Fabrication of PCD Skiving Cutter by UV Nanosecond Laser

Polycrystalline diamond (PCD) skiving cutter has dominated research in recent years. However, the traditional methods of fabrication have failed to cut the diamond with high quality. We propose the two-step laser machining process combining roughing machining with orthogonal irradiation and finishing machining with tangential irradiation. In addition, the processing effect and mechanism of different lasers on the diamond were investigated by a finite element analysis. It’s proved that the ultraviolet nanosecond laser is an excellent machining method for the processing of diamond. Furthermore, the effect of the processing parameters on the contour accuracy (Rt) was studied. The result indicates that the Rt value decreases first and then increases as the increase of the line interval, scanning speed and defocusing amount (no matter positive or negative defocus). Further, Raman spectroscopy was applied to characterize the diamond surface under different cutting methods and the flank face of the tool after processing. Finally, a high-quality PCD skiving cutter was obtained with an Rt of 5.6 µm and no phase transition damage.

Precise Machining Based on Ritz Non-uniform Allowances for Titanium Blade Fabricated by Selective Laser Melting

Selective Laser Melting (SLM) is an increasingly concerned trend in Ti-6Al-4V blade manufacturing, while the SLMed Ti-6Al-4V blade cannot be used directly because of poor surface integrity and high residual stresses. Precise machining after SLM is a feasible solution but also a challenge. The low rigidity of the blade will lead to deformation when machining. The deformation can lead to surface error and may make defect parts. Two-steps machining processes to address the problems were proposed in this paper. First, a non-uniform allowance distribution was allocated and optimized in semi-finishing based on Ritz solution to elastic deformation. The blade was simplified as a cantilever thin plate with various thickness, and the thickness of finishing allowance was designed and optimized on the premise of ensuring the thin-wall stiffness of the blade, so as to realize the design of Ritz non-uniform allowance. Then, finishing machining was conducted to achieve precise parts. A blade deformation model was established to evaluate surface error with cutting force moving and changing. Finite element analysis and experimental validation in ball-end milling of a blade were conducted. FEA results and experimental results showed dimensional errors have been reduced up to 50%. Further surface tests demonstrated that the mean surface roughness reduced from 7.88 μm to 0.815 μm. And the residual surface stresses of the SLM samples changed after semi-finishing machining due to the residual stress relaxation and redistribution. The results demonstrated that the proposed method enhanced the surface quality of blade fabricated by SLM.

Use of ultrasonic surface hardening in modifi cation of surface layer

Overview of the research results got by various scientific schools in the field of application of ultrasonic surface hardening is provided. Wide range of opportunities of ultrasonic surface hardening is shown for the application in the preliminary machining of surfaces before thermal and chemical treatment, coating, and also as finishing machining. The effect of the energy of ultrasonic vibrations on structure changes in the material of the surface layer and on surface microrelief on parts performance is considered. The prospects of using of the ultrasonic surface hardening method in combination with other methods of the material modification are presented. In addition the possibilities of reducing the manufacturing cost of product by introducing ultrasonic surface hardening into the technological process are shown.

On practical application of plasma and laser hardening

Laser and plasma hardening practically do not damage the surface, so the parts after their execution are sent to the assembly without finishing machining, which reduces the complexity and logistics of the process. In conditions of dry friction hardened steel discs 45 and 40Kh increase wear resistance up to 100 times. The service life of parts strengthened by laser and plasma hardening is repeatedly increased. Laser hardening differs from plasma hardening by higher cost of equipment, therefore it is preferable in large-scale production. Plasma installation UDGZ-200, thanks to manual operation, it is possible to temper the surfaces inaccessible or inaccessible to other hardening methods. This, together with the low cost of equipment, makes plasma hardening cost-effective in conditions of single-unit and small-scale productions.

Experimental Investigation of the Influence of Wire Arc Additive Manufacturing on the Machinability of Titanium Parts

The manufacturing of titanium airframe parts involves significant machining and low buy-to-fly ratios. Production costs could be greatly reduced by the combination of an additive manufacturing (AM) process followed by a finishing machining operation. Among the different AM alternatives, wire arc additive manufacturing (WAAM) offers deposition rates of kg/h and could be the key for the production of parts of several meters economically. In this study, the influence of the manufacturing process of Ti6Al4V alloy on both its material properties and machinability is investigated. First, the mechanical properties of a workpiece obtained by WAAM were compared to those in a conventional laminated plate. Then, drilling tests were carried out in both materials. The results showed that WAAM leads to a higher hardness than laminated Ti6Al4V and satisfies the requirements of the standard in terms of mechanical properties. As a consequence, higher cutting forces, shorter chips, and lower burr height were observed for the workpieces produced by AM. Furthermore, a metallographic analysis of the chip cross-sectional area also showed that a serrated chip formation is also present during drilling of Ti6Al4V produced by WAAM. The gathered information can be used to improve the competitiveness of the manufacturing of aircraft structures in terms of production time and cost.