Ryutaro Tanaka

Thermal Conductivity of Metal Powder and Consolidated Material Fabricated via Selective Laser Melting

Selective Laser Melting (SLM) is a direct fabrication of part through layer by layer powder deposition and successive laser beam irradiation based on Computer Aided Design (CAD) data. One of the important properties in SLM is thermal conductivity of metal powder. This is because the ability of metal powder to conduct heat will affect the consolidation process during SLM. In this paper, thermal conductivity of metal powders with different particle diameters and their mixture was analysed. Other than that, thermal conductivity of consolidated materials fabricated via SLM process was also studied. In order to measure the thermal conductivity of metal powder, a theoretically verified method which was previously developed by the authors was used. Determination of thermal conductivity of consolidated material was analysed using laser flash technique. It was found that the thermal conductivity of powder metal was influenced by bulk density and particle diameter of metal powder. In this study also, metal powders of different particle diameters were mixed with various volume ratios, and its effect was discussed. Thermal conductivity of the consolidated materials was also examined, and its relation to porosity was elaborated.

Study on Reduction of Residual Stress Induced during Rapid Tooling Process: Influence of Heating Conditions on Residual Stress

This paper deals with the reduction of residual stress induced during the selective laser melting with a mixture of ferrous based metal powder. To evaluate the residual stresses induced during layered manufacturing processes, a strain gauge is attached on the bottom face of the base plate. The residual stress within the consolidated structure is calculated from the amount of strain change measured by the strain gauge when the consolidated structure is cut with an end mill. The influences of base plate thickness and consolidated structure height on the residual stresses are investigated. In addition, the effect of pre-heating and post heating by a laser beam irradiation are evaluated. The results showed that the deformation of the base plate increased with the increase of the consolidated layer and the decrease of base plate thickness, and the deformation was flattened when the consolidated structure was completely removed with the end mill. The deformation was related to the induced residual stresses. The residual stress distribution within the consolidated structure in the z direction was extremely large at the top layer of the structure and the boundary between the base plate and consolidated structure. The residual stress at the first layer of the structure decreased when the base plate was heated before consolidating the deposited powder. The residual stresses decreased when each of the consolidated layers was repeatedly heated by the laser beam irradiation.

Cutting Tool Edge Temperature in Finish Hard Turning of Case Hardened Steel

This study deals with the influence of tool characteristics on the cutting edge temperature in turning case hardened steel. The cutting test is undertaken with the inserts which have different thermal conductivity and coating layer. The tool edge temperature is measured with a two-color pyrometer. The tool edge temperature increases with the increase in cutting speed. The higher thermal conductivity cutting insert causes lower tool edge temperature. The coating hardly affects the tool edge temperature. The white layer thickness increases with increasing cutting speed reaching a maximum at certain cutting speed and decreases with cutting speed.

Study on thermal and strain behaviour in selective laser sintering process

This paper investigates thermal and strain behaviour in the selective laser sintering process with a mixture of SCM, Cu and Ni metal powder. In-process monitoring of strain change and temperature at the base plate is proposed in order to investigate thermal and strain behaviour induced by selective laser sintering. A strain gauge was attached to the bottom surface of the base plate while a thermocouple was inserted at a distance of 2 mm from the top surface of the base plate. Changes in the strain and the base plate temperature were observed using an oscilloscope during the laser sintering process. The results showed that the development of strain within the sintered structure was affected by the processing temperature. Besides that, after the laser sintering process was completed, the strain value increased gradually and became constant as it reached room temperature. This strain value was found to correspond with the test models deformation. In addition, the effects of laser scanning direction and laser energy density during the process were observed. Measurement of the test models deformation was also carried out to discover its relationships to strain change and processing temperature. The results showed that the sintered structure produced by laser scanning of a sector along the width induced less residual strain, which resulted in less deformation. In contrast, both residual strain and deformation were found to be higher when the laser scanning was carried out along the length. Furthermore, when a low laser energy density was used, less deformation of the sintered structure could also be obtained.

Wear Characteristics of Coated Carbide Tools in the Face Milling of Ductile Cast Iron

This study reports an experimental investigation about the wear behavior of TiN and TiCN coated carbide tools during the face milling of pearlitic and ferritic ductile cast iron. Pearlitic ductile cast iron caused the highest cutting forces and flank wear in both TiN and TiCN coated tools. Due to its protective effect, the TiCN coated carbide tool outperformed the TiN coated carbide tool regarding flank wear. The main issue when face milling ferritic ductile cast iron with TiN coated tools was notching wear. The principal reason for notch wear was pointed as adhesive wear caused for the high tendency of ferrite to adhere on the tool. The results demonstrated that the TiCN coating did not showed notching wear when face milling ferritic ductile cast iron, therefore a good choice of coating material can prevent notching wear.

Relationship between Cutting Heat and Tool Edge Temperature in End Milling of Titanium Alloy

In this study, tool edge temperature was measured by a two-color pyrometer with an optional fiber. During one revolution of spindle, the tool edge passes over the fine hole at workpiece after cutting workpiece. An optical fiber inserted into the fine hole transmits infrared ray radiated from tool edge to two detectors with different spectral sensitivities. One peak signal from each detector can be obtained by each spindle revolution. The tool edge temperature can be calculated by taking the ratio of outputs from these two detectors. The relation between cutting heat calculated from cutting force and tool edge temperature was discussed. The tool edge temperature at the same cutting heat could be compared. The wet cutting condition caused lower tool edge temperature than the others at the same cutting heat. MQL and dry showed almost same tool edge temperature. The dispersion of tool edge temperature in wet cutting is wider than that in dry cutting and MQL cutting.

Difference of Feed Marks in Cutting Fluids when Turning Stainless Steel

In this study, the difference of finished surface roughness and feed mark shape in lubricity of the cutting fluids were investigated in turning SUS440C. In the cutting speed of 20m/min, the oil having excellent oiliness caused the smallest finished surface roughness among the tested cutting fluids at the feed rate of 0.1mm/rev, while, the oil having high extreme pressure property was best at the feed rate of 0.2mm/rev. The feed marks were hardly recognized at any conditions. In the cutting speed more than 20m/min, the finished surface roughness in any lubricant conditions showed almost the same or slightly larger compared with that in dry conditions. The feed marks were recognized, and the transcription of cutting edges shape under wet conditions trended to be the same or worse than dry conditions.

Pulsed Laser Surface Treatment for Improvement of Machinability

The surface of worn dies are often machined to remove the worn layer and then to re-form its shape. But, in machining operations for hardened materials, the high cutting force sometimes yields bending deflection of low stiffness tools, and results the decrease in productivity and accuracy.In this study, surface treatment by pulsed laser is applied for the high hardness materials to improve the machinability in the machining operation. Die steels are used as work material machined with ball endmills of carbide in the experiments where the cutting force and the actual depth of cut are measured to obtain the specific cutting energy and to evaluate the machinability. In endmilling operations of the nitrided die steels, the actual depth of cut is decreased by the bending deflection of endmill. However, the surface treatment with laser moderates the decreasing of the actual depth of cut. It is confirmed that the surface of workpiece pre-treated with laser has larger roughness than un-treated ones, and the specific cutting energy is decreased by laser surface pre-treatment.

Effects of Supplying Oil Mist and Water Mist with Cold Air on Cutting Force and Temperature in End Milling of Difficult-to-Cut Materials

This paper discusses the cutting temperature and cutting force in end milling difficult-to-cut materials cooled with several types of mists and low-temperature air. The cutting tool was a throwaway end mill with a carbide tip coated with titanium aluminum nitride. The Ti-6Al-4V titanium alloy and AISI D2 hardened steel were used as workpieces. The tool flank temperature and cutting force were measured simultaneously during side milling. The temperature was measured using a two-color pyrometer with an optical fiber. Oil mist and water mist from a mist generator were supplied to the cutting point along with cold air at approximately -27 °C. Compared with dry cutting, the cooling effects of supplying an oil mist and/or cold air were less than for other supply conditions in titanium alloy cutting. However, when water mist was added, the tool flank temperature clearly decreased. The cutting force increased for cases that included water mist. The adhesion of the titanium alloy to the cutting edge of the worn tool was significantly suppressed by supplying water and oil mist with cold air. Tool flank wear also decreased under those lubrication conditions.

Machine Learning of Cutting Conditions in Drilling Using Artificial Neural Network

Machining has traditionally been one of the major operations within most manufacturing systems and intelligent machining will play an important role in feature manufacturing systems. This paper concerns the machine learning, specifically classification and recognition of cutting conditions in drilling process. Awareness of the cutting conditions can enhance the auto-diagnosis of an intelligent machining system. In this paper, features representing the drilling process are generated from the converted forms of thrust force and torque and extracted with wavelet packet transform (WPT) and then selected by principal component analysis (PCA). Data instances are generated from experiments with different cutting conditions including workpiece material, drill diameter, feed rate, and spindle speed. A feed-forward network trained with back-propagation method (BPNN) is applied to distinguish between the patterns of each cutting condition. The different contributions of features and the recognition results of cutting conditions are discussed.