Fixture Assembly Research Articles

Influence of conical hybrid stock and computer-aided design/computer-aided manufacturing abutments on the strain developed around implant and the screw loosening

Abstract Aim Evaluate effect of conical hybrid stock and computer-aided design/computer-aided manufacturing (CAD/CAM) abutments on the strain developed around implant and the screw loosening. Patients and methods Sixteen epoxy resin blocks containing implant assembly (fixture, abutment, abutment screw, cemented zirconia crown) divided into two equal groups (eight blocks) in each group as fallow: group (A): eight blocks with implants attached to Stock abutment with conical hybrid connection to retain the crown to the implant. Group (B): Eight blocks with implants attached to customized CAD/CAM milled abutment with the same size and connection to retain the crown to the implant. The samples were subjected to dynamic cyclic loading 150 000 cycles using chewing simulator. A digital torque gauge was used to evaluate screw loosening by measuring removal torque value (RTV) before and after cyclic loading. Strain gauge was installed around implants in buccal, palatal aspects of each implant, and a load of 100 N was applied vertically and another load of 65 N was applied obliquely by using universal testing machine and the strain was determined using strain meter. Results For GA, percentage of initial removal torque loss (RTL) was (17.988 ± 1.248%) and significantly increased after loading (30.763 ± 1.176%). For GB, percentage of initial removal torque loss was (24.350 ± 1.239%) and increased significantly after loading (33.313 ± 2.840%). For strain results under vertical and oblique loading, there was no statistically significant difference in both groups in stock and cad cam abutments and the strain measurement under oblique loading were significantly higher than the strains measured under vertical loading in both groups. Conclusions Screw loosening occurred in both stock abutments and CAD/CAM abutments but CAD/CAM abutments yielded greater removal torque reduction (RTV) reduction% than the stock abutments and stock abutments showed little stress values around implant than CAD/CAM abutment without statistically significant difference. Off-axial loads will generate more stresses around implants.

Intelligent design of reconfigurable flexible assembly fixture for aircraft panels based on smart composite jig model and knowledge graph

The current demand for aircraft panel assembly fixtures necessitates agile manufacturing solutions. Traditional welding fixtures struggle to meet diverse panel types, high quantities, and short manufacturing cycles. Conversely, reconfigurable flexible assembly fixtures offer universality, efficiency and ease of maintenance but heavily rely on designers' experience, hindering knowledge reuse. Existing research on computer-aided fixture design (CAFD) primarily addresses specialized fixtures, neglecting reconfigurable flexible ones, lacking fixture design knowledge systems. Aiming at the above problems, the study proposes an intelligent design method for the reconfigurable flexible assembly fixture for aircraft panels based on the smart composite jig model (SCJM) and knowledge graph (KG). Firstly, based on the SCJM of the aircraft panel type assembly fixture (PSCJM), a configuration design method is proposed to carry out the multi-level design of reconfigurable assembly fixture to instantiate PSCJM containing fixture configuration rules and a module library based on model definition (MBD). Then, a knowledge retrieval method is proposed to search the suitable fixture design knowledge based on KG, assisting designers in achieving the flexible design of aircraft panel reconfigurable assembly fixtures. Finally, practical engineering design validation confirms the method's feasibility and effectiveness in obtaining the reconfigurable flexible assembly fixture design scheme for aircraft panels.

Assessment of Additive Manufacturing Technology for Rotor Fixture used in Gas turbine Assembly

Abstract: The study involves an examination of the rotor fixture assembly to understand its functionality under standard boundary conditions. The fixture components were modelled in NX CAD. To achieve the desired weight reduction and equivalent stiffness, Finite Element Analysis was conducted both before and after the Topology Optimization process using the Density-based method in ANSYS. The objective was to optimize rotor fixture design for additive manufacturing to reduce weight and lead time. Finite Element Analysis and topology optimization were used to redesign the fixture, resulting in a 16.3% mass reduction for the solid model and 27.5% for the shell model while maintaining stiffness. Metal additive manufacturing reduced lead time by 46% despite a 17% increase in cost compared to conventional machining. Future work may involve lattice structure design and part distortion prediction using Ansys additive software for further improvements.

Investigation of the stability and contact stiffness of workpiece inside fixture in different machining conditions

The dynamic stability of machining processes is influenced by the dynamic stability of the workpiece and fixture assembly. This effect has not yet been sufficiently considered. Achieving dynamic stability by simply applying a large amount of clamping force is a basic method and involves damages such as elastic deformation of relatively thin workpieces, damage to the clamping surfaces, and high wear of fixture components resulting in malfunction. In spite of this, to the best knowledge of the present authors, the contact stiffness between workpiece and fixture as an influencing parameter has not been sufficiently paid attention by researchers and these parameters have not been taken into account in the equations of dynamic stability. The contact stiffness itself is influenced by the machining parameters. In the present study, the changes in contact stiffness in different machining conditions are investigated as a partial undertaking to fill the gap existing in the modeling of the machining dynamics. In this paper, by defining the mathematical model of the workpiece-fixture system and calculating the matrices of contact stiffness and fixture stiffness, the results of changes in various machining parameters in the stiffness of the workpiece-fixture system have been investigated. The results showed that high contact stiffness cannot be provided simply by applying the maximum force of the clamps. Rather, by increasing the spindle speed, the contact stiffness will increase significantly. Furthermore, by increasing the spindle speed, further increase in the contact stiffness will be achieved with lower feed rates, which will not be economically viable.

Designing cranial fixture shapes and topologies for optimizing PEEK implant thickness in cranioplasty

Cranial defects are often caused by trauma, diseases or malignancy. To repair such defects, skull reconstruction or cranial implants are required for protecting intracranial structures and normalizing cerebral hemodynamics. To relieve Intracranial Pressure (ICP) surgeons restore cranial defects using the preserved bone of a patient. In case of non-availability of natural bone cranial implants are fabricated using biocompatible materials including Titanium Alloys (Ti-6Al-4V) and polyether-ether-ketone (PEEK). Patient-specific implants (PSI) manufactured using 3D printing, 3D imaging technologies and 3D modeling software, are preferred over conventional manufacturing methods. During cranial fixation bone fragments, grafts and bone flaps are fixed to the cranium to offer stable closure in surgery. Effective attachment of an implant to a defective skull is influenced by the joints and fixture arrangements at the interface. These fixtures can have various designs, materials and joining procedures. PEEK behaves similarly to bone during deformation, which means it is receptive to titanium fixations and supports soft tissue adhesion due to its inert nature. This study considers PEEK as an implant material for reconstructing a bone-defected skull with Ti-6Al-4V fixtures attached at the skull-implant interface. This work compares Ti-6Al-4V fixture shapes (Linear, Square and Burrhole) with different orientation angles and topologies (‘+’ and ‘X’) attached to PEEK cranial implants of variable thicknesses (1–7 mm). Using Finite Element Method (FEM)/Finite Element Analysis (FEA), von Mises stress analysis was analyzed to identify the implant thicknesses that would bear an external load of 1780 N and ICP of 15 mmHg without failure. With a yielding limit of 100 MPa for PEEK, all proposed design arrangements for the fixture plates in the skull-implant assembly were well within these limits exhibiting a maximum von Mises stress of 51.985 MPa for the least implant thickness of 1 mm and weight 12.90 g. Considering all the designs, a Linear Fixture shape with 45° angular orientations placed in ‘X’ topology exhibited least stress of 18.477 MPa and was therefore proposed as the most optimized design for the skull-implant fixture assembly. Selection of an optimized design arrangement is also dependent upon other clinical factors, such as number of screws used, the Additive Manufacturing (AM) technique for fabricating/cutting of precise slots within the implant. The skull and flexibility of the fixture plates are also considered in relation to the required operating theatre time and skills of the surgical team.

Multi-objective optimisation of assembly fixturing layout for large composite fuselage panel reinforced by frames and stringers

Multi-objective optimisation of assembly fixturing layout for large composite fuselage panel reinforced by frames and stringers

P-Diagram을 활용한 AIAG-VDA 통합 공정 FMEA의 효과적 실행 방법

Purpose: This paper proposes a method to prevent the omission of possible failure modes or the selection of inappropriate failure modes during AIAG-VDA PFMEA implementation.BRMethods: During the development of AIAG-VDA-integrated PFMEA, we established a method for the effective determination of failure modes and causes through the creation and application of P-diagrams. To accurately identify potential failure modes, all processes illustrated in the flow diagram of the process were decomposed, and the process was decomposed into work units. In addition, the work performance factor 4M or 5M necessary to perform the decomposed work units was determined. Furthermore, the work interruption factor that interfered with each of work performance element was determined. Potential failure modes were identified based on the last found disturbance factors. Finally, a method of deriving a potential failure mode was established by applying the proposed procedure to the assembly of LCD and equipment.BRResults: By applying the proposed process FMEA to the LCD and fixture assembly process, we confirmed the effects of potential failure modes that could not be derived by conducting process FMEA without process disassembly.BRConclusion: The proposed process FMEA implemented in the actual field was effective in preventing potential failure modes.

Finite Element Analysis Methodology for Additive Manufactured Tooling Components

Fused deposition modeling (FDM) for additive manufacturing is constantly growing as an innovative process across the industry in areas of prototyping, tooling, and production parts across most manufacturing industry verticals such as Aerospace, Automotive, Agricultural, Healthcare, etc. One such application that is widely used is for tooling on the shop floor e.g. for pick-off tools, assembly fixtures etc. For tooling applications printing the solid fill component with +45/- 45 raster is common practice. There is a requirement for finite element analysis to validate the strength of 3D printed components for some specific applications in tooling, but due to the anisotropic behavior of 3D printed parts and the unavailability of all mechanical properties FE analysis of 3D printed parts is sometimes challenging. Advance approaches like multiscale modeling approach requires specialized & costly analytical tools. So, to understand the behavior of additively manufactured parts the team has conducted a few tests and compared the results. In this work, solid-filled dog-bone tensile test and three-point bending test specimens were printed with +45/-45 raster orientation and tested in the lab. Tensile test specimens were built with flat, on-edge, and up-right orientations and tested to determine the directional properties of young’s modulus. Using mechanical properties from the tension test 3 points bending test is simulated in FE software- ANSYS. The FE modeling was done in two ways, in first model orthotropic properties were assigned to the specimen, and for second model isotropic properties were assigned. For isotropic modeling least value of young’s modulus is used. Simulation results of three-point bending test shows that in the linear region of force-deflection curve, deformation values from FE model with both orthotropic and isotropic modeling are in good agreement with the experimental results. Also, the difference in stress results between isotropic and orthotropic FE model is almost negligible. To support this observation, study is performed for various conditions. The specimens were printed with ABS material on Ultimaker® and ASA material on Stratasys® Fortus 360mc™ machine with T12, T16 and T20 nozzle settings. Study shows, for tooling applications if the 3D printed solid-filled components are designed with a certain factor of safety then validating its strength with isotropic material properties will give acceptable results. The advantage of this approach is getting the isotropic mechanical properties is easy and modeling with FE modeling will be simple.

Design and Analysis of Distortion in Welding Fixture for Frame Assembly

This paper focuses on the Design and Analysis of Welding Fixture for Anti-vibration under carriage Bogie Frame Assembly for Compact Track Loader. The application of a Bogie assembly is to offering smoother transitions over uneven terrain, and the ability to travel at higher speeds with better materials retention. Due to the nature of welding process involving localized heat generation from moving heat source, rapid heating in the welded structures, and subsequent rapid cooling, problems such as residual stresses and distortions of welded structures remain important challenges in the industry. To assemble the respective child parts and to meet the required tolerances on the bogie frame assembly welding fixture specially designed with the help of CAD Software. In practice, welding distortion creates unwanted effects on manufacturing accuracy, appearance and strength of welded parts. By using Finite Element Analysis (FEA), the analysis is carried out to find welding distortion of Bogie Frame assembly. Along with optimum clamping force has been calculated which required for controlling the welding distortion. After successful Design and Analysis, the Welding fixture has been manufactured and has been implemented at shop floor. This welding fixture used for accurate assembly of the child parts with required tolerances , as well as helps in reduction of production loss and also manufacturing lead time for welding, positioning and holding parts.

Solving a multi-dimensional matching problem for grouping clamping points on car body parts

Modern car body production is faced by an increasing number of car models as well as individualizing options, which leads to the need for more adaptable assembly equipment, e.g. grippers and fixtures that can switch between models in a matter of seconds. Based on known clamping positions, automated jigs consisting of several clamps can already adapt to different part geometries.To enable an efficient flexible jig, exactly one clamp must be assigned to each clamping point of each model taking into account different optimization criteria. Therefore, clamping points need to be grouped across all different models in the planning phase. Grouping of clamping points e.g. in order to minimize adaptation time or tooling costs is usually performed manually.In this paper, the grouping optimization problem is formalized, and a mathematical algorithm is introduced to solve this multi-dimensional matching. The envisaged approach uses a greedy algorithm to get an initial solution, which is optimised to a technically feasible solution considering economical aspects. To conclude, a short evaluation of the achieved results - especially in comparison with expert based grouping - is given.

A framework for planning a reconfigurable assembly system for press brake production

This article presents the design of a framework for the development of a reconfigurable assembly system (RAS) to facilitate the assembly of press brakes varieties. A consideration of press brake varieties is achieved by examining the parts taxonomy of press brakes from which a framework for assembly process plan is developed that considers all the types of press brakes identified from the classification. Also, a layout for the RAS is developed by considering a prototype of the major enabling equipment of the system which is a reconfigurable assembly fixture (RAF). The development of the assembly process plan and layout of the RAS enabled the design of a reconfiguration model for operation in the RAS. The designed assembly framework will provide: rapid and physical reconfiguration of the RAF in the RAS; generation of assembly sequence for press brake varieties; and allocation of assembly operations to assembly work cells in the system. [Submitted 27 May 2020; Accepted 3 December 2020]

Experimental analysis of nonlinear characteristics of absorbers with wire rope isolators

Abstract Four different configurations of a mass supporting system consisting of a few prototypes of wire rope isolators are considered in the article. These are named “triangle,” “star,” “parallel,” and “serial” configurations. Reasonable models of a fixture assembly that could be utilized as models for cargo transportation are tested statically and dynamically in the laboratory. The main aim of this study is to investigate the impact of the configuration of damper settings on the effectiveness of vibration and shock isolation (in three directions) and to develop a suitable method to determine nonlinear properties and stiffness characteristics of the tested system. The purpose is also to investigate the sensitivity of the tested systems on the eccentricity of vertical loads and its influence on identification results. Experiments are carried out on the specially designed stand for the model parameters identification.

Ergonomics Assessment and Redesign of Helicopter Transmission Assembly Fixture Using Digital Human Models

Digital Human Modeling (DHM) is an integral part of computerized engineering studies. In this study, an assembly fixture has been designed that will be used in the assembly of the helicopter transmission and it has been analyzed for compliance of ergonomic conditions using DHM technique. Rapid Upper Limb Assessment (RULA) and Biomechanical Motion Analyses (BMA) were used in the analyses. The ergonomic competence of the human was analyzed empirically for two different assembly conditions. The assembly fixture redesigned has significant ergonomic advantages over the conventional ones. According to the analyses was provided that 79.6 % advantage in compression loading and 94.3 % advantage in moment loading, which occurs on the L4-L5 lumbar vertebra discs. As a result, it was revealed that the ergonomic assembly fixture designed for workers to work in a more comfortable and safe manner was suitable for its purpose.

Implantation of Neuropixels probes for chronic recording of neuronal activity in freely behaving mice and rats.

How dynamic activity in neural circuits gives rise to behavior is a major area of interest in neuroscience. A key experimental approach for addressing this question involves measuring extracellular neuronal activity in awake, behaving animals. Recently developed Neuropixels probes have provided a step change in recording neural activity in large tissue volumes with high spatiotemporal resolution. This protocol describes the chronic implantation of Neuropixels probes in mice and rats using compact and reusable 3D-printed fixtures. The fixtures facilitate stable chronic in vivo recordings in freely behaving rats and mice. They consist of two parts: a covered main body and a skull connector. Single-, dual- and movable-probe fixture variants are available. After completing an experiment, probes are safely recovered for reimplantation by a dedicated retrieval mechanism. Fixture assembly and surgical implantation typically take 4-5 h, and probe retrieval takes ~30 min, followed by 12 h of incubation in probe cleaning agent. The duration of data acquisition depends on the type of behavioral experiment. Since our protocol enables stable, chronic recordings over weeks, it enables longitudinal large-scale single-unit data to be routinely obtained in a cost-efficient manner, which will facilitate many studies in systems neuroscience.

A Monolithic Vertical Integration Concept for Compact Coaxial-Resonator-Based Bandpass Filters Using Additive Manufacturing

This letter reports on a compact, low-cost, and low-loss monolithic integration concept for additively manufactured coaxial-resonator-based bandpass filters (BPFs). Size compactness and low weight are achieved by vertically stacking capacitively loaded coaxial resonators and by monolithic integration that eliminates the need for assembly screws or fixtures. Furthermore, the proposed vertical integration concept allows for: 1) flexible cross couplings to be realized enabling highly selective transfer functions through transmission zero (TZ) generation and 2) for fairly complex geometries to be manufactured using low-cost stereolithography apparatus (SLA). For proof-of-concept demonstration purposes, a two-pole BPF with fractional bandwidth (FBW) of 8.5% and a three-pole/one-TZ BPF with FBW 6.2% at 3.8 GHz were designed, SLA-manufactured, and measured. They exhibited low levels of insertion loss (IL) (<; 0.1 dB), high effective quality factors >1833, and wide spurious-free operation.

Efficient Spot Welding Sequence Simulation in Compliant Variation Simulation

Abstract Geometrical variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometrical variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components, can be achieved using the method of influence coefficients (MICs), based on the finite element method (FEM). The sequence with which the spot welding operation is performed influences the final geometrical deformations of the assembly. Finding the optimal sequence that results in the minimum geometrical deformation is a combinatorial problem that is experimentally and computationally expensive. Traditionally, spot welding sequence optimization strategies have been to simulate the geometrical variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, a method is proposed where the springback calculation in the inspection fixture is bypassed during the sequence evaluation. The results show a significant correlation between the proposed method of weld relative displacements evaluation in the assembly fixture and the assembly deformation in the inspection fixture. Evaluating the relative weld displacement makes each assembly simulation less time-consuming, and thereby, sequence optimization time can be reduced by up to 30%, compared to the traditional approach.

Design and Deployment of Fixture on Assembly Line to Improve Productivity

In this research, fixture was designed and implemented on assembly line to improve ergonomics along with reducing the required time and manpower. It reduced the required manpower in half and subsequently led improvement the productivity. Providing ease in operation, fixture significantly reduced fatigue to the workers. The aim of this paper was to design and development of fixture for engine door assembly. The problem with assembly was analysed and fixture is proposed to tackle the key issues. To eliminate traditional trial and error approach, the fixture was designed using CAFD along with FEA validation. The proposed fixture manufactured and deployed in current assembly line. It improves total profitability and quality of process by achieving significant reduction of 40% in assembly time. Prior to fixture, time needed for assembly was 24 minutes. After the fixture, this assembly time reduces to 14.4 minutes i.e. 40% reduction is observed.

Automatic positioning methodology and algorithm for modular jigs and fixtures components

One of the steps in designing a modular jig or fixture assembly is that of selecting the appropriate components. Among these components, those forming the jig’s body must be chosen for closing the dimensional chains between the other locating, clamping, or indexing components. The methodology starts by defining the components’ virtual connectors, specifying the rules for establishing their coordinates systems, and then is defining the rules to be followed for aligning and assembling two adjacent components. Different cases are described and only some of them are detailed, for clarity reasons. The algorithm is looking to determine a series of components from which the first is in a fixed position, related to other locating or clamping jig’s component. A hierarchical tree is generated, using available components, having in each node a component which is assembled with a previous one using the above-mentioned connectors. Interference criteria is checked for selecting possible solutions only. A stop criterion related to the number of components in a branch is used, Solutions from the different branches are compared using the distances to an end component.

Design concept evaluation technique via functional link matrix and fuzzy VIKOR based on left and right scores

ABSTRACT This article presents a new technique for determining the weights of design features by searching for functional links between their sub-features. The method further applies fuzzy VIKOR based on left and right scores to determine the optimal design concept from a decision matrix obtained from three experts view. The application of this technique to the design of a Reconfigurable Assembly Fixture (RAF) shows that it is a viable method for determining the weights of design features and identifying the optimal design concept from a set of alternative designs. In order to support the viability of this technique, the results obtained from its application to the design of a RAF was compared with the results of other Multi-Criteria Decision-Making (MCDM) methods when applied to the design of the RAF. The comparison shows that the technique is feasible and can be employed to determine the weights of design features in order to identify optimal design at the conceptual phase.

Optimal design of fixture layouts for compliant sheet metal assemblies

A preeminent factor in the geometrical quality of a compliant sheet metal assembly is the fixture layout that is utilized to perform the assembly procedure. Despite the presence of a great number of studies about the optimization of assembly fixture layouts, there is not a comprehensive algorithm to optimize all design parameters of fixture layouts for compliant sheet metal assemblies. These parameters are the location and type of hole and slot in each part, the slot orientation, and the number and location of additional clamps. This paper presents a novel optimization method that optimizes all these parameters simultaneously to maximize the geometrical quality of the assemblies. To attain this goal, compliant variation simulations of the assemblies are utilized along with evolutionary optimization algorithms. The assembly springback and contacts between parts are considered in the simulations. After determining the optimal design parameters, the optimal positions of locators are fine-tuned in another stage of optimization. Besides, a top-down design procedure is proposed for applying this method to multi-station compliant assemblies. The presented method is applied to two industrial sample cases from the automotive industry. The results evidence a significant improvement of geometrical quality by utilizing the determined fixture layout from the presented method compared with the original fixture layouts of the sample cases.