1,541 research outputs found
Topological model for machining of parts with complex shapes
Complex shapes are widely used to design products in several industries such
as aeronautics, automotive and domestic appliances. Several variations of their
curvatures and orientations generate difficulties during their manufacturing or
the machining of dies used in moulding, injection and forging. Analysis of
several parts highlights two levels of difficulties between three types of
shapes: prismatic parts with simple geometrical shapes, aeronautic structure
parts composed of several shallow pockets and forging dies composed of several
deep cavities which often contain protrusions. This paper mainly concerns High
Speed Machining (HSM) of these dies which represent the highest complexity
level because of the shapes' geometry and their topology. Five axes HSM is
generally required for such complex shaped parts but 3 axes machining can be
sufficient for dies. Evolutions in HSM CAM software and machine tools lead to
an important increase in time for machining preparation. Analysis stages of the
CAD model particularly induce this time increase which is required for a wise
choice of cutting tools and machining strategies. Assistance modules for
prismatic parts machining features identification in CAD models are widely
implemented in CAM software. In spite of the last CAM evolutions, these kinds
of CAM modules are undeveloped for aeronautical structure parts and forging
dies. Development of new CAM modules for the extraction of relevant machining
areas as well as the definition of the topological relations between these
areas must make it possible for the machining assistant to reduce the machining
preparation time. In this paper, a model developed for the description of
complex shape parts topology is presented. It is based on machining areas
extracted for the construction of geometrical features starting from CAD models
of the parts. As topology is described in order to assist machining assistant
during machining process generation, the difficulties associated with tasks he
carried out are analyzed at first. The topological model presented after is
based on the basic geometrical features extracted. Topological relations which
represent the framework of the model are defined between the basic geometrical
features which are gathered afterwards in macro-features. Approach used for the
identification of these macro-features is also presented in this paper.
Detailed application on the construction of the topological model of forging
dies is presented in the last part of the paper
Virtual manufacturing: prediction of work piece geometric quality by considering machine and set-up
Lien vers la version éditeur: http://www.tandfonline.com/doi/full/10.1080/0951192X.2011.569952#.U4yZIHeqP3UIn the context of concurrent engineering, the design of the parts, the production planning and the manufacturing facility must be considered simultaneously. The design and development cycle can thus be reduced as manufacturing constraints are taken into account as early as possible. Thus, the design phase takes into account the manufacturing constraints as the customer requirements; more these constraints must not restrict the creativity of design. Also to facilitate the choice of the most suitable system for a specific process, Virtual Manufacturing is supplemented with developments of numerical computations (Altintas et al. 2005, Bianchi et al. 1996) in order to compare at low cost several solutions developed with several hypothesis without manufacturing of prototypes. In this context, the authors want to predict the work piece geometric more accurately by considering machine defects and work piece set-up, through the use of process simulation. A particular case study based on a 3 axis milling machine will be used here to illustrate the authors’ point of view. This study focuses on the following geometric defects: machine geometric errors, work piece positioning errors due to fixture system and part accuracy
A common geometric data-base approach for computer-aided manufacturing of wind-tunnel models and theoretical aerodynamic analysis
A more automated process to produce wind tunnel models using existing facilities is discussed. A process was sought to more rapidly determine the aerodynamic characteristics of advanced aircraft configurations. Such aerodynamic characteristics are determined from theoretical analyses and wind tunnel tests of the configurations. Computers are used to perform the theoretical analyses, and a computer aided manufacturing system is used to fabricate the wind tunnel models. In the past a separate set of input data describing the aircraft geometry had to be generated for each process. This process establishes a common data base by enabling the computer aided manufacturing system to use, via a software interface, the geometric input data generated for the theoretical analysis. Thus, only one set of geometric data needs to be generated. Tests reveal that the process can reduce by several weeks the time needed to produce a wind tunnel model component. In addition, this process increases the similarity of the wind tunnel model to the mathematical model used by the theoretical aerodynamic analysis programs. Specifically, the wind tunnel model can be machined to within 0.008 in. of the original mathematical model. However, the software interface is highly complex and cumbersome to operate, making it unsuitable for routine use. The procurement of an independent computer aided design/computer aided manufacturing system with the capability to support both the theoretical analysis and the manufacturing tasks was recommended
From computer-aided to intelligent machining: Recent advances in computer numerical control machining research
The aim of this paper is to provide an introduction and overview of recent advances in the key technologies and the supporting computerized systems, and to indicate the trend of research and development in the area of computational numerical control machining. Three main themes of recent research in CNC machining are simulation, optimization and automation, which form the key aspects of intelligent manufacturing in the digital and knowledge based manufacturing era. As the information and knowledge carrier, feature is the efficacious way to achieve intelligent manufacturing. From the regular shaped feature to freeform surface feature, the feature technology has been used in manufacturing of complex parts, such as aircraft structural parts. The authors’ latest research in intelligent machining is presented through a new concept of multi-perspective dynamic feature (MpDF), for future discussion and communication with readers of this special issue. The MpDF concept has been implemented and tested in real examples from the aerospace industry, and has the potential to make promising impact on the future research in the new paradigm of intelligent machining. The authors of this paper are the guest editors of this special issue on computational numerical control machining. The guest editors have extensive and complementary experiences in both academia and industry, gained in China, USA and UK
Modeling of deformed swept volumes with SDE and its applications to NC simulation and verification
Representation of swept volumes has important applications in NC simulation and verification as well as robot-motion planning. Most research on .the representation of swept volumes has been limited to rigid objects. In this study, a sweep deferential equation (SDE) approach is presented for the representation of deformed swept volumes generated by flexible objects.
The deformed swept volume analysis is integrated with machining physics to account for tool deformation/deflection for the NC simulation. End milling is modeled and analyzed and the tool deformations are calculated and integrated with the SDE program. A program is developed in C++ for the generation of deformed swept volumes. Using Boolean subtraction, the deformed swept volume of the tool is cut from the workpiece to simulate the machined part. It is shown that this representation approach constitutes an efficient and accurate NC simulation technique for collision detection, geometric verification as well as surface error prediction
A knowledge-based approach for the extraction of machining features from solid models
Computer understanding of machining features such as holes and pockets is
essential for bridging the communication gap between Computer Aided Design and
Computer Aided Manufacture. This thesis describes a prototype machining feature
extraction system that is implemented by integrating the VAX-OPS5 rule-based
artificial intelligence environment with the PADL-2 solid modeller. Specification of
original stock and finished part geometry within the solid modeller is followed by
determination of the nominal surface boundary of the corresponding cavity volume
model by means of Boolean subtraction and boundary evaluation. The boundary model
of the cavity volume is managed by using winged-edge and frame-based data
structures. Machining features are extracted using two methods : (1) automatic feature
recognition, and (2) machine learning of features for subsequent recognition. [Continues.
Automatic compensating cleanup operation
Journal ArticleToday's part geometries are becoming ever more complex and require more accurate tool path to manufacture. Machining process efficiency is also a major consideration for designers as well as manufacturing engineers. Although the current advanced CAD/CAM systems have greatly improved the efficiency and accuracy of machining with the introduction of Numerically Controlled (NC) machining, excessive material may still be left on the finished part due to machining constraints, including the inaccessibility of the designed part geometry with respect the cutter, machine motion constraints like ramp angles, specific cutting patterns, etc. Polishing operations such as grinding and hand finishing are quite time consuming and expensive and may damage the surface of the part or introduce inaccuracies because of human errors. Although most of the existing machining approaches attempt to reduce such excessive restmaterials by modifying NC tool paths, none of them is satisfactory. They can be time consuming, error prone, computationally intensive, too complicated to implement, and limited to certain problem domains. A compensating cleanup tool path will be developed in this research to automatically remove these excessive material from the finish part. This method greatly reduces the burden of hand finishing and polishing and also reduces the error and complexities introduced in manually generating cleanup tool paths in the shop floor. More important, the tool path generated by this method will reduce the machining time and increase tool life compared with optimized tool path which left no excessive material behind
Evaluation of servo, geometric and dynamic error sources on five axis high-speed machine tool
Many sources of errors exist in the manufacturing process of complex shapes.
Some approximations occur at each step from the design geometry to the machined
part. The aim of the paper is to present a method to evaluate the effect of
high speed and high dynamic load on volumetric errors at the tool center point.
The interpolator output signals and the machine encoder signals are recorded
and compared to evaluate the contouring errors resulting from each axis
follow-up error. The machine encoder signals are also compared to the actual
tool center point position as recorded with a non-contact measuring instrument
called CapBall to evaluate the total geometric errors. The novelty of the work
lies in the method that is proposed to decompose the geometric errors in two
categories: the quasi-static geometric errors independent from the speed of the
trajectory and the dynamic geometric errors, dependent on the programmed feed
rate and resulting from the machine structure deflection during the
acceleration of its axes. The evolution of the respective contributions for
contouring errors, quasi-static geometric errors and dynamic geomet- ric errors
is experimentally evaluated and a relation between programmed feed rate and
dynamic errors is highlighted.Comment: 13 pages; International Journal of Machine Tools and Manufacture
(2011) pp XX-X
Analytical and experimental study of feed rate in high-speed milling
In the context of high-speed milling (HSM), during the machining process dynamic machine response has to be identified. To achieve this, we have to calculate the feed rate evolution in linear and circular interpolation according to dynamic performance of machine. In addition to that, actual trajectory for transition passages between two interpolations must be estimated with take into account of specific machining tolerances. This article proposes a model of machine tool behavior for a tool path with linear and circular interpolations and machining cycle time prediction. The method involves subdividing the trajectories into elementary geometries according to the type of interpolation (circular or linear). At points where different trajectories meet, there is often a discontinuity in curvature or in tangency, which decreases the feed rate. At the points of discontinuity in tangency, a fillet radius is inserted. In this article, the influence of the geometry for elementary trajectories was determined. Then, the value of the fillet radius between linear and circular contours in different combinations was modeled. An industrial application was carried out in order to validate models
and to determine the influence of feed rate evolution on the machining cycle time
A CAD/CAM concept for High Speed Cutting compatible rough machining in die, mould and pattern manufacturing
Die, mould and pattern manufacturing plays a central role in the production of capital
and consumer goods. Ever-shorter product life cycles and the expanding diversity of
features require continued cuts in production lead times.
Recently, these developments in the market, accompanied by a simultaneous demand
for improved quality at a lower cost, are becoming clearly noticeable. Along with the
streamlining of organizational structures and advanced technological developments,
it is above all the introduction of CAD/CAM software that offers great potential for
reducing lead times for components with free surfaces.
The role of milling in the integrated process chain of die, mould and pattern manufacturing
is steadily gaining importance. This is due to the ongoing further development
of milling-machine technology, the cutting tools and their coatings, and of the
CAD /CAM systems themselves. Generally speaking, the milling process is divided
into the operations of roughing and finishing. For rough milling, efficient machining
means high stock-removal rates together with close contour approximation and low
tool wear. Rough milling is normally carried out layer by layer, i.e. in a 2.SD machining
operation with constant depth per cut because the rate of material removal and
process reliability are usually highest when this method is used. High-speed cutting
(HSC), which has been the subject of extensive university research for far more than
ten years, has meanwhile become established as a finishing process in many companies.
However, the application of HSC demands the observance of geometric and,
above all, technological constraints. A considerable degree of optimization can be
achieved when these constraints are applied to rough milling.
In the integrated process chain, the CAD/CAM system performs the task of calculating
NC programs based on CAD data which meet the requirements posed by
rough and finish machining operations. While general interest was focused on the
development of CAM strategies for HSC finish machining, advanced development of
technology-oriented CAM modules for upstream roughing operations was neglected.
The paper at hand deals with the development of a CAM module for rough-machining
complex components in die, mould and pattern manufacturing. It provides an insight
into the process-technological demands made on HSC operations and their application
in rough machining, from which guidelines and requirements on technologically oriented NC functions for CAM software were derived. These encompass both the
complete development of an interactive, dialogue-based user guidance function and
the algorithmic conversion of the calculation routines. The concept at hand was almost
entirely implemented and integrated in the CAD/CAM system developed by
Tebis AG, Germany, which was conceived especially for die, mould and pattern manufacturing
and is scheduled for introduction to the free market starting in April 2001
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