Makerspace

The Bantam PCB Mill is a CNC (Computer Numerically Controlled) tool specially designed to cut custom circuit boards. The Bantam Mill is also capable of machining traditional milling materials like plastics and metals. In this workshop you will cut a circuit board which can be soldered together into a working circuit. After taking this workshop you are certified to use our Bantam PCB Mill during drop-in hours. Refer to the makerspace calendar to find when this workshop is offered.

You will learn:
 - To operate a PCB Mill
 - Rules and Safety Protocols

Before attending this workshop:
 - Download the Bantam Milling Software to your laptop
 - Register to attend the workshop

The Bantam PCB Mill creates printed circuit boards by milling (precisely removing surface material) from PCB blanks, which are simply plastic sheets coated in copper. Copper is conductive while plastic is not. By precisely removing surface material we can create paths (AKA traces) which transport electricity from one component of the circuit board to the next. 

Besides PCB blanks, the Bantam Desktop Mill can also machine materials such as brass, aluminum, wood, delrin and other plastics. For a full list of approved materials check here.

Add picture of PCB Black, Cut PCB, Finished PCB

Safety Considerations

Hazards

• Particulate Matter (hazardous to eyes and lungs)
• Rotating Parts

Safety Considerations

• No long sleeves, wrist bracelet, necklace, rings, etc.
• No "dangly bits"! (Anything that can be caught in the spindle)

Not Required but may be helpful

• Gloves for sharp corners, points, burrs
• Safety Glasses for particulate matter

Selecting a Material

Maximum Stock Size: 4"x5"x1.35"

Materials We Carry

• Single Sided FR1 (4"x5") - $1.40/ea
• Clear Polycarbonate (4"x5"x0.375") - $3.35/ea
• High Density Polyethylene (4"x5"x0.375") - $4.00/ea
• White Delrin (4"x5"x0.25") - $3.00/ea
• Aluminum 6061 (4"x4"x0.25") - $5.00/ea

Approved Materials

• PCB - Single Sided / Doubled Sided FR1
• Plastics - Delrin, ABS, HDPE, Acrylic
• Metals - Aluminum 6061, Carbon Steel, Stainless 316, Tool Steel, Brass, Titanium
• Linoleum

Loading Material

1. Apply 1-2 strips of Nitto (thin double-sided) tape to the bottom of your stock
2. Align the stock flush against the bottom left corner, the firmly push the material down onto the spoilboard.
3. Swing out the probing clip, ensuring it makes an electrical connection with the board. (Assuming the material is conductive!)
   Check! Make sure the probing clip is still making contact with the board. Otherwise you can cause damage to the mill.

Designing for the Bantam Mill

The Bantam Mill works well with the following file types:

• BRD Files (Eagle Workshop)
• SVG Files (2D CAD Workshop)
• STL Files (3D CAD Workshop)

Switching Tools

Be sure to follow the on-screen instructions exactly when changing tools in order to prevent damage to the machine. 

1. Remove the built-in wrenches from the top of the machine
2. Loosen the collet until you feel resistance
3. Now place a finger under the tool to prevent it dropping and breaking on the spoilboard (or have a friend lend an extra hand). Now using the wrenches apply pressure again to further loosen the collet.
4. Remove the existing tool, slide in your new tool
5. Holding the new tool in place with an extra finger, tighten the collet until you are met with resistance.
6. Using the wrenches, tighten down the collet just a bit more (don't overdo it!). The collet only needs to be tightened slightly to get a good grip.

Software Steps

• Home the Machine
  • When you power on the machine you should be prompted with a pop-up box asking you to home the machine. Click "Start Homing" the rest of the process is automated.
• Initial Setup
  • Open the dropdown with your file's name
    • Specify Milling Tools
      • The software should recommend tool(s) that may work for your design. Verify that these tools will work, or manually specify which tools you'd like to use.
      • TIP: The 1/32" Flat End Mill works well for most scenarios.
    • Specify Toolpaths
      • Side to mill - Which side of the board do you want to mill first (only important for double-sided PCBs)
      • Traces, Holes, Outlines - These features can be toggled on/off. Only selected features will be milled.
  • Brackets and Accessories
    • Ensure that you see "Installed" next to the PCB Bracket. You should also be able to see the PCB bracket rendered on the screen. If not, click "Locate" and carefully follow the onscreen instructions.
• Material Setup
  • Material Size - Specify the exact size of the material you are using. Use calipers to get an accurate measurement. 
    • If you are using FR1 (circuit board material) you can use these measurements 
      • X: 127mm
      • Y: 101.6mm
      • Z: 1.61mm - 1.71mm
  • Material Placement
    • Click Material Offset Probing Routines" > "Z-only Stock Probing"
      • Now, carefully follow the instructions on screen. The software will automatically calculate the thickness of your material including the Nitto tape. Double-check that this value makes sense (it should be somewhere in the range of 1.61-1.71 mm).
• Plan Setup
  • Place Plan - Specify exactly where the design should be cut with respect to the bottom left corner.
    • You can specify exact coordinates, or if you prefer you can click "Plan Offset Probing Routines" to have the software find the coordinates of the material's corner.
• Before starting the cut...
  • Double check material exists where you placed the design
  • Install the tool fan (optional)
  • Use the vacuum while cutting to clean away swarf (optional)
  • Be prepared to stop the cut

Stop Button

Be aware the Bantam Mill is a powerful but also dangerous tool. Improper use of the mill can lead to irreversible damage to the machine. The main issue that you want to look out for is the mill trying to jam a tool where it shouldn't go (through your material, spoilboard, bracket). If at any point you are fear for your safety or the safety of the machine DO NOT hesitate to slap the red button on the right side of the machine. When the button is fully depressed all machine operations should cease immediately.

Afterwards

Don't forget to thoroughly clean the machine using the shop vac after you finish!

Materials

• Single-sided blank
• Battery (CR1220)
• Battery Holder (BH-98-1)
• 5mm 20mA LED (Yellow or Red) 
• Resistor: >50 ohms (minimum of 42 ohms)
• Button (B3F-10XX)

(Resistor Value = (Battery Voltage – LED voltage) / desired LED current)