1,490 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
Machining of complex-shaped parts with guidance curves
Nowadays, high-speed machining is usually used for production of hardened
material parts with complex shapes such as dies and molds. In such parts, tool
paths generated for bottom machining feature with the conventional parallel
plane strategy induced many feed rate reductions, especially when boundaries of
the feature have a lot of curvatures and are not parallel. Several machining
experiments on hardened material lead to the conclusion that a tool path
implying stable cutting conditions might guarantee a better part surface
integrity. To ensure this stability, the shape machined must be decomposed when
conventional strategies are not suitable. In this paper, an experimental
approach based on high-speed performance simulation is conducted on a master
bottom machining feature in order to highlight the influence of the curvatures
towards a suitable decomposition of machining area. The decomposition is
achieved through the construction of intermediate curves between the closed
boundaries of the feature. These intermediate curves are used as guidance curve
for the tool paths generation with an alternative machining strategy called
"guidance curve strategy". For the construction of intermediate curves, key
parameters reflecting the influence of their proximity with each closed
boundary and the influence of the curvatures of this latter are introduced.
Based on the results, a method for defining guidance curves in four steps is
proposed
Octree-based production of near net shape components
Near net shape (NNS) manufacturing refers to the production of products that require a finishing operation of some kind. NNS manufacturing is important because it enables a significant reduction in: machining work, raw material usage, production time, and energy consumption. This paper presents an integrated system for the production of near net shape components based on the Octree decomposition of 3-D models. The Octree representation is used to automatically decompose and approximate the 3-D models, and to generate the robot instructions required to create assemblies of blocks secured by adhesive. Not only is the system capable of producing shapes of variable precision and complexity (including overhanging or reentrant shapes) from a variety of materials, but it also requires no production tooling (e.g., molds, dies, jigs, or fixtures). This paper details how a number of well-known Octree algorithms for subdivision, neighbor findings, and tree traversal have been modified to support this novel application. This paper ends by reporting the construction of two mechanical components in the prototype cell, and discussing the overall feasibility of the system
Implementation of hierarchical design for manufacture rules in manufacturing processes
In order to shorten the product development cycle time, minimise overall cost and smooth transition into production, early consideration of manufacturing processes is important. Design for Manufacture (DFM) is the practice of designing products with manufacturing issues using an intelligent system, which translates 3D solid models into manufacturable features. Many existing and potential applications, particularly in the field of manufacturing, require various aspects of features technology. In all engineering fields geometric modelling wluch accurately represents the shape of a whole engineering component has become accepted for a wide range of applications. To apply DFM rules or guidelines in manufacturing processes, they have to be systematised and organised into a hierarchical rule system. Rules at the higher level of the hierarchical system are applied to more generic manufacturing features, and specific rules are applied to more detailed features. This enables the number of rules and amount of repetition to be minimsed. Violation of the design for manufacture rules in the features, their characteristics and manufacturing capabilities are further examined in this hierarchical system. Manufacturabillty analysis, such as production type, materials, tolerances, surface finish, feature characteristics and accessibility, are also taken into consideration.
Consideration of process capabilities and limitations during the design process is necessary in order to minimise production time and as a result, rnanufactunng cost. The correct selection of manufacturing processes is also important as it is related to the overal cost.
As a result of this research, a hierarchical design for manufacture rule system is proposed which would aid designers in avoiding designs that would lead to costly manufacturing processes
Wear behaviour of laser cladded Ni-based WC composite coating for Inconel hot extrusion : practical challenges and effectiveness
In forging, tooling costs make up a significant percentage of the total manufacturing cost. To combat tool failure, forging dies can be manufactured using or including layers of high wear-resistant alloys. The present work compares the manufacturing process challenges and wear response of traditional Nitriding to laser cladding using Ni-based WC on an H13 substrate for IN718 extrusion. The results have shown that machining of NiCrSiB + WC matrix material is problematic, both with regards to cutting tool wear and achievable surface finish. Assessment of pre- and post-extrusion Nitrided H13 and NiCrSiB + 30%WC laser clad dies shows more significant wear features in the case of the additively coated die. Crack formation and surface discontinuities attributed to the effects of material porosity and die heating are also discussed
Micro-manufacturing : research, technology outcomes and development issues
Besides continuing effort in developing MEMS-based manufacturing techniques, latest effort in Micro-manufacturing is also in Non-MEMS-based manufacturing. Research and technological development (RTD) in this field is encouraged by the increased demand on micro-components as well as promised development in the scaling down of the traditional macro-manufacturing processes for micro-length-scale manufacturing. This paper highlights some EU funded research activities in micro/nano-manufacturing, and gives examples of the latest development in micro-manufacturing methods/techniques, process chains, hybrid-processes, manufacturing equipment and supporting technologies/device, etc., which is followed by a summary of the achievements of the EU MASMICRO project. Finally, concluding remarks are given, which raise several issues concerning further development in micro-manufacturing
- âŠ