Fixture Clamping Force Analysis during Milling Process

This paper presents a analytical method to calculate the minimum clamping force to prevent slippage between the workpiece and spherical-tipped fixture elements during milling process. After the contact deformation between the workpiece and spherical-tipped fixture element is determined, the relationships between the workpiece displacement and the contact deformations are obtained. Based on the static equilibrium equations, these equations are combined and linear equations are obtained to calculate the tangential contact forces between the workpiece and spherical-tipped fixture element. According to the maximum tangential contact force, the minimum clamping force to prevent slippage between the workpiece and spherical-tipped fixture elements is calculated. At last, this method is illustrated with a simulation example.

Research on the Design Method of Component-Based Modular Fixture

On the basis of the traditional assemble method of components modular fixture, the establishment of a component-based modular fixture design method was proposed in the paper. First of all, the concept of modular fixture components was put forward, and then the components according to different functions were classified, and the relationship table between the components and elements were established. At last of this paper, the application of this method was introduced through an instance. While designing fixture for part family, this method can utmost save design time and minimize the quantity of disassembling of combined fixture element, reduce the wear and tear of components, and shortening the time of manufacturing.

The System Design of Graphics Library of Fixture Element Based on .NET

According to the structure characteristic of the fixture design, the architecture of graphics library of fixture element is established. Based on the technologies of network, library, .NET and the developing mechanism of AutoCAD/MDT, the implemented strategy of the system of graphics library of the fixture element is presented. The remote sharing of the fixture resource information is realized. The system provides process engineer of the fixture design with assistant tools.

Fixture optimization for sheet panel assembly considering welding gun variations

Sheet panel assembly in automotive body manufacturing typically involves fixturing (including locating and clamping), joining (especially welding), and unclamping. Research has shown that the choices of fixturing schemes are important and that fixture optimization can generally improve the assembly dimensional quality with reduced assembly distortions. However, these research studies generally modelled weld guns as constant disturbances (such as deterministic forces) without considering the weld gun variations to avoid the complexity of Monte Carlo simulations. In the current paper, a fixture optimization model is formulated to minimize the assembly dimensional variations under welding gun variations. It is shown that, by using the proposed weld gun variations model, an assembly variation simulation can be converted to a deterministic assembly model, eliminating the need for Monte Carlo simulation. The efficiency improvement makes it feasible for a full scale optimization solution for optimal fixture locations with welding variations. The current paper further introduces the fixture-element models for continuous variable optimization in finite-element analysis, an enabler for fixture optimization. Numerical examples are shown to demonstrate the proposed methods.

FIX-DES: A Computer-Aided Modular Fixture Configuration Design System

This paper presents a computer-aided modular fixture design system: FIX-DES. When fixturing requirements are specified as locating/clamping surfaces and points, a fixture configuration will be automatically generated by (1) selecting fixture elements from a fixture element database to form fixture units based on fixture element assembly relationships and (2) placing the fixture units and elements into position on a baseplate while the fixturing requirements and assembly relationships (e.g., hole alignment) are maintained. The fixture element assembly relationships can be automatically established when the geometric models and fixturing functions of the fixture elements are specified so that the FIX-DES system can be easily applied to different fixture systems. The system also provides the interactive design and design modification functions for human expert involvement. The system was developed with core programs in C/C++ and interface programs in a specific CAD environment. The system has been successfully applied in industry and can be easily transferred to other CAD systems. The overall structure of the FIX-DES system is introduced in the paper. The development of the automated fixture configuration design (AFCD) functions are presented in detail. Finally a fixture configura-tion design example is given to illustrate the application of the system.

An approach to automating modular fixture design and assembly

In the development of a modular fixture design system, it is essential to have a modular fixture element database that can be integrated with a CAD system, in addition to the other considerations such as fixture configuration, interference checking, etc., which are also important to fixture designers. This paper describes a new method to create the fixture element database and model the fixturing towers (i.e. subassemblies). By using this method, the database can be effectively created and is easy for use in fixture assembly. The modular fixture tower database is used to represent the subassembly of fixtures. This will simplify the fixture design and assembly process. A built-in interference checking methodology is embedded in the planning stage that will ensure a collision-free fixture design. The system is developed using the knowledge- based system, ICAD, and interfacing with UG-II for modelling the workpiece. Examples of fixture design generated by the system are also provided to illustrate the development.

User Interactive Flexible Fixturing System

The focus of this work is on developing a user interactive flexible fixturing system which is used for synthesizing and testing fixture layouts for use in assembly operations. The system is designed to develop fixtures that utilize a specific type of three-point frictional constraint The first component of the system is the synthesis program which employs an analysis strategy that uses graphical techniques to characterize the stability of given fixture configurations. A stability threshold based on fixture element contact friction is identified to provide an indicator for the stability of layouts, and on-screen graphical displays are available to compare the stabilities of multiple configurations. A synthesis strategy is introduced to provide a guide to aid in the selection of constraining element arrangements on part surfaces. The second component of the system is the verification phase which allows arbitrary polygonal objects to be constrained with newly synthesized fixture layouts in a flexible test cell so that experimental results can be compared to analysis results. The entire system is demonstrated through examples and comparisons are made between the analytical results and experimental verification data.