Leonardo R. Silva

Performance of aerodynamic baffles in cylindrical grinding analyzed on the basis of air layer pressure and speed

Over the years, grinding has been considered one of the most important manufacturing processes. Grinding is a high precision process, and the loss of a single workpiece in this stage of the production is unacceptable, for the value added to the material is very high due to many processes it has already undergone prior to grinding. This study aims to contribute toward the development of an experimental methodology whereby the pressure and speed of the air layer produced by the high rotation of the grinding wheel is evaluated with and without baffles, i.e., in an optimized grinding operation and in a traditional one. Tests were also carried out with steel samples to check the difference in grinding wheel wear with and without the use of baffles. Keywords : grinding, aerodynamic baffle, optimized process

Global analysis of aerodynamics deflectors efficiency in the grinding process

The conventional grinding methods in some cases are not very efficient because the arising of thermal damages in the pieces is very common. Optimization methods of cutting fluid application in the grinding zone are essential to prevent thermal problems from interaction of the wheel grains with the workpiece surface. The optimization can happen through the correct selection of the cut parameters and development of devices that eliminate air layer effects generated around the grinding wheel. This article will collaborate with the development of an experimentation methodology which allows evaluating, comparatively, the performance of the deflectors in the cutting region to minimize the air layer effect of the high speed of the grinding wheel. The air layers make the cutting fluid jet to dissipate in the machine. An optimized nozzle was used in order to compare the results with the conventional method (without baffles or deflectors) of cutting fluid application. The results showed the high eficciency of the deflectors or baffles in the finish results.

Behavior of surface integrity in cylindrical plunge grinding using different cooling systems

The superficial texture of the material can exert a decisive influence on the application and performance of the machined component. The conventional fluids used in grinding processes are environmental risk and can also be dangerous to the health. The disposal of these toxic fluids is expensive and the contamination in the proximities of the machines can present risks to the health for the personnel in the shop floor. This paper analyzes the performance of the minimum quantity lubricant (MQL) technique and compares it with the conventional cooling method, developing an optimized fluid application method using a specially designed nozzle, through which a minimum amount of oil is sprayed in a compressed air flow. This paper also explores and discusses the concept of the MQL in the grinding process of hardened AISI 4340 steel. The performance of the MQL technique in grinding was evaluated based on an analysis of the surface integrity (roughness, microstructure and microhardness). As a result, it was realized that the MQL technique provides very similar characteristics to conventional process and can be applied in industry, thus contributing to an environment friendly manufacturing.

Analysis of the performance of superabrasive and alumina grinding wheels with different bonds and machining conditions

This paper presents a review of researches on CBN (cubic boron nitride) grinding wheels with the purpose of identifying the state of art in abrasive machining and serving as the basis for future researches and laboratory tests. The scientific studies investigated here report on interesting results involving grinding, published by Brazilian and foreign authors. The methods and the results are presented and discussed. In addition, a grinding setup is presented which provides more reliable experimental results about the surface integrity of fragile materials. This setup was obtained for grinding tests in several grinding conditions during the wheel service life, using alumina and vitrified and resin bond CBN grinding wheels. Results of cutting force, surface roughness and G ratio are also presented and discussed. They confirm the excellent machining capacity of the CBN wheel, with stable behavior in cutting force and roughness results during the tests. The G ratio values are in agreement with the results found by other researchers.

Desgaste de ferramentas no torneamento com alta velocidade de corte da superliga "waspaloy"

The purpose of this work is to study the wear mechanisms in several geometries of ceramic tools (Al2O3 + SiCw and Al2O3 + TiC) and PCBN tools. Several high speed turning experiments were accomplished in nickel-base superalloy (Waspaloy) with hardness of approximately 40 HRC under dry cutting condition. The nickel based superalloys are known as difficult to cut materials due to their high hardness, high mechanical straight at high temperature, chemical affinity to tool materials and lower thermal conductivity. The results showed that the material of the tool and geometry influence the behavior of wear mechanisms. In general, the dominant type of wear was notching and the mechanisms were abrasion, attrition and probable diffusion in most of the used tools.

COMPORTAMENTO TERMOMECÂNICO NA MICROUSINAGEM DO AÇO AISI 4140: SIMULAÇÃO NUMÉRICA COM VALIDAÇÃO EXPERIMENTAL

In the last decade, various researches has shown how the finite element software can be used to predict the chip formation, cutting forces, temperature, tool wear, residual stresses in workpiece and other important parameters in machining. This article presents simulation using FEM (Finite Element Method) with experimental validation in orthogonal microturning of AISI 4140 steel. Machining simulation using FEM AdvantEdge® were applied to predict the cutting and thrust forces, von Mises stress, maximum cutting stress, plastic deformation, deformation rate and cutting temperature distribution. The work aims to evaluate the evolution of these variables as a function of feed rate using uncoated carbide tools. The orthogonal cutting was validated by comparing the cutting forces obtained experimentally with simulated results. Predictions of cutting temperature, plastic deformation and deformation rate during the machining of AISI 4140 steel were also obtained. The combination of finite element technique with actual measurements of cutting test allows to improve and to optimize the machining conditions. Experimental and simulated results showed close values as regards the cutting force. Keywords: AISI 4140; Finite Element Method; Machining simulation; Cutting temperature; Micromachining.

The Effect of Tool Geometry on the Machinability of Polyamide During Precision Turning

The cutting tool geometry plays a significant role on the performance of conventional machining operations, irrespectively of the work material. For instance, alterations in the cutting edge preparation will result in changes in tool wear rate, cutting forces, temperature, and machined surface finish. This article compares the performance of uncoated carbide tools with standard cutting geometry and tools with modified edge preparation during precision turning of polyamide with and without 30% glass fiber reinforcing. The results indicated that, in general, the turning force components are reduced with the tool nose radius and the specific cutting force (Ks ) decreased as feed rate is elevated, presenting values comparable to metallic alloys. In addition to that, the polyamide without reinforcing presented a three-fold increase in specific cutting force (Ks) compared with the reinforced composite. Finally, the surface roughness increased as feed rate is elevated and tool nose radius is reduced.

Merchant Model Applied to Precision Orthogonal Cutting of Pa66 Polyamide with and without Glass Fiber Reinforcing

Polyamide composites are widely employed in various fields of engineering, such as aircraft, automotive, robots, and machinery owing to their remarkable properties. Precision machining aims the production of advanced components with high-dimensional accuracy and acceptable surface integrity. This work presents a preliminary experimental study based on Merchant theory applied to precision radial turning of PA 66 polyamide with and without 30% glass fiber reinforcing. Distinct feed rate values were tested using uncoated carbide tool (grade K15) without chip breaker. The aim of this study is to evaluate the chip compression ratio (Rc), chip deformation (ε), friction angle (ρ), shear angle (Φ), normal stress (σ), and shear stress (τ). In general, similar results were obtained when comparing the results obtained using Merchant model with the experimental findings.