Papers by Keyword: Form Accuracy

Abstract: This paper proposes to improve the form accuracy of a machined surface produced by an ordinary milling machine by diamond fly cutting using controlled cutting with reference surface (CCRS), an in-process measurement and control method. CCRS improves machined surface accuracy by controlling the relative displacement between the tool and workpiece. Diamond fly cutting using CCRS was demonstrated to reduce the table motion error on an ordinary milling machine.

Abstract: Machining of hard and brittle materials is inherently involved with tool wear, which influences the dimensional and form accuracy of the machined product. Ultrasonic-assisted machining process is suitable for hard-to-cut materials such as ceramics, glass, and metal matrix composites, etc. In the current study, the mechanism of tool wear is investigated during ultrasonic-assisted milling of soda-lime glass as one of hard and brittle materials. Ultrasonic-Assisted Milling (UAM) combines the material removal mechanism of grinding and the milling kinematics with ultrasonic assistance. The effect of different process parameters, i.e. feed rate, depth of cut, cutting fluid, and ultrasonic vibration assistance on the tool wear behavior are investigated. Form accuracy of the machined slots is also investigated. The results showed that UAM produces less tool wear than conventional milling (CM). However, CM gives less error in the slot dimensions than UAM.

Abstract: The stochastic nature of grinding predetermines the necessity of attracting statistical methods to predict output parameters. In this research the form accuracy indices of flat workpieces EFE_max (the main parameter) and two additional indices EFE_a and EFE_q called the arithmetic average and the quadratic average, respectively are used (GOST 24642-81). In the conditions of violating normality and homoscedasticity of distributions the selection of the grain in the Norton high porous wheels (HPW) made of synthetic corundum 5SG (46, 60) K12VXP is made with an emphasis on a non-parametric method, wherein medians and quartile latitudes are used as one-dimensional frequency distributions. This paper states that grinding by the coarse-grained HPW 5SG46 in comparison with the small-grained 5SG60 made it possible to increase the form accuracy by the predicted medians within the same accuracy quality class: for EFE_max – TFE7; for EFE_a and EFE_q – TFE6. The precision of the form accuracy of the parts 30ChGSA increased most significantly: for EFE_max it increased by 5 times, for EFE_a by 3.1 times, and for EFE_q by 4.2 times. The fact that the heights of microasperity remained practically at the same level , μm; , μm was due to the features of the synthetic corundum grain structure. In this study the EFE_max parameter is used for selecting the wheel grain. The auxiliary parameters of form accuracy are used in calculating the correction indexes of basic models in the multivariate dispersion analysis because they have more information about the status of the part surface.

Abstract: Generally, grinding fluid is supplied from a nozzle to a grinding point. However, it is difficult to supply sufficient coolant to the deep grinding point of a hole. Therefore, we have proposed an alternative coolant system that supplies grinding fluid from the inner side of the grinding wheel utilizing the spindle through the supply system of the machining center. In this study, a new tool for small and deep holes was developed to supply grinding fluid in this way. The inside of a 0.45%C steel cylinder was then machined under various grinding conditions. Higher form accuracy and surface roughness were obtained under all conditions by supplying grinding coolant from the inner side of the grinding wheel. In addition, the system prevented tears on the machined surface and loading on the grinding wheel.

Abstract: Nowadays, the demands of large scale surface devices are becoming popular in engineering fields. The grinding process is one of the common methods to achieve the high quality of large scale workpiece. But the final form accuracy of large scale devices is always low. Then it is necessary to analyze the error mechanism of grinding machine on the form accuracy of large scale workpiece. In this paper, the influencing factors of surface grinding machine with horizontal spindle and rectangular table were analyzed firstly. Then the mechanism of guiding accuracy on the surface form accuracy was discussed. It is found that the Z-axis’ guiding accuracy could seriously influence the surface form accuracy. Finally, the face grinding experiment of large scale iron workpiece (420mm×420mm) was performed and the surface form accuracy was measured. The experimental result was in agreement with the theoretical result. It can be concluded that the Z-axis guarding accuracy of grinding machine should be exactly controlled to achieve the high surface precision of large scale device.

Abstract: In this study, an approach by the feed rate control was applied for the improvement of form accuracy in the micro end milling process. In this approach called adaptive control constraint, the feed rate is controlled so that the cutting load is constantly kept and the deflection of tool does not occur. However, this method is not always effective in the micro cutting process that the influence of size effect cannot ignore. Therefore, the relationship between the cutting conditions and the form error in the micro end milling is experimentally investigated. The experiments on the machining of metal mold steel with the micro end mill are carried out and the formulation as function of the cutting conditions and the form error is identified by means of regression analysis. The performance of the feed rate control was validated based on experimental results. As the result, it was confirmed that the form accuracy was improved.

Abstract: This research studies the influence　of constant pressure acting on the magnetic particles brush for the precision machining of planar and curved workpieces. In particular, it examined the effects of constant pressure on improving the formal accuracy of the workpiece. This process method, constant pressure is applied to the magnetic pole of a conventional magnetic brush, the constant pressure acted to the surface of the workpiece through the magnetic particle brush formed at the magnetic pole surface. The authors conducted a plane magnetic abrasive finishing experiment using both the conventional magnetic abrasive finishing process and the newly proposed constant-pressure magnetic abrasive finishing process to compare the deburring characteristics between the processes for removing burrs from holes drilled in brass plate workpieces. In this experiment, a brass disk with a drilled hole was used as a workpiece. As a result, the difference in finishing characteristics was clarified. The results showed that the burr can be removed by use of this new plane magnetic abrasive finishing process and it is more useful than the conventional magnetic brush for improving the shape accuracy of the workpiece.

Abstract: ELID (electrolytic in-process dressing) grinding was proposed by one of the authors for automatic dressing the grinding wheel while performing grinding for a long time. It offers a high effective way and has been widely used for grinding hard and brittle optical materials. However, those surfaces produced by fixed abrasive grinding are characterized by considerable sub-surface damage, micro-crack. Magneto-rheological finishing (MRF) is a novel precision finishing process for deterministic form correction and polishing of optical materials by utilizing magneto-rheological fluid. In this paper, an ultra-precision synergistic finishing process integrated MRF and ELID grinding is proposed for shorten total finishing time and improve finishing quality. A lot of nano-precision experiments have been carried out to grind and finish some optical materials such as silicon, silicon carbide, etc. ELID grinding is employed to obtain high efficiency and high surface quality, and then, MRF is employed to improve further surface roughness and form accuracy. In general, form accuracy of ~ λ/20 nm peak-to-valley (P-V) and surface roughness less than 10 Angstrom are produced in high efficiency.

Abstract: Parallel grinding is an effective method of aspheric moulds machining which is usually made of industrial ceramic such as silicon carbide (SiC) or tungsten carbide (WC), but if the spherical grinding wheel is not being with precision truing and dressing, the roughness and form accuracy of the ground aspheric surface should get worse, for this reason, in this paper, the influence factors of thoroughness and form accuracy induced by the wheel truing and dressing are studied firstly, and a new 3-axis CNC Ultra-precision grinding system which is based on the PMAC (Programmable Multi-axes Controller) is developed, through simultaneous motion of the controlled X, Z and B axis, the form errors which is induced by the grinding wheel can be improved theoretically, and the aspheric mould machining test shown that the surface roughness of Ra 0.025μm and the form accuracy of P-V 1.15μm are achieved.

Abstract: A new CAD system, which is called Volume-CAD (VCAD) have been developed. We carried out research and development of VCAD fabrication process based on VCAD/CAM precision control. In this study, a developed V-CAM had been used for a polishing fundamental experiment of a free form surface. The relationship between NC resolution and form accuracy of polished surface are discussed.