18. (6 points) A cube with an edge length of 6 is cut into several identical smaller cubes with integer edge lengths. If the total surface area of these smaller cubes is twice the surface area of the original large cube, then the edge length of the smaller cubes is . $\qquad$
【Answer】Solution: Since cutting once adds two faces; the sum of the surface areas of the small cubes is twice the surface area of the original large cube;

Therefore, the increased area equals the original surface area;
Therefore, cut once parallel to each of the three faces;
Therefore, the edge length of the small cubes after cutting is: $6 \div 2=3$
Answer: The edge length of the small cubes after cutting is 3.
So the answer is: 3 .