This machine can not only polish flat sheet welds, but also polish the inner and outer surfaces of cylindrical welds. The beam is lowered to a suitable height and the weld is rotated directly below. The machine is polishing the internal weld of the tank. If polish weld seam on flat sheet, place the sheet in the same position and use the same method. The same way to grind the outer weld seam of the tank body. The grinding head is operated at a constant speed to grind the outer weld seam of the tank.