I've been cutting glass plates and
mirrors with my CNC milling machine machine for years. In this video, I describe a few tips and the
general technique that I use.
Clamping the glass plate to the table is
the critical part of the process, and so I built a jig that allows the glass to
be held laterally with shims, but does not require a high clamping force, which
would crack the glass.
Cutting parameters:
.085" dia diamond burr
3000 RPM
1-3 inches per minute feed
Cut depth .130" (full material
thickness)
Flood coolant with soluble oil cutting
fluid
here's a technique
that I use every once
in a while that doesn't have much
documentation on the net I CNC cut glass
and mirrors if you need a piece of glass
or a mirror in a shape especially if it
has curves involved you will not be able
to cut it with a typical score and break
type method I mean at least not for
curves like this so this piece of glass
started off as a plain rectangle and I
cut it using a CNC mill and a diamond
bur tool so the biggest trick with with
milling in general but especially
milling glass is that clamping is is the
trickiest part so I use this jig right
here Oh break my miracle use this jig
right here and the glass gets put inside
here and shimmed so that it can be held
in a horizontal direction and vertical
direction without actually pinching it
obviously if we took a conventional
milling hold down clamp and tightened it
on the glass it would just break
instantly so this has rubber pads on the
underside so the glass sits in here gets
shimmed up vertically and horizontally
and then I just screw this on the rubber
pads just keep the glass from lifting
but during the cut there's not much
lifting force because the diamond bird
is flat it doesn't have flutes so the to
the milling machine isn't trying to pull
the glass up but this just makes sure
that it doesn't come up of course you'll
need cutting fluid and I like using a
soluble oil actually I use it for pretty
much everything aluminum sometimes
plastic and definitely glass and that
keeps the cutter tool cool and also
keeps the glass from heating up at the
point where it's being cut and breaking
due to thermal expansion the feed rate
is quite low
I usually program the file for about
three inches per minute and then slow it
down on the control panel on the front
of the machine to maybe like one inch
per minute and use the dial to kind of
you know judge it up and down this
particular mirror is brutally expensive
I got this from Edmund optics and it's
actually a custom item it's a cold
mirror
meaning that it's transmissive to
infrared and reflective to visible light
and if you think their prices are bad
for stock items just wait until you
order something custom from them so go
in with the absolute slowest feed rate
possible is really the best plan since
cracking one of these would be an
expensive mistake also I don't plunge at
all into a mirror or piece of glass or
at least I never have in the past what I
do is I set up the jig so that it has a
pocket on the outside of the cut so the
cutter tool can go down into the pocket
and then cut across and then come back
up so it doesn't actually have to plunge
through the glass I think the cutter tip
itself would probably not be ideally
suited for that it would really be
better to use a actual glass drill bit
instead of a carbide or instead of a
diamond burr as you can see the edge
finish is really quite nice it's not
sharp to the touch like it would be
after scoring and breaking and you can
round off the corners like that quite
nicely
there's no chipping on the reflective
surface this is the first surface mirror
so the eye you could actually look at it
as a mirror from this side because you
can see there's a double image so when
using it on this side it's the first
surface is reflective so there's no
ghost image there the CNC machine itself
is a Bridgeport series one our two III
with a boss 8 controller so this is a
quite a vintage machine here it's kind
of an Old Yeller
but I shouldn't insult it because it
served me quite well over the years I've
made lots and lots of parts with this
machine and the the iron is quite good
probably better than a lot of modern
import machines the things you know the
table waves and everything are very
solid I used some old CAD cam software
because I don't have enough money to
afford SolidWorks or Master cam and the
machine is controlled through a serial
port from an old dos program on my
garage laptop out here and I've been
using the same setup for a long time
five six years or something and
eventually I'll upgrade I was thinking
of
putting the Ajax servos and controller
on this machine but I really want to
keep the iron because it's just
amazingly solid alright guys see you
next time bye
s
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