Study On Ultrasonic Assisted Grinding Technology Of Quartz Fiber Reinforced Polyimide

Polyimide resin matrix composites are widely used in aerospace industry, national defense industry owing to the advantages of high temperature resistance, good mechanical properties, stable physical and chemical properties and low dielectric constant. Serious issues exist in the traditional machining methods, including severe tool wear, large cutting force and low production rate, due to the structure and physical properties of polyimide resin matrix composites. In this paper, ultrasonic assisted grinding of quartz fiber reinforced polyimide was proposed. An experimental machine was set up, on which the grinding experiments of polyimide resin matrix composites were conducted. Grinding force and surface roughness experiments were tested, and the performances of diamond wheels were discussed. The study can be summarized as follows:(1) According to the characteristics of ultrasonic assisted grinding, a frequency tracking method was proposed. An ultrasonic assisted grinding system was designed, which included an ultrasonic generator, a contactless power transmission system, a ceramic transducer and an ultrasonic horn. Finally, an experimental machine was developed by integrating ultrasonic vibration system on a three axis numerical control vertical milling machine.(2) A comparative study of ultrasonic assisted grinding and common grinding of quartz fiber reinforced polyimide composites was conducted to research the grinding force and grinding performance respectively. The influence of grinding parameters on feed and axial forces was obtained through single factor experiment. The results indicated that the feed force could be reduced by30percent at most and the axial force by35percent at most under the same grinding parameters. As for grinding performance of diamond wheels, blockage of diamond wheels increased fiercely in common grinding, which didn’t exist in the ultrasonic assisted grinding. Considering the comparison of the two processing methods made to evaluate the axial force, ultrasound assisted grinding possess had obvious advantages.(3) This paper presented a study of surface quality of quartz fiber reinforced polyimide materials after ultrasonic assisted grinding. A series of ultrasonic assisted grinding single factor tests and orthogonal tests were carried out under different processing parameters. The results of single factor experiments indicated that the surface roughness increased along with the rise of feed rate, and decreased with the rise of spindle speed, whereas it had no obvious relationship with grinding depth. The results of orthogonal experiments showed that spindle speed had the largest effect on surface roughness, and the grit size of diamond wheels had the least effect. The best surface roughness was obtained with the optimized parameters, where the value of Ra is1.33μm.