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