Johanna Senatore

Analysis of improved positioning in five-axis ruled surface milling using envelope surface

This article covers side milling of ruled surfaces using a milling cutter. Flank milling is useful for machining objects such as impellers, turbine blades, fan vanes and all workpieces defined by non-developable, ruled surfaces. In the present article, we first introduce two types of positioning on ruled surfaces developed within the Toulouse Mechanical Engineering Laboratory. The positioning studied is taken from the geometric situation not taking the instantaneous speed of rotation of the milling cutter into account. The swept profile of the tool is then determined based on the tool motion. Having defined the envelope surface, we seek to analyse improved and standard positioning errors comparing envelope surfaces with the ruled surface. We then introduce an example to illustrate positioning developed through a first theoretical study before experimentation including machining and measurement of the test piece. Finally, we give our conclusions as to the validity of improved positioning without taking the instantaneous speed of rotation of the milling cutter into account.

Correlation between machining direction, cutter geometry and step-over distance in 3-axis milling: Application to milling by zones

Computer-Aided Manufacturing (CAM) occupies an increasingly important role in engineering with all it has to offer in terms of new possibilities and improving designer/manufacturer productivity. The present study addresses machining of free-form surfaces on a 3-axis NC machine tool. There have recently been a large number of studies devoted to planning tool paths on free-form surfaces with various strategies being adopted. These strategies are intended to increase efficiency by reducing the overall length of machining. Often, the choice of the cutter is arbitrary and the work focuses on planning. In order to boost productivity, the present work offers assistance in choosing the cutting tool, the machining direction and cutting by surface zones, adopting a milling strategy by parallel planes. To do so, a comparison is made between milling using a spherical end milling cutter and a torus end milling cutter with the same outer radius. This comparison relates to the radius of curvature of the trace left by the cutter at the point of contact between the tool and the workpiece in relation to the direction of feed motion.

5-Axis Flank Milling of Sculptured Surfaces

This chapter covers the various free-form surface flank milling strategies available, focusing in particular on those for ruled surfaces as widely used in defining turbomachine parts. All these positionings seek to reduce interference between the cutting tool and the surface to be milled so as to respect the tolerances dictated by the Design Office. The range of strategies presented goes from the simplest, using analytical positioning on a particular rule, through to complex procedures defined using global numerical methods that calculate the toolpath in its entirety. Approaches adapted to conical and half-barrel cutter geometries are also addressed. Machining of free-form surfaces is considered from two differing perspectives: either considering a free-form surface to be a set of ruled surfaces onto which the previously mentioned methods are applied, or studying the differential geometry of the cutters and surfaces.

Determination of angular fields outside low and high collisions to mill free-form surfaces on 5-axis CNC Machines

The present article addresses positioning of a flat end milling cutter to ensure avoidance of local and global interference. The activity concerned is end milling of parts modelled by free-form surfaces on 5-axis numerical control machines. The tool positioning defined here uses two corrective angles and thus takes full advantage of all the possibilities for 5-axis machine movement. Local interference is cancelled out from a set of points defining the domain of the surface in collision with the cutter and an angular solution domain is proposed to orient the cutter. Global interference is resolved using a set of points; here too, a collision-free angular domain is defined. To obtain a collision-free tool, the two previously mentioned angular domains are superimposed. An additional corrective method is defined if no solution is found using the previous method. Finally, positioning free from local and global interference is obtained. The method was coded and positioning simulations were used to validate the approachs effectiveness.

Influence of Milling on Surface Integrity of Ti-6Al-4V

The present article addresses the influence of milling on the surface integrity of Ti-6Al-4V. Observation of the machined surface from a macroscopic perspective (naked eye) has highlighted an orange peel phenomenon. Under the machined surface no plastically deformed layer or lengthening of the grains were observed. As far as microhardness is concerned, a slightly softened zone was noted under the machined surface. Diffusion of vanadium from phase β to phase α also occurred but without resulting change to the microstructure. Measurement of microhardness and residual stresses showed that the finishing pass predominated over the roughing pass in terms of its influence on surface integrity. The response surface methodology was used in order to highlight those parameters influencing surface integrity. Its application and processing showed that the most influential factor is the nose radius for roughness and the cutting speed for residual stresses.

Analysis of the twist of ruled surfaces: application to strip machining

Flank milling of ruled surfaces is commonly applied to obtain rotating machine parts as defined using ruled surfaces. To this purpose, a wide range of positioning strategies had been studied to reduce interference between the cutting tool and the surface. Indeed, modelled ruled surfaces are non-developable meaning that they cannot be machined without interference. In order to minimise such interference, the positioning strategies studied tend to become increasingly complex, involving software programming using a dedicated language. To simplify matters and apply developed methods using standard software applications, it is proposed here to reduce interference by breaking the machined surface down into a number of sub-surfaces. The aim with this decomposition is to reduce the twist on each portion. A study of the global twist is presented showing nonlinearity with the length of the rule so that cutting methods can be demonstrated. [Received 28 November 2016; Revised 18 April 2017; Accepted 26 June 2017]