Greg C. Causey

An agile manufacturing workcell design

This paper introduces a design for agile manufacturing workcells intended for light mechanical assembly of products made from similar components (i.e., parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of a different product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers, and modular assembly hardware. The division of assembly, feeding, and unloading tasks between multiple robots is examined with prioritization based upon assembly time. Rapid software changeover will be facilitated by the use of a real-time, object-oriented software environment utilizing graphical simulations for off-line software development. An innovative dual VMEbus controller architecture permits an open software environment while accommodating the closed nature of most commercial robot controllers. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.

Advances in agile manufacturing

An agile workcell has been developed for light mechanical assembly in collaboration with industrial sponsors. The workcell includes multiple Adept robots, a Bosch conveyor system, multiple flexible parts feeders at each robots workstation, CCD cameras for parts feeding and hardware registration, and a dual VMEbus control system. Our flexible pairs feeder design uses multiple conveyors to singulate the parts and machine vision to locate them. Specialized hardware is encapsulated on modular grippers and modular worktables which can be quickly interchanged for assembly of different products. Object-oriented software (C++) running under VxWorks, a real-time operating system, is used for workcell control. An agile software architecture was developed for rapid introduction of new assemblies through code re-use. A simulation of the workcell was developed so that controller software could be written and tested off-line, enabling the rapid introduction of new products.

Design of an agile manufacturing workcell for light mechanical applications

This paper introduces a design for agile manufacturing workcells intended for light mechanical assembly of products made from similar components (i.e. parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of another product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers and modular assembly hardware. The flexible feeders rely on belt feeding and binary computer vision for Dose estimation. This has a distinct advantage over non-flexible feeding schemes such as bowl feeders which require considerable adjustment to changeover from one part to another. Rapid software changeover is being facilitated by the use of a real-time, object-oriented software environment, modular software, graphical simulations for off-line software development, and an innovative dual VMEbus controller architecture. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.

Design lessons for building agile manufacturing systems

Summarizes results of a five-year, multi-disciplinary, university-industry collaborative effort investigating design issues in agile manufacturing. The focus of the project is specifically on light mechanical assembly, with the demand that new assembly tasks be implementable quickly, economically, and effectively. Key to achieving these goals is the ease of equipment and software reuse. Design choices for both hardware and software must strike a balance between the inflexibility of special-purpose designs and the impracticality of overly general designs. We review both our physical and software design choices and make recommendations for the design of agile manufacturing systems.

Gripper design guidelines for modular manufacturing

This paper describes guidelines for the design of grippers for use in modular manufacturing workcells. Gripper design is an important and often overlooked aspect of the design of a complete assembly system. Here, we present guidelines which can be applied to a wide variety of grippers and are divided into two major categories: those that improve system throughput and those that increase system reliability. Designs of several grippers, currently being used in a modular manufacturing workcell, are presented as examples of the application of the guidelines to real world problems.

Guidelines for the design of robotic gripping systems

This paper describes guidelines for the design of grippers for use in modular manufacturing workcells. Gripper design is an important and often overlooked aspect of the design of a complete assembly system. Here, guidelines are presented which can be applied to a wide variety of grippers. Guidelines are divided into three major categories: those that improve system throughput, those that increase system reliability, and those that decrease cost. Designs of several grippers, currently being used in a modular manufacturing workcell, are presented as examples of the application of the guidelines to real world problems.

Design of a flexible parts feeding system

This paper describes the design and implementation of a flexible parts feeding system. While flexibility encompasses every part of the workcell design, including hardware and control software, the ability to feed parts in a wide variety of sizes and shapes is crucial. Conventional feeding methods, such as vibratory bowl feeders, are not practical for flexible workcells because of their specialized nature. This system is composed of three conveyors working together. The first conveyor is inclined and lifts parts from a bulk hopper in a quasi-singulated manner. Parts fall from the first conveyor onto the second, horizontally mounted, conveyor. An underlit window at the end of the second conveyor presents a silhouette image of the parts to a vision system. After the pose of a part has been determined, a robotic arm is used to acquire it. Parts which are in unfavorable orientations or are overlapping are returned to the bulk hopper by a third conveyor. Guidelines for part design which improve the feeding systems performance are also presented.

Testing and analysis of a flexible feeding system

Flexible parts feeding techniques have begun to gain industry acceptance. However, one barrier to effective flexible feeding solutions is a dearth of knowledge of the under lying dynamics involved in flexible part feeders. The paper presents the results of testing the CWRU flexible parts feeder. Data was collected for extended periods while feeding a variety of parts. The data was examined to determine throughput and statistical properties. In addition, tests were performed to examine other aspects of the system. A new metric for specifying the throughput of vision-based flexible feeders is presented, interesting system phenomena are examined, and a statistical analysis of the data is performed.

Modeling and throughput prediction for flexible parts feeders

We illustrate a methodology for modeling and analyzing flexible feeders using generalized semi-Markov process (GSMP) models. Working through the simple case consisting of a single part being fed on a flexible feeder, we show how the throughput of the system may be obtained by both GSMP simulation and analytical techniques for GSMP models. Further, we demonstrate the predictive capability of such models. This is accomplished by generating and validating a model of the system feeding three distinct part types (at the same time) and then modifying the model to allow other feeding scenarios to be predicted. These scenarios include the effect of feeding the parts in a specific order, the effect of using a robot with different speed capabilities, and the effect of using a different-sized presentation conveyor. We validate the predictions with physical testing.

An object-oriented controller architecture for flexible parts feeding systems

A new flexible parts feeding system has been designed and constructed at Case Western Reserve University. To complement the feeder, an object-oriented software architecture has been designed and implemented. Design goals of the software were the ability to rapidly introduce a new part into the system without major re-programming and the creation of a software architecture that would be applicable to the general class of vision-based parts feeders (rather than just our own implementation). The system currently feeds two different types of parts and can switch on-the-fly between part types. Throughputs in excess of 60 parts per minute have been achieved during testing.