Papers by Keyword: Micro-Hole

Abstract: It was difficult to prepare micro-hole with large aspect ratio by traditional processing technologies. In order to solve the problem, a preparation was proposed. It was carried out by casting method. Carbon fiber and metal wire coated graphite paint were used as hole core respectively. And morphology and geometrical characteristic of micro-hole were observed and analyzed by scanning electron microscope and laser scanning confocal microscope. The results showed that average diameter and aspect ratio of micro-hole obtained by the group of carbon fiber hole core were about 0.2 mm and above 1700, respectively. For the other group, about 0.5 mm and 700, respectively. The micro-hole obtained by the metal wire coated graphite paint hole core was more close to circle. Its shape factor was about 0.72. The roughness of micro-hole value obtained by carbon fiber hole core was close to 3.2 μm, smaller than that of the metal wire coated graphite paint.

Abstract: Stainless steel is difficult to machine, especially micro-hole machining. In order to obtain the effect of drilling force by tool material and cutting parameters, the drilling experiments on stainless steel 1Cr18Ni9Ti have been done by diameter of 1.2 mm containing cobalt high speed steel and carbide drill. According to the experimental results, analysising the reason of drilling force change under different parameters and establishing a carbide drill drilling force empirical formula which combined with the regression analysis method.

Abstract: this paper introduced the existing ladder-shaped micro hole machining method, analyzed the existing problems of present micro hole machining equipment; solved some key problems such as how to clean up the iron filings in micro blind holes rapidly and completely, compensate tool wear and other problems; And finally developed a special purpose machine tool for machining ladder-shaped micro hole, which can achieve fully automated machining.

Abstract: Electrochemical discharge machining (ECDM) is the preferred non-traditional process technology in recent years, The main processing is applied to machining non-conductive hard brittle materials. This study investigated the precision and stability of quartz fabricated by ECDM and explored the optimal processing parameters including size of electrode, machining speed as well as pulse-on and pulse-off duration. Microgrooves machined under the optimal processing parameters with adjusted rotational speed and feed rate were examined to understand the effect of different ECDM parameters on machining performance. The results indicate that micro-holes of better morphology could be obtained under pulse voltage of 40 V, electrolyte concentration of 5 M, electrode size of 125 μm. Moreover, rotational speed of 1500 rpm and pulse-on/pulse-off (ms) ratio of 1:0.6 gave higher machining accuracy with smaller hole diameter and shorter machining time. Finally, microgrooves machined under the optimal processing parameters showed the best accuracy in dimension and cross-sectional morphology at rotational speed of 2500 rpm, pulse-on /pulse-off (ms) ratio of 1:1.6, and feed rate of 3000 μm/min.

Abstract: Electrochemical micro-machining (EMM) has become one of the main machining methods for production of miniaturized parts and components. Utilizing the developed EMM set-up, the effects of ultrasonic wave frequency on characteristics of localized dissolution and accuracy of micro-hole in EMM are investigated and evaluated. The experiment results demonstrate that the accuracy of micro-hole and characteristics of localized dissolution can become better with the increase of ultrasonic wave frequency. The accuracy of micro-hole machined by 26KHZ can improve about 30% than that by 16KHZ. Moreover, the ability of localized dissolution by 26KHZ can be increased about 27%-30%.

Abstract: A new method for drilling micro-hole called EDM-ECM combined processing is proposed in this paper. This method consists of EDM shaping and ECM finishing, and they are carried out in sequence on the same machine tool with the same electrode but different dielectric medium. Micro-hole drilling experiment was done by micro-EDM, micro-ECM and EDM-ECM combined processing. The results show that the machining efficiency is improved by 9.2 times compared to conventional micro-ECM, and machining precision and shape accuracy of micro-hole are much better. The surface quality and mechanical property of the workpiece are improved, since the recast layer and surface defects generated by EDM are removed completely by ECM finishing. It proves that this combined machining method is possible and useful in the field of micro-hole drilling.

Abstract: With the ever increasing energy demands, unconventional gas becomes the new force in energy field. However, shale gas horizontal drillings are prone to instability problems because of the brittleness of gas shale. The casing programs of shale gas wells in China and North America demonstrate that the more drilling problems are encountered with the larger borehole sizes. In the thrust faults, based on vutukuri's size effect theory and Mclamore's failure criteria, a new prediction model of collapse pressure in transversely isotropic rock mass is proposed to analyze the critical mud weight of micro-hole in gas shale formations. The trajectory sensitivity analysis is also carried out. The results show that micro-hole drilling technique in thrust faults can significantly reduce the collapse pressure of directional wells by 12% approximately.

Abstract: An effective approach of quality inspection for micro hole is proposed by studying on the geometric feature of micro hole edge. The edge of micro hole is detected exactly with the digital image processing techniques, such as, the median filter, the threshold value transformation, and so on. The least square circle fit arithmetic and a new roundness measurement arithmetic are synthetically used in the processing of geometric feature recognition of micro hole. The practical results prove that the method with exact conclusion and high precision can satisfy the quality inspection requirement of micro hole.

Abstract: The austenite 1Cr18Ni9Ti stainless steel is one of difficult-to-cut materials. It has poor dilling process, especially for micro-hole machining. The main reasons are the tiny drill, poor rigidity, easy to deviation. Moreover, the chip is difficult to discharge, so the drilling force is increased and the drill bit is easy to break, or even it is impossible for micro-hole drilling. In this paper, the vibration drilling process is adopted. The vibration drilling 1Cr18Ni9Ti stainless steel micro-hole process mechanism is researched. The stainless steel micro-hole drilling experiments are conducted. The results show that the vibration drilling can be a better solution for 1Cr18Ni9Ti stainless steel micro-hole processing.

Abstract: Through the analysis of the basic principles of vibration drilling and vibration drilling process, in the drilling device and the cutting parameter sides , combined with the actual structure of the workpiece as well as the ultrasonic vibration drilling processing methods to elaborate, using the ultrasonic vibration drilling device to carry out the TC4 titanium alloy micro-hole drilling test. The test prove that selecting reasonable cutting parameters can solve the problem of drillingTC4 titanium alloy micro-hole that size is Φ1.5mm × 12mm , fully reflects the superiority of the ultrasonic vibration drilling. A new method was afforded for titanium alloy micro-hole drilling.