CNC Machining 101

An introduction to 3-axis CNC machining using the Blacktoe router
Bo Pollett
Neil Moloney
12/10/13 - 19:00
 David Stewart
 Andrew
 Fred Briggs
 Robb Stacy
2.5D Machining
 Cuts profiles and pockets
 Drills holes
3D Machining
 Complex curvature
 Smooth surfaces
Create large projects
True 3D surfaces with accurate depths
Dimensions are accurate to +/- .010
CNC operated from CAD model file
Able to cut foam, plastic, wood, MDF,
aluminum, and composites
Can not undercut in a single operation
Takes a long time to get smooth surfaces
Can not cut very hard materials like Steel or Ti
Requires more understanding and training than
2D machining like the laser cutter
Requires attention or it will misbehave
 Ensure end mill does not hit a clamp/screw
 Ensure the feed is not so fast as to overheat the
material or overstress the motor
 Stop the machine if there is an unexpected failure
Bay size is 48 X 24 X 4 IN
 There is a 1 inch margin for machine operation on all sides
so max material size is 47 X 23 X 2.5 IN
 The bay has provisions for clamps, but screws work better
for harder materials
Can be chucked with 1/8 or 1/4 end millsRPM Speed is
5000 – 28000 RPM
Run Feed up to 100 in/min (faster is not always better)
Has +/- .010 IN accuracy
Can be jogged manually or by the computer
Has built in vacuum provisions
Has a electronic depth sensor
Has emergency stops to prevent overrunning
Z-Axis (2.5 IN)
Cutting Bay
Y-Axis (23 IN)
Local (0,0) for the part
X-Axis (47 IN)
Cut out 2D shapes using a DXF file
Minimum Inside radius
Different end mill bits can create bevels, etc.
Different depths can be used for engraving or
Gcode is crated in ArtCAM. For cutting flat sheet like carbon fiber or plywood there are
several options
Border and Raster
This method created a smooth edge and leaves clean
witness marks on the bottom of the part. This is useful for
pocketing out areas in softer material since the bit will
have to climb cut
Radial Boundry
This is the more common practice since the end mill will
be in contact with a cutting edge in only one direction.
This also cuts the inside first which reduces the chance for
the part to slip.
6-8 R cutting
depth to prevent
cutter bending
Various cutter styles can be used depending
on the geometrical requirements
When pocketing out an area, the end mill selection will determine if you have a flat
bottom or a scalloped surface. Additionally, a ball nose end mill wil lcause all the
inside corners to be radiused.
Gcode for 3D parts is always raster in
ArtCAM. You can select between raster in
X, in Y, or in both. This will let you choose
the direction of your “scallops”.
Reducing the scallop effect can be
accomplished through several methods
which will be discussed in the next slides.
Bigger stepovers make rougher surfaces
Smaller stepovers make smoother surfaces
These are good for soft materials like foam that can be easily
sanded later
These are good for hard materials where big stepovers would
cause too much heat buildup. Smaller stepovers allow for faster
speed as well which compensates for the small amount of
cutting on each pass.
.75D Stepover
.5D Stepover
Creating inside corners that are larger than your end mill radius will ensure you do
not bind in corners. Binding can cause bits to break, parts to shift, or poor surface
.25” Radius Inside Corner
.375” Radius Inside Corner
.25” Radius End Mills
Cleaning – use the vacuum and brush to clean
out all the areas where dust and debris can
Ensure that all the tools and materials used
are put away
Empty the vacuum if it is getting full
Record your time so we can keep the machine
Clamping can be used to hold
light materials (soft or thin)
 Must be cut slowly or part will
Dense or thick materials must
be held with screws
 Jog the cutter to the extents of
your tool path to check your work
size so you don’t cut into a screw
0,0,0 can be set using the
monitor or the hand controller
Z=0 can be set at the top of
your material or at the bottom
Create a CAD model in Google Sketchup or
other CAD program (.stl file)
Create a toolpath in ArtCAM (.art file)
 Export the Gcode
Run the Gcode in CNC USB (.tap file)
The mill has a spinning blade
 Don’t put your hand under the
mill when running
The mill is loud
 Use ear protection
The mill likes to spit out
 Wear eye protection
Create a CAD model as an .STL file
Turn on computer and CNC board
Import the File to ArtCam
Align the model with the workspace
Define the Toolpaths
Generate the G code
Import the G code into CAM operator
Insert the proper end mill (use wrench and lock button)
Zero the machine head
Put on safety glasses and ear protection
Turn on the vacuum and spindle
Run the G code in CAM software
Part cutting is complete and spindle returns to home
Turn off spindle and vacuum
Remove part and clean up area
Log your time and turn off the computer
CAD software
 Sketchup, Turbo CAD, AutoCAD, Inkscape, SolidWorks, Creo (Pro E), Catia
CAM Software
 ArtCam, MasterCam, FreeMill, CamBam, PyCam
Informational Sites
 Great source of terminology
 ArtCAM walkthrough
 ArtCAM tutorial videos
 CNC USB website
 CNC USB Tutorial
We will use a STL file in ArtCAM to create a 3D
raster Gcode file
We will run the Gcode to trim styrofoam into
a flying wing using raster along the streamline
We will use ArtCAM to import dxf files of the
outline of the keychains, The hole for the plastic
inset, and the hole for the keyring
 Secure the material to the board
 Ensure safe operation (eye and ear protection)
 Cut the holes then the outline with a cutting bit
 Remove and clean station

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