Development of Fixture Layout Optimization for Thin-Walled Parts:A Review

An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.

Flexible Fixture Design for the Top and End Surface Processing of NP2_NP4 Cylinder Heads

This paper focuses on the design of fixtures for NP2 and NP4 cylinder heads on a horizontal machining center of flexible machining automatic lines.It began with an analysis of the diagrams of part processing and working procedure which formed the basis for the design of the processing technology scheme,a selection of suitable machine tools,and the setting of processing parameters.Fixtures tailored to the chosen machine tools were then designed to meet the processing requirements.Additional aspects of the project included the design of part drawings,calculation of working time quota,design of auxiliary guides,support clamping,and hydraulic circuits,all aimed at fulfilling practical production requirements.

Leaky Cable Fixture Detection in Railway Tunnel Based on RW DCGAN and Compressed GS-YOLOv5

The communication system of high-speed trains in railway tunnels needs to be built with leaky cables fixed on the tunnel wall with special fixtures.To ensure safety,checking the regular leaky cable fixture is necessary to elimi-nate the potential danger.At present,the existing fixture detection algorithms are difficult to take into account detection accuracy and speed at the same time.The faulty fixture is also insufficient and difficult to obtain,seriously affecting the model detection effect.To solve these problems,an innovative detection method is proposed in this paper.Firstly,we presented the Res-Net and Wasserstein-Deep Convolution GAN(RW-DCGAN)to implement data augmentation,which can enable the faulty fixture to export more high-quality and irregular images.Secondly,we proposed the Ghost SENet-YOLOv5(GS-YOLOv5)to enhance the expression of fixture feature,and further improve the detection accuracy and speed.Finally,we adopted the model compression strategy to prune redundant channels,and visualized training details with Grad-CAM to verify the reliability of our model.Experimental results show that the algorithm model is 69.06%smaller than the original YOLOv5 model,with 70.07%fewer parameters,2.1%higher accuracy and 14.82 fps faster speed,meeting the needs of tunnel fixture detection.

Application of Genetic Algorithm in the Layout of Fixture Components

Automation in the layout of fixture components is important to achieve efficiency and flexibility in computer aided fixture design. Based on basic genetic algorithm and particulars of different fixture components, a method of layout space division is presented. Such techniques as suitable crossover rate, mutation rate and selection arithmetic element are adopted in the genetic operation. The results show that genetic algorithm can effectively be applied in the automatic layout of fixture components.

Modeling and Compensation Technology for the Comprehensive Errors of Fixture System

Error modelling and compensating technology is an effective method to improve the processing precision.The position and orientation deviation of workpiece is caused by the fixing and manufacturing errors of the fixture.How to reduce the position and orientation deviation of workpiece has become a technical problem of improving the processing quality of workpiece.In order to increase machining accuracy,an implementation scheme of fixture system comprehensive errors（FSCE） compensation is proposed.A FSCE parameter model is established by analyzing the influence of contact points on the position and orientation of workpiece.Meanwhile,a parameter identification method for FSCE parameter model is presented by using the 3-2-1 deterministic positioning fixture,which determines the model parameters.Moreover,a FSCE compensation model is formulated to study the compensation value of the cutting position.By using RenishawOMP60 Probe and combining vertical machining centre（SKVH850） equipment with SKY2001 Open CNC System,on-machine verification system（OMVS） is built to measure FSCE successfully.The processing error can be reduced by analyzing the cutting position of the tool with the homogeneous transformation of space coordinate system.Finally,the compensation experiment of real time errors is conducted,and the cylindricality and perpendicularity errors of hole surface are reduced by 30.77% and 28.57%,respectively.This paper provides a new way of realizing the compensation of FCSE,which can improve the machining accuracy of workpiece largely.

LOCATORS OPTIMIZATION FOR MEASURING FIXTURE DESIGN

'N-2-1' principle is widely recognized in the fixture design for deformablesheet metal workpieces, where N, the locators on primary datum, is the key to sheet metal fixturedesign. However, little research is done on how to determine the positions and the number of Nlocators. In practice, the N locators are frequently designed from experience, which is oftenunsatisfactory for achieving the precision requirement in fixture design. A new method to lay outthe N locators for measuring fixture of deformable sheet metal workpiece is presented, given thefixed number of A'. Finite-element method is used to model and analysis the deformation of differentlocator layouts. A knowledge based genetic algorithm (KBGA) is applied to identify the optimumlocator layout for measuring fixture design. An example of a door outer is used to verify theoptimization approach.

A Study on Modular Fixture Design with Intelligent Selection of Elements and Interactive Assembly

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Application and Realization of Rapid Searching Technology in the RL & SM Universal Fixture System

A searching-machining system of RL & SM (Rapid Location and State Memory) universal fixture is here introduced, and the concept of rapid searching technology and manufacturing information transformation is then described, with the appropriate control methods and key techniques for its realization being proposed and also practically realized. Theoretical analysis and experimental results show that the proposed idea and methods are feasible to serve as in the practical application of the RL & SM system.

Topological Optimization Method for Aeronautical Thin-Walled Component Fixture Locating Layout

Fixture locating layout has a direct and influential impact on aeronautical thin-walled component(ATWC)manufacturing quality.The purpose is to develop a topological optimization method for ATWC fixture locating layout to minimize the manufacturing deformation.Firstly,a topological optimization model that takes the stiffness of ATWC as the objective function and the volume of the locating structure as the constraint is established.Secondly,ATWC and the locating structure are regarded as an integrated entity,and the variable-density method based topological optimization approach is adopted for the optimization of the locating structure using ABAQUS topology optimization module(ATOM).Thirdly,through a subsequent model reconstruction referring to the obtained topological structure,the optimal fixture locating layout is achieved.Finally,a case study is conducted to verify the proposed method and the comparison results with firefly algorithm(FA)coupled with finite element analysis(FEA)indicate that the number and positions of the locators for ATWC can be optimized simultaneously and successfully by the proposed topological optimization model.

Parametric Design of Modular Fixture Structure

Based on an example of its typical structure, the concept of modular fixture structure module is presented, and the structure module system of modular fixture is summarized. Then the parametric design of structure is discussed, and its advantages are also emphasized.Furthermore, some specific methods are provided, such as the selection of fixture components, the determination and input of parameters, drawing representative model,and the creation of drawing. Finally an applied example of strcture parametric design is presented.

Numerical simulation of horizontal transversal displacement under different fixed clamping force of welding fixture for superalloy during TIG welding

A numerical model is established by Abaqus software for superalloy during tungsten inert gas （TIG） welding with welding fixture to simulate the weld temperature filed, stress and strain field, and weld plate＇s horizontal trasnsveral shift. The clamp force perpendicular to the weld plate varying with welding time was analyzed. The maximum clamp force during welding process was calculated. Under the condition of insufficient of clamping force, a half or one third of the maximum clamp force for example, the weld plate＇s horizontal transversal displacement could happen and also be computed.

Case-based retrieval approach for machining fixture design utilizingontology

In order to develop an intelligent case-based reasoning （CBR） system to reuse fixture de- sign knowledge, ontology technology was integrated in CBR system by semantic annotation of fixture design case. Domain ontology of fixture design was constructed; concepts and relations were de- fined and represented. The 2-level similarity evaluation approach of domain ontology was presented. The concept similarity of cases was calculated as the first grade case retrieval. Numerical measure- ment was the second grade case retrieval, which adopted various methods to calculate different types of attribute values. The problem of similarity measurement of fixture design case was resolved. Pro- totype system based on the proposed method was illustrated and the retrieval approach was proved to be efficient.

A Rapid Location and State Memory Fixture System for Arbitrarily Shaped Part

A new fixture system-Rapid Location and State Memory (RL&SM) fixture system is presented.It is based on RFPE technique.In which a new method-adaptable location system is used to locating arbitrarily shapedpart.It solves the problems of part location,stock driftand accessibility of all sides of the part in machining.Any part can be machined entirely in a single setup by an appropriate machine tool.RL&SM fixture system consists of four parts:state memory,setup,data measure and information handling.The principle,components and work process of it are discussed,and some of the key techniques for industrialization are also presented.Keywords:Universal fixture,Rapid location,State memo-

Case-based Agile Fixture Design

In order to realize the agility of the fixture design, such as reconfigurability, rescalability and reusability, fixture structure is function unit based decomposed from a fire new point of view. Which makes it easy for agile fixture to be reconfigured and modified. Thereby, the base of case based agile fixture design system info is established.Whole case based agile fixture design model is presented. In which, three modules are added relative to the other models, including case matching of fixture planning module, conflict arbitration module and agile fixture case modify module. The three modules could solve the previous problem that the experience and result are difficult to be reused in the process of design.Two key techniques in the process of the agile fixture design, the evaluation of case similarity, and restriction based conflict arbitration, are listed. And some methods are presented to evaluate the similarity and clear up the conflict.

Numerical simulation about the effect of fixture on the welding stress and distortion of thin aluminum plate joints

The effect of welding jig on the welding stress and buckling distortion of thin aluminum plate joints was simulated by finite element method （FEM）. The results show that the restraint distance and the heat conduction ability of the fixture do have essential effects on the residual stress and distortion. The residual compressive stress and distortion will be increasing with the increase of the restraint distance, while the residual compressive stress and distortion will be decreasing with the increase of the heat conduction ability of the fixture.

Deformation Analysis and Fixture Design of Thin-walled Cylinder in Drilling Process Based on TRIZ Theory

Thin-walled cylindrical workpiece is easy to deform during machining and clamping processes due to the insufficient rigidi.Moreover,it’s also difficult to ensure the perpendicularity of flange holes during drilling process.In this paper,the element birth and death technique is used to obtain the axial deformation of the hole through finite element simulation.The measured value of the perpendicularity of the hole was compared with the simulated value to verify then the rationality of the simulation model.To reduce the perpendicularity error of the hole in the drilling process,the theory of inventive principle solution(TRIZ)was used to analyze the drilling process of thin-walled cylinder,and the corresponding fixture was developed to adjust the supporting surface height adaptively.Three different fixture supporting layout schemes were used for numerical simulation of drilling process,and the maximum,average and standard deviation of the axial deformation of the flange holes and their maximum hole perpendicularity errors were comparatively analyzed,and the optimal arrangement was optimized.The results show that the proposed deformation control strategy can effectively improve the drilling deformation of thin-walled cylindrical workpiece,thereby significantly improving the machining quality of the parts.

Study on Case-Based Fixture Design

Fixture is an important manufacturing activity. A fixture design system based on case-based reasoning (CBR) is proposed in this paper. A new method of case representation on the basis of fixture function is presented, where the case representation is constituted of workpiece knowledge, processing feature knowledge, and fixture feature knowledge. Running the prototype system shows that the knowledge representation method, using cases, s a better way to transform and explain the design knowledge.

Development of the 3D-Designed Lathe Fixture of a Float Brake Caliper

According to the technique requests of the brake caliper in the process of production, a special fixture of float brake caliper has been developed based on 3 D design in this paper. The development process and verified data from 3D modeling and kinematics simulation for this special fixture show that this 3D-designed process can conveniently forecast the assembly interference of the fixture and accurately add the mass of lead brick before the prototype is made. In this way the flutter caused by the unbalanced lathe fixture can be eliminated and the precision of run-out tolerance in cylinder hole compared with machine tool spindle can be improved, thus the processing quality of the cylinder hole in a brake caliper can be greatly guaranteed.

New Filler Material for Reference Free Part Encapsulation Fixture

Reference free part encapsulation (RFPE) is a non-traditional universal fixturing technique. In this paper, new filler material-a lower melting point alloy for RFPE technique is introduced. Based on experiment, the shrinkage and expansion rate, the effect of filler on workpiece drift and the effect of filler thickness on cutting distortion are studied. The alloy has a good mechanical and physical performance and the need of RFPE fixturing can be perfectly satisfied. The result shows that if the formula and process parameters of filler material are properly selected, it can obviously improve the quality of the workpiece, enhance the machining efficiency and reduce the manufacturing cost.

A Study on Flexible Fixture CAD Methods in FMS

The significance of study on flexible fixture CAD methods is summarized. Based on the AUTOCAD software, represented with slot Modular fixture dements, the flexible fixture CAD methods are discussed, such as part representative model,feature modeling,design method,structure of the graphic library, optimization of assembly drawing structure, optimal choice of interactive function, and CAD Information database management.