Optimization of Fixture Number in Large Thin-Walled Parts Assembly Based on IPSO

There are lots of researches on fixture layout optimization for large thin-walled parts.Current researches focus on the positioning problem,i.e.,optimizing the positions of a constant number of fixtures.However,how to determine the number of fixtures is ignored.In most cases,the number of fixtures located on large thin-walled parts is determined based on engineering experience,which leads to huge fixture number and extra waste.Therefore,this paper constructs an optimization model to minimize the number of fixtures.The constraints are set in the optimization model to ensure that the part deformation is within the surface profile tolerance.In addition,the assembly gap between two parts is also controlled.To conduct the optimization,this paper develops an improved particle swarm optimization(IPSO)algorithm by integrating the shrinkage factor and adaptive inertia weight.In the algorithm,particles are encoded according to the fixture position.Each dimension of the particle is assigned to a sub-region by constraining the optional position range of each fixture to improve the optimization efficiency.Finally,a case study on ship curved panel assembly is provided to prove that our method can optimize the number of fixtures while meeting the assembly quality requirements.This research proposes a method to optimize the number of fixtures,which can reduce the number of fixtures and achieve deformation control at the same time.

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.

Optimization of material removal strategy in milling of thin-walled parts

The optimal material removal strategy can improve a geometric accuracy and surface quality of thin-walled parts such as turbine blades and blisks in high-speed ball end milling.The dominant conception in the material removal represents the persistence of the workpiece cutting stiffness in operation to advance the machining accuracy and machining efficiency.On the basis of theoretical models of cutting stiffness and deformation,finite element method (FEM) is applied to calculate the virtual displacements of the thin-walled part under given virtual loads at the nodes of the discrete surface.With the reference of deformation distribution of the thin-walled part,the milling material removal strategy is optimized to make the best of bracing ability of still uncut material.This material removal method is summarized as the lower stiffness region removed firstly and the higher stiffness region removed next.Analytical and experimental results show the availability,which has been verified by the blade machining test in this work,for thin-walled parts to reduce cutting deformation and meliorate machining quality.

Initial residual stress experiment and simulation of thin-walled parts for layer removal method

Thin-walled parts have low stiffness characteristic. Initial residual stress of thin-walled blanks is an important influence factor on machining stability. The present work is to verify the feasibility of an initial residual stress measurement of layer removal method. According to initial residual stress experiment for casting ZL205 A aluminum alloy tapered thin-walled blank by a common method,namely hole-drilling method,three finite element models with initial residual stress are established to simulate the layer removal method in ABAQUS and ANSYS software. By analyzing the results of simulation and experiments,the cutting residual stress inlayer removal process has a significant effect on measurement results. Reducing cutting residual stress is helpful to improve accuracy of layer removal method.

Filling mode and regularity of vertical centrifugal casting process of titanium alloy in thin-walled cylinder cavity

The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode of the melt in the cylinder cavity varies with casting wall-thickness. When the casting wall-thickness is less than or equal to the thickness of the first layer during the filling process, the melts fill the cavity from the bottom to the top.When the casting wall-thickness is greater than the thickness of the first layer during the filling process, the melts first fill the largest radius parts of the cavity with a certain thickness of the first layer from the bottom to the top of the cavity, and then they fill the cavity from the larger radius part to the smaller radius part. The melt filling ability increases with the increment of the mold rotational speed and the pouring temperature. In another aspect, the melt filling ability rises with the decrement of the melt viscosity, and the melt with the better filling ability is prone to fill the cylinder cavity layer by layer.

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.

Relative Varying Dynamics Based Whole Cutting Process Optimization for Thin‑walled Parts

Thin-walled parts are typically difficult-to-cut components due to the complex dynamics in cutting process.The dynamics is variant for part during machining,but invariant for machine tool.The variation of the relative dynamics results in the difference of cutting stage division and cutting parameter selection.This paper develops a novel method for whole cutting process optimization based on the relative varying dynamic characteristic of machining system.A new strategy to distinguish cutting stages depending on the dominated dynamics during machining process is proposed,and a thickness-dependent model to predict the dynamics of part is developed.Optimal cutting parameters change with stages,which can be divided by the critical thickness of part.Based on the dynamics comparison between machine tool and thickness-varying part,the critical thicknesses are predicted by an iterative algorithm.The proposed method is validated by the machining of three benchmarks.Good agreements have been obtained between prediction and experimental results in terms of stages identification,meanwhile,the optimized parameters perform well during the whole cutting process.

Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace,national defense,energy and precision physical experiments.However,the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools.In this paper,an elliptical vibration cutting(EVC)with active cutting edge shift(ACES)based on a long arbor vibration device is proposed for ultraprecision machining the pure iron parts by using diamond tool.Compared with cutting at a fixed cutting edge,the influence of ACES on the EVC was analyzed.Experiments in EVC of pure iron with ACES were conducted.The evolutions of the surface roughness,surface topography,and chip morphology with tool wear in EVC with ACES are revealed.The reasonable parameters of ultraprecision machining the pure iron parts by EVC with ACES were determined.It shows that the ACES has a slight influence on the machined surface roughness and surface topography.The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge,so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed.A typical thin-walled curved surface pure iron part with diameter φ240 mm,height 122 mm,and wall thickness 2 mm was fabricated by the presented method,and its profile error and surface roughness achieved PV 2.2μm and Ra less than 50 nm,respectively.

缸体类零件内腔硬质阳极氧化加极装置设计与改进

[目的]某型号压气缸在现场安装时出现过盈配合问题,内腔硬质阳极氧化膜厚度分布不均及顶部膜厚过大是主因。[方法]设计并制作了加极装置,结合阳极氧化试验和有限元分析对其中的辅助电极进行改进。[结果]使用加极装置后,内腔阳极氧化膜厚度分布均匀,都在要求的10~20μm范围内。[结论]在硬质阳极氧化过程中使用合适的加极装置有利于控制缸体零件内腔阳极氧化膜的厚度,提高膜厚均匀性。

电真空器件隙缝腔零件微细加工技术工艺研究

针对G波段分布作用速调管中关键零件隙缝腔零件的高精度设计要求开展微细加工技术研究。基于现有加工经验及加工设备条件,通过创新性的工艺设计、结合大量工艺试验探索,突破了微小尺寸、超高精度零件的精密加工技术,满足了毫米波及太赫兹电真空器件中关键零部件的制造需求,提升了高频段电真空器件制造技术水平。

基于CATIA中core-cavity造型的应用

从CATIA软件中的树命令比较,利用core-cavity方法的步骤繁多,所花时间是很多的,但这样却弥补了传统实体造型方法的缺陷,并且能为模具供应商提供有力的数据支持,而且文件中的部分数据参数还可单独取出,增加了利用率,对于设计人员来说是非常有价值的。由于这种方法的设计思路是很清晰的,初级设计人员能很容易读懂它,充分体现了资源共享。

薄壁深腔小脱模斜度箱体塑件注塑模具设计

针对某办公设备上的薄壁深腔小脱模斜度箱体塑件为研究对象,根据塑件深腔、薄壁、脱模斜度小的结构特点和适用于大批量生产的技术要求,设计了一副包含:定模芯入子优先抽芯结构、动模芯入子优先抽芯结构和四边滑块侧向抽芯结构的复杂注塑模具。模具设计采用四边滑块侧向抽芯机构,解决塑件两侧脱模方向倒扣及塑件表面脱模斜度小、高度方向太深易黏定模的问题,同时可以优化分型面结构,提高加工效率;模具设计的定模芯入子优先抽芯结构,通过在两处环形筋位处设置的前模芯镶件入子,利用镶件的排气特性,解决定模侧两处环形深的筋位在注塑成型时易出现困气、烧焦及填充困难的问题,通过优先抽芯前模芯的镶件入子,解决此两处深的筋位黏模的问题;模具设计的动模芯入子优先抽芯结构解决了塑件深腔、薄壁结构包紧力过大顶出困难的问题,利用动模芯入子的优先抽芯结构,先脱出动模型芯,即可轻松顶出塑件同时不会造成顶出变形。针对塑件成型时易出现的问题,经过模具结构优化设计,模具在后续实际生产中表现优异、符合预期。

汽车座椅管束塑件注射模设计

以汽车座椅头枕管束塑件为例,介绍了带侧向滑块抽芯的深腔注射模,并详细说明了该模具的设计要点和结构分析及功能等,并且给出了具体的结构设计方案。对于该塑件“比较长”的特点,该模具在推板组成、滑块组成、冷却运水设计、排气系统、脱模系统以及结构设计等方面均优于常规模具。通过生产验证,结果表明,该模具整体结构紧凑、工作稳定、成型件缺陷少、生产效率高,达到客户需求。该模具设计方案可为同行提供一定的参考。

筒体类零件模腔可变式辊轧成形装置设计

针对筒体类零件模腔可变式辊轧成形新方法,设计了一种稳定可靠的辊轧成形装置,介绍了该装置的结构组成及工作过程,并对该装置的合理性进行了辊轧试验验证,结果表明该装置结构可靠、功能完整,成形工件外形准确无缺陷,从而为该类零件的成形提供了一种新的选择,具有较为广泛的应用前景。

基于Mastercam X圆弧薄壁型腔零件铣削工艺分析及加工

本文针对圆弧薄壁型腔零件能够快速的进行数控铣削加工,保证零件产品质量。本文利用Mastercam X自动编程软件对圆弧薄壁型腔零件进行二维建模、刀具选择、切削参数设置、铣削刀路轨迹生成和模拟仿真,生成加工G代码实现圆弧薄壁型腔零件快速的铣削。利用Master cam X进行自动编程和高速铣削方式,避免手工编程中复杂的坐标值计算和程序错误,保证零件加工精度,提高零件光洁度和加工效率。

通信腔体类零部件电镀铜/银工艺

介绍了通信腔体类零部件电镀光亮Cu/Ag的工艺流程和关键事项,并分析了光亮镀铜层和镀银层的外观、厚度、结合力和显微硬度。通过反复试验,探索了不同电流密度下镀层厚度与电镀时间的关系,为实际生产中腔体类零部件电镀提供参考。

基于塑料盒的家族制塑料模具设计

以某塑料盒上盖和下盖为研究对象,对产品结构、模具设计等进行了较为系统的研究,最后设计了用于塑件产品注射成型的模具装配图,为家族制塑料模具的设计提供相应的技术参考。

腔体类零件内腔化学氧化工艺及设备研究

介绍了腔体类零件内腔化学氧化工艺流程、溶液配方和自动生产设备组成、性能及设备配置;阐述了流镀法对腔体类零件内腔进行化学氧化原理、过程步骤,重点介绍了腔体类零件气动装夹、溶液转换器结构,自动实现多种溶液间相互转换、处理以及智能化控制和生产管理系统。

一种微细电火花线切割用黑金丝设计及其应用研究

分析了形状复杂微型孔和型腔精密模具零件微细电火花线切割加工中存在的问题,提出了有效解决方案。从应用角度出发,设计了复合重构表层黑金丝材料,优化了电极丝的放电性能,满足了微细电火花线切割加工形状复杂微型孔和型腔精密模具零件应用要求,提高了加工精度和表面质量。

基于特征技术的注塑模具型腔设计制造系统

针对一般注塑模具型腔设计制造周期问题,构建了基于特征技术的注塑模具型腔设计制造系统.该系统采用基于特征库的交互式特征识别方法识别产品中的特征,建立产品的特征模型.通过侧凹特征的判别确定模具的优化脱模方向,并确定模具的分型线和分型面.模具型腔可采用分型面分割模板的方法获取.同时提出了模具型腔特征提取算法来提取模具型腔中的特征,制订模具型腔的加工策略.研究结果表明,该系统可以有效缩短模具型腔设计制造周期,加快模具开发的进程.