Hey so I am engraving polycarbonate using a 30 degree tipped engraving bit from harvey tool. I am cutting a depth of .009 at .7 IPS and 21000 RPM. I am engraving a reversed image into what becomes the back of the piece. When the piece is finished it all looks good but I am getting a slight ridge on the back of the piece where the lines are. This is not critical in this case but I have some up coming projects where it will be. I am pretty sure this can be resolved my adjusting my speeds and feeds but am having no luck. Any info anyone could share would be great