Álisson Rocha Machado

The effect of extremely low lubricant volumes in machining

Abstract Cost, the effect on the environment, and health issues are all relevant when considering the choice of a lubricant and application system in a modern metal cutting process. The need to use less, limit the disposal and operator contact are all now very important. This paper shows the results of preliminary tests using very low quantities (200–300 ml h −1 ) of lubricant when machining steel. The low quantities were applied in a fast flowing air stream. The results are compared to traditional flood cooling as a benchmark with 5.2I min −1 . The results show that surface finish, chip thickness and force variation are all affected beneficially with the low coolant volume compared to flood cooling.

Performance of cutting fluids during face milling of steels

Abstract An experimental investigation on the performance of an emulsion of mineral oil, semi-synthetic and synthetic cutting fluids when face milling AISI 8640 steel with coated cemented carbide tools were carried out. Dry cutting was also performed for comparison purpose. Tool life, power consumption and surface roughness were monitored during the machining trials. In order to study the cooling ability of the cutting fluids, cutting temperatures were measured during turning of AISI 1020 steels, using the tool–workpiece thermocouple method. The highest cutting temperatures were generated when machining dry, followed in a decreasing order, by the application of the synthetic, emulsion of mineral oil and semi-synthetic cutting fluids. A reverse effect was found in terms of the power consumption during machining. The best tool life was recorded when machining dry, followed, in a decreasing order by the application of synthetic and semi-synthetic cutting fluids. Comb cracking was the major failure mode of the cutting inserts during machining. Dry machining produced slightly better surface finish than machining in the presence of cutting fluid.

TOOL PERFORMANCE AND CHIP CONTROL WHEN MACHINING Ti6A14V AND INCONEL 901 USING HIGH PRESSURE COOLANT SUPPLY

Abstract Single point continuous turning tests were carried out on Ti6A14V and Inconel 901 using various geometries of straight grade (K20) cemented carbide inserts using a high pressure coolant jet directed at the tip of the tool where the chip is formed. Trials were also carried out using a conventional coolant supply for comparison. The test results show that improved tool life can be achieved when machining the titanium-base alloy under the high pressure coolant jet while shorter tool life was obtained when machining the nickel-base alloy. The use of high pressure coolant supply during machining generally maintains constant cutting forces and reduces the chip-tool contact length, thus increasing stresses at the tool edge. This behavior tends to accelerate notching that is predominant when machining the Inconel 901 alloy, resulting in shorter tool life. This effect is not obvious when machining Ti6Ai4V where the tools failed mainly due to excessive flank wear. Effective chip control was achieved when m...

Some observations on wear and damages in cemented carbide tools

Cutting tools are subjected to extremely unfavorable conditions during machining operations. High cutting temperatures, compressive and shearing stresses, chemical attacks, variable cyclic thermal and mechanical loads are some adverse conditions that wear and damage these tools. Therefore, it is crucial to understand the process of tool wear and damage and how the cutting parameters affect it in order to underpin decisions regarding the most favorable conditions to address the problem. This article treats on some forms and mechanism of wear and damage that cemented carbides can undergo during machining. Special attention was given to damages caused during interrupted cutting (e.g., milling), such as fracture, chipping and thermal fatigue. Experimental details and results of the latter phenomenon, which was studied under different cutting conditions, are discussed and confronted with literature. Keywords : Cemented carbide tools, milling, tool damage, thermal fatigue

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).

Cooling ability of cutting fluids and measurement of the chip‐tool interface temperatures

Many machining researches are focused on cutting tools mainly due to the wear developed as a result of high temperatures generated that accelerate thermally related wear mechanisms, consequently reducing tool life. Cutting fluids are used in machining operations to minimize cutting temperature although there is no available indicator of their cooling ability. In this study, a method to determine the cooling ability of cutting fluids is proposed. A thermocouple technique was used to verify the chip‐tool interface temperature of various cutting fluids during turning operation. The method consists of measuring the temperature drop from 300°C up to room temperature after heating a standardised AISI 8640 workpiece and fixing it to the chuck of a lathe and with a constant spindle speed of 150 rpm the cutting fluid was applied to a specific point. The temperature was measured and registered by an infrared thermosensor with the aid of an AC/DC data acquisition board and a PC. The convective heat exchange coeffici...

Burr formation in face milling of cast iron with different milling cutter systems

Abstract Two face milling cutter systems, both with PCBN (polycrystalline cubic boron nitride) tools, were used to study burr formation in high-speed machining of grey cast iron under various cutting conditions. Surface roughness parameters Ra and Ri, tool life (based on flank wear, VBmax) and burr formation (length of the burr, h) were recorded and used for comparing machining performance. The best performance in terms of tool life and surface roughness was obtained with the milling cutter system consisting of 24 teeth and 24 square wiper inserts. Machining with this cutter configuration produced acceptable surface roughness values, well below the rejection criterion, after machining a batch of 3000 motor blocks in addition to achieving a significant reduction in the burr length.

An optimisation procedure to determine the coefficients of the extended Taylor's equation in machining

Abstract An optimum experimental design to determine the coefficients of the Extended Taylors Equation in machining is proposed. The technique is based on the minimisation of the ratio between maximum and minimum singular values of the matrix of sensitivity of the tool life related to the machining parameter variations. This procedure generates the best set of cutting conditions to be used in tool life tests which results in a fast convergence of the coefficients and their confidence intervals. This technique was compared to the commonly used fractional factorial design when face milling AISI 1045 steel with cemented carbide cutting tools. The results showed a considerable reduction in the number of tests required to obtain a reliable equation when the optimum experimental procedure was used when compared to the factorial design.

Burr produced on the drilling process as a function of tool wear and lubricant-coolant conditions

This work shows the resulting height and shape of the burrs produced by drilling holes with ratio L/D = 3. The tool used in the tests was the solid twist HSS drill coated with TiAlN, with diameter of 10 mm, to drill the microalloyed steel DIN 38MnS6. The height of the burr was studied under different lubricant/coolant systems, namely: dry machining, use of Minimum Quantity Lubrication (MQL) at the flow rate of 30 ml/h, and fluid applied in the conventional way (flooding). The following cutting fluids were used: vegetable oil (MQL), mineral oil (MQL and flooding) and semi-synthetic oil (flooding). The trials were carried out at two cutting speeds (45 and 60 m/min) and the criterion adopted for the end of the test was the catastrophic failure of the drill. The results showed that the height of the burr increases primarily with the wear of the tool and that this increase is almost exponential after 64% and 84% of drills life, for the speeds of 45 and 60 m/min, respectively. Furthermore, the results generally showed that the smallest burr height was obtained for the dry machining and the largest for the MQL systems.

Effects of machining parameters when reaming aluminium–silicon (SAE 322) alloy

Abstract This paper evaluates the dimensional stability (diameter, roundness and cylindricity) and surface roughness of reamed cylindrical holes using K10 cemented carbide welded blade reamers on aluminium–silicon hypoeutectic (SAE 322) cast alloy at various cutting conditions in order to optimise the cutting process. The following parameters were individually varied: depth of cut, cutting speed, feed rate, helix angle, number of blades, margin size and rake face finishing of reamers. Power consumption during the reaming operation was also recorded. The test results show that satisfactory hole quality can be achieved during reaming by employing smaller depths of cut, lower cutting speeds, higher feed rates as well as straight-flute reamers with many blades [Experimental Methods for Engineers, 3rd Edition, McGraw-Hill, New York, 1978] and small margins. Reaming at higher feed conditions improves the accuracy of holes produced at the expense of an increase in power consumption and deterioration in the surface finish generated. The use of reamers with many blades can improve the accuracy, surface finish and roundness of holes produced at the cost of poor cylindricity and higher power consumption during machining.