Purpose The purpose of this paper is to carry out an assembly tolerance analysis by means of a combined Jacobian model and skin model shape. The former is based on small displacements modeling of points using 6 × 6 transformation matrices of open kinematic chains in robotics. The latter easily models toleranced features with all kinds of geometric deviations. Design/methodology/approach This paper presents the procedure of performing tolerance analysis by means of the Jacobian model and skin model shape for assemblies. The point cloud-based discrete representative is able to model the actual toleranced surfaces instead of the ideal or associated ones in an assembly, which brings the simulation tools closer to reality. Findings The proposed method has the advantage of skin model shape which is suitable for geometric tolerances management along the product life cycle and contact analysis of kinematic small variations, as well as, with the Jacobian, enabling transformation of locally expressed parts deviations to globally expressed functional requirements. The result of the case study shows the accuracy of the method. Research limitations/implications The proposed approach has not been developed fully; other functional features such as the pyramid are still ongoing challenges. Practical implications It is an effective method for supporting design, manufacturing and inspection by providing a quantitative analysis of the effects of multi-tolerances on the final functional key characteristics and for predicting the quality level. Originality/value The paper is original in taking advantages of both Jacobian model and skin model shape to consider all geometric tolerances in assembly.
Introduction:An orthosis is a medical device used in orthopaedic and traumatology for the treatment of certain pathologies. It has the main function of restraining articulation movements after a trauma, a surgery, a distortion or for arthrosis patients. The typical treatment for bones fractures foresees the use of a tailor-made plaster cast which has several disadvantages: its weight generally causes discomfort, it cannot be taken off without breaking it, it can cause skin rashes, and it cannot ventilate the treated area [1,8]. These issues can lead to serious medical complications such as compartment syndrome, ischemia, heat injury, pressure sores and skin breakdown [1,12]. Therefore, the application of traditional casts to orthopaedics patients might not represent, to date, the best option. To overcome the above-mentioned drawbacks, a number of strategies based on reverse engineering (RE) and additive manufacturing (AM) techniques have been carried out and proved to be a valid alternative for the treatment of arm-wrist-hand pathologies [3,6,7,14]. The most common framework for the creation of these personalized casts starts with the acquisition of the arm geometry by means of 3D scanning technologies. The scanned data is processed to generate a CAD model of the custom-made orthosis that is finally fabricated thanks to AM techniques.Two principal strategies can be identified at the state of the art to create the CAD model: i) the adaptation of a pre-defined template to the scanned geometry [9]; ii) a manual procedure performed within a CAD environment [4,5,8,10,11]. Most methodologies described in literature neither guarantee the achievement of a valid result from a medical perspective [4,8] nor allow an easily usable and scalable framework for the application in clinical practice. Specifically, these last goals would be reached by implementing a fully automatized procedure that: i) does not require CAD technical skills to the user; ii) does not needs significant time for the generation of the CAD model; iii) are validated against a set of clinical trials. To reach such an ambitious and challenging result, a first important step consists of creating a systematic procedure, which would allow to create a consistent orthosis model using common CAD tools. To this aim, the present work focuses on defining a procedure to design an arm-wrist-hand cast for the treatment of wrist fractures, starting from 3D scanned data, by using CAD tools, hence following a RE paradigm. Taking into account medical guidelines, the procedure is conceived to be easily automatized, thus reducing as much as possible the human interaction. Moreover, in order to prove the soundness as well as the scalability and possible automatization, the devised procedure underwent a validation campaign on six case studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.