Surface Roughness Control Based on Digital Copy Milling Concept to Achieve Autonomous Milling Operation

AbstractIn order to develop an autonomous and intelligent machine tool, a system named Digital Copy Milling (DCM) was developed in our previous studies. The DCM generates tool paths in real time based on the principle of copy milling. In the DCM, the cutting tool is controlled dynamically to follow the surface of CAD model corresponding to the machined shape without any NC program. In this study, surface roughness control of finished surface is performed as an enhanced function of DCM. From rough-cut to semi-finish-cut and finish-cut operations, the DCM selects cutting conditions and generates tool paths dynamically to satisfy instructed surface roughness Ra. The experimental verification was performed successfully

CONSTRUCTION OF OFFSET SURFACES WITH A GIVEN NON-NULL ASYMPTOTIC CURVE

In the present work, we study construction of offset surfaces with a givennon-null asymptotic curve. Let $\alpha \left( s\right)$ be a spacelike ortimelike unit speed curve with non-vanishing curvature and $\varphi \left(s,t\right)$ be a surface pencil accepting $\alpha \left( s\right)$ as acommon asymptotic curve. We obtain conditions such that the offset surfacepossesses the image of $\alpha \left( s\right)$ as an asymptotic curve. Wevalidate the method with illustrative examples

Usinage de formes gauches : génération de trajectoires outils à hauteur de crête constante

National audienceWe present in this communication a method to generate constant scallop height tool paths in 3-axis milling with ball endmill. This machining strategy is interesting because it minimises the number of tool paths for a given geometrical specification of form deviation and surface roughness. Our approach is based on the concept of the machining surface which provides a surface representation of the tool paths and an exact model of the scallop generated by the tool path. This approach is confronted with the methods previously developed in the literature in term of precision and more particularly on the processing of curvature discontinuities. Then the constant scallop height tool path planning is evaluated on surfaces of great curvature variations.Nous présentons une méthode de génération de trajectoires à hauteur de crête constante en fraisage à trois axes avec outil hémisphérique. Cette stratégie d'usinage est intéressante dans la mesure où elle minimise le nombre de passes pour des spécification géométriques de défaut de forme et d'état de surface données. Notre approche s'appuie sur le concept de la surface d'usinage qui procure une représentation surfacique des trajets de l'outil et permet une modélisation exacte de la crête laissée par l'usinage. Cette approche est comparée aux méthodes usuelles développées dans la littérature selon des critères de précision et de capacité à traiter les discontinuités en courbure des surfaces. Le problème de la planification des trajectoires iso-crêtes sur une surface présentant d'importantes évolutions de courbure est abordé par la suite

A surface based approach for constant scallop height tool path generation

International audienceThe machining of sculptured surfaces like molds and dies in 3-axis milling relies on the chordal deviation, the scallop height parameter and the planning strategy. The choice of these parameters must ensure that manufacturing surfaces respect the geometrical specifications. The current strategies of machining primarily consist in driving the tool according to parallel planes which generates a tightening of the tool paths and over quality. The constant scallop height planning strategy has been developed to avoid this tightening. In this paper, we present a new method of constant scallop height tool path generation based on the concept of the machining surface. The concept of the machining surface is exposed and its use to generate constant scallop height tool paths. The approach is confronted with existing methods in terms of precision and in particular its aptitude to treat curvature discontinuities

Second order surface analysis using hybrid symbolic and numeric operators

Journal ArticleResults from analyzing the curvature of a surface can be used to improve the implementation, efficiency, and effectiveness of manufacturing and visualization of sculptured surfaces. In this paper, we develop a robust method using hybrid symbolic and numeric operators to create trimmed surfaces each of which is solely convex, concave, or saddle and partitions the original surface. The same method is also used to identify regions whose curvature lies within prespecified bounds

Constant scallop height tool path generation

Journal ArticleAn approach for the automatic generation of constant scallop height tool paths is presented. An example is shown generated from a B-spline model, although it can be used with many types of sculptured surfaces. The approach utilizes surface subdivision techniques and a new algorithm for tool path generation. The new algorithm is based on computer graphics shading algorithms and on methods from graph theory. A tool path with a constant scallop height renders minimum waste tool moves and hence results in much better machine time. Since neither numerical methods nor high order derivatives are required by the algorithm, it provides an efficient and robust method for tool path computation. Besides, the new algorithm is capable of producing tool paths whose milling directions are based on local surface geometry