Introduction to CNC with VCarve
Pumping Station: OneUpdated 2016-07-02
What is CNC?
Computerized Numerical Control
Translation: Robot tools!
Scope of this class
3-axis routing with 2.5D designs● A 3D object with no overhangs● Continuous XY movements with discrete Z steps
2.5D Examples
ShopBot projects: what’s possible?
X
Y
Z
The ShopBot’s 3 axes
Typical CNC workflow
Design
CADLine art
3D Model
CNC codeCAM
(Computer aided manufacturing)
MachineModel data
LayoutTooling
Feeds & Speeds
Typical CNC workflow
Design
CADLine art
3D Model
CNC codeCAM
(Computer aided manufacturing)
MachineModel data
LayoutTooling
Feeds & Speeds
VCarve’s capabilities
Other design software● CAD
○ Paid■ Inventor - @PS1■ Solidworks■ AutoCad
○ Free■ Fusion360 - @PS1■ OnShape■ SketchUp
… or anything that can output vector shapes
● Graphics○ Paid
■ Adobe Illustrator - @PS1○ Free
■ Inkscape - @PS1● Misc.
○ Free■ Blender ■ 123D Make
Vector designs● Curved or straight
lines instead of discrete pixels
● Can resize without degradation
● Common formats: SVG, AI, DXF
http://vector-conversions.com/vectorizing/raster_vs_vector.html
CAM – Computer-aided manufacturing
Process for converting designs into instructions that a CNC machine can understand
CNC code formats: G-code, OpenSBP
Example CNC code(Not for human consumption!)
3 Main CNC Toolpaths
● Profile - cuts along a path
● Pocket - removes material over an area
● Drill - plunge down with no X-Y movement
Choosing the right tool
End Mill properties● Cutting diameter● Shank diameter● Nose shape: square, V, ball● # of flutes (cutting surfaces)● Flute shape: up/down spiral, straight, roughing● Material
Good starting choice for wood: ¼” or ⅛” square 2-flute straight bit
Example router bittoolstoday.com
Important CAM variables - Cuts
● Pass depth - Cut depth per pass○ depth = bit diameter
● Cut depth - Total/final depth cut● Stepover - Distance between
adjacent passes○ Pocket cuts only○ 40% of bit diameter
All variables affect time and quality of job. Poor choices can cause tool wear or damage
Important CAM variables - Rates
● Spindle Speed - RPM of tool (12000-16000 rpm)● Feed rate - How fast does the tool move in X-Y?● Plunge rate - How fast does the tool move in Z?
a. ~50% of Feed rate
Chip Load Calculators can be found in Shopbot Controller, Online, HSM AdvisorChip Load Charts can be found Online
Calculating Feed Rate
Chip Load * # Flutes * Spindle Speed = Feed Rate
Material removed per flute cut. Varies with material and cutter diameter.
Approx. values for wood:⅛” cutter: 0.005”¼” cutter: 0.01”
Start at ~12000 RPM on ShopBot
Calculating Feed Rate - Example
Cutting plywood with a ¼” 2-flute end mill
Chip Load * #Flutes * Spindle Speed
0.01” * 2 * 12000 RPM = 240 inches/minute
Max ShopBot feed rate: ~360 inches/minute - much less for short cuts
Vectric V-Carve
- Demo -
Vectric V-Carve
Homework:1. Import or Create vector linework for a pocket and
profile cut into V-Carve or Aspire2. Practice creating pocket and profile toolpaths