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On the other hand, crawler-type centerless grinder also attracted the attention from industry and academia. designed the vacuum of hydrostatic crawler increase load capacity and stiffness of the track centerless grinding machine for high-precision applications in a plane. proposed the effectiveness of the dynamic model display hydrostatic crawler improve stability. survey tracked the basis of centerless grinder fixture mechanism system, and presents a theoretical model to predict driving grinding system the ability to resolve the fixture stable. In addition, developed a 2-D geometric model forecast track centerless grinder lobe generation and model analysis of the grinding process.
From the production cost point of view, the two types of the centerless grinding machine is very suitable for the production of small species and largevolume the loading / unloading of the workpiece is very easy and fast. However, the centerless grinding machine a special-purpose machines and more expensive, it disadvantages a large variety and small batch production, in recent years, the rapid increase in demand. As a solution to this problem, the authors propose a new centerless grinding machine technology, you can perform surface grinder before. This method is based on the concept of ultrasonic crawler centerless grinding machine developed by Wu et al. (2003, 2004). Method, a compact unit based ultrasonic elliptical vibration crawler, a blade of their respective holders installed on a surface grinder table. This function ultrasonic crawler cylindrical workpiece is held in conjunction with the blade and control the workpiece speed on the end face of the elliptical motion.
According to the relative movement of the workpiece grinding wheel, three types of centerless grinding operation is performed in the proposed method type: tangent feed type, feed type, and through the feed. The tangential feed type, Xu. (2010) created, taking into account the model 2-D grinding machine, in order to clarify the elastic deformation of the workpiece rounding process and process parameters workpiece roundness, simulation experiments confirm the results. Further, Wu and Xu (2010) proposed an actual increase in the material removal rate, and the final roundness maintained in the tangential feed of the high-level method. Feed type, Xu and Wu (2011) experiments confirmed its performance a simulated forecastWorkpiece rounding process. The simulation and experimental results obtained show that the eccentric angle 6 °, high machining accuracy can be obtained under a lower grinding wheel feed rate, the greater the cutting and faster workpiece rotation speed. The purpose of this document is to verify that feed type centerless grinder surface grinder. To do this, first the corresponding experimental device through the feed type centerless grinding machine is constructed by modifying the second is the existing tangent to feed type workpiece motion control tests to ensure that the speed of the workpiece and into the pass rate can completely control ultrasonic crawler, achieve high-precision grinding operations. Then grinding the actual operation carried out to clarify the effects of the main process parameters, such as the eccentric workpiece stock removal, ultrasonic crawler tilt angle and perspective applied voltage, the amplitude of the machining accuracy, i.e. the cylindrical workpiece round. 2. Surface grinder feed centerless grinding operation principles.
Figure 1 illustrates the principle of operation through feed centerless grinding method and detailed experimental device construction. Establish the instrument by installing the grinding unit, composed of an ultrasonic elliptical vibration, the holders of the track, blades and holders, guide plate and the bottom plate to a surface grinder table. Grinding units, the crawler sub-structure bonding the piezoelectric device ceramic (PZT) separated the two electrodes (a and b) to the metal elastomer stainless steel (SUS 304). When both A (AC) signal phase difference (VA = the VP-PSIN (2 feet), VB = VP-PSIN (2 ft +), wherein (more than 20 kHz frequency f and VP-P) and the amplitude AC voltage) application of piezoelectric ceramics, bending and longitudinal ultrasonic vibration is very pleased to ultrasonic crawler. The synthetic vibration displacement in both directions, create an oval face metal elastomer (2005) motion. Therefore, the friction between the ultrasonic track the movement of the workpiece, the elliptical motion can be controlled through the workpiece. Constraints between the workpiece, the grinding wheel, the relative position of the blade and ultrasonic crawler wheel To determine ˛ eccentric angle (see Figure 1 (a)). When the ultrasonic crawler is parallel to the grinding wheel axis, i.e. gamma = 0 ° (hereinafter referred to as the tilt angle), the crawler generated by the frictional force FF between the workpiece and the ultrasonic elliptical motion in the x direction only, and is used to control the rotational movement of the workpiece, In the tangential feed type (Wu et al, 2005; Xu et al, 2010), and the feed type (2011) centerless grinder, so that the circumferential speed of the workpiece the same as the track surface of the end face of the bending vibration velocity. However, through the feed type centerless grinding the workpiece need not only rotational movement, but also through the feed motion along the z-direction, and therefore the ultrasonic crawler is, in a small angle of inclination, i.e. gamma ≠ 0 (see Figure 1 (a)), to provide adequate components FFA, friction, to control the workpiece through the feed motion. As can be seen, in traditional feed centerless grinder small taper lead size grinding wheel across a greater area of the wheel major stock removal shown in FIG. 1 (b), wherein the the trimming depth and HD trimming length. After the wheel, set at a given distance from the ultrasonic crawler track on the end face, the workpiece is located in the space between the grinding wheel and the ultrasonic crawler guides and Fed. Once the interference with the workpiece clockwise rotation of the actual action of the grinding wheel in the axial direction into the NW direction of the wheel speed of the workpiece in a VFA feed rate. Once the workpiece through the trimming area, the desired stock removal rate and the spark process begins, until it loses contact with the grinding wheel. In addition, the blade is wedge angle (often referred to as the blade angle) and the value of 60 degrees is generally set in the best workpiece Harrison and Pierce (2004) rounded prove. Experimental apparatus and the workpiece motion control test.