CNC Machining 101An introduction to 3-axis CNC machining using the Blacktoe router

Instruction

Bo Pollett Neil Moloney

Class List

12/10/13 - 19:00 David Stewart Andrew Fred Briggs Robb Stacy

3-Axis Machining Capabilities

2.5D Machining Cuts profiles and pockets Drills holes

3D Machining Complex curvature Smooth surfaces

Project Ideas

Blacktoe CNC Router Capabilities

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

Blacktoe CNC Router Limitations

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

Blacktoe Specifications

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

Coordinate System

X-Axis (47 IN)

Z-Axis (2.5 IN)

Y-Axis (23 IN)

Cutting Bay

Local (0,0) for the part

2D CNC Parts

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

pockets

2.5D Tool Path Options

Gcode is crated in ArtCAM. For cutting flat sheet like carbon fiber or plywood there are several options

Border and RasterThis 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 BoundryThis 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.

Cutter Selection

6-8 R cutting depth to prevent cutter bending

Various cutter styles can be used depending on the geometrical requirements

2.5D Bottom Surface Radius

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.

Example of 3D Part

Another 3D Example

3D Tool Path Options (Raster)

http://www.arch.virginia.edu/arch549/handouts/artcam-toolpaths.html

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.

Stepover on Complex Surfaces

.75D Stepover .5D Stepover

Bigger stepovers make rougher surfacesThese are good for soft materials like foam that can be easily sanded later

Smaller stepovers make smoother surfacesThese 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.

Smooth Radius Transitions

.25” Radius End Mills

.25” Radius Inside Corner .375” Radius Inside Corner

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 finish.

Machine Maintenance

Cleaning – use the vacuum and brush to clean out all the areas where dust and debris can accumulate

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

running

Locking Parts to the Work Bed

Clamping can be used to hold light materials (soft or thin) Must be cut slowly or part will

slide 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

Part Held with Clamps & Spray Glue

Large Part Held with Screws

Setting the Home Location

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

Software Process

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)

ArtCAM CNC USB

Safety

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

debris Wear eye protection

Steps for Building a Part

1. Create a CAD model as an .STL file2. Turn on computer and CNC board3. Import the File to ArtCam4. Align the model with the workspace5. Define the Toolpaths6. Generate the G code7. Import the G code into CAM operator8. Insert the proper end mill (use wrench and lock button)9. Zero the machine head10. Put on safety glasses and ear protection11. Turn on the vacuum and spindle 12. Run the G code in CAM software13. Part cutting is complete and spindle returns to home14. Turn off spindle and vacuum15. Remove part and clean up area16. Log your time and turn off the computer

References

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

▪ http://www.hsmworks.com/docs/cncbook/en/ ArtCAM walkthrough

▪ http://www.arch.virginia.edu/arch549/handouts/artcam-toolpaths.html ArtCAM tutorial videos

▪ http://www.youtube.com/user/delcamartcam▪ http://www.artcam.com/videos-and-tutorials.asp

CNC USB website▪ http://www.planet-cnc.com/index.php?page=software

CNC USB Tutorial▪ http://www.planet-cnc.com/files/CNCUSBController.pdf

Let’s Start Making

Project 1 – Airplane

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

Project 2 - Keychains

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