May it have served as cutting lube? What do you think?
I don’t know, sometimes I have to machine a pre-existing object, so the paper
has been removed, and at other times use virgin stock with it on.
In practice, I haven’t seen much difference, although in the back of my mind
I’m thinking, that paper is stuck on with adhesive so would it stick the light weight
chips to the cutter.
Polycarbonate’s super power is impact resistance, scratch resistance not so much.
There are formulations, where a thin glass hard like layer is applied during manufacture
to help this.
Polycarbonate starts to slump at 140 Deg C and melts at 300 Deg C.
This is one of the reasons that 3D printed “under the bonnet” items are made from
ASA or some other higher melting point plastics are used.
If you want to remove the tooling marks in the bottom of the cut, there are two
common ways to do this, Flame cleaning where you use a very gentle lpg gas flame
and pass around the cut surface, I’ve done this and it works but you have to keep the flame
moving at a consistent pace.
The other method is to use Vapour cleaning, the 3D printer crowd use this method to
cleanup and eliminate Layer lines, I haven't done this as I looked at the materials safety
data sheet, and thought I’d give it a miss.
I don’t know if it’s my imagination or not, but looking at the tool marks at the bottom of the
cuts (on the outer periphery) it looks like the tool is digging in at times, so the tool is porpoising
along as it’s making the cut, It might pay to check the backlash in the Z axis, on your type
of machine the Y axis can contribute to this as well, if you look at the wheels on the Y axis
and they appear to have a white ring around them, then they have worn in a little and need a snug up.
Love to see your work, always puts a smile on my dial.
Dave