Flat Rake Face Research Articles

Estimation of temperature in the cutting area during orthogonal turning of grade 2 titanium

The authors introduce an experimental-analytical method for determining the average temperature values in the PSZ (primary shear zone) and the SSZ (secondary shear zone) during orthogonal turning of grade 2 titanium with a use of an uncoated carbide tool with a positive rake angle and a flat rake face. The presented method is based on an algorithm in which the values of shear stress in the PSZ and the SSZ are calculated by means of the Johnson–Cook constitutive equation and Oxley’s model of cutting mechanics. Average temperature values in the PSZ and the SSZ are determined by iteratively finding the minimum difference between the calculated stress values. As its inputs, the algorithm uses the values of the feed and the tangential cutting force components, the value of chip flow velocity on the rake face, and the constants of the Johnson–Cook constitutive equation. The model was validated with a use of empirical data collected during the experiments. The test rig consisted of a KNUTH Masterturn 400 precision lathe equipped with a dynamometer, a high-speed camera, and a thermal imaging camera.

Comparison of the machinability of the 316L and 18Ni300 additively manufactured steels based on turning tests

This paper focuses on the machinability of additively manufactured steel alloys (316L stainless steel and 18Ni300 Maraging steel) by reference to their conventional metallurgical conditions. The machinability of both metallurgical conditions has been evaluated by longitudinal turning tests under laboratory conditions using two different cutting tool geometries (flat rake face and chip-breaker geometry) and covering different cutting speeds, depths of cut and feed values. Cutting forces, chip morphology and surface roughness were investigated as machinability indicators. The influence of chip-breaker on process performance was also analysed. For a comprehensive discussion of the results, microstructure, chemical composition, surface roughness and mechanical strength of both metallurgical conditions were studied. The paper quantitatively demonstrates that despite the higher mechanical strength of additively manufactured alloys, no significant power requirements were verified for the finishing cutting of tested alloys, when compared with conventional materials. Also noteworthy, is the surface quality improvement of the printed samples due to the most favourable conditions for chip formation. The usage of a chip breaker insert had higher impact on reducing required cutting energy than on controlling chip geometry.

Approximately Model of the Maximum Temperature on the Chip Surface.

This article presents an approximately model that allows for the determination of the maximum temperature of the chip surface in dry orthogonal turning. The mathematical formula describing the maximum temperature of the chip surface was formulated based on experimental data. The experiments were carried out for orthogonal cutting of austenitic steel AISI 321 with flat rake face carbide inserts that were made of tungsten carbide H10F, both uncoated and coated, with coatings of varied arrangement. Thermographic images of the cutting zone were used to verify the correctness of the approximately model. The obtained results show good agreement between the modelling results and experimental studies. The discrepancy of the maximum temperature values of the top surface of the chip does not exceed 6.4%.

Temperature and Heat Partition Testing in the Cutting Zone for Turning AISI 321 Steel

This article shows selected results of experimental tests and the results of analytical and numerical modelling of the thermal characteristics of the cutting process. The tests were conducted for the case of the dry turning of austenitic steel AISI 321 with cutting tools with a flat rake face. The research aimed to determine the actual division of thermal fluxes in the zone of contact between the chip and the rake face. As a result of such work, a formula for a new heat partition coefficient and a formula for calculating the average contact temperature were developed. The results showed that the formulas developed can be a useful tool to estimate heat distribution in the cutting zone quickly.

THERMOVISION MEASUREMENTS OF THE TEMPERATURE IN THE CUTTING ZONE FOR TURNING AISI 321 STEEL

The article presents the methodology of conducting research on temperature distribution in the cutting zone for orthogonal turning without the use of a cooling liquid. AISI 321 austenitic steel was chosen as the workpiece material to be tested, while TNMA160408 carbide inserts, with a flat rake face made of H10F carbide, were chosen as the cutting edges. The research used infrared imaging, which still poses many research problems. The author's own method of calibration of the measurement chain is also presented. In addition, the most common causes of inaccuracies in thermovision measurements of cutting temperatures are discussed. The obtained temperature distribution maps were related to the average contact temperature determined by the method of natural thermocouple – chips/rake face.

Tool–Chip Interface Temperature Measurement in Interrupted and Continuous Oblique Cutting

The objective of this work is to fabricate instrumented cutting tools with embedded thermocouples to accurately measure the tool–chip interface temperature in interrupted and continuous turning. Thin-film thermocouples were sputtered directly onto the flat rake face of a commercially available tungsten carbide cutting insert using micromachined stencils and the measurement junction was coated with a protective layer to obtain temperature data 1.3 μm below the tool–chip interface. Oblique interrupted cutting tests on AISI 12L14 steel were performed to observe the influence of varying cutting speeds and cooling intervals on tool–chip interface temperature. An additional cutting experiment was conducted to monitor the interface temperature change between interrupted and continuous cuts.

Comparison Between Cemented Carbide and PCD Tools on Machinability of a High Silicon Aluminum Alloy

The high content of silicon of aluminum casting alloys challenges the tool life of conventional cemented carbide inserts, and polycrystalline diamond (PCD) tools appear as an interesting material to machine these alloys because they improve substantially the durability of cutting tools and consequently the productivity of machining. However, the surface roughness, cutting forces and chip morphology are equally important factors in machining evaluation. Therefore, an experimental study is performed aiming at comparing the performance of cemented carbide and PCD tools taking into account cutting forces, surface roughness and chip morphology, under dry longitudinal turning, performed for the AlSi9Cu3 alloy produced by permanent mold casting process. Different chip breaker geometries were also considered, and their influence on the referred parameters was also investigated. Analysis of variance was employed to study the different contributions of inserts, cutting speed, feed rate, depth of cut and their interactions in machinability performance. The results show low cutting forces and better results for surface roughness for uncoated cemented carbide tools, with simpler chip breakers and flat rake face PCD tool, but an efficient chip control was obtained for inserts with small grooves with high cutting forces and power consumption. Nevertheless, the feed rate and depth of cut have the highest influence on the machinability performance of the alloy under investigation.

Analysis of Three-Dimensional Cutting Process With Thin Shear Plane Model

A new and basic analytical model of three-dimensional cutting is proposed by assuming multiple thin shear planes with either the maximum shear stress or minimum energy principle. The three-dimensional cutting process with an arbitrarily shaped cutting edge in a flat rake face is formulated with simple vector equations in order to understand and quickly simulate the process. The cutting edge and workpiece profile are discretized and expressed by their position vectors. Two equations among three unknown vectors, which show the directions of shear, chip flow, and resultant cutting force, are derived from the geometric relations of velocities and forces. The last vector equation required to solve the three unknown vectors is obtained by applying either the maximum shear stress or minimum energy principle. It is confirmed that the directions and the cutting forces simulated by solving the proposed vector equations agree with experimentally measured data. Furthermore, the developed model is applied to consider the three-dimensional cutting mechanics, i.e., how the chip is formed in the three-dimensional cutting with compressive stress acting between the discrete chips, as an example.

Characteristics of uncurled and reversely curled chip during orthogonal cutting

It has long been recognized that initially continuous chips are born curled. In this paper a new pattern of chip curl—reverse chip curl, named as chip down-curl, is observed during manufacturing of staggered integral high-finned tube using orthogonal planing with tools with flat rake face when rake angle is large enough and cutting thickness is small. With the increase of cutting thickness or decrease of rake angle, chips become uncurled and further increase of cutting thickness or decrease of rake angle leads to chip up-curl. The variations of chip curvature and conditions under which chips do not curl are obtained by experiments. The mechanisms of uncurled and reversely curled chip formation are investigated by analyzing microstructure of chip root. It is found that the uneven deformation that occurs on cross-section of chip results in reversely curled chip formation and no visible shear deformation that occurs on the primary shear zone of chip leads to uncurled chip formation.

Analysis of an equivalent tool face for the cutting speed range prediction of complex grooved tools

Manufacturers need to obtain optimal operating parameters with a minimum set of experiments as well as minimizing the simulations in order to reduce machining set up costs. The cutting speed, V c , is one of the most important cutting parameter to evaluate; it clearly most influences, on one hand, tool life, tool stability, and cutting process quality, and on the other hand controls production flow. In addition, in today's applications, complex groove geometries have made more difficult the assessment of cutting models for the prediction of tool-material–work-material combination behaviour. In this paper, an original approach based on the experimental estimation of the friction coefficient and enabling to simplify the complex groove geometry in a flat rake face is presented. A model for cutting force prediction is also proposed. Four different complex grooved inserts and three different cutting tool material grades for each insert are studied for the modelling approach. Orthogonal cutting simulations using the Thirdwave Systems’ AdvantEdge code package are compared with experimental measurement. Results show good agreement and that this approach may reduce both number of experiments and simulation times to determine the cutting speed range. Finally, the paper ends with discussions and concluding remarks.

溝型チップブレーカ工具による切削過程の三次元有限要素法解析

This paper describes the simulation analysis of 3-dimensional cutting processes with chip breaker. The simulation method is based on dynamic-explicit elastic-plastic finite element method (FEM) and heat transfer FEM using forward Euler scheme, which are suitable for an FE model including a large number of nodes such as 3-dimensional problem. First, the turning processes with flat rake face tools have been simulated for the basic investigation into the effects of rake angle. In the results, the radius of chip up-curl, cutting force and temperature decrease, while the radius of chip side-curl increases with increasing rake angle. Secondly, the cutting process with the groove tool has been simulated. The results make it clear that the groove on the rake face decreases the cutting force and temperature, and it improves the machinability. In addition, the simulation results with changing the primary land width indicate that the difference of tool contact area with chip greatly influences the 3-dimensional chip shape.

Cutting performance of grooved rake face cut-off tool.

The applications of a new cut-off tool equipped with a grooved rake face are discussed in relation to the cutting performance compared with that of the conventional (flat rake face) cut-off tool. The experimental results indicate the following: 1) cutting surface roughness and chip disposal are improved, and cutting forces are decreased; 2) cutting forces and their fluctuations are markedly decreased as the oxygenjet is supplied to the tool edge at the range of cutting speed that the built-up edges grow; 3) the ceramic cut-off tool is capable of grooving steel work, as the cut-off tool has a grooved rake face and the oxygenjet is supplied to the tool edge.

すくい面が平面からなるドリルの切削と長ピッチ形切りくず生成機構の解析

Main cutting edge configuration of flat rake face drills is geometrically analyzed and compared with the geometry of a conventional twist drill. Applying the cutting model and energy method proposed in previous papers, in which the condition of side-curl of chip is considered, to the case of flat rake face drill, chip formation relating radius of side-curl of the chip and shear angle distribution along the cutting edge, and cutting torque and thrust force can be predicted in both formation processes of a conical-helical chip and a long-pitch helical chip. The differences of torque and thrust force respectively derived from theoretical basis between both chip formation processes are small and the result is experimentally confirmed. The torque and thrust force of the conventional twist drill having a 32° helix angle are almost equal to those of flat rake face drill with rake angle α1=15-20° which is specified in grinding the rake face of the drill.

Drilling with flat rake face and conventional twist drills—I. Theoretical investigation

A cutting analysis, based on oblique cutting models, is developed for the drill lips of flat rake face (modified) drills. The analysis predicts reasonable deformation and force distributions along the drill lips. An analysis for conventional drills is also attempted with less success. The concept of geometrical similarity is studied and shown to be useful for prediction of forces in drilling and for the design of twist drills.

Drilling wih flat rake face and conventional twist drills—II. Experimental investigation

The predicted effect of geometrical similarity on the deformation and forces of different sized conventional and modified drills has been experimentally confirmed. The flat rake face modified drill considerably reduced the forces in drilling. The cutting analysis for the lips of modified drills has been found to be qualitatively and quantitatively sound. Statistical methods have been used to process the data and verify the theoretical predictions.