Anselmo Eduardo Diniz

Cutting conditions for finish turning process aiming: the use of dry cutting

To avoid the use of cutting fluids in machining operations is one goal that has been searched for by many people in industrial companies, due to ecological and human health problems caused by the cutting fluid. However, cutting fluids still provide a longer tool life for many machining operations. This is the case of the turning operation of steel using coated carbide inserts. Therefore, the objective of this work is to find cutting conditions more suitable for dry cutting, i.e., conditions which make tool life in dry cutting, closer to that obtained with cutting with fluid, without damaging the workpiece surface roughness and without increasing cutting power consumed by the process. To reach these goals several finish turning experiments were carried out, varying cutting speed, feed and tool nose radius, with and without the use of cutting fluid. The main conclusion of this work was that to remove the fluid from a finish turning process, without harming tool life and cutting time and improving surface roughness and power consumed, it is necessary to increase feed and tool nose radius and decrease cutting speed.

Correlating tool wear, tool life, surface roughness and tool vibration in finish turning with coated carbide tools

Abstract Experiments have been carried out in an attempt to monitor the change of workpiece surface roughness caused by the increase of tool wear, through the variation of the vibration in finish turning, under different cutting conditions. The vibration was measured by two accelerometers attached to the tool and the parameter used to make the correlation with surface roughness was the r.m.s. of the signal. The tool of one experiment was photographed at different stages of the cut in order to explain the wear formation and the behaviour of surface roughness as the cutting time elapsed. The material machined was AISI 4340 steel and the tool was coated carbide inserts. The results show that vibration of the tool can be a good way to monitor on-line the growth of surface roughness in finish turning and, therefore, it can be useful for establishing the end of tool life in these operations. Another conclusion is that, when coated tools are used, the behaviour of surface roughness as cutting time elapses is very different from that when uncoated tools are used.

Influence of refrigeration/lubrication condition on SAE 52100 hardened steel turning at several cutting speeds

Nowadays, the use of cutting fluids on machining operations has been questioned, due to problems they may cause to the environment, due to damage to human health and also more due to the severe laws regarding industrial waste that have been passed. Therefore, industries are being forced to review the production processes aiming either, at elimination or, when it is not possible, a sharp reduction in the use of these fluids. The technique of minimum volume of oil (MVO) has been studied in machining processes as one alternative to the use of abundant cutting fluid. Research has shown that this technique, which is the pulverisation of a minimum volume of oil in a flow of compressed air, in several cases, reduces tool wear when compared to complete dry cutting, causing the improvement of the workpiece surface quality and an increase in tool life. In this work, the influence of MVO (oil flow of 10 ml/h) in the wear of a cubic boron nitride (CBN) tool, when turning 52100 hardened steel, was studied. Aiming at a comparison of the results, the experiments were also carried out under two other conditions: dry cutting and cutting with abundant soluble oil (wet cutting). During the experiments, the influence of cutting speed on CBN tool wear for the three refrigeration conditions was also checked. Besides this, tool wear and workpiece surface roughness was also measured as cutting time elapsed.

Correlating tool life, tool wear and surface roughness by monitoring acoustic emission in finish turning

Abstract Experiments have been conducted in an attempt to monitor the changing of workpiece surface roughness caused by the increase of tool wear, through the variation of acoustic emission in finish turning, under different cutting conditions. The signal-processing analysis was done on the raw signal, on the AErms signal filtered using a high bandpass and on the AErms signal filtered using a smaller bandpass. The relationship among several parameters of acoustic emission such as zero crossing rate, mean AErms and standard deviation of AErms was established. The material machined was 1045 steel. The cutting force was also monitored. The results show that acoustic emission can be a good way to monitor on-line the growth of surface roughness in finish turning and therefore can be useful for establishing the end of tool life in these operations. Based on the results obtained pointing out the best acoustic emission parameters to monitor surface roughness, a set-up is proposed to reach to this goal.

Experimental evaluation on grinding wheel wear through vibration and acoustic emission

The dressing process is necessary to reestablish the surface of the grinding wheel, when its grains lose their edges and break due to the wheel wear. Dressing must be done to avoid part rejections caused mainly by roughness increase. The determination of the exact moment to accomplish the dressing process (known as the end of wheel life) is still a problem without a precise solution. Generally, machine operators decide when to dress the wheel based on their own experience. During the last years, several works have been done in order to build grinding monitoring systems that could determine the end of grinding wheel life in a more precise way, without the need of an operator. The objectives of this work follow this trend. Hardened steel workpieces were ground until their surface roughness reached values considered intolerable for grinding process. At the same time, vibration and acoustic emission sensors attached on two points of the grinder machine monitored the process, in order to indirectly establish the wheel condition and the moment to dress it. Besides that, the signals from these sensors were also used to determine the duration of spark out and elastic deformation phases of the grinding cycle. The vibration sensor proved to be the best one to establish the end of wheel life; the acoustic emission sensor is the most suitable to determine the time spent on elastic deformation and both acoustic emission and vibration sensors are able to detect the end of spark out phase.

Influence of the relative positions of tool and workpiece on tool life, tool wear and surface finish in the face milling process

The main goal of this work is to study the influence of the relative positions of tool and workpiece on tool life and on surface finish of the workpiece in the process of face milling flat surfaces. Aiming to achieve this goal, several milling experiments were carried out with different relative positions of tool and workpiece. The tool flank wear and the surface roughness of the workpiece were measured as cutting time elapsed. The tools were photographed at different stages in their lives. The main conclusion of this work is that, as the j parameter increases (this parameter measures the distance between the end of the mill diameter and the beginning of the workpiece, as can be seen in Fig. 1), tool life decreases. The surface roughness of the workpiece is not strongly influenced by the variation of this relative position and its growth is not closely related to the increase in wear of the primary cutting edge.

Application of cutting fluids in machining processes

In the last decade a lot has been discussed about the suitability of using cutting fluid in abundance to cool and lubricate machining processes. The use of cutting fluid generally causes economy of tools and it becomes easier to keep tight tolerances and to maintain workpiece surface properties without damages. In the other hand, it brings also some problems, like fluid residuals and human diseases. Because of them some alternatives has been sought to minimise or even avoid the use of cutting fluid in machining operations. Some of these alternatives are dry cutting and cutting with minimum quantity of fluid (MQF). The main goal of this work is to discuss these tendencies. Therefore, topics like kinds and methods of applications of modern cutting fluids and what are new in this area will unavoidably be considered. MQF and dry cutting techniques, their applications and where it is not possible to apply them will also be focused. To exemplify the topics, this work will describe some of the researches been developed in two important Brazilian Universities: State University of Campinas (UNICAMP) and Federal University of Uberlândia (UFU).

Influence of Cutting Conditions on Tool Life, Tool Wear and Surface Finish in the Face Milling Process

The main goal of this work is to study the influence of cutting conditions - cutting speed, feed velocity and feed per tooth - on tool life and surface finish of the workpiece in the face milling of flat surfaces. Aiming to achieve this goal, several milling experiments were carried out with different cutting speeds, feed velocities and feeds per tooth. In the first phase of the experiments, cutting speed was varied without varying feed velocity, which caused a variation in feed per tooth. In the second phase of the experiments, cutting speed and feed velocity were varied in such a way that feed per tooth was kept constant. Tool flank wear and surface roughness of the workpiece were measured as cutting time elapsed. The main conclusions of this work are that a) cutting speed has a strong influence on tool life, regardless of whether feed velocity or feed per tooth varies and b) an increase in surface roughness of the workpiece is not closely related to an increase in wear of the primary cutting edge.

Utilization of minimum quantity lubrication (MQL) with water in CBN grinding of steel

The use of cutting fluids is fundamental to machining processes, mainly when it comes to high heat generation, which is the case of grinding. Thus, lubrication and cooling provided by cutting fluids improve the final quality of the workpiece. However, cutting fluid usage provide some drawbacks concerning environmental, costs and health issues. Therefore, new methods for application and optimization of cutting fluids are being researched aiming to reduce the amount of fluid used, as well as the minimization of cutting fluid hazards. The present study analyzes the behavior of a recently proposed optimization method, up to now only tested in turning, which consists of adding water to minimum quantity lubrication (MQL). Three different proportions were tested in this study: 1/1, 1/3 and 1/5 parts of oil per parts of water. The following output variables were evaluated: surface roughness, roundness errors, grinding power and diametric wheel wear. Also, optical microscopy and microhardness measurements were conducted, in order to detect burns and surface alterations. The obtained results were also compared to conventional (flood coolant) cooling-lubrication and traditional MQL (without water). MQL with water (1/5) presented better results of surface roughness and roundness errors, when compared to traditional MQL, and the results are very close to when using flood coolant. For grinding power and wheel wear, the results for MQL with water (1/5) were the best among the tested conditions.

Toroidal milling of hardened SAE H13 steel

It is estimated that around 65% of the cost of a die or mould is related to the machining processes. Moreover, the literature says that 70% of the time spent in the machining processes of this kind of parts is used in finishing and semi-finishing operations. The high complexity of the machined surfaces makes mandatory the use of ball nose tools, with large overhang, what increases vibration in the process. These problems have to be minimized, since dies and moulds demand a very good surface finish and tight dimensional tolerances. A frequently used strategy to attenuate these problems is to carry out semi-finishing operations with cutters containing circular inserts, because these inserts produce smooth transitions among the passes and a smaller and more uniform stock material for the finishing operation. The main goal of this work is to evaluate the performance of rounded inserts of carbide and cermet in the semi-finishing milling (called toroidal milling) of H13 steel with hardness of 50 HRc. The influence of radial depth of cut, cutting speed and feed per tooth on tool life will also be considered. It also intends to test the feasibility of using minimum quantity of lubricant (MQL) technique instead of dry cutting in this kind of machining operation.