Computer-aided process planning is a critical function in the overall scheme of computer-integrated manufacturing (CIM). Progress in CIM is key to increased productivity. Furthermore, as new CIM systems evolve, the latest advancements from the constituent areas must be incorporated. Toward that end, our ongoing research deals with the development of methodologies to enable the inclusion of a new class of machine tools characterized by their ability to carry out machining operations in parallel. In this paper, we identify and elaborate on the effects of parallelism on computer-aided process planning, which are brought about by these new machine tools.

In the integration of CAD and CAM, it is necessary to relate machine tool kinematics and control in a CAM process to the geometrical data in a CAD model. The data stored in a CAD model is usually static in nature and represented by unitless parameters. Yet, in machine tool motion and control, the data should be transformed into a time dependent domain. In this paper, a general theory on the conversion from desired paths to motion trajectory is analytically derived. The geometrical properties of a desired path, including position, tangent, and curvature are related to the kinematics of coordinated motion including feedrate, acceleration, and jerk. As a result, the motion commands used as control references to track arbitrary space curves for five-axis computer-controlled machines can be generated in a rather straight-forward as well as systematic way.

At present, hob cutters have mainly been used for the tooth cutting of gears. The each blades of the hob cutter have generally been designed with the same module size, therefore, it is not possible to cut gears of another module size using the aforementioned hob cutter. In our research, from the above viewpoint we have through theoretical analysis of a new hob cutter, tried to design a module hob cutter which is able to cut gears of several module sizes during rough cutting. Hereinafter, we are to call this new hob cutter “Variable Module Hob Cutter (= VMHC)”. This “VMHC” is not uniform in the whole length of hob cutter. It is designed so that the module size is made to vary in accordance with axial direction. With this “VMHC”, not only is it possible for us to cut the tooth profile of gear in any variety of module sizes, but also it is expected to be very suitable for cutting bevel gears by using general type hobbing machine. Most of bevel gears are manufactured by a unipurpose machine tool. Bevel gears, however, are able to be manufactured easily even by using the general type hobbing machine by applying the conventional method of tooth cutting and this hob cutter. The bevel gears have been difficult to manufacture by the conventional hob cutter. However, we will be able to expect to get “VMHC” easily through use of CNC technology.

The deviations of a gear’s real tooth surface from the theoretical surface are determined by coordinate measurements at the grid of the surface. A method has been developed to transform the deviations from Cartesian coordinates to those along the normal at the measurement locations. Equations are derived that relate the first order deviations with the adjustment to the manufacturing machine-tool settings. The deviations of the entire surface are minimized. The minimization is achieved by application of the least-square method for an overdetermined system of linear equations. The proposed method is illustrated with a numerical example for hypoid gear and pinion.

Parallel machines represent a new generation of machine tool. Through reducing the number of setups both the efficiency and the accuracy of the machining process is increased within the part domain. While Flexible Manufacturing Systems (FMSs) and Machining Cells (MCs) are said to be agile, the parallel machine is the first stand-alone machine which can claim to have this property. This makes them ideally suited for machining small batch sizes and for rapid prototyping. Unfortunately like FMSs and MCs these machines will be largely underutilized if agile data generation, processing and transfer mechanisms are not incorporated into CAD/CAM systems. One major hurdle to achieving this objective is the development of an automatic process planning system for parallel machines. This presents new challenges beyond those encountered in process planning for sequential machining. In this paper we discuss two aspects of parallel machines which impact on process planning. These are (1) the part domain for parallel machines and (2) the machine configuration.

This paper addresses the impact of data fusion on engineering and manufacturing information systems. Data fusion is the integration and analysis of data from multiple sensors to develop a more accurate understanding of a situation and determine how to respond to it. (Sensor fusion, a related term, has a somewhat different, more implementation oriented focus. The difference between these two concepts is addressed specifically in Section 1.) Although data fusion can be applied in many situations, this paper focuses on its application to manufacturing and how it changes some of the more traditional, less adaptive information models that support the design and manufacturing functions. Data fusion requires changes, primarily extensions, to these traditional information models. Engineering models normally address geometry, features, and performance characteristics of a part, while manufacturing models address machine tool characteristics and how they interact with the workpiece and operations scheduling. For data fusion and adaptive control, these models must include the dynamic behavior and interactions between the workpiece and the machine tool. In addition, these models must specify how these dynamic behaviors can be seen and interpreted by various types of sensors (e.g. temperature, pressure, and vibration). On a broader level it must also consider how the machine tools and robots interact within a work cell or production line. The paper consists of four parts. The first section explains what data fusion is and its impact on manufacturing. The second section describes what an information system architecture is and explains the natural language-based information modeling methodology used by this research project. The third section identifies the major design and manufacturing functions, reviews the information models required to support them, and then shows how these models must be extended to support data fusion. The fourth section discusses the future directions of this work.

In most machining processes, large amounts of energy are needed to accomplish the machining operation. When this energy is transmitted through a structure that has minimal damping characteristics, such as a lathe or a milling machine, self sustained oscillations (chatter) can develop. When chatter develops, it can be viewed as a basic performance limitation of the machine tool. In order to suppress the chatter, a real-time controller using digital signal processing techniques has been implemented. This paper discusses a novel way of computing the transfer function of the machine tool-work piece combination and illustrates how a real-time active chatter controller could be designed and integrated into existing machine tools to overcome this performance limitation. Currently, experimental verification of the analytical work is being pursued.

A typical boring bar is a metal cutting tool with large overhang ratio, due to which it is characterized by low dynamic stiffness. Therefore, during cutting process, it is susceptible to cutting instability, known as machine tool chatter. In this paper, the use of an active dynamic absorber to actively control machine tool chatter in a boring bar is studied. An active dynamic absorber is designed such that it can be easily assembled with a commercially available steel boring bar. A piezoelectric pusher is used as the actuator for the active dynamic absorber. The dynamic equations of the boring bar with active dynamic absorber are calculated from experimentally obtained frequency response functions of the system. Optimal control theory is applied to the dynamic equations to calculate state variable feedback parameters. The state variable feedback is implemented using a Digital Signal Processing (DSP) chip. Cutting tests were performed with this setup for different cutting conditions, and for different overhangs of the boring bar. Stable cutting operations were performed using the boring bar with active dynamic absorber, for length to diameter (L/D) ratio upto 9.

In order to reach the inside surfaces of some workpieces, a prototype for milling extension is developed. The milling extension has a low static stiffness and is prone to machine tool chatter, therefore vibration control in this type of machining is of importance. The paper proposes the application of an active dynamic absorber to the milling process. A finite element model for the milling extension with consideration of the cutting dynamics is developed. An annular ring serving as the dynamic absorber mass is connected to the main system through active force generating systems which are piezoelectric translators functioning as actuators. The annular ring and the actuators are functioning as an active dynamic absorber in the theory to suppress the vibration of the milling system. Optimal control algorithms are used to calculate the Kalman feedback control for the equivalent lumped-mass milling structure model. Transient responses of the system are obtained. Oscillation of the milling extension equipped with the active dynamic absorber is attenuated appreciably, therefore the surface finish of a workpiece is improved. Harmonic responses are also obtained with and without the feedback control to show the superiority of the active control technique. A proof-of-concept experiment is designed and conducted to verify the theoretical prediction. Comparisons between the simulation and experimental results are made.

An advanced design methodology is proposed for the face-milled spiral bevel gears with modified tooth surface geometry that provides a reduced level of noise and has a stabilized bearing contact. The approach is based on the local synthesis of the gear drive that provides the “best” machine-tool settings. The theoretical aspects of the local synthesis approach are based on the application of a predesigned parabolic function for absorption of undesirable transmission errors caused by misalignment and the direct relations between principal curvatures and directions for mating surfaces. The meshing and contact of the gear drive is synthesized and analyzed by a computer program. The generation of gears with the proposed geometry design can be accomplished by application of existing equipment. A numerical example that illustrates the proposed theory is presented.

Computerized investigation of the influence of alignment errors on the transmission errors and the shift of the bearing contact is proposed. The investigation is performed for an imaginary hypoid gear drive with conjugate tooth surfaces. It is proven that the transmission functions caused by misalignment are periodic discontinues almost linear functions with the frequency of cycle of meshing. The above functions can be totally absorbed by a predesigned parabolic function. The shift of the bearing contact caused by misalignment has been determined as well. The performed investigation is based on computerized simulation of meshing and contact of gear tooth surfaces. The machine-tool settings for the generation of the designed gear drive have been determined. Numerical example that illustrates the developed theory is given. The performed investigation allows to determine the influence of gear misalignment on transmission errors, and design a low-noise hypoid gear drive by a properly predesigned parabolic function of transmission errors.

In the field of process planning most of the working time is spent for the following activities: machine tool and tool assignment determination of the set-up and process sequence definition of tool paths optimization of cutting parameters The quality how these activities are done influence substantially manufacturing cost that are to be minimized. The more complex a planning task is the more difficult it is for the planner to work out an optimal solution within reasonable time. In this article it will be discussed how process planning of prismatic workpieces considering drilling and milling machining can be optimized by computer assistance.

In this paper, the method of computational fluid dynamics are employed for examination of the formation of a pulsate turbulent waterjet in a Helmholtz resonator type nozzle. The analysis is based on the numerical solution of the conservation equations of mass and momentum, and the standard k-ε turbulent model. The evaluation of the flow characteristics within the nozzle is carried out. Also, the experiments show substantial advantages of this nozzle over a conventional waterjet as a machining tool. The end results of this work will be a knowledge necessary for the improvement of nozzle design and better formation of water and slurry jet.

A new technology, called Stress Coupling Activated Damping (SCAD © ), was applied successfully to a lathe boring bar. It reduced high frequency vibrations by up to 20 db. It can be applied to a wide range of structural designs. The geometries of the damped structures are not limited to thin plates but can be applied to tubes, I-beams, and complex structures. This allows SCAD © technology to be applied to several industry design problems, including the metrology, medical, aerospace, automotive and machine tool industries. SCAD © will also allow boring bars to: 1) be optimized for stiffness, frequency and loss factor, 2) be ‘tuned’ to a specific resonant frequency, 3) have improved damping regardless of boring bar diameter, 4) lengthen the usable tool length without a significant increase in cost, and 5) decrease cutting surface vibration induced pattern.

In most machining processes, large amounts of energy are needed to accomplish the machining operation. When this energy is transmitted through a structure that has minimal damping characteristics, such as a lathe or a milling machine, self sustained oscillations (chatter) can develop. When chatter develops, it can be viewed as a basic performance limitation of the machine tool. In order to suppress the chatter, a real-time controller using digital signal processing techniques has been implemented. This paper discusses a novel method for the real time computation of the transfer function of the machine tool-workpiece combination and illustrates how a real-time active chatter controller can be designed and integrated into existing machine tools to overcome this performance limitation.

This paper considers a passive damping method that can be applied to beam-like structures such as machine tool bases and columns. The method uses viscoelastic materials to dissipate energy in the manner of classic constrained-layer damping; however, the layers are embedded within the structure as opposed to being applied externally. This provides a robust means of incorporating damping without encountering several of the common disadvantages associated with external damping treatments. An analytical solution to the amount of damping that can be achieved using embedded layers is available, but is known to be inaccurate when the viscoelastic stiffness approaches that of the structural components. Therefore, a new prediction of the maximum damping level that can be expected in a structure is developed and presented here. This prediction gives good results in a wide variety of applications, and offers insight into the relationship between key design parameters. Finite element and experimental verification of the maximum damping predictor are also presented.

This research discusses the methodology of developing a symbolic closed form solution that describes the dynamic stability of multi-flute end milling. A solution of this nature facilitates machine tool design, machining parameter planning, process monitoring, diagnostics, and control. This study establishes a compliance feedback model that describes the dynamic behavior of regenerative chatter for multi-flute tool-work interaction. The model formulates the machining dynamics based upon the interconnecting relationship of the tool geometry convolution and the machining system compliance. The tool geometry convolution characterizes the cutting forces as a function of the process parameters and the material properties, while two independent vibratory modules, the mill tool and the workpiece, represent the machining system compliance. The compliance feedback model allows the development of a corresponding characteristic equation. By investigating the roots of the characteristic equation, this research symbolically expresses the stability of the system as a function of the cutting parameters, the tool geometry, the workpiece geometry, and the vibrational characteristics of the machine tool. Machining experimentation examining the fidelity of the regenerative charter model is discussed. The dynamic cutting forces, cutting vibration, and surface finish of the machining process confirm the validity of the analytical prediction.

It is widely recognized that a solid model based on a non-manifold boundary representation can have a more complicated surface topology than one based on a manifold boundary representation, but non-manifold topology has other capabilities that may be more valuable to the application developer. Non-manifold topology can be put to use in existing application areas in ways that differ significantly from the techniques developed for manifold modeling and it can be put to use in new applications that have not been satisfactorily solved by manifold topology. Several applications of non-manifold topology that would be difficult or impossible to implement using a purely manifold geometric modeler are illustrated: automatic formulation of finite element analyses from solid models, automatic generation of machining tool paths for 2½-dimensional pockets, and construction of geometric models using topological constraints. These applications demonstrate how a non-manifold model partitions the entire space in which an object is embedded, preserves elements of the model that would be discarded by conventional schemes, and permits the implementation of a common merge operation. All three applications have been implemented using a two dimensional non-manifold (non-1-manifold) geometric modeler.

The realistic modeling of automatized manufacturing processes is part of the project Virtual Enterprise. Central issue of the project is the functional and shape oriented representation of a typical industrial enterprise. Based on the main business processes, the Virtual Enterprise displays the internal relations and information flows between the different departments of an enterprise (e.g. business planning, research & development, operations scheduling, manufacturing, sales etc.). The visualization of the Virtual Enterprise is realized by a virtual environment (VE) allowing the user to explore interactively the complex world of an industrial enterprise. The paper outlines the key concepts as well as the basic architecture and the object oriented data model of the Virtual Enterprise. It describes the graphical submodels for the generation of the scene and the technical submodels for the realistic presentation of the behavior of the technical objects. The paper presents the implementation of the prototype of the Virtual Enterprise including a survey over the hard- and software configuration of the system. Goal of the prototype is the realistic representation of the manufacturing area with its machine tools, robots and transport systems. Finally the current state of work is given.

One of the main requirements for efficient and economical material removal is optimal machine tool design. The main objective of this paper is to investigate the dynamic characteristics of a shaping machine using finite element method. In the first part, experimentation and computation are combined to formulate and validate the mechanical model of the shaper. A parametric study is done in the second part. The main housing along with the ram of a typical shaper is analyzed during the process of shaping. This assembly is modeled using triangular shell elements. The eigenvalues and the eigenvectors are obtained. There is an acceptable degree of agreement between analytical results and the experimental observations. The cutting force is determined experimentally and using this the response of the shaping machine is determined. The dynamic acceleration response so obtained is compared with the experimentally obtained response. An exhaustive stress analysis is done. The system is sensitive to changes in certain parameters which are identified and analyzed, with optimization of the structural weight and machining accuracy being the criteria.