Interference Checking Research Articles

Research on Automatic Design of Extendable TrussBased on CAD Software

This paper provides a method of automatic design for extendable truss based on CAD software. The method mainly consists of parametrical design, automatic assembly, interference checking and extraction of model properties. With Visual C + + as programming language, secondary development was done on automatic assembly and other related modules of CAD software, which can achieve parametrically automatic assembly, interference checking and automatically extracting properties of extendable truss model. Thus, this method can guide the design staff performing program design, improve the correctness and accuracy of design, shorten the design cycle of extendable truss and also has reference value on rapid design and development for other products.

Profile Study of Formed Milling Cutter for Screw Based on Non-Instantaneous Envelope Method

Through analyzing the shape of screw of oil extraction progressing cavity pump, the spiral surface equation of screw was established; and from the relative motion between formed milling cutter and screw, the basic profile equation of formed milling cutter was established with the method of non-instantaneous envelope. According to the actual use of formed milling cutter, aim at the problem of wear for formed milling cutter, established profile equation of front cutting edge and constant back cutting edge, and finally to get a complete profile equation of formed milling cutter. The correctness of milling cutter profile is ensured by interference checking for profile equation of formed milling cutter. The profile equation of formed milling cutter provides a theoretical foundation for the design and manufacture, and it would have great significance to the actual production.

Application and Research of Digital Technology in Optimal Design of CNC Floor Boring and Milling Machine

This paper focuses on application of the three-dimensional digital modeling, numerical analysis and optimization, digital control and other key technologies which provide technical support for the design and development in CNC floor boring and milling machine manufactruing. The three-dimensional digital modeling, digital assembly, interference checking help to eliminate some hidden trouble before processing and assembly. Numerical simulation reduces the cost and shortens the cycle of designand manufactruing in the optimal design of the machine. This technique has been successfully applied to a CNC Floor Boring and Milling Machine Model, which has been running for three years and achieved satisfactary economic result.

A case for an SC-preserving compiler

The most intuitive memory consistency model for shared-memory multi-threaded programming is sequential consistency (SC). However, current concurrent programming languages support a relaxed model, as such relaxations are deemed necessary for enabling important optimizations. This paper demonstrates that an SC-preserving compiler, one that ensures that every SC behavior of a compiler-generated binary is an SC behavior of the source program, retains most of the performance benefits of an optimizing compiler. The key observation is that a large class of optimizations crucial for performance are either already SC-preserving or can be modified to preserve SC while retaining much of their effectiveness. An SC-preserving compiler, obtained by restricting the optimization phases in LLVM, a state-of-the-art C/C++ compiler, incurs an average slowdown of 3.8% and a maximum slowdown of 34% on a set of 30 programs from the SPLASH-2, PARSEC, and SPEC CINT2006 benchmark suites. While the performance overhead of preserving SC in the compiler is much less than previously assumed, it might still be unacceptable for certain applications. We believe there are several avenues for improving performance without giving up SC-preservation. In this vein, we observe that the overhead of our SC-preserving compiler arises mainly from its inability to aggressively perform a class of optimizations we identify as eager-load optimizations. This class includes common-subexpression elimination, constant propagation, global value numbering, and common cases of loop-invariant code motion. We propose a notion of interference checks in order to enable eager-load optimizations while preserving SC. Interference checks expose to the compiler a commonly used hardware speculation mechanism that can efficiently detect whether a particular variable has changed its value since last read.

Study on Cutter Trace Calculation and Interference Checking for Complex Surfaces NC Machining

Cutter trace calculation and interference checking play a dominant role in the NC machining of complex surface. In this paper the conceptions of the final movement and the orientation-distance have been proposed. It is proved that the two points with minimal orientation-distance on a pair of smooth surfaces are conjugate points. Thus the conjugate problem between the two surfaces is converted into optimization process of orientation-distance function. Combining minimal orientation-distance principle with five-point optimization method, the minimal orientation-distance algorithm has been proposed to calculate the cutter trace. The cutter trace and the cutter interference are achieved respectively by local and global optimization of the orientation-distance function based on the minimal orientation-distance algorithm and GA. The validity of this new algorithm is also proved by helicoids NC machining.

Virtual Design and Structural Optimization of Dry Twin Screw Vacuum Pump with a New Rotor Profile

Twin screw vacuum pump is an important kind of dry vacuum pump, which is widely used in the oil-free vacuum system. The design of the screw rotor profile directly influences the working performance and manufacture cost of the screw pumps. In this paper, a new rotor profile for twin screw vacuum pump is introduced which is comprised of the cycloid curve, the dedendum circle arc, the involute curve and the addendum circle arc. The processes of three-dimensional modeling, motion simulation, interference checking and structural optimization for twin screw vacuum pumps are studied by means of Solidworks software. The works provide theoretical basis for optimal designing and reference for test prototype manufacturing. The results showed the performance of the vacuum pump according with the designer’s intention.

Advanced Control Technologies for 5-Axis Machining

Demand for 5-axis machine tools has grown rapidly with the appearance of high-performance machines and growing requirements for high-efficiency to enhance competitiveness. To meet market needs, FANUC provides innovative CNCs, including the FS30i-A and FS31i-A5, that control up to 24 axes simultaneously with maximum paths of 10 enabling high-speed and high-precision multiple-axis and path control. FANUC's wide-ranging functions developed for powerful 5-axis machining include tool center point control and tilted working plane command, which enable high-precision complex shape machining minimizing changeover. Nano smoothing, interpolation for generating smooth curves on a nanometer scale, enables high-quality workpiece machining. 3D interference checking enhances the safety of machines whose motion has become increasingly complex. Operability has also been improved to facilitate programming and simulation for 5-axis machining. This report presents the latest control technologies maximizing 5-axis machine tool performance.

Interference-free toolpath generation using enveloping element for five-axis machining of spatial cam

This paper presents an interference-free toolpath generating method for five-axis machining of a spatial cam. The notion of the proposed method is that the cutting tool is confined within the meshing element and the motion of the cutting tool follows the meshing element so that collision problem can be avoided. Based on the envelope theory, homogeneous coordinate transformation and differential geometry, the cutter location using the conical end mill is derived and the cutting path sequences with the minimum lead in and lead out are planned. Curvatures of the cam surface and the cutting tool are evaluated to offer the criterion for interference checking. To ensure the machining accuracy, the scallop height is used as a basis for generating appropriate toolpaths. The cutting simulations with solid model are performed to verify the proposed toolpath generation method. The proposed methodology can be used to automate the programming of tool paths for five-axis machining of spatial cam.

Optimizing algorithm of interference checking and it’s implement in vehicle electric-brake virtual assembly system

Interference detection is the key technology of design system based on virtual reality, however, with low efficiency and long time-consuming, traditional geometry intersection method is far from the requirement of real-time precise interference detection of complex objects. With the comparison of sphere-tree, axis-aligned bounding box (AABB) and oriented bounding box(OBB) optimizing algorithms, the theoretical basis and flow chart of swift interference detection based on AABB decomposition is presented. Hierarchical bounding box is constructed to approach geometry solid gradually, the components which are impossible to cause interference are removed, so the operand of interference detection is decreased greatly and the efficiency of algorithm is improved. At last, the optimizing algorithm of the interference checking is applied in virtual assembly system electric-brake virtual assembly system, which is developed in Unigraphics(UG) by comparing the operating time with or without the above algorithm. The comparison experiment results show that the AABB optimizing algorithm of the interference checking can shorten the operating time for complicated objects and show very extensive applied prospects.

A digital mock-up visualization system capable of processing giga-scale CAD models

In the automotive, aerospace and naval industries, digital mock-up tools are always used for assembly examination, layout examination and interference checking. Generally, a digital mock-up is assembled from giga-scale CAD models. Because of limitations of computer hardware resources, a digital mock-up represented by traditional planar facets is too large to load into a computer’s memory for rendering. This article proposes a new geometric compression representation to represent given CAD models with curved triangular patches. Based on the compression representation, our digital mock-up visualization system can import several giga-scale CAD models into a computer’s memory simultaneously. A high performance rendering strategy to display the curved triangular patches is also presented. In the rendering strategy, a dynamic subdivision algorithm is introduced which is different from conventional LOD techniques in order to reduce memory consumption. In addition, an algorithm to convert CAD models to the curved triangular patches is introduced.

A composite B-spline method for cutter path generation on free-form surfaces

This paper presents a composite B-spline method for cutter path generation on free-form surfaces on a point-by-point basis, with appropriate radial offset and interference checking along the cutter path. It is aimed at developing a more efficient and accurate free-form surface machining method for an open-architecture CNC system with B-spline interpolation capability. In this method, the cutter paths over the free-form surface are composed of a sequence of B-spline segments. The length of each spline segment is determined by the desired deviation, within some given tolerance, from the curve of the surface over which the cutter path is to be generated. If the spline segment does not satisfy the specified dimensional tolerance, control points of the spline segment are adjusted to modify the curve shape according to the required accuracy. As a result, the deviation between the actual cutter paths and the desired surface curves will always fall within the allowable tolerance. In addition, by adjusting the position of the control points, the adjacent spline segments are made at least C1 geometrically continuous. The distance between adjacent cutter paths in the side step direction is determined by checking the scallop height between them. To make the cutting process more efficient, a modified adaptive iso-parametric curve generation approach is employed. The resulting cutter paths are more compact and accurate compared with those from commonly used cutter path generation techniques.

LayTracks: a new approach to automated geometry adaptive quadrilateral mesh generation using medial axis transform

AbstractA new mesh generation algorithm called ‘LayTracks’, to automatically generate an all quad mesh that is adapted to the variation of geometric feature size in the domain is described. LayTracks combines the merits of two popular direct techniques for quadrilateral mesh generation—quad meshing by decomposition and advancing front quad meshing. While the MAT has been used for the domain decomposition before, this is the first attempt to use the MAT, for the robust subdivision of a complex domain into a well defined sub‐domain called ‘Tracks’, for terminating the advancing front of the mesh elements without complex interference checks and to use radius function for providing sizing function for adaptive meshing. The process of subdivision of a domain is analogous to, formation of railway tracks by laying rails on the ground. Each rail starts from a node on the boundary and propagates towards the medial axis (MA) and then from the MA towards the boundary. Quadrilateral elements are then obtained by placing nodes on these rails and connecting them inside each track, formed by adjacent rails. The algorithm has been implemented and tested on some typical geometries and the quality of the output mesh obtained are presented. Extension of this technique to all hexahedral meshing is discussed. Copyright © 2004 John Wiley & Sons, Ltd.

Mechanical Product Disassembly Sequence and Path Planning Based on Knowledge and Geometric Reasoning

An algorithm is introduced which uses the information provided by the mating features of parts in the product to find the candidate parts for disassembly and to carry out disassembly path planning. A complete and accurate interference checking approach is used to ensure no global collision while disassembling a part. In some cases, it cannot be implemented by geometric reasoning alone, so a set of criteria and heuristic rules based on knowledge, constraints, relationships among parts, and quantitative disassemblability assessment are used. It can also be carried out interactively by the user when necessary. The proposed method is integrated with the CAD model of the product. The user can visually disassemble the product while planning, so it is easier to carry out the disassembly planning and generate an optimal sequence.

A study on 3-D Digital mockup systems for shipbuilding

Simulation-based design and virtual manufacturing based on 3-D digital mockup is an evolving technology that is widely used in mass production industries. The use of this technology facilitates design and production optimization by selecting from several potential design options and production strategies. This paper presents an effective usage of 3-D digital mockup systems for ship hull structures focusing on work strategy planning/evaluation. The newly developed system enables visualization and simulation of process planning for hull blocks, as well as interference checks in assembly stage and evaluation of production stage workability. A converter has also been developed to integrate data from CAD systems into commercial visualization/simulation software. The system has been applied to the production design of actual ships, and several useful lessons have been learned.

New method of tool orientation determination by enveloping element for five-axis machining of spatial cam

A new methodology is presented for the determination of a feasible tool orientation of a ball-end milling cutter for collision and gouging avoidance in five-axis machining of spatial cam. Since the meshing element is used as a generating element for a spatial cam, the meshing element is in tangency with the spatial cam. The notion of the proposed collision-free method is that the ball-end milling cutter is confined within the meshing element. Based on envelope theory, homogeneous coordinate transformation and differential geometry, curvatures of the cam surface and the cutting tool are evaluated for interference checking. To evaluate machining efficiency, the contact length is calculated for various tool orientations. The toolpath is verified through a solid cutting simulation. The proposed methodology can be used to automate the programming of tool paths for five-axis machining of spatial cam.

Hierarchical multiresolution reconstruction of shell surfaces

We present an adaptive, hierarchical Hh-multiresolution reconstruction algorithm to model shell surface objects from a matched pair of triangulated surfaces. Shell surfaces are an interval of contours of trivariate functions with prismatic support. In the H-direction, a hierarchical representation of the scaffold is constructed. For any adaptively extracted scaffold from the hierarchy, a sequence of functions in the h-direction (regularly subdivided mesh) is constructed so that their contours approximate the input shell to within a given error ε. The shell surfaces can be made to capture sharp curve creases on the shell while being C 1 smooth everywhere else. Using an interval of iso-contours of smooth trivariate spline functions, rather than a pair of inner and outer surface splines, one avoids the need for interference checks between the inner and outer surface boundaries.

Feature modelling: a validation methodology and its evaluation

Geometric modelling techniques for computer-aided design are provided with formal validation methods to ensure that a valid model is made available to applications such as interference checking. A natural and popular extension to geometric modelling is to group geometric entities into features that provide some extra meaning for one or more aspects of design or manufacture. These extra meanings are typically loosely formulated, in which case it is not possible to validate the feature-based model to ensure that it provides a correct representation for a downstream activity such as process planning. This paper presents a methodology used to validate the feature-based representation which is based on the capture of designer’s intents related to functional, relational and volumetric aspects of the component geometry. The feature-based validation method has itself been validated through its application to a series of test parts which have been either drawn from the literature or created to demonstrate particular aspects. It is shown that the prototype system that has been developed is indeed capable of meaningful feature-based model validation and additionally provides extensive information that is potentially useful to a range of engineering and manufacturing analysis activities.

A Fast Interference Checking Algorithm for Automated Fixture Design Verification

Fixtures are tooling devices used to locate, support and hold workpieces during a manufacturing process. The major purpose of a computer-aided fixture design (CAFD) system is to provide a fixture design based on fixturing principles and workpiece information. Interference checking between the machining tool and fixture units, as well as between fixture units, is one of the important functions of automated fixture design. This paper presents a fast interference checking algorithnt for automated modular fixture design validation. It is based on the study of the geometric characteristics of modular fixture components and the machining tool. The fixture component model is simplified into a 2D contour model with height information. The tool-path model is represented by a moving dot for 3-axis operations, or a moving line segment in 5-axis operations, as the fixture component model is expanded according to the tool radius. The method is different from the popular collision detection procedure using swept volume and is more efficient for fixturing verification. Application of this method will greatly reduce the computation complexity for fixturing interference checking. The method is implemented with a CAFD system. An example is given at the end of the paper.

Generation of Five-Axis Cutter Paths for Turbomachinery Components

A simple, yet useful algorithm is developed to generate tool paths with global interference checking for five-axis point milling of turbomachinery components. Based on the projected distance between the surface data and the cutter-axis of a cylindrical ball-end mill, interference between the surface of a workpiece and the cutter can be detected. Given the cutter contact points of the surface and the cutter’s size, it can produce the cutter location data without incurring interference through relatively rotating and tilting the workpiece. Applications of the developed procedure to five-axis machining of centrifugal compressor impellers with 13 and 15 blades are illustrated to demonstrate the usefulness and reliability of the approach.

An approach to automating modular fixture design and assembly

In the development of a modular fixture design system, it is essential to have a modular fixture element database that can be integrated with a CAD system, in addition to the other considerations such as fixture configuration, interference checking, etc., which are also important to fixture designers. This paper describes a new method to create the fixture element database and model the fixturing towers (i.e. subassemblies). By using this method, the database can be effectively created and is easy for use in fixture assembly. The modular fixture tower database is used to represent the subassembly of fixtures. This will simplify the fixture design and assembly process. A built-in interference checking methodology is embedded in the planning stage that will ensure a collision-free fixture design. The system is developed using the knowledge- based system, ICAD, and interfacing with UG-II for modelling the workpiece. Examples of fixture design generated by the system are also provided to illustrate the development.