A permanent magnet tool in ultrasonic assisted magnetic abrasive finishing for 30CrMnSi grooves part

The grooves of hydraulic cylinders are the main feature of its sealing structure. However, improving of the surface quality of grooves is a challenge problem using the present processing method such as magnetic abrasive finishing (MAF) and ultrasonic assisted magnetic abrasive finishing (UAMAF). A novel permanent magnet tool in UAMAF is developed for finishing 30CrMnSi grooves parts. The trapezoidal cross-section permanent magnet with a curved bottom is designed and applied with ultrasonic vibration. The ultrasonic vibration is produced by a 50 kHz piezoelectric transducer and transferred to a horn. The horn and permanent magnet are connected by the metal welding glue. The permanent magnet can absorb and excite bonded magnetic abrasives to process the surface of the grooves. Experimental measurements of magnetic field intensity and ultrasonic amplitude of the permanent magnet tool are conducted to certify the characteristics of UAMAF. The magnetic field intensity in the middle position is higher than the other positions on the curved bottom of the permanent magnet. The average ultrasonic amplitude of the permanent magnet at the curved bottom is 5.076 μm, and the maximum ultrasonic amplitude is 8.26 μm. Ultrasonic vibration slightly weaken the magnetic field intensity by 0.2 mT. The surface quality of the bottom surface and the sidewall of grooves parts under UAMAF and MAF are measured experimentally. Advantages of UAMAF are noticeable in the middle and later stages of processing between 15 and 25min. The boron carbide abrasives can allow for the lowest surface roughness value of 0.507 μm and the greatest roughness decline rates of 90.79% under UAMAF. The material removal ratio of UAMAF is 1.9 times than that of MAF. UAMAF can achieve a more uniform surface quality compared to MAF. The sidewall of grooves parts under UAMAF has a better surface quality than the bottom of grooves parts. It provides a novel method for finishing the grooves of hydraulic cylinders. •A permanent magnet tool in ultrasonic assisted magnetic abrasive finishing is developed. •Ultrasonic waves at 50 kHz can be used to excite the NdFeB permanent magnet. •Ultrasonic vibration will slightly weaken the magnetic field intensity by 0.2 mT. •UAMAF can improve the surface quality of the bottom and sidewall of grooves part.