyze different manufacturing configurations of tubes used in mechanical assemblies, such as exhaust system manifolds. It can be included in the knowledge-based expert system category and has been implemented into a CAD platform as a dedicated module able to take into account manufacturing requirements related to tube bending, hydroforming, and cutting. The expert's knowledge, in terms of set of rules and criteria, has been implemented by means of the automation tools of CATIAV5R10 according to the socalled methodological formal approach. The resulting module is able to join different tubes starting from their geometrical models, obtaining a set of manufacturing alternatives. Each of them is verified with respect to collisions with a bending machine and also in terms of hydroforming process feasibility. Only those solutions that satisfy these checks are accepted as feasible and ranked according to three evaluation criteria related to manufacturing cost and easiness. The system is completely automatic and able to analyze more than 100 different configurations in <10 min. The feasible solutions are saved as CAD model to allow FEA of hydroforming and other possible CAE activities. Unfeasible solutions are deleted but reported and documented in a log file. The feasible solution rank is given in a table and has been developed according to a multicriteria approach to make optimal solution detection easier. The proposed test case aims to show and discuss these capabilities. By this module, two or more components of the exhaust system manifold can be manufactured in one stroke as a single component, starting from the same pipe and next trimmed to obtain the desired final parts. This capability can be used to reduce scraps and improve cycle time of the manufac-turing process. Copyright © 2007 by ASME.

Keywords: CAE , Design to manufacturing , Knowledge based expert system , Tube bending , Tube hydroforming

The findings emphasized by this paper are posited on the multidisciplinary design teaching, in particular about a method used within the Politecnico di Milano, Facoltà del Design, Inter-Faculty MSc Degree Course in Design & Engineering (D&E). The new awareness of the importance of knowledge of the years when the Faculty of Design was born, was one of the crucial elements of the productive system, together with the reassessment of business organization [7], [14]. Consequently, the University was forced to reconsider knowledge conveyance, that doubted the potentiality of the "deductive method" and considered the new "inductive method" [4], [11]. The paper will further describe the new Inter-Faculty MSc Degree Course in Design & Engineering, that was born in 2004, with the idea to form designers able to solve technical problems of medium-high complexity products/projects. The MSc Course in D&E is the only Design Course at the Politecnico di Milano structured including the participation of students and teachers from3 faculties (Engineer Industrial Process Engineering, Industrial Engineering and Design) and for that the students have to attend a specific educational ground to uniform their knowledge [9], [12]. The heart of D&E course, as the other Design faculty courses teaching structure, is the Industrial Design Studio based on the idea of "learning by doing" [6]. In this case the Design Studio is structured to help students to manage the resources of different knowledge typologies, this peculiarity will be described by analysing the aforesaid idea.

Keywords: Design engineering , Multidisciplinary teaching , Teaching processes

This article is focused on the integration between KBE (Knowledge Based Engineering) applications for Design Automation (DA) and companies' data repositories managed by PLM (Product Lifecycle Management), and PDM (Product Data Management) systems. In particular, the authors conducted their research proposing a method to retrieve data or documents of pre-existing components from a document repository, before proceeding to design products. As result of that, designers save time spent in design, verifying loops and documents producing, thanks to the reuse of existing components or product. In order to illustrate their approach, the authors developed an application where the KBE system checks the availability of existing components or products before let the designer proceed to design. New produced documents are stored into the data repository for next design activities. The paper is organized as following: first, it starts with the description of some relevant aspects in engineering design: product and process representation, knowledge reuse and sharing, PDM and KBE functionalities; then, the paper continues analyzing the functionalities of KBE and PDM system in order to introduce the issue of the integration; third, it goes on describing the approach followed by the authors; next, it describes the application above mentioned and performed by the authors on these topics; finally, the results of the work are reported.

Keywords: Design Automation , KBE , PLM

Surface polishing is a typical example of a machining process based on mixed chemical-mechanical phenomena, as pointed out in the recent literature on the polishing process (CPM - Chemical Mechanical Polishing). In this work, a model is proposed for the assessment of surface roughness evolution in the polishing process of glass moulds, used in the manufacturing of ophthalmic lenses, in order to identify the influence of the operating parameters on the material removal rate (MRR). In this model the evolution of surface roughness during the polishing process is based on Reye hypothesis. According to such hypothesis, the removed material in a specific time interval is proportional to the friction work: the removed material per unit area can be computed by adequately integrating the bearing ratio curve (Abbott-Firestone) of the surface; the friction work per unit area is proportional, according to the dynamic friction coefficient, to the integral of the product of pressure and velocity in the time interval. A similar result can be also obtained adopting other wear models, e.g. the Preston or Archard approaches. The model validation was performed on ground glass flat samples polished with increasing values of MRR. Pressure and velocity distributions on the sample surface were established according to the polishing machine operating parameters by means of the Hertz theory; the surface roughness of the sample was mapped using an atomic force microscope (AFM). The developed model shows a satisfactory estimate of surface roughness evolution during the polishing process and confirms the experimental results found in literature.

Product design and optimisation today involves so many fields of expertise, many of which are in rapid evolution, that it can be very difficult for the designer to manage them. This paper describes the development of the DGLs (Design Guidelines), a knowledge-based tool that could be of great help to designers and engineers in modifying their products to get compatibility with different manufacturing and verification technologies. The current release of the DGLs, heavily influenced by the adoption of some ISO-GPS (Geometrical Product Specification) concepts, has been validated using the Rapid Prototyping technique called FDM (Fluid Deposition Modelling) and the CMM (Coordinate Measuring Machine) verification technique. © Springer-Verlag London Limited 2007.

Keywords: Design Guidelines , Geometrical Products Specifications (GPS) , ISO Technical Committee 213 (ISO/TC 213) , Knowledge based systems (KBS) , Rapid Prototyping

It is well known that the geometrical accuracy is a very relevant problem in Incremental Forming operations, since the material is not well sustained and, then, the elastic springback plays a significant role during the process. A number of researches are involved in the study of geometrical precision after the forming stage but considering the sheet clamped to the equipment. However, it is well known that material coupling is carried out after trimming, when it could change its shape after the new equilibrium. In the paper here addressed the above concept is kept in touch and a wide experimental campaign has been set-up in order to acquire experimental information on the effect of unclamping and trimming after incremental forming processes. The obtained results are able to suggest to the process designer some best practices which are accurately discussed in the paper.

Keywords: Incremental forming , Precision , Sheet metal forming

In this work we focus our research on the product design related aspects; currently we deal with modularity, product architecture and change propagation issues along the design process. In order to apply abstract concepts to design practise different approaches and tools have been proposed; anyway presently concrete software solutions and applications examples are still lacking. Companies modify their products for a number of reasons and rarely start from new ideas when designing. Due to the lack of suitable tools and methodologies designers are not aware of modifications impacts and propagations when trying to change or update a product. In this paper we present our research efforts in developing a methodology and the related software tool to support change management during the product redesign. It is conceived as guiding tool based on a product multilevel representation: from functional contents to implementation design; currently the designer can obtain a complete presentation of the product parts characteristics and their relations. In this way the resulting graphical model becomes a company tacit knowledge repository about the product. Operational functionalities are provided to support the designer during his activities. This work has been carried out and tested on the redesign process of a washing machine in collaboration with an Italian company, leader in house working appliances.

Keywords: Change propagation , Modular structure , Product architecture