Key Engineering Materials Vols. 304-305

Abstract: The intelligent monitor and control system for grinding process is proposed in this paper, it utilizes the nonlinear modeling theory and self-learning capability of neural network to setup non-liner mapping relations between grinding conditions and AE signals, and to realize grinding process intelligent monitor and control by picking-up grinding AE signals on line. Grinding quality can be monitored on-line, starting parameters for grinding process can be selected, on-line intelligent adjustment of grinding conditions also can bee realized by using this system.

Abstract: The helix flute grinding was important to machine a complex revolving tool. The geometric parameters (especial its rake angle, flute depth and flute width) have essential effect on the performances of the tool. Using the 6UPS parallel grinding machine developed from BEIHANG, especially after analyzing its special machining and structure features, this paper gave general analysis to all factors which will influence the flute shaping. According to the moving relationship between grinding wheel and the tool, a simulation modeling system was established. This system could be adopted to optimize and quantitative design that influence parameters deeply. The parameters refer to the grinding wheel defluxion, the grinding wheel thickness, the grinding wheel offset position along the X direction, and the flute depth. Experiments were carried out to verify the influence results.

Abstract: In this paper, a new on-line diamond grinding wheel dresser, which is comprised of high-speed rotatory dressing wheel, micro-feed mechanism and control system, is presented. The principle of micro-feed machine working at requiring dressing depth, the control method of the dressing wheel speed adjusting and dressing depth, and structure of the control system are also introduced. The experiments we have done show that the dresser reach the goal of diamond grinding wheel on-line dressing.

Abstract: Micro-drills are becoming more and more important in precision and micro fabrications. They have been widely used in applications, e.g., precision and micro drilling. In this paper, a novel method is advanced and used for regrinding of chisel edges of helical micro-drills. In this method, a geometric model is established for the chisel edge regrinding. Based on the kinematic relationship of regrinding, the model simplifies machine movement so as to facilitate an easy operation. Computer simulation is applied to the regrinding process of the micro-drills. The results demonstrate that the proposed method is effective in regrinding chisel edges, which allows for a more reasonable distribution of the angles along the chisel edge of a drill, and enhances the drilling performance.

Abstract: The material removal rate (MRR) model was investigated in abrasive jet precision finishing (AJPF) with wheel as restraint. When abrasive wore and workpiece surface micro-protrusion removed, the size ratio for characteristic particle size to minimum film thickness gradually diminishing, the abrasive machining from two-body lapping to three-body polishing transition in AJPF with grinding wheel as restraint. In the study, the material removal rate model was established according to machining mechanisms and machining modes from two-body to three-body process transition condition, and active number of particles in grinding zone were calculated and simulated. Experiments were performed in the plane grinder for material removal mechanism and academic models verification. It can be observed from experimental results that the surface morphology change dramatically to a grooved or micro-machined surface with all the grooves aligned in the sliding direction in two-body lapping mode. On the other hand, the surface is very different, consists of a random machining pits with very little sign of any directionality to the deformation in the three-body machining mode. Furthermore, the material removal rate model was found to give a good description of the experimental results.

Abstract: The effect of cutting parameters such as water pressure, nozzle traverse speed and standoff distance on the granite cutting performance as characterized by kerf width, kerf taper, and striation drag angle are researched with a series of experiments using garnetabrasive and ultra high pressure abrasive water jet numerical control machine tool. The relationship between system pressure and abrasive mass flow rate is also studied. The research results show that the abrasive mass flow rate is only proportional to water pressure and the effect of other cutting parameters is not significant. It is found that an increase in water pressure is associated with an increased kerf width and a decreased kerf taper. The kerf width decreases with the enhancement of nozzle traverse speed, and resulting in a significant increase in kerf taper as the nozzle traverse speed increases. The kerf width increases with the enhancement of standoff distance, and hence it causes a significant increase in kerf taper at the standoff distance domain from 3mm to 4mm and then a little decrease in kerf taper at the standoff distance increasing from 4mm to 5mm. The striation drag angle decreases with an increase in water pressure and a decrease in nozzle traverse speed.

Abstract: Magnetic field distribution (MFD) plays an important role in magnetic abrasive finishing (MAF). The mathematical models of the MFD in MAF have been established, and forced behavior of magnetic abrasive (MA) in the magnetic field has been analyzed in this paper. The MFD characteristics of the grooved poles have been numerically simulated, and the distribution law of magnetic force, interaction force and interface pressure have been investigated based on a single particle. The calculated results show that the MFD in the finishing zone is directly affected by the pole structure and working gap. The mapping function of interaction force and interface pressure corresponds to corner-effect in the peak point of the pole, and the magnetic brush stiffness is changed by the diameter and magnetization characteristics of MA, and the magnetic flux intensity (MFI). The numerical simulations are in a good agreement with the experiments. All of results mentioned above will offer an important method to study further on the finishing mechanism.

Abstract: Ultra-high grinding speed and point contact are the salient natures of Quick-point grinding. Based on the damage dynamics theory, there are impact damages with a lot of micro-cracks and micro-defects and adiabatic shearing caused by ultra-high strain rate in the contact layer in such grinding manner. The micro-damages are relation to the strain rate and the materials properties, and increase with raise of strain rate. Because of the weakening effect of strain rate, the dynamic strength of the contact layer in Quick-point grinding is decreased and the grinding performance of ductile and brittle materials is also changed. The dynamic strength model of the contact layer in Quick-point grinding was built in this paper, and the weakening effects of strain rate caused by impact micro-damages on the dynamic strength of the layer and the materials removal mechanism in grinding layer were analyzed through the study on the theory and the experiments.

Abstract: Grinding is inherently characterized by high specific energy requirements, a high grinding zone temperature. Many methods have been employed in grinding high grinding zone temperature. But all have their shortfalls, both in cooling environmental pollution. Here a new high efficiency cooling technology—cryogenic mist jet impinging (CPMJI) cooling technology is offered. In this technology, coolant is carried by high-pressure cryogenic air (–20°C) and reaches the machining form of mist jet to enhance heat transfer in machining zone. This paper mainly cooling effects of CPMJI in surface grinding, compared with grinding with compressed flood cooling. CPMJI seems to have better effects than other cooling methods.