一种孔系组合夹具夹紧装置构形设计方法

介绍一种针对棱柱形工件的孔系组合夹具夹紧装置的自动构形方法。首先确定工件的夹紧区域并离散化,然后根据工件的形状确定夹紧装置的个数,进而确定候选夹紧方案,并提出夹紧方案的质量评价标准。最后通过实例验证上述方法的可行性和精确性。     

面向快速夹具的工件夹持点自动规划

为解决薄壁类零件在装夹中出现的弯曲变形问题,研究了面向快速夹具的工件夹持点的自动规划方法.将工件数字化模型向定位基准面投影获得二维边界图,通过对边界图的规约化处理,确定主夹持点的位置区域;根据主夹持点的自动规划规则,规划出合理的主夹持点位置.根据薄板弯曲变形理论计算分析重心区和悬臂区的变形情况,确定辅助夹持点的合理位置和个数.从而完成工件夹持点的自动规划.通过某塑料机壳零件的夹持点自动规划实例,验证了所提理论的科学性和方法的有效性.     

工件夹具的可行夹紧区域确定方法

提出一种根据形封闭原理确定工件可行夹紧区域的方法。该方法针对预先确定定位配置的情况,依据形封闭原理计算出可以使工件达到形封闭的可行夹紧区域,夹具布局设计人员可以在该区域内选取所需的夹紧位置。该方法可以有效地处理工件的夹紧表面为凹面的情况。     

薄壁弧形件铣削加工装夹方案的优化

在航空制造业中,为了减轻工件的重量,大量使用薄壁结构零件。对于这类工件,改进工件的夹具布局能够有效地减少工件的变形。本文通过对弧形薄壁件铣削加工夹紧点的位置进行优化来减少工件的变形,并提出了6条启发式规则。这些规则根据各区域内工件的最大变形,依次确定各夹紧点的移动方向,具有较快的优化速度。     

第二讲 工件在夹具内怎样固定和夹紧

我们已经概括地介绍了工件定位的有关知识和在夹具内的定位方法,这是工件装在夹具内的一个主要方面,只知道这一方面是很不够的,还必须知道的另一个主要方面,就是工件在夹具内怎样固定和夹紧。工件从定位到固定和夹紧这一整个的过程叫做安装。工件安装在夹具内时,尽管定位方法正确,如果固定和夹紧的方法不好,工件的质量同样会出毛病,所以说工件的固定和夹紧与工件的定位是同样重要的。工件固定和夹紧的基本方法工件安装在夹具内定位以后,位置就确定了,但是如何保持工件在加工过程中,它的位置固定不变呢?这还需要夹紧。在夹具中工件的夹紧和固定是用夹紧元件和夹紧机构来实现的。工件夹紧后应能承受切削力、本身重量     

高速开关阀控制的可变夹紧力夹具

针对恒定夹紧力夹具对零件加工精度的影响,提出一种变夹紧力夹具方案。该夹具根据切削力的大小,优化分析工件最佳的夹紧点位置及各点的夹紧力,能够自动调整夹紧力的大小,以适应切削力,减少加工系统的切削变形。采用同工步数字控制技术,实现自适应夹紧功能,采用高速开关阀作为液压系统的动态控制元件控制夹紧力的大小。     

基于MATLAB优化算法的汽车缸盖多重夹紧力的优化分析

首先通过分析缸盖与夹具定位元件、夹紧元件之间的接触特点,建立了相应的接触副模型。在假定夹具夹紧点的布局位置以及夹紧顺序固定的基础上,以定位元件与工件接触区域半弹性变形所导致的工件最小位移为第一目标函数,同时以接触点变形最小总余能为第二目标函数。根据工件的具体加工过程静力平衡列出约束条件,构建了夹紧力的多目标优化模型。最后,根据多目标优化模型得到相应的结果。夹具的多重夹紧力经过该模型优化后,对应所需的夹紧力显著降低,这对提高加工精度和减少成本具有重要的意义。     

基于 ANSYS的车身柔性薄板焊装夹具优化设计

介绍薄板焊装夹具在国内外研究进展,然后在＂N-2-1＂定位原理的基础上,建立了适合车身焊接工艺的工件定位点优化设计的数学模型,提出了一种可以快速确定工件定位点位置以及夹具布局方案的设计方法。利用ANSYS有限元软件对模型进行了实验分析和验证,得出板料有限元网格的大小、夹具的定位点、夹紧点及夹紧力的大小等对接触变形的影响。结果表明该模型和方法快速、准确、合理,达到了预期设计的目标。     

夹具夹紧方案优化设计

综合分析夹具夹紧误差的各种影响因素及其影响方式,并根据影响方式归纳产生夹紧变形的两大原因,即由夹紧副变形导致的工件位置误差与由外力导致的工件变形,由此建立夹紧副变形与工件位置误差的通用关系模型;以工件位置误差最小为目标,建立了夹紧力的优化模型,可以同时实现夹紧力大小与作用点的稳健优化设计。最后用一典型实例说明了夹紧力的优化结果。所介绍的方法不仅适用于夹具设计,而且对机器人多手指抓取规划同样适用。     

机床工件夹紧信号采集系统的设计与应用

数控机床通常采用的工件夹紧信号采集系统,需根据工件尺寸不断调整检测开关的位置来感知中心拉杆的位置以保证夹紧工件,存在浪费人力、物力以及影响加工效率的问题,因此,提出一种新的机床工件夹紧检测装置。介绍了工件夹紧信号采集系统,分析了工件夹紧信号检测步骤。通过实验表明,该装置具有能适应各种规格工件且无需反复调整检测装置的特点。     

孔系组合夹具的零件定位方案自动确定方法

提出了一种孔系组合夹具的一般定位方式,该定位方式包括工件定位边与定位元件之间接触边的类型及其组合形式,每一个定位方案由3个固定在基础板上的定位元件组成,其中定位元件包括圆柱销和半V形定位块以及两者之间的各种组合。提出了建立定位方案集合的实施算法,将3个定位元件在基础板上的位置问题分解为两个步骤。首先根据2个定位边的类型和位置,确定2个定位元件的所有可能位置集合,然后根据给定3个定位边以及其中2个定位边上的定位元件位置和类型,确定第3定位元件全部可行定位位置集合。该方法可用于建立孔系组合夹具可行定位方案集合。     

A Clamping Design Approach for Automated Fixture Design

In this paper, an innovative clamping design approach is described in the context of computer-aided fixture design activities. The clamping design approach involves identification of clamping surfaces and clamp points on a given workpiece. This approach can be applied in conjunction with a locator design approach to hold and support the workpiece during machining and to position the workpiece correctly with respect to the cutting tool. Detailed steps are given for automated clamp design. Geometric reasoning techniques are used to determine feasible clamp faces and positions. The required inputs include CAD model specifications, features identified onthe finished workpiece, locator points and elements.     

Optimal Fixture Design Accounting for the Effect of Workpiece Dynamics

This paper presents a fixture layout and clamping force optimal synthesis approach that accounts for workpiece dynamics during machining. The dynamic model is based on the Newton– Euler equations of motion, with each fixture–workpiece contact modelled as an elastic half-space subjected to distributed nor-mal and tangential loads. The fixture design objective in this paper is to minimise the maximum positional error at the machining point during machining. An iterative fixture layout and clamping force optimisation algorithm that yields the "best" improvement in the objective function value is presented. Simulation results show that the proposed optimis-ation approach produces significant improvement in the work-piece location accuracy. Additionally, the method is found to be insensitive to the initial fixture layout and clamping forces.     

A feature-based approach for optimal workpiece localization and determination of feasible clamping regions

In this paper, we present an approach for optimally selecting the locating positions of workpieces and identifying feasible clamping regions that meet the requirements of the form-closure principle for fixture layout. This approach firstly finds an optimal configuration of locating points on a set of faces of the workpiece which minimizes the error transfer from locating points to machining features. In the formulation of the optimization, the error transfer is modeled using an error transfer matrix. The eigenvalues of the matrix are used as objective functions of the optimization. Secondly, this approach computes the clamping wrench cone and its member wrench can form a form-closure fixture layout, together with the formerly selected locating points. Finally, it generates the feasible clamping regions by projecting the clamping wrench cone onto faces of the clamping feature faces. An example is included to illustrate the effectiveness of the proposed approach. Compared with traditional methods in which only error transfer from the locating points to the workpiece’s mass-center is considered, the error transfer control in this approach is more effective and of greater efficiency. In addition, the clamping wrench cone projection method for the generation of feasible clamping regions is more suitable for handling cases with concave clamping faces than traditional convex-combination-based methods.     

Fixture Clamping Force Optimisation and its Impact on Workpiece Location Accuracy

Workpiece motion arising from localised elastic deformation at fixture-workpiece contacts owing to clamping and machining forces is known to affect significantly the workpiece location accuracy and, hence, the final part quality. This effect can be minimised through fixture design optimisation. The clamping force is a critical design variable that can be optimised to reduce the workpiece motion. This paper presents a new method for determining the optimun clamping forces for a multiple clamp fixture subjected to quasu-static machining forces. The method uses elastic contact mechanics models to represent the fixture-workpiece contact and involves the formulation and solution of a multi-objective constrained oprimisation model. The impact of clamping force optimisation on workpiece location accuracy is analysed through examples involving a 3-2-1 type milling fixture.     

叶片机器人砂带磨抛点云匹配算法优化

为解决机器人磨抛路径中工件坐标系难以计算的问题及校正工件装夹误差,将三维点云配准技术应用到叶片机器人砂带磨抛系统中。由三维激光扫描仪扫描工件型面获得工件点云,采用基于主成分分析(PCA)的全局配准算法和改进的迭代最近点(ICP)算法完成了扫描点云和工件模型离散点云间以及不同工件扫描点云间的匹配,以获取工件坐标系和校正工件装夹误差。相关仿真和试验结果表明,优化后的算法在匹配速度与精度上有了长足改进,且加工后产品精度和质量都能满足实际加工要求。