Work-holding Devices Research Articles

Thermal experiments and analysis on adhesive cleaning of work-holding devices by grinding

In the light-activated work-holding devices, hardened adhesive residues on the fixture plate need to be removed to make it available for the subsequent work holding. There are several ways to remove the cured adhesive from the gripper, such as laser-based degradation, and softening and removing with high temperature pressured water wash. These processes are associated with the generation of carbon black, affecting transparency which compromises the efficiency of the light-activated device. A novel peripheral grinding-based cleaning process has been developed to strip the adhesive from the fixture plate. The present research is aimed to analyze the effect of variation in grinding parameters, viz., spindle speed, feed, depth of cut, and the grain size of the grinding wheel on the temperature of the adhesive being ground and cleaning of the adhesive-filled channel. Aggressive values of grinding parameters are selected to achieve the desired removal of adhesive, putting a step towards sustainability. Moreover, a comprehensive investigation of the temperature of the grinding zone and the grinding wheel is made by inspecting the effective cleaning of the cured adhesive-filled channel. Higher values of spindle speed (11.57 m/s) and feed (0.406 mm/rev) resulted in an improved, cleaned surface of the ground adhesive-filled channel. Moreover, the grinding wheel with a more prominent grain size (46/Ø 0.35 mm) and porosity was proved to be more effective in the cleaning process by reducing and maintaining the grinding temperature (~52 °C) of the adhesive-filled channel.

Extension of the Stream-of-Variation Model for General-Purpose Workholding Devices: Vices and Three-Jaw Chucks

Nowadays, advanced manufacturing models, such as the stream-of-variation (SoV) model, have been successfully applied to derive the complex relationships between fixturing, manufacturing, and datum errors throughout a multistage machining process. However, the current development of the SoV model is still based on 3-2-1 fixturing schemes, and although some improvements have been done, e.g., N-2-1 fixtures, the effect of general workholding systems, such as bench vices or three-jaw chucks, has not yet been included into the model. This article presents the extension of the SoV model to include fixture and datum errors considering both bench vices and three-jaw chucks as fixturing devices in multistage machining processes. The model includes different workholding configurations, and it is shown how to include the workholding accuracy to estimate part quality. The extended SoV model is validated in a three-stage machining process by both machining experimentation and CAD simulations. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —Part quality estimation in multistage machining systems is a challenging issue. The stream-of-variation (SoV) model is a straightforward model that can be used for this purpose. However, the current model is limited to fixture based on punctual locators, and common shop-floor devices are not considered yet. To overcome this limitation, this article extends the current SoV model to include vices and three-jaw chucks as workholding devices. The proposed methodology lets practitioners estimate the manufacturing capability of a process considering the technical specifications of these devices (e.g., parallelism and perpendicularity of vice surfaces and total indicator runout of chucks), or it can be used for diagnosing workholding issues. The model assumes that the workpiece acts as a rigid part and errors as deformations during clamping are assumed to be negligible in comparison with fixture- and datum-induced errors.

Design of a fixture for wire-cut EDM: A generic approach

The increase in the need for high precision parts across various engineering fields demands a rapid pace in terms of manufacturing products, which leaves a little window for lead times related to auxiliary manufacturing requirements like tooling and fixtures. Similar to their application in conventional machining processes, fixtures serve as work-holding devices for non-conventional machining processes as well. This paper tries to bridge the gap between fixtures in traditional and non-conventional machining processes by developing a generic approach for designing a fixture for Wire-Cut EDM based on the methodologies followed for conventional processes. Different phases of the design process have been discussed in detail including the need to manufacture new or modify existing fixtures. Ashby charts method for material screening, and AHP and TOPSIS for material ranking have been included to help select the correct material. Additionally, due consideration is given to manufacturing and assembling the fixture body with the optimal processes to ensure cost savings. The approach can cut down on the lead time required from the conceptualization to the actual assembly of the fixture from a month to about a week depending upon machine availability on the shop-floor.

Dynamic Analysis Of Hydraulic Actuated Mandrel

Machining is an important part of the manufacturing process, as it involves precise metal removal to achieve quality, accuracy, and precision. The proper selection of cutting tools and work holding devices is essential in machining. In the manufacturing process, a work holding device is crucial. A mandrel is a work holding device that is used to grip a component during machining at high speeds and low feeds. The current work describes the design of a Hydraulic Actuated Mandrel, which is a useful work-holding device that firmly grips the work piece. The proposed material for the mandrel manufacture is Chromium Vanadium steel, because it provides uniform gripping forces and leaves no residual stresses on the work piece. Empirical relationships are used to calculate the forces and pressures exerted by the cutting tool on the work piece and the work holding device. The theory of thin cylinders is used to calculate the theoretical maximum hoop and longitudinal stresses. ANSYS software is used to create the statical model. The developed model was assessed by applying forces and pressures to the mandrel, which results in deformations and stresses. The theoretical stresses on the mandrel are compared to the stresses obtained from ANSYS. The correlation between the two analyses is found to be satisfactory. Modal analysis is used to obtain the natural frequencies and mode shapes for the same model, which are also useful for dynamic analysis. To determine the dynamic response of a structure under the action of dynamic loads, the “Mode Superposition Transient Dynamic Analysis” method is used. By using the natural frequencies and mode shapes obtained from modal analysis the dynamic analysis is done in ANSYS on the model. At various nodes, time-varying deformations are obtained. The deformations obtained in dynamic analysis at various nodes are compared to those obtained in static analysis. The level of agreement between them is deemed to be reasonable.

Proposal of computer aided process planning of parts machining using workholding devices

Proposal of computer aided process planning of parts machining using workholding devices

Variation propagation of bench vises in multi-stage machining processes

Variation propagation has been successfully modeled by the Stream of Variation (SoV) approach in multistage machining processes. However, the SoV model basically supports 3-2-1 fixtures based on punctual locators and other workholding systems such as conventional vises are not considered yet. In this paper, the SoV model is expanded to include the fixture- and datum-induced variations on workholding devices such as bench vises. The model derivation is validated through assembly and machining simulations on Computer Aided Design software. The case study analyzed shows an average error of part quality prediction between the SoV model and the CAD simulations of 0.26%.

Optimization of machining fixture layout using integrated response surface methodology and evolutionary techniques

Fixtures are the work-holding devices, widely used in manufacturing, to completely immobilize the workpiece during machining. The position of fixture elements around the workpiece strongly influences the workpiece deformation which in-turn affects the machining accuracy. The workpiece deformation can be minimized by finding the appropriate position for the locators and clamps. Thus, it is necessary to model the complex behavioral relationship that exists in the fixture–workpiece system. In this research paper, response surface methodology is used to model the relationship between position of locators and clamps and maximum deformation of the workpiece during end-milling, and then the developed model has been optimized by genetic algorithm and particle swarm optimization. As the predictive model is being developed by response surface methodology, a huge reduction in computational complexity and time is achieved during the optimization of machining fixture layout. Also, it is evident that the approach which integrates response surface methodology and particle swam optimization produces better results.

Flexible design, analysis and programming methodology of robotic welding cells for multiple configuration products

This paper presents the way in which constraint-based parametric solid modelling can support flexible programming of robotic welding cells for widely varying configurations of the same product family. The key to flexibility is parametric definition of the robot environment i.e., product configuration, product parts, work-holding devices etc., and of the path itself. Robot inverse kinematics is implicitly employed through constrained motions of the robot links defined in the CAD system. 3D exact simulation models are generated by embedding motion interpolators for each motion defined. Possible collisions or other undesirable states in robotic task implementation are discovered through the solid modeller. A production cell, where security doors are manufactured, is used as a case study where two industrial robots perform seam and spot welding, respectively.

Conceptual Design of Fixtures Using Machine Learning Techniques

Fixtures are work-holding devices which are used to locate and hold a workpiece during most of the machining operations. The design of a fixture is a complex and an intuitive process, which requires knowledge and experience. Automating the fixture design process is difficult and this is attributed to the problem of capturing the design knowledge. Recent advances in artificial intelligence, in particular in machine learning, have provided methods for capturing design knowledge. In this paper, an attempt to use machine learning for capturing the fixture design knowledge and using it for generating the conceptual design of fixtures automatically is presented with case studies.

Establishment of economic production rate, production batch size, and production sequence in manufacturing systems with flexible routing

Through automation, manufacturing systems today are being built with increased flexibility to accomodate alternate routings and perform complex operations. Through the technology of programmable fixturing, fixtures and other workholding devices can easily be configured to accommodate varying workpiece shapes and sized. Although increased flexibility is a desirable feature, it does in many cases increase the complexity of planning for production as a result of theincreased number of operations sequences that are available to the analyst. In this paper, the problem of lot sizing and process sequencing in a shop with sequence-dependent production rate, setup cost, and unit processing cost is addressed. Using standard lot sizing model with backorder, the paper develops two separate solution procedures, one based on dynamic programming and the other on graph theory, to simultaneously determine the production rate, operation sequence, and other lot sizing parameters that yield a minimum manufacturing cost plan. In doing so, the procedure automatically integrates the functions of process planning and inventory control. These two functions have traditionally been kept separate in most manufacturing organizations. The implementation of the model in a totally computerized process planning systems is also discussed.

An NC lathe simulator for part programming and machine operation training

The objective of this study is to develop a simulator, entitled nc-lathe to simulate the NC lathe operation and to train the part programming technique. nc-lathe includes five basic modules: operation selection module, part program development module, machine set-up module, simulation animation module, and design considerations module. The operation selection module consists of a rule-based expert system to aid in the selection of work-holding devices and machining operations. The part program development module includes a part program editor for developing and editing a part program for the designed part. The machine set-up module allows the user to set up the machine before the operation. The simulation animation module consists of a syntax checker, an operation troubleshooter, and a simulation animation subsystem. The syntax checker is designed for verifying the part program. The operation troubleshooter consists of a rule-based expert system to diagnose several most frequent operation problems during the simulation with probable causes and recommendations. On the simulation animation screen, a dynamic pictorial information is provided for simulating the NC lathe operation. Ten cases with a variety of machining operations on the lathe were used to validate the system. The results indicate that the performance of nc-lathewas equivalent to that of real NC lathes. The results of user interface evaluation demonstrate that nc-lathe provides an efficient and user-friendly interface. Evaluation of the system's performance indicates that nc-lathe could be used as a tool to help students to learn part programming.

Optimal Selection of Workholding Devices for Rotational Parts

Abstract This paper outlines a methodology for selecting the optimal sequence of workholding devices for manufacture of rotational parts, in order to minimize the total workholding time. The algorithm is based on dynamic programming and takes into account the holding surface, the machining surface and the direction of machining in order to specify the optimal plan.

Automatic Determination of Work-Holding Parameters for Turned Components

This paper describes the development of SETUP which is one of the modules of TECHTURN (1), a technologically oriented system for turned components. The SETUP module takes into account the geometrical data of the blank and the component, the technological requirements placed on the component such as surface roughness, concentricity and run-out, and the available work-holding devices for the machine on which the component is to be made. The system automatically determines the following parameters: (a) the work-holding method, that is the use of a chuck, or a chuck and centre or centres; (6) the number of setups required to complete the job; and (c) the clamping positions on the blank and component. In determining this, the system takes into consideration the different clamping devices available on the machine, and their characteristics. If more than one setup is essential, the system tries to balance the stiffnesses of the component in the different setups. This ensures that the stiffness of the component will have a minimum effect when the cutting conditions are calculated. The system can deal with cylindrical blanks as well as castings and forgings, which, often, are of complex shape. To demonstrate the working of the SETUP module, several examples are included.

Selection of workpiece size for accurate turning

When a tool is fed parallel to the axis of a rotating shaft the machined surface should theoretically be perfectly cylindrical. During turning, the generated surface deviates from the true cylindrical form and consequently has form errors due to lack of rigidity of the various links in the machine-fixture-tool-workpiece system, dimensional wear of the tool and temperature effects on the work size. The effects of various work-holding devices on form errors were investigated and the best workpiece size for different materials to yield minimum errors was determined.

Recent developments in magnetic work-holding devices for machine tools

Recent developments in magnetic work-holding devices for machine tools