Grinder to cut hardboard

I laser cut some part incorrectly out of hardboard. I had a grinder (for metal) installed on my RotoZip. I was lazy and decided to use it to trim up the hardboard. It doesn’t cut very well. In fact it burns. It burns in a way that you can’t tell where the laser was cutting and where I was cutting.

The part looks as if I knew what I was doing!