Papers by Author: Ming Chen

Abstract: Pull broaching fir-tree slots of gas turbine is one of the most productive precision machining processes when machining simple surfaces or complex contours. Tool edge chipping and wear of uncoated broaching tool become a serious problem in the currently broaching of gas turbine discs. Therefore, tool coating can be used to improve the wear resistance of broaching tool. AlCrN-based coatings have been developed as a high hardness coating for cutters due to excellent resistance to oxidation which is higher than that of conventional coatings. However, few researches had paid attention to investigating AlCrN-based coating tool performance in the broaching process, especially in machining of heat-resisting material of heavy-duty gas turbine discs. In this paper, experiments of broaching heat-resisting material X12CrMoWVNbN1011 were investigated. In order to obtain suitable and ideal broaching tool, the AlCrN coated or uncoated T15 broaching tools were also compared. Cutting force, cutting temperature, and tool wear were measured in the broaching experiments. Results showed that: (1) with a little changed cutting load and tool edge radius, AlCrN-based coating was found to have more significantly influence in improving the tool life as comparing to uncoated tool. The similar wear forms was observed by comparing coated tool and uncoated tool. The conclusions of the study can help to improve heavy-duty gas turbine disc broaching process and broaching tool. (2) Owing to AlCrN coating’s unique combination of heat resistance and hardness, broaching tool could reach higher cutting performance levels. AlCrN coated tool compared with uncoated tool have much better performance in term of cutting strains or cutting temperature.

Abstract: Ultra-high strength steel 30Cr3SiNiMoVA is a typical difficult-to-cut material. During the machining process of 30Cr3SiNiMoVA, tool wear is an important factor which needs to be investigated seriously. In this work, one kind of CVD coated tools was used to investigate the tool wear mechanism of face milling of Ultra-high Strength Steel 30Cr3SiNiMoVA. Cutting forces during the wear process were measured with a kistler dyna-mometer. Surface roughness and tool wear evolution were determined.

Abstract: Ultra-high strength steel 30Cr3SiNiMoVA has excellent mechanical properties, including high strength and hardness, a certain degree of ductility and toughness. The superior properties have awarded a wide application of 30Cr3SiNiMoVA in the aviation industry. But on the other hand, The ultra-high strength steel 30Cr3SiNiMoVA is a typically difficult-to-cut material, The difficult-to-cut features in the process of which include high cutting temperature and cutting force, severe tool wear, low productivity and so on. So selection of appropriate cutting parameters is very important in the process. In this paper, high-speed milling tests were carried out, to investigate the performance of 30Cr3SiNiMoVA under given conditions. Basing on the results of the experiments, Empirical formulas of surface roughness and cutting force were got. Finally, the multi-objective optimization on cutting parameters was conducted. The optimized parameters in the test conditions were a_p=10mm, V=50/min, fz=0.06mm/z, a_w=0.4mm.

Abstract: In this study, micro- crystalline diamond(MCD), fine grade diamond(FGD) and nano- crystalline diamond(NCD) thin films are successfully coated on WC-Co micro drills(φ=400µm) adopting hot filament chemical vapor deposition (HFCVD) technique. The microstructure and cutting performance of micro drills for applying to drill electrical discharge machining(EDM) graphite coated with MCD, FGD and NCD films are systematically investigated by means of field emission scanning electron microscope(FESEM) and Raman spectroscopy. After drilling of 1500 holes, wear behavior of these micro drills is analyzed by FESEM and NCD coated micro drills exhibit minimum flank wear compared with the other samples due to the relatively good wear resistance and friction properties of NCD films.

Abstract: Since metal matrix composites (MMCs) have increasing applications in industries, this paper presents an experimental investigation on machinability of SiC_p reinforced aluminium metal matrix composites. 14 wt.% of SiC_p reinforcement addition composite was studied in end milling using CVD coated carbide tools under different cutting parameters. By experimental results, the relationships of cutting force and surface roughness with cutting speed and feed were discussed. Some defects concerning surface topography such as ploughed furrow, pits, matrix tearing, etc. were examined by SEM.

Abstract: Tool breakage monitoring is crucial to automation fabrication, especially for high-density hole machining, such as PCB (Printed Circuit Board). A tool breakage feature extraction method in PCB micro-hole drilling is presented in this paper. The vibration signal is analyzed by wavelet transform. The decomposed signals energy ratio at each frequency band is computed as monitoring features. The monitoring performance of different features selection is given. The vibration signals are observed to provide the capability in distinguishing micro drill breakage with proper features extraction and classifier design.

Abstract: Printed circuit board (PCB) composed of glass fiber reinforcement plastic and copper foil is a kind of typical composite material. The cutting process of fiber reinforcement plastic materials such as carbon fiber or glass fiber reinforcement plastic materials have been studied for many years, but the drilling process of printed circuit board using microdrill is more complicated than common carbon fiber reinforcement plastic materials. It is event that the cutting force changed when drill different material. The variation of drilling force may cause some problems such as drill break, board delamination. So it is important to study the drilling force in PCB drilling. The precision dy-namometer was used in experiments and cutting process was analyzed in this paper. The drilling process of PCB experience six stages and the drill will meet aluminum board, glass fiber reinforce-ment plastic (GFRP) and base strip. According to the drilling force in one circle, the peak force ap-peared at the moment of drilling copper foil and another smaller peak force appeared at the moment of drilling aluminum board and base board. The experiment results show that thrust force increased with federate and decreased with rotational speed.

Abstract: More and more attention is put on the machinability of printed circuit board (PCB) with the increasing demand of PCBs driven by the strong need of the market of the electronic products. In this paper, drill wear and burr size, as two main objects of experimental investigation, have been observed and analyzed in drilling PCB through-holes. The results of the drilling experiment conducted with normal drill and specialized drill, indicate that appropriate chisel edge thinning is in favor of decreasing flank wear of the drill, but has no apparent effect on reducing burr size for PCB through-holes drilling.

Abstract: As a typical high strength material, titanium alloy Ti-6Al-2Sn-4Zr- 2Mo-0.1Si (TA19) is used to manufacturing the compressor power-brake of aircraft engine and the aircraft skin. All the machining experiments were carried out on a CNC-milling center under the stable conditions of cutting speed, feed rate, and depth of cut. The performance and wear mechanisms of coated- and uncoated carbide tools have been investigated in this paper to evaluate the machinability of TA19 in face milling. The three tools used were PVD-TiN+TiAlN, CVD-TiN+Al2O3+TiCN and uncoated carbide inserts. The results indicated that PVD coating had the best performance than other tool materials in milling titanium alloy TA19, and the cutting force and the wear value were the smallest than that for CVD-coated and uncoated tools. The failure types of PVD-, CVD- and uncoated inserts were the crater wear and micro tipping; the crater wear and tipping; tipping. Abrasive wear and adherent wear were the predominant mechanism of PVD-TiN+TiAlN carbide insert in face milling TA19 alloy. For CVD- and uncoated carbide, adherent wear was predominant.

Abstract: Different parameters of Minimum Quantity Lubrication (MQL) system, including air pressure, oil quantity, nozzle position, might have different influences on the cutting force and the cutting temperature. This paper presents an experiment of end-milling titanium alloy with MQL system. The objective of the experiment is to investigate the influences of MQL parameters in milling of Ti-6Al-4V. The results of experiment show that there are different effects on the cutting force and the cutting temperature with different MQL parameters, which will help to select different parameters in the end-milling process of Ti-6Al-4V.