I teach high school metals classes and I have to say that your cuts look similar to what I see coming from my students the first couple of times they try it. Just keep working at it and you should see better results. It almost looks to me like your travel speed was a little fast. That actually is the biggest problem I have with my students, getting them to slow down and let the machine do the work. Either too high or too low a travel speed can cause dross to form.There is usually a range of travel speed that will produce dross free or minimal dross cuts. That range is something you will have to find while playing around with the machine.

Good Luck,