36 / 2021-03-25 16:51:28

A New Knurling Technology Using Ultrasonic Vibration

Knurling, Ultrasonic vibration, Groove, Pressing force, Texture

Sliding surface in mechanical system is required to move smoothly and stop at target position. Sliding surface can move and stop by applying adequate friction force. Friction force is controlled by developing technology creating small texture on the surface with a few to a few hundred micrometer intervals. On the other hand, ultrasonic vibration is used in many manufacturing fields. It is well known that surface roughness is improved and welding residual stress is reduced using ultrasonic vibration. In this study, machining technology is developed creating wear resistant texture on large area sliding surface with high precision and efficiency using ultrasonic vibration during knurling. This technology is named as Micro Ultrasonic Knurling : MUK. In this paper, the effect of ultrasonic vibration on knurling is examined by the fundamental experiment.

First, a processing machine using the 3-axis feed table is designed and made in order to examine the effectiveness of MUK. The pressing tool with texture is fixed by bolts at the tip of holder. An experiment is made using specimens with extra super duralumin (JIS, A7075P) and copper (JIS, C1100P). Pressing force is fixed and surface of the specimen is observed. For both specimens, clear marks are formed in wider range and the groove is enlarged, deeper and clearer marks are formed when ultrasonic vibration is used during knurling. The effect of ultrasonic vibration for the specimen made of copper is larger than that made of extra super duralumin.

Next, small grooves are created by an indenter on the surface of workpiece in order to evaluate above mentioned results. The indenter is set at the tip of horn and pressed in vertical direction. Workpiece is fed in lateral direction. Width and depth of groove are measured. Two ultrasonic vibrations with different frequencies are used. As a result, groove is wider and deeper using ultrasonic vibration. Width and depth of copper are wider and deeper than those of extra super duralumin. Width and depth are almost proportional to frequency of ultrasonic vibration.