Thin Floor Milling Using Moving Support

During milling the thin floor of a pocket which locates on a monolithic structure, it is very difficult to achieve high accuracy and good surface quality due to its low rigidity. In this paper, a novel approach is proposed to overcome the difficulties that encountered during milling of the thin floor. The method is realized by using small axial depth of cut but placing a moving support at the back surface of the thin floor during machining, in which the support will move with the cutter at the same velocity. An experimental platform is built to demonstrate the validation of the proposed method. The experimental results show that the proposed method can effectively improve the accuracy and surface quality during milling the thin floor of a pocket of the monolithic structure.

EVALUATION OF SURFACE QUALITY AND DIMENSIONAL ACCURACY OF ELASTOMERIC IMPRESSION MATERIALS AFTER VARIOUS DISINFECTION PROTOCOLS

To evaluate surface quality and dimensional accuracy of elastomeric impression materials after various disinfection protocols. A Total of 150 samples were made i.e..50 from each type of impression material. Specimens were immersed in disinfectant solutions namely 0.2% chlorhexidine,5.25% hypo,0.2% povidone iodine, running tap water and ozone water for disinfection and examined for surface quality using stereomicroscope and dimensional accuracy using digital Vernier calipers. Silicones exhibited best dimensional accuracy & surface quality when treated with ozone water after 24 hours of disinfection whereas polyether exhibited good surface quality & dimensional accuracy when treated with control (tap water) after 24 hours of disinfection.

Multiobjective Optimization of Turning Cutting Parameters for J-Steel Material

This paper presents a multiobjective optimization study of cutting parameters in turning operation for a heat-treated alloy steel material (J-Steel) with Vickers hardness in the range of HV 365–395 using uncoated, unlubricated Tungsten-Carbide tools. The primary aim is to identify proper settings of the cutting parameters (cutting speed, feed rate, and depth of cut) that lead to reasonable compromises between good surface quality and high material removal rate. Thorough exploration of the range of cutting parameters was conducted via a five-level full-factorial experimental matrix of samples and the Pareto trade-off frontier is identified. The trade-off among the objectives was observed to have a “knee” shape, in which certain settings for the cutting parameters can achieve both good surface quality and high material removal rate within certain limits. However, improving one of the objectives beyond these limits can only happen at the expense of a large compromise in the other objective. An alternative approach for identifying the trade-off frontier was also tested via multiobjective implementation of the Efficient Global Optimization (m-EGO) algorithm. The m-EGO algorithm was successful in identifying two points within the good range of the trade-off frontier with 36% fewer experimental samples.

Lapping and Polishing of Sapphire Wafer with Fixed Abrasive Pad

The processing technology of sapphire with a high material removal rate a good surface quality is critical for its applications. The experiment of sapphire lapping and polishing was carried out by using three different fixed abrasive pad (FAP). Their material removal rate (MRR) and surface roughness (Ra) were measured and analyzed. Results indicate that a MRR of 5.6μm/min reaches in rough lapping and a MRR of 0.4μm/min in fine lapping. The average surface roughness Ra of rough lapping and fine lapping is 142nm and 1.2nm respectively. The processing efficiency of sapphire wafer is effectively improved and a good surface quality is obtained when FAP adopted.

Research of Sapphire Wafer Scribing by Using UV Laser

The Processing advantages of UV laser were discussed in this paper. A series of experiments were carried out, some good results was achieved, which proved UV laser is fit for sapphire wafer processing. Then how processing parameters affects machining quality was discussed, which provides guidance to machining practice. The formation of grooves with good surface quality can be achieved by selecting appropriate laser parameters.

The Experiment Research of Precision Grinding of Li-Ti Ferrite with Graphite Grinding Wheel

Li-Ti ferrite used in aviation occasions needs good surface quality. In conventional grinding it is difficult to meet the surface demand. Accordingly, this paper proposed a new grinding process to change the situation. The process employed graphite grinding wheel which is always used in ultra-precision grinding of steel piece. The process can obtain good surface quality and ensure certain material removal rate. The ground surface appearance is nearly mirror-like. The lowest surface roughness of Ra value of the ground surface is 0.05μm in the experiment. The ground surface morphology is made up of spread glazed area and dispersed minute pits. The ductile regime dominates the material removal mechanism and no surface damage is induced in the process. In consideration of the results in the experiment it can be seen that grinding with graphite grinding wheel is a good finishing procedure in ferrite machining because of its obtained high surface quality.

Study on Semi-Fixed Abrasive Lapping of Ultra-Thin Silver Electrode Layer

Silver electrode layer of piezoelectric ceramic transducer requires good surface quality and high efficiency. Efficiency of traditional lapping and polishing is very low. Ultra-precision grinding technology is also unsuitable for the thickness of workpiece is extremely thin. Semi bonded abrasive lapping is a new ultra-precision processing method. The new ultra-precise method can achieve good surface quality in short time, and removal stock of workpiece is small. In order to research the optimal technology of semi bonded abrasive lapping about silver electrode layer, this paper research several major processing parameters by experiments. The results show that appropriate processing load can obtain better surface roughness of silver electrode layer，and surface roughness of silver electrode layer has little change with different processing speed. By using ultra-fine semi bonded abrasive plate, 94.08KPa processing load and 40 rpm polishing speed, after 30 minutes, surface roughness of silver electrode layer is 11nm, and removal stock is 11.5μm.

Nanofabrication of High-resolution and Nanofocusing X-ray Optics Based on Silicon and Diamond: Obstacles and Progress

Nanofocusing, high-resolution X-ray optics demand good surface quality, the absence of tapered sidewalls, and a depth reaching into tens, sometimes hundreds of microns, all requirements that must be satisfied over large areas. In this report, we discuss our motivation for choosing group IV materials (predominantly Si, and C in its diamond form) for nanofocusing and high resolution in the hard X-ray portion of the spectrum. We elaborate on the design and nanofabrication procedures, and detail the etching parameters that offer a path for overcoming obstacles in making better optics. We briefly review tests for the assessing the quality of the optics.