A. Ber

Influence of high-pressure flushing through the rake face of the cutting tool

Abstract The influence of flushing in metal cutting, including flow rate, composition and type of coolant, coolant pressure and direction, IS the subject of many investigations. In the current study high pressure flow was used, penetrating through the cutting tools rake face and reducing the temperatures in the most critical area. During the investigation the pressure was increased up to 25 bar. Mainly grooving operations were investigated, in which chip symmetry simplifies fine analysis. It was found that flow rate and pressure have a significant influence on tool life and wear behavior as well as on the chip shape and the metallurgical structure of the chip itself. The narrowing and curling effect of the chip, improving chip exit from the slot, is viewed as related to temperature reduction. The investigation covered different cutting tool materials and different workpiece compositions. It was found that the phenomenon of built-up edge was minimized, especially when machining stainless steel and similar high alloy materials.

A Method for Cutting Force Evaluation of End Mills

Abstract Using the same approach presented last year, a further developed version of cutting force evaluation is introduced. In the current case the method is implemented for Helical End Mills. A combination of one standard experiment of force measurement and an adequate data processing, enables to acquire conveniently the components of the local cutting force applied on the cutting edge. The advantage of this method is its independence of dynamic effects (splndle rotation speed and the dynamometer natural frequency). It also enables to compute the components of the total cutting force applied on the tool for all combinations of cutting depths and heights. The paper presents the methods principle, a simulation of its performance and an example of experimental verification. It isdirected to contribute to the promotion of cutting tool development and computer Integrated manufacturing.

New Approach of Cutting Tool Materials — CERMET (Titanium Carbonitride-Based Material) for Machining Steels

Abstract This paper deals with new cutting tool material called CERMET that can cover the range of machining steels. i.e., carbon steel, alloy steel, austenitic steels and cast iron. The advantage of this new cutting tool material is that it can run at a high cutting speed relating to the equivalent of cutting tool material based on tungsten carbide. This new family of cutting tools can also cover the am of coated cutting tools. CERMET cutting tools can be used successfully in turning, milling, threading, grooving and any other profiling application.

Modifications of the cutting edge geometry and chip formation in milling

Summary The research describes the development of milling inserts with new cutting-edge geometries, three-dimensional chipformer configurations, and non-straight and non-continuous cutting edges. The investigation can lead to optimization of the cutting edge and the rake and clearance faces while improving tool life, accuracy, surface quality and chip flow. Results with molded chipformers, helical cutting edges and constant rake and clearance angles are discussed. The geometries include continuous helical and non-continuous, serrated cutting edges for chip splitting and improved force distribution. Higher machining stability, lower forces and improved chip formation can be achieved. With the serrated edge, the chip splits depending on feed and machining direction. Measured chip thickness is larger than the calculated one while chip length is smaller.

Characterization of CVD Coated Carbide Layers and Their Thermal Properties

Summary The Chemical Vapor Deposition process (CVD) of cutting tool materials makes possible significant improvements in machining performance. The dependence of the cutting speed and tool life on the properties of the substrate and the coating layers makes it necessary to employ cutting tests and other sophisticated equality control testing. Combinations of testing may yield an optimal system for the development and use of coated carbide inserts. The different mechanical and thermal properties and especially the thermal conductivity of the different coatings provide protection against high temperatures and wear. Different sequences and combinations of coating layers of carbide, nitride and oxide were investigated principally with the aid of the Scanning Electron Microscope and tool life tests. By an understanding of the physical properties of the coating and their microstructure, it was possible to optimize both the sequence and the structure of the coatings. The increase of the thermal conductivity of carbides and nitrides with higher temperatures results is an advantage of these types of coatings at low cutting speeds, On the other hand, at higher cutting speeds oxides provide advantages as the thermal conductivity decreases with an increase of temperature and less heat transfers into the carbide substrate. Therefore, a combination of different coating layers gives the best resistance to wear over a wide range of applications and machining conditions. A comparison of coated and uncoated carbides provides a base for decisions as to the right carbide grade for a specific application.

Chip Control in Cut-off Tools

Abstract This paper deals with the family of “Cut-Off” tools. In said family of tools, the role of chip control, i.e. chip formation and chip flow is quite essential, since it should enable the extraction of the generated chip out of the machined slot without causing any damage to the workpiece. It is important not only to have chip curling, but also material low toward center of rake face in order to narrow the chip In comparison to the slot. Chip formation Characteristics, chip cross-section and chip curling were investigated experimentally while influencing parameters such as insert geometry and Cutting conditions were studied. The study of the chip formation at the cross-section plane (perpendicular to the chip flow direction) was specially emphasized. The results lead to the understanding and definition of tool performance in terms of insert geometry. cutting conditions and chip form.

A criterion to optimize cutting tool geometry

Abstract The study deals with cutting tool geometry and with the correlation between a stress related parameter σ ¯ r of the cutting geometry and actual tool life test results in turning. A value σ ¯ r = 1.5 was found optimal for ISO P20 solid WC tools while machining AISI 1045 work material. A previously published paper showed that in the case of HSS cutting tools the optimum with respect to tool life was at the value of σ ¯ r = 2.5 for different cutting operations. The principle issue being dealt with in this study is whether the stress factor σ ¯ r can be regarded as a generalized geometric properly of cutting tools, and within which limits. The paper presents test results and discusses applications. The study was carried out at the J.W. Ullmann Center for Manufacturing Systems and Robotics Research, Department of Mechanical Engineering, Technion - Israel Institute of Technology.

A Method for Drilling Parameters Evaluation, Applied for Drill Point Development

During an investigation of machining parameters in drilling with Polycrystalline Diamond drills, methods to measure and evaluate the drill performance were developed. These methods enable the acquisition of all cutting forces, as well as cutting force distribution out of one standard drilling experiment. Using these methods, new geometries of one-flute and two-flute P.C.D. drills were designed, tested and evaluated. The developed methods may, with some modifications, serve as a tool in the design of cutting tools for other cutting operations.

Investigation of Turning Systems where Controlled Elasticity Improves Machining Performance

Abstract This research deals with the development of a tool system that uses controlled tool elasticity to improve machining performance. The system was investigated experimentally and results are analyzed. Performance is described in terms of cutting forces, tool deformation and surface texture of the workpiece, under different machining conditions. As a result of corner radius and the variable approach angle, surface roughness is improved, compared to using standard ISO inserts. Calculations and measurements of surface roughness are made as a function of tool geometry and machining conditions. By incorporating a controlled elasticity, a single system may be used for axial turning in both directions, as well as for radial turning and grooving.

Residual Stresses in Machined Surfaces. Elaboration of Linear Equation and Design of Annular Test Specimen

One of the most important methods of measuring residual stresses (R.S.) is the relaxation method. It is principally based upon the geometrical change of the specimen form, from one state of internal equilibrium (in stress distribution) to a new one, due to removal of a layer from one, side of the specimen. Stablein equation (1931) and those developed by Frisch and Thomsen (1950) are used even to-day in computation of surface R.S. However, the use of these equations is quite, laborious and calls for some treatment of the test results before implementation. Furthermore, these equations were developed primarily for the computation of R.S. introduced in the whole volume of the component by some non uniform plastic flow (cold or hot plastic process). In the current work a new equation was derived for machined components by approaching the part as formed from two separated wholenesses:- the surface layer as a Machined Affected Zone (M.A.Z.) bounded to a stress-free body. Superposition of the two results-in linear relations between a constant (based upon components parameters) and the measured test values, i.e. the thickness of the etched film and the change in the curvature radius after each step. Results obtained from test performed by Metcut were implemented in the computation and compared with those acquired while using Stablein equation. The correlation was more than satisfactory.