Cause Analysis：

1. Horizontal sharpening, the wear scar is perpendicular to the axis of the electrode; 2. The wear scar is rough, resulting in scattered discharge points; 3. The pointed tip does not meet the requirements.

solution：

1. Use longitudinal sharpening; 2. Use a grinding wheel with smaller particles; 3. Determine the size of the sharpening part according to the arc concentration requirements.