Week07 Adults¶
Week 7 Group Assignment: Computer-Controlled Machining¶
Assignment pages:
As an entire lab, Mr. Dubick showed us a live demo of the ShopBot. We were given access to the lab’s digital CNC workflows. The provided workflows are the only workflows we are allowed to use when running the machines, to ensure they are always up to date. We discussed safety, additional tools, tips and helpful hints, controls and commands, and more detailed below.
Mr. Dubick recommended Make: Design for CNC as a great book on furniture design. He also shared this video on making a simple Fusion cabinet design.
Definitions¶
These terms come up constantly in CNC work. It’s worth having clear definitions before touching the machine.
RUNOUT The wobble or eccentricity of a spinning tool as it rotates. If a bit isn’t perfectly centered in the collet, it traces a slightly larger circle than its actual diameter. Even 0.01mm of runout matters enormously in PCB milling where trace gaps can be 0.2mm. Caused by dirty collets, worn spindles, or improperly seated bits. We don’t need to address this manually because the ShopBot has an automatic tool changer.
ALIGNMENT How accurately your material, machine axes, and toolpaths are oriented relative to each other. Includes tramming (spindle perpendicular to bed), XY squareness, and workpiece alignment to the machine coordinate system. Misalignment on a PCB board means traces shift and won’t match your design.
FIXTURING (Material Fixturing) How you physically hold the workpiece to the bed so it doesn’t move during cutting. Methods include double-sided tape, vacuum tables, screws/clamps, or sacrificial boards. For PCB milling, double-sided tape is most common. Bad fixturing = ruined board.
SPEEDS Spindle RPM — how fast the tool is rotating. Too slow causes rubbing and heat; too fast on the wrong material causes melting or tool breakage. Usually specified in RPM (e.g., 10,000–30,000 RPM for PCB milling).
FEEDS How fast the tool moves horizontally through the material, in mm/min or in/min. Feed and speed are paired — running high RPM with too slow a feed causes rubbing and burning; too fast a feed snaps the bit.
MATERIALS The physical properties of what you’re cutting — hardness, abrasiveness, chip formation behavior, thermal sensitivity. Determines your speeds, feeds, tooling choice, and dust/safety precautions.
TOOLPATHS The programmed routes the cutting tool follows, generated by CAM software from your design. Types include isolation routing (cutting around traces), drilling (vias/holes), and board outline (profile/cutout). Toolpath strategy affects cut quality, machining time, and tool wear.
Safety¶
PPE — Personal Protective Equipment¶
- Safety glasses
- No loose clothing
- Hair, jewelry, ID tags, and sweatshirt strings all secured
- Closed-toe shoes
- Ear protection should not block out all noise — you must be able to hear in case of emergency
Key Points¶
- Only use the machine when an experienced adult is present in case of emergency.
- Make sure the dust vacuum is on and not full before you begin the process.
- When working in a group: Announce your actions!
- When the machine is running, stand behind the yellow tape.
- Remain by the computer with eyes on the machine while it is cutting so you can pause the program quickly if needed — keep your hand by the space bar.
Issues and Emergencies¶
- Minor, non-threatening issues: Use the space bar to Pause/reset.
- Emergency: Press the red emergency button to stop. Tell the adult in charge — the machine/system will need to be reset.
Start of Day Routine¶
- Do not adjust the valves
- The startup program takes about 9 minutes to run — the green button starts the drill head
- Open vents > turn on vacuum
Homing and Alignment¶
The machine startup program sets X,Y home coordinates to the corner by the walkway farthest from the computer, and Z zero to the height of the last spot of the tool head holder.
- No jogging all 3 axes at once
- Uses proximity sensors to adjust XYZ
- Home Z about an inch above your wood
- Don’t go above 7 inches — this can cause it to go out of range of the proximity sensor
- Always check your wood at the beginning; on humid days, check again at the end
Material Fixturing¶
Measure your material thickness before adhering to the ShopBot table.
Nail Gun
- Nail gun is in the cabinet under the computer
- Use plastic nails, sized 1/2 inch larger than material thickness
- Plastic nails don’t cause problems in later production (sanding, cutting, laser engraving) and shear off easily when removing the project
- Do not use metal nails — they can become shrapnel
Air Cuts¶
Air cuts are done first to confirm the machine will cut in the correct location.
- Bring the bit down to about an inch above your board
- Use the
ZZcommand to zero the origin in air - Load your file (File > Part Load)
- Start the spindle
- Read and follow all prompts
- Run — use space bar to pause, red button for emergency stop
Note
You must restart the spindle after an emergency stop.
Why air cuts?
- Confirms you are in the right spot on your wood
- Lets you verify things are working correctly before cutting actual material
Relevant commands during air cuts:
| Command | Action |
|---|---|
ZZ |
Zeros and sets new origin |
JZ [value] |
Jogs Z axis to input value |
C3 |
Rehome (run after air cut is complete) |
After air cuts, run C3 to rehome, then JZ 3 (or jog to about an inch above the wood) before starting your actual cut.
Aspire Software¶
- DXF (Drawing Exchange Format) files are primarily 2D
- When exporting from Aspire to Aspire: check settings — no offset, X and Y at bottom left corner
- Add dogbones in Aspire, NOT in Fusion
- To check cut time: Toolpaths > Outside > right-click/hover > Cut Time
ShopBot¶
Key Facts¶
- Has an automatic tool changer
- Bed dimensions: 48” (Y) x 96” (X) — look for the sticker on the gantry
Interface¶
- Red screen: shows live XYZ positions and command console
Main Commands¶
| Command | Action |
|---|---|
C3 |
Home |
JX [value] |
Jog X axis |
JY [value] |
Jog Y axis |
JZ [value] |
Jog Z axis |
Full reference: ShopBot Command Reference (PDF)
Running a File¶
Don’t just click next through the prompts — read what the machine is telling you.
- First pop-up: Start router > hit the green button
- Check/listen for the spindle
- Press OK on screen
End of Day¶
- Bleed the machine — this removes air and moisture that can rust out the system
- Turn off everything
Other Tools¶
Kerf Testers Available on the walls of the lab. Can be used as a starting point for kerf value, but always check with your specific project wood.
Shaper3D
- Handheld CNC
- Has a gimbal - auto corrects to follow your lines
- Like the beeps in a car when you list towards the lines on the roads
- Portable, lightweight, handheld, safer than the typical CNCs
- Great for Inlays and decorative work
Shaper3D procedure:
- Shaper3D set up includes a bench attachment for smaller pieces. For large pieces you can put the domino-like marking tape directly onto your material. The material must be flat. Use the lever, marked in this image, to level the wood.
- The settings menu is in the top right of the screen. Internet connection, and machine information is found there.
- The menu option under settings is scan. Use that to set up the machine. You must have at least 3 rows of marking tape. Move the machine in the scan option until all the markers appear blue on screen.
- Select your design by clicking the design menu on the right under scan. Then import or create your design. Import files in svg format. The create menu is very simple, but you can copy, paste, and rotate objects. Dorian created a butterfly with the pen feature, and a flower with the circle option. Mr. Dubick loaded a leaf design for us to practice on.
- Choose your cut by clicking on the cut menu on the lower right.
In the cut menu you will see the depth of your cut, we used 0.125 inch. The pocket or type of cut, the diameter of the drill bit, we used an 0.125 inch drill bit. The Z-touch for zeroing the z-axis, and the speeds.
Once selected a moving dotted line will mark your toolpath or the pocket cut will be crosshatched.
Cut
You must have both hands on the handles or the machine will not work.
Turn on the vacuum for dust control. A mask would also be good because the chips created from this process are very fine.
Flip the switch in the center to turn on the drill.
Press cut with your right hand to start your cut.
It is important to follow the dots. The machine will stop if you go backwards or stray from the path.
Press retract with your left hand to bring the drill up.
Switch the machine off if you are in between cuts.
Vacuum the station when you are done.
