PERSONAL ROBOTICS
■ FIGURE 17. First layout
for CNC cutting keychains
for Maker Faire.
hybrid of all the
different packages. For
example, my first
attempt at running the
machine involved
manual jogging and
running the motor
tuning setup within
EMC2. I then mounted
the standard tool
holder which is
designed to work with
a Dremel model 300 rotary tool and
then placed a felt-tip marker in it to
test out some drawings. I drew
several patterns using the various
tools and had success drawing on
paper taped to the work surface
(Figure 18). By now, I was feeling
more confident that I knew what I
was doing so it looked like it was
finally time to cut something.
■ FIGURE 18.
About 1.5”
square pattern
of lab glassware.
more substantial than packing foam.
MAKE: IT HAPPEN!
CUT IT OUT, ALREADY!
I installed my trusty old Dremel
model 385 Multipro and found it
wasn’t quite a snug fit. I shimmed it
with some thin card stock and was
able to use it for cutting in foam. In
fact, I even used one of the few
pieces of packing foam from the box
to carve the sample torus file in
EMC2 (Figure 19). Sure was nice of
PROBOTIX to provide some test
material!) Carving foam was fun for a
while, but then it was time to find a
way to make a sacrificial work surface
and come up with a clamping system
so we could cut something a bit
■ FIGURE 20. Custom-machined
aluminum shoulder washer holds a
CD steady as the Dremel routes a
gear pattern.
About this time, Maker Faire
Austin was approaching and The
Robot Group was preparing a list of
projects for the show. As we had a
nice new CNC router, we decided to
showcase it at the Austin event. We
decided the best way to demonstrate
the power of the router was to make
small give-aways of some type. After
toying with cutting shapes out of
recycled vinyl LPs (the finished vinyl
pieces turned out to be too fragile),
we decided on recycled CDs as our
media. This required a clamp that
■ FIGURE 19. First cut of Torus (rough
lower edge due to mismatch of cutter
and Z depth).
could hold down the CD so it could
be held tight while being cut. Again,
another Robot Group member came
to the rescue. Rick Abbott machined
an aluminum shoulder washer that
perfectly fit the hole in the center of
the CD (Figure 20). That solved my
HISTORICAL OVERVIEW
CNC was preceded by NC (Numerically Controlled) machines, which were
hard wired and their operating parameters could not be changed. NC was
developed in the late 1940s and early 1950s by John T. Parsons in collaboration
with the MIT Servomechanisms Laboratory. The first CNC systems used NC
style hardware, and the computer was used for the tool compensation
calculations and sometimes for editing.
Punched tape continued to be used as a medium for transferring G-codes
into the controller for many decades after 1950, until it was eventually
superseded by RS-232 cables, then floppy disks, and now is commonly tied
directly into plant networks. The files containing the G-codes to be interpreted
by the controller are usually saved under the .NC extension. Most shops have
their own saving format that matches their ISO certification requirements.
The introduction of CNC machines radically changed the manufacturing
industry. Curves are as easy to cut as straight lines, complex 3-D structures are
relatively easy to produce, and the number of machining steps that require
human action have been dramatically reduced.
With the increased automation of manufacturing processes with CNC
machining, considerable improvements in consistency and quality have
been achieved with no strain on the operator. CNC automation reduced the
frequency of errors and provided CNC operators with time to perform
additional tasks. CNC automation also allows for more flexibility in the way
parts are held in the manufacturing process and the time required to change
the machine to produce different components.
**From Wikipedia
December 2008 73
