Can you be more specific as to how it is making the wavy line? It could be several things causing your issue? I had issues with mine right out of the box, but they were minor as I am very mechanically inclined and was able to fix them. One big issue was the arm on the back of the carriage that is supposed to hit the right and left stop switches was bent and would not activate the switches. So when you turned it on, it tried to drive the carriage right out the right side of the machine.... Very unnerving for the new user. Fortunately I was familiar with this type of cutter and new something was wrong right away.