Parameter optimization is an important step in the laser powder bed fusion (L-PBF), since process defects greatly impact the mechanical properties of the final parts, especially in components that undergo cyclic loading, such as molds and dies. The present study used the H13 tool steel to show that it is possible to perform a good parameter optimization quickly and with relatively few samples. The Box-Behnken experiment design model was used along with the application of the response surface methodology. Laser power, scan speed, and hatch spacing were used as independent variables, and density and porosity were chosen as the response. Power and speed most influenced the responses, but the interaction between power and speed, and power and hatch also had a significant influence. New optimized samples showed lowest porosity, confirming the effectiveness of the model. Density can be used during parameter optimization without impairing the optimization quality.

The needs to comply with an increasingly competitive international market lead industries to some innovative solutions, such as the use of robotic arms as machine tools. Although these solutions present some well known drawbacks, there are some advantages and niches of application where success is possible. The present work investigates the use of such pieces of equipment to machine aluminum alloys AA2024 applying high speed machining (HSM) technique, assessing surface finishing as a function of different orientation angles between end mill and machined surface. It also tests the best condition to machine foam for prototyping applications. Results indicate that the directions close to the normal are the best compromises because of dynamic stability of the robot arm structure and roughness as low as 4 µm Ra are possible to be achieved in aluminum alloys. A complex shape such as a semi sphere can be easily machined in foam for rapid and accurate prototype machining. Surface finishing can be very smooth and well suitable for industrial applications in such materials.

The present work studies some aspects of the turning process applied on hardened steel using multilayer coated carbide tools at high cutting speeds. The influence of cutting parameters (vc, f, and depth of cut - d.o.c.) on tool temperature, tool wear, cutting forces, and surface roughness were analyzed. The current literature reports many studies using PcBN on hardened steel, but it is also important to know the results when using coated carbide tools, mainly for economical reasons. Temperature was measured by a thermocouple positioned at the lowest insert face, underneath it. Temperature near the rake face was calculated using the measured gradient within the insert thickness. To measure the gradient a special technique was used with one embedded thermocouple near the rake face and one underneath. Tool wear measurements demonstrated the capability of such tools in turning hardened steel with reasonable tool life. Forces measured resulted in relatively low values, being the radial component the largest of all. For the different cutting conditions studied, the doc has the greatest influence on force and temperature. Additionally, the best surface roughness values were smaller than 0,4 µm Ra.

This paper presents specific cutting energy measurements as a function of the cutting speed and tool cutting edge geometry. The experimental work was carried out on a vertical CNC machining center with 7,500 rpm spindle rotation and 7.5 kW power. Hardened steels ASTM H13 (50 HRC) were machined at conventional cutting speed and high-speed cutting (HSC). TiN coated carbides with seven different geometries of chip breaker were applied on dry tests. A special milling tool holder with only one cutting edge was developed and the machining forces needed to calculate the specific cutting energy were recorded using a piezoelectric 4-component dynamometer. Workpiece roughness and chip formation process were also evaluated. The results showed that the specific cutting energy decreased 15.5% when cutting speed was increased up to 700%. An increase of 1º in tool chip breaker chamfer angle lead to a reduction in the specific cutting energy about 13.7% and 28.6% when machining at HSC and conventional cutting speed respectively. Furthermore the workpiece roughness values evaluated in all test conditions were very low, closer to those of typical grinding operations (~0.20 mm). Probable adiabatic shear occurred on chip segmentation at HSC.