Frédéric Monies

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.

Influence of dry plunge-milling conditions on surface integrity of magnesium alloys

Plunge milling is a machining process used to remove material rapidly in roughing operations. It is known to offer significant increases in productivity as compared with conventional milling, especially in the case of deep milled workpieces. However, this improvement of productivity also entails the increase in machining conditions so it could be harmful to surface integrity. In this study the authors consider the case of a dry plunge milling process applied to two wrought Mg-Zr-Zn-RE alloys and one cast Mg-Zr-Zn-RE alloy with two different types of inserts. First, the study involves obtaining surfaces through experimental designs. Second, plunge milling conditions are correlated with surface integrity factors, such as roughness, microstructure and microhardness. This study suggests plunge milling conditions to offer a trade-off between surface integrity and chip flow.

Plunge milling time optimization via mixed-integer nonlinear programming

A new approach to minimize time machining through Mixed-Integer Nonlinear Programming.Mathematical formulation of cutting parameter optimization for plunge milling.Machine-tool and cutter-related constraints taking into account control laws.Optimal cutting parameters obtained, tailored to each elementary tool trajectory.Gains as high as 55% are obtained when compared with standard industrial methods. Plunge milling is a recent and efficient production mean for machining deep workpieces, notably in aeronautics. This paper focuses on the minimization of the machining time by optimizing the values of the cutting parameters. Currently, neither Computer-Aided Manufacturing (CAM) software nor standard approaches take into account the tool path geometry and the control laws driving the tool displacements to propose optimal cutting parameter values, despite their significant impact. This paper contributes to plunge milling optimization through a Mixed-Integer NonLinear Programming (MINLP) approach, which enables us to determine optimal cutting parameter values that evolve along the tool path. It involves both continuous (cutting speed, feed per tooth) and, in contrast with standard approaches, integer (number of plunges) optimization variables, as well as nonlinear constraints. These constraints are related to the Computer Numerical Control (CNC) machine tool and to the cutting tool, taking into account the control laws. Computational results, validated on CNC machines and on representative test cases of engine housing, show that our methodology outperforms standard industrial engineering know-how approaches by up to 55% in terms of machining time.

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]

Variability influence of machining context on tool tips wear estimation – application to dry turning of 42CrMo4 steel

The present study evaluates the incidence of machining context variability such as tool tip grade or material grade changings on the dispersion of tool wear prediction. This permits adaptive model recalibration taking into account the overall machining context. By mixing both analytical model and experimental tests, the proposed approach exhibits the sensitivity of uncertain parameters on wear phenomenon. These sensitivities are further used to predict model accuracy for a given machining context. All the experiments have been conducted on 42CrMo4 steel grade using an exhaustive choice of available dedicated tips.