Edward Red

Grind-free tool path generation for five-axis surface machining

Abstract This paper discusses automatic tool path generation for five-axis filleted end mill finish-surface machining. A new method of automatic five-axis tool path generation is introduced called Grind-Free (GF) tool path generation. GF surfaces result from tool paths that avoid gouging and have scallops that are within the surface profile or waviness tolerances. New algorithms are presented for determining tool forward step and tool path step-over that produce a GF surface. Gouge-free tool paths can be generated directly from CAD data based solely on local and global machining constraints. The proposed methodology for GF tool path generation has been implemented in the C language using the CODE/Robline system. Surfaces were machined on a Boston Digital 505 five-axis milling machine to confirm this method.

A dynamic optimal trajectory generator for Cartesian Path following

This paper considers a dynamic and adaptive trajectory generator for negotiating paths using S-curves. Applying constant jerk transitions between the constant acceleration and deceleration periods of the trajectory, the trajectory will optimally transition to the desired speed setting. Optimal is defined to be the minimum time to transition from the current speed to the set speed for the move segment when jerk and acceleration are limited. The S-curve equations will adapt to instantaneous changes in speed setting and path length. An integrated motion planner will determine allowable speeds and transitional profiles based on the remaining move distance.

Emerging Design Methods and Tools in Collaborative Product Development

Product development uses the engineering design process to conceptualize and design new products, while relying on computer-aided application tools like CAD/CAE/CAM that are unfortunately designed for single users. In the absence of multiuser engineering applications, this paper uses surveys and facility visits to show an increased reliance on social communication tools for closing design collaboration feedback loops. Product development requires collaboration among myriad personnel and organizations, each having unique complementary experiences and capabilities. Collaborative design has a primary goal: reduce time-to-market and competitive costs for new products, while retaining quality of product performance and minimizing environmental impact. The focus of this paper is to compare contemporary methods and tools used in collaborative product design at notable corporations to emerging multiuser computer-aided applications. This comparison will define a future where design mistakes and time-to-market are reduced, collaboration is not only truly concurrent, but simultaneously concurrent, and where design rationale is more easily captured and shared for later review and for educational training.

On-line Cartesian trajectory control of mechanisms along complex curves

New methods have been developed to control a mechanisms realtime Cartesian motion along spatially complex curves such as Non-Uniform Rational B-splines (NURBS). The methods dynamically map the critical trajectory parameters between parameter space, Cartesian space, and joint space. Trajectory models that relate Cartesian tool speeds and accelerations to joint speeds and accelerations have been generalized so that they can be applied to most classes of robots and CNC mechanisms. A simple and efficient predictor-corrector method uses finite difference theory to predict the parametric changes required to generate the desired curvilinear distances along the trajectory, and then correct the erorrs arising from this prediction. Polynomial approximation methods successfully approximate joint speeds and accelerations rather than require a closed-form inverse Jacobian solution. The numerical algorithms prove to be time bounded (fixed number of computational steps), and the generated trajectories are smooth and continuous. Both simulation and physical experiments using an Open-Architecture Controller demonstrate the feasibility and usefulness of the developed trajectory generation algorithms and methods. The methods can be conducted at trajectory rates greater than 100 Hz, depending on mechanism complexity.

Architectural Limitations in Multi-User Computer-Aided Engineering Applications

The engineering design process evolves products by a collaborative synthesis of specifications, personnel and organizations. Unfortunately, collaborative effectiveness is thwarted by existing single-user computer-aided applications like computer-aided design, computer-aided analysis, and others. These applications and associated file management systems assign editing rights to one technical person, e.g., a designer, analyst, or a process planner. In the absence of collaborative computer-aided engineering applications, we conducted a survey to establish that product collaboration is limited to interactive, either formal or ad-hoc design sessions, social communication tools, serial model sharing, terminal/screen sharing, and to conference call interactions. Current computer-aided (CAx) tools do not permit simultaneous model changes by a collaborative team editing the same model. Although over a decade of prior research has demonstrated multi-user feasibility for computer-aided applications, the architectural breadth of this research has apparently not yet compelled developers and end-users to develop and adopt new multi-user computer-aided applications devoted to product development. Why have collaborative engineering CAx tools not been commercialized for mainstream use? This paper uses several multi-user prototypes, including the first Computer-Aided Engineering multi-user prototype called CUBIT Connect, to expose additional architectural hurdles to implementing new multi-user collaborative paradigms. These challenges relate to variable algorithmic performance times, multi-threading and event driven client notification processes, distributed access level security, and model change management in design sessions.

Reconfigurable Mechanisms for Application Control (RMAC): Applications

AbstractBuilt upon the direct control architecture, the Reconfigurable Mechanisms for Application Control (RMAC) architectural framework is described in reference [1]. This companion paper describes several applications that are of historical significance to the RMAC architecture and also shows the flexibility and simplicity of direct control reconfiguration. We first present two direct control applications that have encouraged RMAC development. The first application describes the reconfiguration of a large 3-axis mill into a Coordinate Measuring Machine (CMM), where the popular PC-DMIS CMM planning software uses a device driver interface to plan and control inspection processes on the mill directly, without process plan conversion to typical machine control languages. Second, a robot is converted into a rapid prototyping commercial application, using direct control of the robot from popular CAD/CAM systems. RMAC flexibility is then demonstrated on a 3-axis prototype mill by reconfiguring the mill as eith...

Calibration control of robot vertical assembly

Calibration methods that apply relative techniques to map robot inaccuracy increase robot flexibility by allowing for greater use and application of off-line path planning techniques. To successfully implement the off-line techniques described in this article, methods have been integrated for off-line tool control frame (TCF) calibration, data base integration, and on-line robot inaccuracy correction. The TCF calibration methods presented in this article successfully determine the TCF origin of the end-effectors and sensors attached to the robot distal link to within the robot repeatability. When the methods were applied to a SEIKO DTRAN RT-3000 robot, the TCP origins were statically predicted correct to within 0.025mm (0.001 in.). On-line methods determine robot inaccuracy by mapping robot configurations relative to operational parts or to spatial templates, in contrast to the contemporary global mapping approaches. For the Seiko robot the resulting inaccuracy distributions permit simple error correction equations to be applied, improving robot positioning accuracy to less than ±0.1 mm in locally large regions and to within the repeatability of the robot ±0.025 mm) in smaller regions. This represents an order-of-magnitude decrease in robot inaccuracy.

Multi-User Computer-Aided Design and Engineering Software Applications

This chapter will introduce multi-user computer-aided engineering applications as a new paradigm for product development, considering past collaborative research and the emerging wave of cloud-based social and gaming tools. In a historical context, computer-aided design and engineering models have become much more complex since their inception in the middle of the twentieth century. However, the way design teams approach these models has, at least in one sense, not changed much; a given model can still only be accessed by one user at a time, despite the fact that the entire design team needs to evolve the model. Single user applications have become a productivity bottleneck and do not provide interfaces or architectures for simultaneous editing of models by a collaborative team. Single user applications convert any hope for process concurrency into a serial sequence of design activities. When the single user designer experiences difficulties, the process halts until the designer can reach out to other experts to resolve the problems, which usually requires some form of external collaboration. Unfortunately, single user applications are deficient when it comes to complex and globalized product development. The chapter herein will consider how multi-user architectures will change the single user paradigm from serial to simultaneously collaborative, promote new on-demand access methods like cloud serving, and bring long hoped for efficiencies to product development. We will investigate three research areas of importance to this emerging paradigm: (1) multi-user CAx architectures, including cloud serving; (2) multi-user CAx requirements; and (3) multi-user CAx standards. Of these three, architectures are most investigated, with numerous proof-of-concept prototypes, while requirements and standards, the least investigated, partially explain the reason for non-adoption and non-commercialization of this powerful new paradigm.

Effective Collaboration through Multi user CAx by Implementing New Methods of Product Specification and Management

ABSTRACTThis paper presents a new design process in which design specifications and task distribution are determined from a parallel multi user prospective. Using this method, projects are more easily decomposed into tasks that can be performed concurrently, thus decreasing the design time. Also, a framework is provided to determine the correct distribution of available talent and stakeholders that can be utilized on a given project. The research suggests that by involving the necessary stakeholders in a multi user setting, changes can be made quickly and without additional approval wait time. By including individuals from the various areas of required talent, persons of expertise will be able to work together in a mode of shared design rather than an iterative design process. Decreasing iterations as well as reducing wait time for approval will reduce the overall design time significantly. This method has been tested and validated utilizing controlled tests simulating real life situations of much larger ...

Robotic TCF and rigid-body calibration methods

For off-line programming to work, systematic methods must be developed to account for non-ideal performance of the parts and devices in the manufacturing cell. Although much of the literature focuses on robot inaccuracy, this paper considers practical methods for the tool control frame (TCF) calibration and rigid-body compensation required to close the inverse kinematics loop for target driven tasks.In contrast to contemporary estimation methods, a closed-form, easily automated, solution is introduced for calibrating the position and orientation (pose) of orthogonal end-effectors when the distal robot joint is revolute. This paper also considers methods for measuring and compensating the small rigid-body perturbations that result from non-repeatable part delivery systems or from geometric distortion. These methods are designed to eliminate r*theta* error from the rigid-body prediction and can be conducted in real-time. Without accurate TCF calibration and rigid-body compensation, even the most accurate robot will fail to complete an off-line programmed task if the task tolerances are stringent.