Geometrical analysis of thread milling – Part 1: Evaluation of tool angles

Thread milling is a method which is increasingly used for machining thread. For this operation, a helical interpolation is required. Furthermore, the thread mill is a tool whose geometry is rather complex. Its envelope profile is linked to the thread profile and a single tooth of the thread mill is composed of three continuous cutting edges. The present study proposes a geometrical model and an analytical formulation to define the rake face and the cutting edge. Further, the calculations of cutting planes and cutting angles are explained. The analysis shows specific aspects of thread mills, in particular the fact that the flute angle may lead to a negative rake angle. This study is a contribution to cutting geometry aspect and constitutes a step for cutting force model in thread milling

Investigation of tool geometry effect and penetration strategies on cutting forces during thread milling

The application of thread milling is increasing in industry because of its inherent advantages over other thread cutting techniques. The objective of this study is to investigate the effect of milling cutter tool geometry on cutting forces during thread milling. The proposed method can compare the performance of milling cutters in spite of the different number of tooth. The best thread milling cutter among the studied tools was determined from the cutting forces point of view. Furthermore, this study also pinpoints the best penetration strategy that provides minimum cutting forces. Lower cutting force variations will lead to fewer vibrations of the tool which in turn will produce accurate part.Postdoc de V Sharma financé par la région Bourgogn

Geometrical analysis of thread milling – Part 1: Evaluation of tool angles

Thread milling is a method which is increasingly used for machining thread. For this operation, a helical interpolation is required. Furthermore, the thread mill is a tool whose geometry is rather complex. Its envelope profile is linked to the thread profile and a single tooth of the thread mill is composed of three continuous cutting edges. The present study proposes a geometrical model and an analytical formulation to define the rake face and the cutting edge. Further, the calculations of cutting planes and cutting angles are explained. The analysis shows specific aspects of thread mills, in particular the fact that the flute angle may lead to a negative rake angle. This study is a contribution to cutting geometry aspect and constitutes a step for cutting force model in thread milling

Analysis and modeling of green wood milling: Chip production by slabber

During the primary transformation of wood, logs are faced with slabber heads. Chips produced are raw materials for pulp paper and particleboard industries. Efficiency of these industries is partly due to particle size distribution. Command of this distribution is no easy matter because of great dependence on cutting conditions and variability in material. This study aimed a better understanding and predictionof chip fragmentation. It starts with a detailed description of cutting kinematic and interaction between knife and log. This leads to the numerical development of a generic slabber head. Chip fragmentation phenomena were studied through experiments in dynamic conditions. These experiments were carried out thanks to a pendulum (Vc = 400 m/min). It was instrumented with piezoelectric force sensors and high speed camera. Obtained results agreed very well with previous quasi-static experiments

Experimental characterization of friction coefficients at the tool-chip-workpiece interface in cutting: Evaluation of lubrication efficiency of mineral oil

Collaboration avec le LTDS/ENISEThe characterization of friction coefficients at the tool-chip-workpiece interface remains an issue. This paper presents a new experimental set-up able to simulate similar tribological phenomena as the ones occurring at the tool-chip-workpiece interface. Especially, this system aims to reach contact pressures up to 3 GPa and sliding velocities between 0 to 1000 m/min, and to obtain an open-tribosystem (continuous regeneration of the tool-workmaterial contact). This system has been applied to the characterization of the tool-chip-workpiece interface during the cutting of an AISI4142 treated steel with TiN coated tools. Two environments have been tested: dry cutting, lubrication with a basic mineral oil. The effect of the mineral oil has been investigated

Micro-orthogonal Cutting of Metals

Collaboration avec l'EPFLHigh speed micromilling with single point or multi-edge cutting tools of diameters smaller than 300 m is finding increasing applications for the production of small very precise metallic parts. Because of the small value of the ratios cutting depth to cutting edge radius and cutting depth to characteristic microstructural dimensions, one may expect that the extensive technological data base available for conventional metal cutting, may not directly transfer to micromilling and that size effects will influence the cutting pressures in micromilling as compared to those in macromilling. To address this issue, we have developed a micro-orthogonal cutting test facility in which chip thickness can be controlled to within a few microns and cutting forces can be measured. Using this facility, we are conducting a rather fundamental investigation of micro cutting processes to identify possible size effects. Besides measuring specific cutting pressures, we also aim at identifying mechanisms of chip formation and how they are affected by microstructure, fracture damage accumulation and microtool geometry. We intend to contrast these observations with observations made in macro orthogonal cutting of the same materials as those tested in micro orthogonal cutting. This paper will describe the test facility and present preliminary results obtained during micro-orthogonal cutting experiments

Influence of cutting process mechanics on surface integrity and electrochemical behavior of OFHC copper

The authors gratefully acknowledge the support received from IC ARTS and CEA ValducSuperfinishing machining has a particular impact on cutting mechanics, surface integrity and local electrochemical behavior. In fact, material removal during this process induces geometrical, mechanical and micro-structural modifications in the machined surface and sub-surface. However, a conventional 3D cutting process is still complex to study in terms of analytical/numerical modeling and experimental process monitoring. So, researchers are wondering if a less intricate configuration such as orthogonal cutting would be able to provide information about surface integrity as close as possible to that one generated by a 3D cutting process. For that reason, in the present paper, two different machining configurations were compared: face turning and orthogonal cutting. The work material is oxygen free high conductivity copper (OFHC) and the cutting tools are uncoated cemented carbide. The research work was performed in three steps. In the first step, the process mechanics of superfinishing machining of OFHC copper was performed. In the second step, the surface integrity and the chemical behavior of the machined samples were analyzed. Finally, in the third step, correlations between input parameters and output measures were conducted using statistical techniques. Results show that when applying low ratios between the uncut chip thickness and the cutting edge radius, the surface integrity and cutting energy are highly affected by the ploughing phenomenon. Otherwise, the most relevant cutting parameter is the feed. In order to compare face turning with orthogonal cutting, a new geometrical parameter was introduced, which has a strong effect in the electrochemical behavior of the machined surface

The effect of an organic pentasulfide EP additive in turning and milling operations

Coopération avec Ecole Centrale LyonBecause a cutting fluid could be equally used for different cutting operations, this study proposed to investigate the behavior of a well-known extreme-pressure additive (pentasulfide) in both turning and milling operations of a steel workpiece. The experimental approach is based on the coupling of mechanical tests (turning, milling, and tribological tests) with physico-chemical characterizations (Auger Electron Spectroscopy and X-Ray Photoelectron Spectroscopy) of the friction surfaces (chip and tool). In the case of milling, it was shown that the presence of a pentasulfide additive has a beneficial effect on the specific cutting energy (kc) and flank wear (Vb). These results are correlated with the presence of iron sulfides (FeS and FeS2) on the flank face of the cutter mill and on the chip face in contact with the mill. No such additive effects are found in case of turning. A lubrication model is proposed for the case of milling based on an indirect lubrication of the tool/workpiece and tool/chip contacts due to the transfer of iron and its reaction with sulfur compounds to produce iron sulfides. Because milling is a discontinuous cutting process, this lubrication mechanism is much more efficient than that observed in turning. Indeed, the tool faces are re-fed iron sulfides each time they leave the workpiece

An Experimental and Analytical Method for Investigating Plastic Flow in Form Tapping

While threaded holes made by cutting taps result in material removal, in form tapping, the tap displaces the work material by plastic flow to form the thread section. The aim of the present work is to study, both experimentally and analytically, the 3D-plastic flow in form tapping of low-alloy steels. An experimental technique for producing and measuring the 3D displacement is proposed. Experimental results of displacements are used in the analytical analysis. The Green-Lagrange strain tensor is determined from the measurements obtained. The deviator stress tensor is calculated by using the constitutive law of the work material. The stress equilibrium allows the stress distribution resulting from the form tapping process. The results obtained show the quantification of the 3D-plastic flow, demonstrating that the external layer of the thread is strongly deformed. KEY WORDS: form tapping, plastic flow, thread formation

Tribological aspect of lubrication in form tapping of high strength steel

Collaboration avec le LTDSThis study aims at analyzing the tribochemical mechanisms of lubrication during the process of form tapping and consequently optimizing the formulation of the lubricant. In order to correlate the tribochemical reactions with the performance of a lubricant, we measure the alteration of tapping torque according to ASTM D5619 standard. The objective of the study also relates to the identification of the additives and the association of their properties to the performance of lubrication. The goal is to characterize the nature of the tribofilm created at the bottom of the threads which is the zone the most severely affected by the working tool. X-ray Photoelectron Spectroscopy (XPS) is used to characterize the surface of formed threads. This study demonstrates a link between the sulphur reactions on the metallic surface and the friction reducing performance of lubricant during form tapping.Thèse CIFRE TOTA