Modular Fixturing Systems Research Articles

A computer-aided design and analysis of a modular flexible fixturing system for aircraft fuselage panel assembly

A computer-aided design and analysis of a modular flexible fixturing system for aircraft fuselage panel assembly

Modular intelligent fixture system for flexible clamping of large parts

In this work a modular intelligent fixture system for flexible clamping of large parts is presented. The fixture modules consist of a hybrid material structure involving metal frame elements and mineral casting. These modules can be combined and connected to realize fixtures adapted to the geometry of the workpiece and requirements of the machining processes. By integrated pipes and interfaces, an internal hydraulic supply and active cooling is possible even for combined modules. Temperature and acceleration sensors allow for an active thermal control and process monitoring. The modules and first test fixtures are investigated in experiments.

Accuracy analysis of the modular fixturing systems with grid pattern threaded holes

Using a baseplate with a grid pattern threaded holes and the machine tool to accurately locate the modular locators upon the baseplate, the positional accuracy of the workpiece can be improved and results a relatively inexpensive modular fixturing systems. A stochastic mathematical model of the geometrical accuracy and a solving algorithm for these modular fixturing systems are proposed. Four types of modular fixturing systems with grid pattern threaded versus the most important classical modular-fixturing systems with multipurpose holes are analysed. Monte Carlo approach is used to calculate and to compare the locating accuracy of these modular fixturing systems.

Assemblability analysis of the modular fixturing systems with accurate grid pattern holes using Monte Carlo simulation

This paper focuses on the assemblability of modular fixturing systems. Two types of stochastic models are proposed: for two holes-two pins (2H2P) and for two holes-two pins-two holes (2H2P2H), both used by modular fixturing systems with multipurpose grid pattern holes. The probability of successful assemblies to engineering specifications is calculated using the Monte Carlo simulation. The weights of the assemblability criterion variables are analysed and several design recommendations are indicated.

Multi-point Clamping with Automatic Collision Avoidance for Aircraft Structural Parts Machining

In order to solve the problem of machining motion collision between cutter and fixtures, a multi-point clamping system with automatic collision avoidance is proposed for aircraft structural parts. The system is developed in consideration of part localization and modular clamping functions, and independent of CNC machine tools for the convenience of application. And then, a model-based collision detecting algorithm is designed, which can be implemented by comparing the cutter's actual position extracted by ultrasonic sensors, and the calibrated positions of clamping points. Finally, a modular fixture system with automatic collision avoidance was manufactured and tested. From machining experiments, it indicates that the proposed fixture system can be highly efficient and very flexible to meet the aircraft structural parts machining requirements.

Design of self-tuneable mass damper for modular fixturing systems

Enhancing dynamic characteristics of fixtures for large workpieces is essential to assure chatter free machining of heavy-duty milling operations. Variable stiffness tuned mass dampers (VSTMD) can effectively improve the dynamic stiffness of modular fixtures by changing their dynamic characteristics. The theory of a new VSTMD concept is presented. Their realisable optimal tuning is determined and the results are compared to the standard constant stiffness TMDs. By means of the developed automatic tuning procedure, stiffness is varied via a rotary spring, while damping is provided by eddy currents. The prototype and the effectiveness of the concept are experimentally validated by heavy-duty milling tests on a modular fixture.

AN AUTOMATIC FIXTURE DESIGN SYSTEM FOR CREATING PRISMATIC PARTS

A modular fixture system is a flexible alternative to a dedicated fixture. In this paper, an automatic modular fixture design system is suggested for creating prismatic parts. The system contains fixture planning, fixture modelling, and fixture assembly. The part geometrical database and process plans are considered as inputs to the system. A rule- based method is applied to assign the feasible locating scheme and the locating and clamping datum. The search strategy is designed to determine the most suitable locating and clamping points. The final fixture assembly is made with the standard fixture components using the CATVBA Editor inside CATIAV5. The proposed methodology is successfully validated with a case study.

Research and Application on Heterogeneous CAD Platforms of Modular Fixture System

Application on multi-platforms for a computer-aided fixture design (CAFD) system is significant. But now, relative less attention is focused on this direction. On above backgrounds, research was carried out on data construction, data description, data conversation as well as data parsing. In modular fixture system, components in the modular fixture base were described according to their CSG-based primitives. So, XML was used to represent the simple data because of its widely using on net and different operational systems. By developing interfaces between diverse CAD systems, the modular fixture system can be applied on heterogeneous environments and reinventing the wheel can be avoided.

Towards an intelligent fixturing system with rapid reconfiguration and part positioning

This paper presents the methodologies for rapid reconfiguration and part-to-fixture positioning in an intelligent fixturing system. Both aproaches are based on a modular fixturing system consisting of movable actuators and sensors. The reconfiguration methodology utilises an object-oriented approach to ensure that the fixture can work with various setups without the need of altering the control software. The part-to-fixture positioning approach calculates dimensional tolerances that can be used for guidance in automated part-fixture positioning.

Automated synthesis of modular fixture designs using an evolutionary search algorithm

Fixture design is a complex problem that requires a designer to ensure that a workpiece is located deterministically, totally restrained and sufficiently supported during a manufacturing process. The use of modular fixtures, while presenting an opportunity to improve the responsiveness of a manufacturing system, adds to the complexity of the fixture design problem. The complexity is a result of the large number of fixture elements in a modular fixture system and the constraints of specified locations in which fixture elements can be placed in a grid-based modular system. This paper presents an evolutionary search algorithm that aids a fixture designer by exploring the large number of possible fixture designs and suggesting an appropriate one. The algorithm can explore the large solution space using a flexible and generic representation and it considers fixture layout and fixture configuration constraints concurrently in arriving at appropriate solutions. The initial results of the algorithm are promising.

형상공간 접근 방식에 기반한 모듈식 고정쇠의 적재가능성 분석

In modular fixturing systems, a given part or a subassembly is fixed by placing fixture elements such as locators and clamps adequately on a plate with a lattice of holes. It is known that the minimal number of point contacts to restrict translational and rotational motions on a plane is four and the type of three locators and a clamp(3L/1C) is the minimal future. Brost and Goldberg developed the complete algorithm to automatically synthesize 3L/1C types of fixtures which satisfy the condition of form closure. Due to the nature of the fixture, the clearance between the fixture and the part is extremely small. It is hard to load the part repeatedly and accurately for human as well as for robot. However the condition of loadability has not been taken into account in the B&G algorithm. In this paper, a new method to decide a given fixture to be loadable by using configuration space is proposed. A method to plan for a part to be loaded by using compliance safely even in the presence of control and sensing uncertainty is proposed is well.

An Integrated Approach to Collision-Free Computer-Aided Modular Fixture Design

This paper describes a CAD-based methodology for developing a modular fixture design system using the Unigraphics (UG) solid modeller, integrated with a modular fixture element database, based on a hole-based IMAO modular fixturing system. A parametric modelling technique has been applied to construct the database. An integrated methodology is introduced in the system in which the functions of interactive, semi-automated and automated fixture design systems are combined collaboratively in a single environment. This provides the flexibility and functionality for making the design process more efficient. The interactive fixture design module helps the designer to select the fixturing faces, points and elements for building a fixture. Semi-automated and automated fixture design modules are built by transforming the designers' experience and knowledge into rules and algorithms to automate the selection of fixturing points and elements, More importantly, the system aims at producing a tool-collision-free fixture design using a machining interference detection submodule based on a cutter swept volume approach.

Clamping Fault Detection in a Fixturing System

When a workpiece is located and clamped in a fixture, the dynamic response can be used to characterize its corresponding clamping condition. When the contact condition between the workpiece and the fixture is changed, the system response frequency will change accordingly. The identification of insufficient clamping forces is investigated in this study. This paper also presents the modeling and analysis of the contact condition between fixtures and components in a modular fixturing system. Analytical models were obtained using the finite element approach. Virtual spring elements are used to model the dynamic effect of surface contact in the model, and the estimation of the virtual spring constants is also presented. Experimental results are compared with the analytical predictions.

Contact condition modelling for machining fixture setup processes

Manufacturing automation often requires high precision and highly accurate equipment to achieve satisfactory performance. In many cases, precision and accuracy depend highly on the surface contact conditions between machine components. Described in this paper is the modelling of the response frequency of a modular fixturing system with multiple components in contact, and it has demonstrated that it is possible to monitor the contact conditions based on a fixture system's dynamic response frequencies. The virtual spring element based on the Hertz theory is used to recapitulate the fixture contact conditions in the finite element modelling. Possible contributing factors to contact conditions, such as material properties, surface finish, hardness and the contact area between the workpiece and fixture device, are investigated in the estimation of the virtual spring constant. Experimental analysis is also conducted to verify the analytical model. The application of this model can be used for control, monitoring, and design of general clamping devices in many manufacturing processes.

A reconfigurable modular fixturing system for thin-walled flexible objects

This paper presents a novel reconfigurable modular system for the fixturing of thin-walled, flexible objects subject to a discrete number of point forces. The paper comprises two parts: description of the conceptual design of our new reconfigurable fixture, and a brief review of our earlier work on the optimal reconfiguration of the object-support locations.

Feature-based description of modular fixturing elements: The key to an expert system for the automatic design of the physical fixture

This paper reports on the development of an expert system for the design of the physical fixture for the fixturing of prismatic parts on machining centers. A brief description of the Brite project 3480 IDEFIX in which the system was developed is given. With as input the faces on which positioning, clamping and/or supporting should be done, the expert system generates the necessary assembly of modular fixturing elements (i.e. the physical fixture). New in the approach is the description of modular elements by means of form features. This method permits the description of an arbitrary modular fixturing system (with the only restriction that it has to be based on a grid of holes) and the use of the same logic to determine the assembly of modular elements.

Modular fixture design: a designer's assistance

Abstract This paper presents software to assist the tool designer of modular fixturing assembly. The software comprises a knowledge-based Adviser, a fixturing component assembly program and a CAD system. The Adviser assists the tool designers in selecting components from a modular fixturing system (MFS). The fixturing component assembly program will then position and assemble the modular fixturing components. The final assembly is then displayed in the CAD system. An example is also included to demonstrate the working principle of the software.

A systematic conceptual design of modular fixtures

The replacement of dedicated fixtures by modular fixturing systems seems to be a trend in the manufacturing field, especially in meeting the desire for greater flexibility but the selection of appropriate modules from a modular fixturing system and subsequent assembly is itself not an easy task. This research provides a systematic design method to help dedicated fixture users to convert to modular fixturing system users. This method classifies modules into five functional groups and then selects proper modules from each group in accordance with the functional request of the fixture assembly. This systematic design of modular fixtures helps a dedicated fixture user to build an economical and efficient modular fixturing system.

Integrated modular fixture design, pricing and inventory control expert system

Abstract The aim of this paper is to trace the evolution of modular fixturing systems (MFS) and its impacts on high-precision machining industries. The strength of current computer-aided tools for modular fixture design is reviewed together with their weaknesses. Recent trends in the integration of knowledge-based and 3D solid CAD techniques for modular fixture design, pricing and inventory control are described. The functionality, design and knowledge representation techniques of a 3D Modular Fixture Design EXpert, MOFDEX system forms the core of this paper.

Design and implementation of robot-operated adaptable and modular fixtures

This paper presents the design issues and hardware implementation for robot-operated automatic modular and adaptable fixtures. Modular fixtures are workholding devices made from stackable self-contained modular elements. Adaptable fixtures provide surface contact with the workpiece and therefore can adapt to the workpiece geometry. These fixtures are shown to have several advantages over conventional fixtures. Issues in modularity and adaptability for workpiece fixturing are discussed for the purpose of evaluating automatic modular fixtures in flexible manufacturing systems. The basic design requirements for robot-operated modular and adaptable fixturing systems are developed and classified into mechanical and operational. Automatic assembly issues such as the use of special mating surfaces, compact actuators for active modules, as well as the importance of communications between the robot manipulator and the modular fixture are discussed.Hardware design and implementation of a shape memory alloy actuated locking module and a discrete conformable surface module are presented. Performance characteristics such as free-play, stiffness and time response were evaluated experimentally for the locking module. Several workpiece geometries are tested on the comformable surface module.