Papers by Keyword: Wheel Dressing

Abstract: An experimental study was undertaken to explore the conditions and performance on rough and finish grinding fir-tree root forms of turbine blades made of a nickel-based alloy using vitrified CBN wheels and water-based grinding fluid. This work was motivated by switching the grinding of fir-tree root forms from grinding with conventional abrasive wheels to vitrified CBN wheels for reducing overall production cost and enhancing productivity. Grinding experiments were conducted to measure grinding forces, power, surface roughness, and stress near the blade roots under various dressing and grinding conditions. Wheel re-dressing life in terms of the total number of good parts ground between dressing was tested with the condition producing the maximum material removal rate while satisfying preset part quality and process requirements. It was found that the maximum material removal rate achievable in rough grinding was restricted by the stress limit and the wheel re-dressing life was dominated by the radial wheel wear limit. The targeting part quality and process requirements were achieved. It was proved that vitrified CBN grinding process is feasible and very promising to machine fir-tree root forms.

Abstract: An experimental study is reported on the grinding of a nickel-based alloy using vitrified CBN wheels. This work was motivated by switching the grinding of fir-tree root forms of jet engine blades from creep-feed grinding with conventional abrasive wheels to vitrified CBN wheels. The objective is to explore process limits and practical grinding parameters for judging the switch in terms of overall costs and productivity. Straight surface grinding experiments were conducted with water-based fluid on rectangular blocks at a fixed wheel speed v_s = 45 m/s, various depths of cut a = 0.05 - 1.0 mm, and workspeeds v_w = 2 - 40 mm/s. Grinding power, forces, surface roughness, and radial wheel wear were measured. Specific material removal rate of 8 mm³/(mm.s) was reached in rough grinding using a wheel dressed for achieving surface roughness R_a = 0.8 µm in finish grinding. It was found that shallow depths of cut combined with fast workspeeds, or less creep-feed modes, are more suitable for achieving high material removal rates with vitrified CBN grinding. Rough grinding is restricted by high grinding temperatures with newly dressed wheels and by chatters with worn wheels.

Abstract: A software system for CNC dressing involute grinding wheel was developed. When the ordinary grinding wheel was used in gear form grinding, the key was to handle the on-line dressing of involute wheel. Based on involute generation principle, an algorithm by taking straight line to approach involute with equal error was mainly studied. The NC program for dressing involute wheel was prepared by using VC++6.0 as programming tool, and wheel dressing experiment was completed. Experimental result shows that the proposed algorithm is valid，and the developed program is feasible with friendly interface. The success of this software system lays the foundation for further developing CNC gear form grinding system.

Abstract: Aiming at the dressing of involute grinding wheel, the mathematical model of involute interpolation is established. Taking the normal tolerance δ as accuracy index, the dense degree of interpolation points can be changed constantly with the change of developable angle increment △θ so that the numbers of interpolation points can meet the requirements not only for interpolating accuracy, but for interpolating efficiency. The wheel dressing software developed by using VC++ as programming tool can be applied for dressing the involute grinding wheel which can be used to grind involute gears with different teeth and modules. The results of simulation experiment verify the feasibility and correctness of the software.

Abstract: Based on the gear meshing theory, the mathematical model of inner helical gear form grinding is established. In order to get rid of the grinding interference, numerical simulation is used to optimize the diameter of grinding wheel and its installation angle. The wheel profile obtained by means of numerical simulation is transformed into the end section of tooth firstly, and then compared with the theoretical involute tooth. Substitute the optimized diameter of grinding wheel and its installation angle into meshing equation, the wheel profile can be obtained by solving meshing equation with Newton iteration method. Wheel dressing and simulating analysis software are prepared based on VC++6.0.

Abstract: On the basis of establishing the mathematical model of grinding wheel profile by means of analytic method, the grinding wheel profile was determined. Different factors affecting gear form grinding was analyzed by means of numerical simulation. The form grinding wheel dressing software for grinding helical gear was developed, and the instruction for dressing grinding wheel profile was generated. Wheel dressing results show that the dressing software is correct and feasible.

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: Large-scale surface such as mould should have low roughness as well as high accuracy of geometry profile. And it is an essential method to reach the accuracy request with grinding process. In this research, due to the variety of geometry profiles, an Arc Envelope Grinding Method (AEGM) is presented, the difficult problem of grinding large-scale revolution surface can be solved. Meanwhile, the grinding wheel dressing and its shape precision are the keys to the precision of revolution surface in the grinding with AEGM. In this paper, the influences of setting error of diamond point dresser, which dress the grinding wheel into an arc section by using numerical control function of NC grinding machine, upon the shape accuracy of plate-shaped grinding are analyzed. It is shown that shape error of the grinding wheel increases with the increases of dresser setting error in diameter direction, radius of tip arc on the grinding wheel, while it reduces with the increase of radius of the grinding wheel, and shape error distributes no uniformly but symmetrically along axial direction.