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CNC Machines

In my school, we have desktop CNC machines that uses the Bantom software tool.

They use a subtractive process to make materials. The bit is the tool that spins at thousands of revolutions per second and chips away at the material.

The Bantom software can be found here. To learn more about CNC machines, visit here.

These are also called milling machines, as they can mill out boards designed in CAD softwares such as KiCAD and turn them into working microcontrollers that can be programmed to control electrical components.

Workflow

When working with the milling machine, you must follow a workflow.

Tools:
  • OtherMill Pro
  • Profile & Holes Bit - 1/32” Flat Endmill (Orange Cap)
  • Precise Trace Bit - 1/64” Flat Endmill (Precise Bits) 0.005” PCB Engraving Bit 15 degree Taper Stud this is not a traditional tip
  • Collet wrenches
  • Foam for bed when changing bits
  • FR-1 PCB Board
  • Nitto Tape
Preparation Phase Bantam Tool
  1. Download file
    • Geber
    • Eagle.brd
    • SVG
    • KiCad Files
  2. Clean the Bed
    • Use a vacuum and remove loose materials.
    • Wipe down with alcohol
  3. Material
    • Select material - generic or FR1 NOT FR4
    • Measure the width and height of the conductive material you wish to mill (PCB - FR1)
    • Enter the width and height values.
  4. Tape down the material
    • Use Nitto tape (double-sided tape)
    • No overlaps
    • No wrinkles
    • Make sure to put the tape away once done
  5. Open Bantam Software
  6. Load File
    • Setup File
    • Trace Depth: 0.20 mm
    • Trace Clearance: 1.50mm (Note: you need to change this from the default setting of 0.15)
    • Bits:
      • 1/32” Flat Endmill
      • 1/64” Flat Endmill - select this setting as opposed to 15 degree Taper Stud0.015” 15 degree
      • PCB Engraving Bit 0.005”
    • Probe Material Thickness using the Bit Breaker
      • Pro Tip: Instead of using the arrow keys to move the spindle on bit breaker, use some GCode in the Debug tool
      • Open the Debug tool by selecting the “Show Debug Console” in the BitBreaker menu
      • To send the spindle to a specific X,Y coordinate use the following GCode command:
      • G53G00X(Insert value)Y(Insert Value)
      • G53G00X50Y60 will send the spindle to (50,60)
      • When you are finished typing in the coordinates, click on the “Send Command” button to execute the command.
      • Click on “Probe Material” to find the material thickness.
      • Note that you must flip the electron-conducting switch in the CNC in order for this step to work!
      • Use the GCode to find the thickness in a grid where the board will be milled.
      • When milling multiple boards, use the minimum material thickness of all the points probed. Values can vary from 1.67-1.95mm, which matches the manufacturing tolerance of the board at +/- 0.15mm.
  7. Home Machine
  8. Prep Machine & Configure the job in Bantam Softwarethe Bantam Tool
    • Select tool (end mill or engraving bit) by selecting change
      • Choose tool under New Tool
      • Install the tool by loosening collet and replacing tool
      • Click continue
      • Verify tool position
      • Locate tool
  9. Milling the face of the board
    • Setup the board in the Bantam Software and be sure “Trace and Holes” are selected. Be sure “Outline” is NOT selected
    • Select the ‘PCB Engraving 0.005”’ tool
    • Select the ‘1/64” Flat End Mill’
    • Confirm there are no red areas on the face of the board in the Bantam Software.
    • Verify only the parts to be milled are visible in the software
    • Start milling using the “Mill All Visible” button.
    • Follow-on screen instructions for inserting the correct bits
      • To maximize bit life, be sure to place the white foam on board when changing or installing bits
      • Be sure to periodically check the bits under the microscope before installing to confirm they are still sharp.
  10. Cutting Out the Board after milling the face
    • Deselect Traces and Holes in the Bantam Software
    • Select Outline
    • Add ‘1/32” Flat End Mill’ to the Milling Tools
    • Confirm that only the board outline is visible
    • Start milling using the “Mill All Visible” button.
    • Follow-on screen instructions for inserting the correct bits
      • To maximize bit life, be sure to place the white foam on board when changing or installing bits
      • Be sure to periodically check the bits under the microscope before installing to confirm they are still sharp.
  11. Board Removal
    • Move the PCB board to the loading position and vacuum the board.
    • Use the 5 in 1 paint scraper to remove the board from the machine.
    • Vacuum inside the machine to get residual debris after the board is removed.
    • Put all bits back in their original containers.
  12. Clean Up!
    • Vacuum inside the machine to get residual debris after the board is removed.
    • Put all bits back in their original containers.

Note that not every measurement setup could apply to your CNC machine, so it is important to adapt the above workflow to your machine.

Last update: May 14, 2023