A Critical Review of Tube and Sheet Metal Hydroforming Technology

The hydroforming technology, which is rapidly gaining popularity in the sheet metal and tube forming industry is reviewed. The features and the characteristics of the hydroforming process are described. The uniformly distributed fluid pressure covers the back side of the sheet as a die generates many advantages in the technical point of view as improving the part surface quality, reducing the forming severity and smoothing the thickness distribution. The benefits of using hydroforming technology are examined and analyzed in a technical level. The better part quality, less cost of tooling, materials saving and part weight reduction can be achieved using the hydroforming technology. The design methodologies for the hydroforming process parameters are reviewed and discussed in a certain detail. Computer-aided-engineering such as finite element simulation is suggested for such process parameter design.

A New Crossover Operator for Assembly Sequence Planning by Genetic Algorithms

Assembly Sequence Planning (ASP) is the generation of the best or optimal sequence to assemble a certain product, given its design files. Although many planners were introduced in research to solve this problem automatically, it is still solved manually in many advanced assembly firms. The reason behind this is that most introduced planners are very sensitive to large increases in product parts. In fact, most of these planners seek the exact solution, while performing a part basis decision process. As a result, they are trapped in tedious and exhaustive search procedures, which make them inefficient and sometimes obsolete. To overcome these difficulties, Sebaaly and Fujimoto (1996) introduced a new concept of ASP based on Genetic Algorithms application, where the search procedure is performed on a sequence population basis rather than a part basis, and a best sequence is generated without searching the complete set of potential candidates. This paper addresses the problem of improving the GA performance for assembly application, by introducing a new crossover operator. The genetic material can be divided and classified as ‘good’ or ‘bad’. The new crossover insures the maximum transmission of ‘good’ features from one generation to another. This results in a faster GA convergence. The performance of the new algorithm is compared with that of the ordinary matrix crossover for a modified industrial example, where it proved to be faster and more efficient.

Enabling Technologies for Virtual Parts Handling Environment: An Overview

Due to the current advances in simulation, computer graphics, robotics, and other related technologies, virtual environment has become a future trend in design and development of new products. This paper summarizes the current enabling technologies to develop a virtual environment for parts handling applications, such as parts feeding, assembling, and robotic grasping. A special focus is on developing a physically-based simulation system, which is the core of a virtual parts handling environment. Critical technologies such as object collision detection and response, contact modeling and friction modeling are reviewed. The technological challenges in these areas are also pointed out.

An Analysis of Multiple Peg-in-Hole Insertion Tasks

In this paper an analysis of the physics of a multiple peg-in-hole assembly task is addressed. Insertion of three pegs, arranged in an equilateral triangle, into three holes simultaneously is chosen as an example case. Although a 3 dimensional problem, the small-angle assumption reduces the model to only 3 degrees of freedom: 2 translations in the XY plane and a rotation about the Z axis. The multiple-pegs are viewed as points in a 3 dimensional configuration-space (C-space.) The net force and torque due to contact during chamfer crossing at each point in the C-space are determined. It is shown that the net force and torque are in the directions of minimizing the lateral and angular errors of the pegs. Based on these data together with compliance models of Remote-Center Compliance (RCC) and Spatial RCC (SRCC), the force and torque that occur during multiple-peg insertion using these passive devices are predicted. The result from the prediction is used to compare the performance of the two devices, and to design strategies for successful insertion of this assembly task.

A Newly Developed Algorithm for Treating the Coupled Dynamic Response of Robotic Fixtureless Assembly

The coupled dynamic response of two cooperating robots handling two flexible payloads for the purpose of fixtureless assembly and manufacturing is treated using a new algorithm. In this algorithm, the equations describing the dynamics of the system are obtained using Lagrange’s method for the rigid robot links and the finite element method for the flexible payloads. A new time integration scheme is developed to treat the coupled equations of motion of the rigid links for a given displacement of the flexible payloads. The finite element equations of the flexible payloads are then treated using an implicit approach. The new algorithm was verified using simplified examples and was later used to examine the dynamic response of two cooperating robot arms manipulating flexible payloads which are typical of the automotive industry.

Reconfigurable System Analysis for Agile Manufacturing

Agile manufacturing concept requires an enterprise view and agility embodies concepts like rapid prototyping, reconfigurable equipment, design for upgradability, leveled production and continuous improvement to introduce new products to the market at an affordable price. An agile enterprise needs to consider shop floor issues as well. There is an increase in use of reconfigurable tooling in industries, and much of it is in need of integration. A need exists for improvement in building of production tooling which can be reconfigured when need arises with the smallest possible changeover time. This paper analyzes different production scenarios of a forging cell designed using Petrinet theory. Petrinet theory is effective in design and synthesis of discrete event systems, especially agile systems and incorporates the control logic of the system. The objective of the study was to quantify agility of the system by determining system characteristics at different operating conditions and its ability to accommodate different products. The deterministic model is analyzed using a simulation software package. Conclusions obtained from this study are summarized for evaluation of reconfigurable systems focused on assembly aspects.

The Integration of a SMT Fully-Automated Rework Cell for Fine-Pitch Surface Mounted Devices

Surface mounted components have become the choice of the electronics manufacturing industry to solve problems in the complex circuit boards. New components using increased lead counts on finer pitches make manufacturing difficult. The increased complexity, cost, and lead count of the Surface Mount Technology (SMT) components, and also the increasing compactness of the SMT assemblies have demanded the creation of newer rework tools as an essential part of electronics manufacturing. Therefore, it becomes essential to have a well-controlled process to assure that rework is not only possible but that it is consistent and flawless. Automation is the common answer to achieve both efficiency and quality. This paper describes a system for the automated rework of fine pitch components that is under development as part of the Center for Integrated Electronics and Electronics Manufacturing (CIEEM) at Rensselaer.

Assembly Modeling and Analysis of Integral Fit Joints for Composite Transportation Structures

In order to reduce assembly complexity and enhance the performance of structural elements utilized in transportation systems, a novel approach is presented that uses integral fit joints in the assembly of fiber-reinforced composite structural elements. While the application of composite materials in transportation structures is not new or unique, their use coupled with integral fit joint designs affords a multi-magnitude reduction in the number of components required to assemble transportation systems. Essential to this effort is the need to effectively model and analyze the composite integral fit joint specifically focused on assembly. This paper introduces pertinent issues in the design and assembly of transportation systems, the assembly of their structural joints, and defines assembly models and analysis methods for composite integral fit (CIF) joints.

Preliminary Experiments on Using Direct Calibration As an Approach for Automated Windshield Loading

Assembly experiments are described that were conducted to evaluate direct calibration, a straightforward approach to the calibration problem for sensor-guided assembly systems. In direct calibration, the entire assembly system — the robot, the sensors, and the parts to be assembled — is calibrated for the required assembly task in a single procedure to directly determine the relationship between the part feature information in sensor coordinates and the part location in robot coordinates. This calibration procedure is accomplished in two steps: calibration data are generated by using the robot to move the part(s) to be assembled under the view of the sensors; and the best-fit mapping representing this assembly process is determined. In this research project, the method of direct calibration is applied to the use of a vision-guided robotic system to install windshields in automobiles. Glass installation on the automotive assembly line is a delicate and difficult-to-automate assembly task. In the approach to windshield loading proposed herein, direct calibration is used to provide robust estimates of the location of both the windshield and the windshield opening, or aperture, in the car body. This location information is used to modify the taught insertion path such that each windshield is inserted into the corresponding aperture in the same manner that the windshield at calibration was inserted into the aperture at calibration. To evaluate direct calibration as an approach in windshield loading and to determine the level of performance achievable with common industrial hardware, simplified 3-DOF assembly experiments were conducted. Results from these preliminary experiments indicate that direct calibration is a promising technical approach for the industrial application of automated windshield installation.

An Efficient Algorithm for Accurate Evaluation of Circularity Tolerance

This paper presents a new and accurate algorithm for assessing circularity tolerance from a set of data points obtained from a Coordinate Measuring Machine (CMM). This method, called Selective Zone Search algorithm, divides the workspace into small sectors called search zones and searches for the extreme points in these zones. These extreme points are used to draw a pair of concentric circles with minimum radial separation. The radial difference gives the circularity. The methodology has been tested with several example data sets and the results have been compared with the Least Squares method, Minimum Spanning Circle method and the Voronoi Diagram method.