Geometric dimensioning, tolerancing and inspection

In this paper, a possible application of the DfA (Design for Assembly) principles to deformable parts is proposed. The efficiency of an assembly is expressed with the DfA index, which is influenced by the number of parts compared to the “minimum number of parts” and the assembly time. Deformable parts, if unsupported, can exhibit deformations outside functional limits; however, when assembled, they often need to behave like rigid parts. To achieve the necessary rigidity, a large number of constraints are added. Having a high number of anchor points between a part and the rest of the assembly induces a high assembly time and therefore a low DfA index. This paper aims to provide a methodological framework for designers to define optimal anchor point locations to achieve the desired rigidity with the minimum number of anchor points possible, thereby minimizing assembly time and maximizing the DfA Index. The procedure is based on modal analysis. Subsequent anchor points are added until the predefined rigidity measure, as the natural frequency, is reached. The procedure is validated through a simple case study and then applied to two cases derived from actual industrial applications. It is also shown how the procedure allows for an actual reduction of anchor points.

Keywords: Constraints optimization , Deformable parts , Design for assembly , DfA , Mechanical interface design , Modal analysis , Product architecture

This work collects as a whole the main results obtained in the Design for Sintering project, aimed at improving the effectiveness of a design procedure accounting for anisotropic dimensional change on sintering, through a deep investigation of the related phenomena and mechanisms. The project was developed in cooperation with the main European companies producing sintered components, and it is based on a huge experimental campaign. Ring-shaped parts with different characteristics were produced in different process conditions, and dimensional changes were derived from a careful reconstruction of geometry, measured in the green and sintered state. In the first part of the project, parts characterised by different geometrical parameters and different green densities were produced, using many different powder mixes, from highly shrinking to slightly swelling. The first part of the project highlighted the importance of anisotropic dimensional change in the compaction plane, and a new anisotropy parameter was proposed accordingly. In the second part of the project, the study was then focused on the anisotropy of dimensional changes in the compaction plane, as affected by different compaction strategies. The results were implemented in the design procedure, and process conditions were highlighted ensuring good agreement between real and predicted dimensions.

Keywords: anisotropy , cold compaction , design for sintering , dimensional changes , low alloyed steels

RGB-D cameras have been widely used in various research fields and applications in recent years. With the growing availability of commercial products, choosing the most suitable sensor for a specific application has become more complex. The lack of tools to evaluate and compare the metrological performance of these sensors was addressed by the recent ISO 10360-13:2021 standard, which defines the standards for the metrological characterization of 3D optical coordinate measuring systems. This paper applies the ISO 10360-13 methodology to characterize and compare four RGB-D cameras: three Intel® RealSense™ (D415, D435i, D455) and one Microsoft® Azure Kinect DK. The procedures described in the standard were integrated with three tests: the analysis of systematic errors measured acquiring a planar surface at increasing distances; a test to analyze the resolution performances with a specifically devised artifact; the evaluation of 3D reconstruction performances on two objects with different geometric characteristics. The results highlighted the strengths and weaknesses of each device. The D415 showed better performance in reconstructions from close-range acquisitions. The Azure Kinect DK had the best results for systematic error and resolution. The D455 generally achieved the best performance in the standard tests, followed by the D435i.

Keywords: device characterization , Intel RealSense , ISO 10360-13:2021 standard , Microsoft Azure Kinect DK , performance evaluation

Position-controlled servomechanisms are the core elements of flexible manufacturing plants, primarily utilized to actuate robotic systems and automated machines. To match specific torque and costs requirements, typical servomechanism arrangements comprise precision reducers, which introduce motion errors that heavily limit the final performance achievable. Such errors are complex to model and depend from speed, dynamic loading conditions and temperature. Accurate characterization is fundamental to develop digital twins and advanced control strategies aimed at their active prediction and compensation. To properly assess the servomechanisms behavior and elaborate high-fidelity virtual models, instrumented test rigs have been proposed which can replicate the time-varying working conditions encountered in real industrial environments. In this context, the present paper reports about a novel engineering method for developing an active loading apparatus, namely a programmable mechatronic device that can deliver custom loads in a highly dynamic manner. The proposed system, consisting of a secondary servomotor and related rotating vector reducer, is integrated and synchronized within an existing instrumented test rig and is controlled in torque mode via a programmable logic controller. The paper mainly focuses on the description of the implemented closed-loop control and on the related tuning and calibration processes, demonstrating that the proposed solutions avoid important measurement errors that could compromise the final effectiveness of the system. The study finally explores the potential benefits of introducing a filter to further enhance system performance. At last, to prove the importance of stabilizing the rig and demonstrate the influence of the control parameters on its measurements, a standard test aimed at assessing the reducer transmission error is conducted adopting different parameter settings.

Keywords: Loading system , Mechanical transmission , Servomechanisms , Stabilization , Test rig , Torque control

Robot-based manufacturing cells exhibit strong capability in performing high customizable working cycles involving operations like machining, assembly, painting, welding and gluing. Designing and optimizing such systems require a holistic approach across domains like device layout, logical connections, control systems, and tasks. The AutomationML file format (AML) within the Reference Architectural Model Industrie (RAMI 4.0) framework enhances interconnection and interoperability among engineering tools but lacks established practices. This paper introduces AML for representing flexible manufacturing cells within the Product-Process-Resource paradigm. AML serves as a comprehensive representation of equipment, processed products, and manufacturing operations, aiding design, configuration, virtual simulation, and optimization before physical implementation. A software tool for robotic systems simulation and programming, i.e. RoboDK, is employed to generate customizable virtual prototypes based on AML content for streamlined simulation and assessment. The same AML file facilitates code transfer to physical cell control units. Demonstrated on a robotic deburring cell, this approach highlights AML's efficacy in data representation between virtual and physical environments, paving the way for digital twin mapping and enhanced manufacturing integration.

Keywords: AutomationML , Interoperability , Offline Programming , RAMI 4.0 , Robotics , Simulation

This book is intended for students, academics, designers, process engineers and CMM operators, and presents the ISO GPS and the ASME GD&T rules and concepts. The Geometric Product Specification (GPS) and Geometrical Dimensioning and Tolerancing (GD&T) languages are in fact the most powerful tools available to link the perfect geometrical world of models and drawings to the imperfect world of manufactured parts and assemblies. The topics include a complete description of all the ISO GPS terminology, datum systems, MMR and LMR requirements, inspection, and gauging principles. Moreover, the differences between ISO GPS and the American ASME Y14.5 standards are shown as a guide and reference to help in the interpretation of drawings of the most common dimensioning and tolerancing specifications. The book may be used for engineering courses and for professional grade programmes, and it has been designed to cover the fundamental geometric tolerancing applications as well as the more advanced ones. Academics and professionals alike will find it to be an excellent teaching and research tool, as well as an easy-to-use guide. This 2nd, revised edition includes several improved features: - It highlights the tools provided in the recently published ISO GPS standards, such as ISO 22081-2021 and ISO 2692-2021. - New concepts and rules in accordance with the latest revision to the GD&T standard, ASME Y14.5.1-2019, Mathematical Definition of Dimensioning and Tolerancing Principles. - Most of the drawings have been redrawn and updated even further to the new standards. - Changes have been made to the text and illustrations to improve readability and clarify the content Additional contents and examples have been included. - The chapters dedicated to profile tolerance and tolerances (ISO 14405) have been extended and rewritten.

Keywords: Computer-Aided Design , engineering design , Geometric Product Specification , Geometrical Dimensioning , Geometrical Tolerancing , product design , SOLIDWORKS , Technical drawing

Industry 4.0 conceptualizes the automation of processes through the introduction of technologies such as artificial intelligence and advanced robotics, resulting in a significant production improvement. Detecting defects in the production process, predicting mechanical malfunctions in the assembly line, and identifying defects of the final product are just a few examples of applications of these technologies. In this context, this work focuses on the detection of ultrasound probes' surface defects, with a focus on Esaote S.p.A.'s production line probes. To date, this control is performed manually and therefore biased by many factors such as surface morphology, color, size of the defect, and by lighting conditions (which can cause reflections preventing detection). To overcome these shortfalls, this work proposes a fully automatic machine vision system for surface acquisition of ultrasound probes coupled with an automated defect detection system that leverage artificial intelligence. The paper addresses two crucial steps: (i) the development of the acquisition system (i.e., selection of the acquisition device, analysis of the illumination system, and design of the camera handling system); (ii) the analysis of neural network models for defect detection and classification by comparing three possible solutions (i.e., MMSD-Net, ResNet, EfficientNet). The results suggest that the developed system has the potential to be used as a defect detection tool in the production line (full image acquisition cycle takes ~ 200 s), with the best detection accuracy obtained with the EfficientNet model being 98.63% and a classification accuracy of 81.90%.

Keywords: Artificial intelligence , Image processing , Inspection system , Product characterization , Virtual prototyping

This study presents an investigation into the mechanical and tribological properties of binder jetting 17-4PH (AISI 630) stainless steel, with a focus on the interplay between surface finishing and thermal treatments. A subset of samples was superficially treated with a Low Energy High Current Electron Beam, varying the energy density (J/cm2), whereas another set of specimens was thermally treated by solution annealing and aging (H900). Experimental analyses included visual inspection, roughness measurements, microhardness testing, and wear tests. Optical microscopy provided insights into the surface morphology and treatment-dependent defects. Roughness measurements quantified the surface texture alterations, while microhardness tests determined the effect of treatments on the mechanical properties of the material. Tribological tests evaluated the sample wear resistance and the material behaviour during sliding.

Keywords: BINDER JETTING , LOW ENERGY HIGH CURRENT ELECTRON BEAM , STAINLESS STEEL 17-4PH , SURFACE FINISHING , TRIBOLOG

This study examines the application of two-and three-dimensional tolerance analysis methods in accordance with ISO 2768:2017 and ASME Y14.5-2018 standards to assess dimensional and geometric compliance in mechanical component assemblies. By analyzing a series of case studies—including a simple shaft-hole coupling and a complex pulley assembly—the study compares deterministic and statistical methods, such as Worst-Case Scenario (WCS) and Root Sum Square (RSS), to explore their effectiveness in real-world design. The analysis demonstrates how 3D tolerance methods can capture complex geometrical interactions and cumulative deviations more accurately than traditional 2D approaches, particularly for assemblies with intricate mating features or spatial dependencies. Key differences between ISO and ASME standards, such as the implications of the envelope principle (ASME Rule #1) and the independence principle in ISO, are highlighted to help practitioners choose the appropriate standard for specific applications. © 2024, Huatuo Culture Media Co. Limited.

Keywords: ASME Y14.5:2018 , assemblies , ISO GD&T , mechanical drafting , tolerances

Industrial Robots (IRs) are increasingly adopted for material subtraction or deposition functions owing to their advantages over machine tools, like cost-effectiveness and versatility. Unfortunately, the development of efficient robot manufacturing processes still faces unsolved issues related to the IRs poor positioning accuracy and to the tool path generation process. Novel engineering methods and tools are needed for CAD based programming of accurate paths and continuous robot motions to obtain the required manufacturing quality and tolerances. Within this context, to achieve smoothness along the tool path formed by linear G-code segments, the IR controllers' approximation strategies, summarily reported in the manufacturer's manuals, must be considered. The aim of this paper is to present the preliminary work carried out to identify the approximation algorithms of a Kuka IR when executing linear moves. An experimental study is conducted by varying the controller settings and the maximum translational velocity. The robot behavior has been acquired thanks to the controller tracing function and then processed to yield relations readily employable for the interpretation of G-Code commands and the subsequent generation of proper robot motion instructions. The obtained formulas allow to accurately predict the robot geometric path and kinematics within the corner transition between two linear segments.

Keywords: Corner smoothing , G-code translation , Manufacturing robots , Path approximation , Robot programming

The tolerance-cost optimization plays a central role in the design of industrial components, due to its implications in all production stages. To reduce development times and increase product quality, the systematic application of tolerance-cost optimization from the early design phases requires a deep knowledge of the tolerance effects on both product performance and production cost. However, many factors still hamper its industrial diffusion, comprising three improvement areas: data and parameters sharing, flexibility to application complexity, and integration of simulation tools. Data and parameters sharing are a key factor since directly affect the representation and information transfer of tolerances and manufacturing processes. Both tolerances-cost relations and optimization structure must be properly represented, through a knowledge modelling framework. The present paper introduces an interoperability framework for the Computer-Aided tolerance-cost optimization. Through creating instances for tolerance and manufacturing process information, the interoperability is implemented defining a systematic sequence of steps to breakdown the multi-disciplinary optimization structure. Starting from the assembly structure, with the extraction of information from the 3D models to its transfer for parametric modelling into tolerance simulation and cost estimation environments, the interoperability framework identifies input-output relations and highlights the integration provided by multi-disciplinary optimization structure. The application of the presented framework on an archetypal case study provides an analysis of the suitability of the method, highlighting the further improvements. In this way it is possible to improve the interoperability between design and simulation virtual environments, to optimize tolerances in a concurrent a multi-disciplinary manner.

Keywords: Cost estimation , Model based definition , Multi-disciplinary optimization , Tolerance design , Tolerance-cost optimization

Factory acceptance test is the inspection of equipment and components at the supplier's premises before delivery or final inspection. However, this control can represent a considerable cost for the customer, especially when the manufacturer's company is geographically far from the customer one and inspections must be frequent. In this paper, the authors present a framework to support the factory acceptance test based on augmented reality (AR) techniques and model-based definition aimed at dimensional checks that does not require the physical presence of the customer at the supplier's premises. The supplier must be previously equipped with an automatic measuring machine. Once the component under inspection is placed inside the machine, this reads the type and the position of the features to be measured along with the related specification limits directly from the annotated 3D model of the component. The results are automatically transmitted to the customer's site. Through a tablet, the supplier, guided by the customer, reads the results of the measures directly on the measured object through augmented or mixed reality techniques. Any out-of-specification dimension can be remeasured in real time with the customer's remote assistance using traditional measurement techniques. The proposed architecture, at an advanced stage of experimentation, is discussed with reference to an industrial case study proposed and using an entry level commercial 3D scanner.

Keywords: Augmented reality , Dimensional inspection , Factory acceptance test , Metrology

Preface and Acknowledgements (Editorial)

Keywords: Editorial

Large parts produced by injection moulding are usually subjected to large deformations that may be reduced during assembly. The single parts manufacturing specification should refer to the as produced (free) state. On the other hand, the functional specification, derived from the assembly functional specification should address the “as assembled” state. Geometrical inspection, based on the functional specification requires dedicated fixtures to simulate the “as assembled” state. This contribution suggests a procedure, based on FEM simulation, to correlate the geometric specification at the “as assembled” state with the “as produced” (free) state, applied to an industrial case study. The result of the procedure are free state tolerance limits, e.g., manufacturing specification, that allows conformity of the part to the functional specification once assembled. The part may be inspected based on the manufacturing specification fixtureless during mass production. The result of the case study shows a significant reduction in position and orientation error due to the assembly process as it was expected.

Keywords: Compliant assemblies , Deformable assemblies , FEM simulation , Geometrical Product Specification , Tolerancing

Shaft-hole pattern fits based on the Boundary Condition design criterion allows a 100% acceptability rate, but they may be not economically convenient. If the rejection rate needs to be statistically quantified and the pattern is itself the alignment feature, therefore promoted as datum feature (Intrinsic datum system), there is no trivial solution to create a tolerance stack-up: a unique assembly function cannot be determined. The focus of this contribution is “2x” patterns: different methodologies to create tolerance stack-up assessing assemblability are discussed and verified through Monte Carlo simulation. An equation to transform the variability seen from the Intrinsic datum system to the one seen from an external arbitrary reference system is given. The mutual distance between any two elements of an “nx” pattern is discussed and the implication of multiplicity and datum system is highlighted. A case, derived from an industrial case study, will be discussed by comparing the result from the simulated manual and automated assembly. A path towards “nx” patterns generalization is also presented.

Keywords: Boundary Condition , Rejection rate , Tolerance analysis , Tolerancing , Virtual condition

Automotive market requires more and more power semiconductor modules for the realization of vehicle electrification. With respect to more conventional discrete packages, power modules have more complex manufacturing flow in which there are some process parameters that play a key role for a robust design, mechanical and hydraulic integration with the vehicle. Among these parameters, the flatness of the final product must be controlled in order to guarantee the mounting of power modules on cooling system and the proper working of thermal management. This paper would introduce the technology of liquid cooling solution for electrified vehicles' power module, pointing out the importance of power module flatness. Then, it is proposed an experimental methodology to analyze the warpage behaviour during power at the different process steps and at the end of power module manufacturing. Measurements confirm that flatness is within admitted tolerance (200 μ m), highlighting the ceramic soldering process as the most critical for warpage modification.

Keywords: Design , Flatness , Manufacturing , Power module , Tolerances

The development of cutting-edge technologies in the industrial sector has led to the demand for increasingly specific tools in the optimization of efficiency problems. The automotive sector is the one that makes the most use of these technologies, such as, among all, Virtual Reality (VR) and Augmented Reality (AR). A virtual reality tool is inserted as a guide tool for the user in drawing as quickly as possible the key information for optimizing the process. This research work fits into this context, the goal of which was the implementation of an immersive platform for carrying out accurate measurements within an entirely virtual automotive environment. A VR system of this type allows to check the dimensional and shape tolerances of car components, performing measurement, with high precision and in real time, in a custom-made virtual environment, in which it is possible to simulate the presence of a myriad of components and test their mutual interaction. A comparative test was carried out, obtained by varying the graphical and geometrical model in the VR settings, in order to evaluate the level of usability and the degree of efficiency of a tool for measuring distances between objects in a virtual reality environment, depending on the system parameters. The validation of a measurement instrument in VR is part of an increasingly current technological context in which the need to optimize the time-cost curve embraces the need for increasingly accurate results.

Keywords: Assembly training , Tolerance measurements , Virtual reality

Variation Simulation (VS) allows early validation and certification of the assembly process before parts are built. State-of-the-art VS models of assembly systems with compliant sheet-metal parts are based on Finite Element Method (FEM) integrated with statistical approaches (i.e., Monte Carlo simulation). A critical technical barrier is the intense computational cost. This paper proposes a novel real-time physics-based VS model of assembly systems with compliant sheet-metal parts based on Reduced-Order Model (ROM). Compared to the literature on the topic, this study reports the first application of a ROM, developed for VS by using both intrusive and non-intrusive techniques. The capability of the proposed method is illustrated in a case study concerning the assembly process of the vertical stabiliser for commercial aircrafts. Results have shown that the accuracy of ROM (based on proper orthogonal decomposition) depends on the sampling strategy as well as on the number of reduced modes. Whilst a large CPU time reduction by several orders of magnitude is achievable by non-intrusive techniques (based on radial basis functions for interpolation), intrusive models provide more accurate results compared to the full-order models.

Keywords: Compliant assembly , Proper orthogonal decomposition , Radial basis functions , Real-time physics-based simulation , Reduced-Order Models , Sheet metals , Variation simulation analysis

Snap-fit joints represent a simple, economical and straightforward way of joining two different components. The design of the snap-fit joint is usually performed evaluating peak stresses that must be tolerated by the material without incurring into failure or plastic deformations; in addition, the force needed to join and disassemble parts is estimated in relation to ergonomic issues. Finally, the retention force, that is the force required to start disjoining parts, needs to be estimated. The evaluation of peak stresses or insertion/retention/removal forces is commonly performed through finite element method, having identified the respective deformed configuration. A different approach has been here followed considering that it is not trivial to identify the most critical condition in a full joining/disjoining cycle, when complex geometries are being considered. In detail, the snap joint has been modelled as a multibody model including a flexible body, which replicates the part that undergoes major deflections during the process. The model has been validated against experimental force – time curves, recorded for an existing joint, and it has been used to optimize a parametrised snap-fit design. As a result, the joining force has been reduced up to −84%; the disassembly force has been reduced up to −86% and the retention force has been incremented up to +7%. On the whole, a numerical framework to study these joints has been established, keeping the computational time reasonably low (about 40 min for the entire insertion and removal simulation).

Keywords: Geometrical modelling , Multibody model , Plastic components design , Snap-fit joint , Tolerance analysis

The treatment of burn scars is a much discussed and sensitive topic because an improper therapy can have a significant impact on the quality of people's lives. To accurately assess both the health of scars and the outcomes of treatment, the medical evaluation should be based on objective measurements of progression over time. To overcome the limitations of subjective assessment is to leverage, 3D scanning technologies can be used to acquire topological information about the lesions and extract a set of relevant statistical parameters describing them. Accordingly, the present work aims at addressing both efficiency and reliability of a preliminary method based on the objective investigation of the surface topography of burn scars by applying it on several patients of the Meyer Children's Hospital burns department. A commercial 3D scanner is used to acquire 3D data relative to the scars of five patients. By applying a method based on the computational analysis of scan data, a significant number of roughness-related parameters are retrieved. This information is used to create a coherent dataset that allows the severity of burn scars to be inferred objectively. The developed method facilitates the evaluation of treatment efficacy by assessing wound healing during follow-up visits.

Keywords: 3D scan , Burn scar , Surface roughness