I am new to milling and just an amateur, so please excuse my perhaps basic question. I am currently building a CNC of my own design, and the initial tests seems to be promising. I have done some CD writing and that seems fine. However, yesterday I thought I'll test milling some soft plastic and run a surfacing program but I am not very happy with the results. I made a short video, please have a look at it and tell me what you think, why the plastic is not cut, more like sliced.

Am I having too high, or too slow feed rate? I had it set to 220mm/min (8in/min) and also tried with 180mm/min (7in/min) but it made no difference.
Am I having too little overlap? I am using a 2mm end mill and the overlap is 0.5mm, in other words, I move the mill 1.5mm at each turn around.
Am I having too high or too slow RMP on the spindle motor? I run it with 36V and that supposed to give me about 9000-10000 RPM. Have not measured it, so that's just a guess from the motor performance.

Could any of you give me an advice about why the cuts look like they do in the video?

https://youtu.be/nXi6z5D0_zo

I made some hand wheels (also can be seen in the video) out of the same material before, and those were made using a bench drill machine with a circular cutter in it, and even those cuts look ugly. I really don't know why.

Thanks.