Advances in efficiency in the groove milling of aluminium EN AW 2024-T3 with zig-zag and trochoidal strategies

Manufacturing process engineers must continually take decisions to make the processes efficient. Manufacturing time, surface finish and energy consumption are aspects to be optimized in machining. This study analyzes the efficiency of groove milling in milling aluminum alloys EN AW 2024-T3 with zig-zag and trochoidal strategies. Dynamic milling is designed to maximize the removal rate and optimize the tool performance. This generates a discontinuous cutting with minimum of heat reducing build-up with an optimal chip removal minimizing cutting edge wear. The influence of lateral pitch, feed per tooth, cutting speed and coolant pressure has been analyzed. The depth of curt has been adapted for each strategy and tool type. The study was proposed through a factorial design of experiments by the Taguchi method. The machining time (T) and energy consumption (EC) show a strong influence of the lateral step (a e ) in conventional milling. A similar level of influence appears with the feed per tooth (f z ) on the trochoidal. The roughness (Ra) is more influenced by cutting speed (V c ) for conventional milling and by feed per tooth (f z ) and lateral pitch (a e ) for the trochoidal.

Comparing the Temperature Effect of Dedicated Minimally Invasive Motor System to the Discontinuous Use of Rotatory Burrs in the Correction of Hallux Valgus

The purpose of this study was to compare 2 motor systems for percutaneous osteotomy. The study consisted of 2 stages. In the first stage, bone temperatures during osteotomy using burrs or saw was measured using a thermal camera. In the second stage, the tissue and burr temperature elevation during surgery in 80 consecutive patients (96 feet) with hallux valgus undergoing distal first metatarsal and phalangeal osteotomies (hallux and in 61/96 feet lesser digits) were measured. The burr osteotomy procedure included the use of irrigated 2- or 4.1 mm rotary wedge burrs in discontinuous cutting bursts of less than 20 seconds. Tissue surface temperature was measured with a thermal camera. The temperature generated during the procedure was found to be significantly associated with the burr diameter used but was not affected by the type of motor. At the 6-week visit, thickness of the soft tissues over the first metatarsal head was similar in both groups. Temperature control using a noninvasive thermal camera is recommended to prevent tissue damage associated with heat generated during the use of rotary burrs. A dedicated low-speed high-torque system does not seem to be necessary and standard orthopaedic equipment can be used. Levels of Evidence: Level II: Comparative prospectively collected series

Improvement of grinding technology with vortex cooling of steels that are liable to crack propagation

Complexity of grinding process and phenomena entailing it not always allow reaching required technological results, especially while machining surfaces of parts made of tough-to-machine steels, which are liable to crack propagation. Cracks can occur in these parts during grinding due to considerable temperature difference along the section, which can cause formation of high temporary internal tensile stress. Application of cooled air in grinding process exerts considerable influence over temperature decrease in cutting area. In addition, it depends not only on heat exchange, but also on properties of cold air flow. The greatest effect of temperature decrease can be reached by injection of cold air flow in cutting area with implementation of vortex effect, which occurs in swirl flow of compressed air originating in vortex tube. The study of heat generation during machining by tools with discontinuous cutting surface and vortex air cooling was carried out. Obtained thermophysical parameters of vortex air cooling (increase in speed of stream flowing, expansion degree, share of cold stream and decrease in humidity of air stream) allow reducing heat density due to growth of cooling effect in grinding zone. On the base of experimental studies we developed recommendations for choice of optimal grinding modes by tool with discontinuous cutting surface and vortex air cooling of flat parts made of steels being liable to cracking.

Simulation-based process analysis for discontinuous cutting of generated bevel gears

For manufacturing bevel gears, special tool systems consisting of a cutterhead and carbide stick blades are used. Due to the complex relationship between the machine and process kinematics, however, an analytical analysis of the cutting process has been proven to be very difficult. For this reason, a manufacturing simulation based on planar penetration has been developed. In this paper, the algorithm is to be extended to generate processes for the first time. The concluding validation ensures that the simulated values match the actual cutting conditions. The result is a validated extension of the existing manufacturing simulation.