Hi,
I have a second hand Roland MDX-15. So far I have only used it for cutting/engraving plastics and foam for
buildings. I intend using it for rolling stock in the future. It can (apparently) cut aluminium, brass and NS
if you go very slowly, but I notice that Roland don't advertise their more recent machines as having that
capability- perhaps they realised they were on the limits of what was practical with the machine.
I have experimented with ABS, polystyrene sheet, acrylic sheet, foamex/palight, foam board (expanded
polystyrene core, and Kapa brand foam board (PU core).
With cutting plastics the main problem is heat. The chips heat up and then reattach themselves leaving
you with a nasty burr and also a buildup of plastic around the cutter. If you are engraving or milling a
pocket the melting/remelting can also leave an unsatisfactory finish at the bottom.
The cheap Chinese carbide cutters with 1/8 inch shanks are really intended for milling circuit boards. I
feel they're not all that sharp and they create a lot of heat.
I get my best results by using Clarke FC3 throwaway cutters (about £5 each, and nice and sharp) to remove
the majority of the material. These give a nice finish at the bottom of the pocket. Then use a small FC3 to
remove the last 0.1 mm from the edge, and finally a Chinese 0.5 mm carbide to go into the corners. I have
a non Chinese 0.5 mm cutter (much more expensive, but hopefully sharper) but so far i haven't needed to risk it-
its really easy to break the small cutters, even on plastic.
The FC3 cutters have 6mm shanks and fit the machine perfectly. The machine came to me with a shop made
adaptor for 1/8 inch shank tools, but I found this had excessive run out, and tended to overcut into the corners
of pockets (when using the tool path I just described). I was able to make a replacement for this. I also found that
the machine had excessive backlash on the x-axis which could sometimes be compensated for in the tool path
but not always. I was able to remove most of this backlash once I got hold of a service manual for the machine.
I use Fusion 360 software for the CAM. It allows a lot of control over the tool paths and is free for hobbyists.
Unfortunately they expect backlash compensation to be done in the machine firmware which is not the case
for my machine.
Be aware that the stepper motors only give open loop control of position. With a laser cutter this is not a big
problem because the mechanical forces are unaffected by the material being cut, but with an engraver/mill
the forces depend on the material and depth of cut. More expensive machines control position with servos and
encoders and can compensate for this, with steppers you will have to be more conservative with
cutting speeds and depths.
I hope you find this relevant. I will take some photos later today and upload them.
John