Week 4 - Electronics Production Group Project: Connor, Landon¶
Landon Broadwell and Connor Cruz
Milling Characteristics¶
We used this source to help in finding some of the definitions.
Definitions:¶
| Term | Definition |
|---|---|
| Plunge Rate | The speed that the spindle moves along the Z-axis. |
| Spindle Speed | The amount of times the spindle revolves in a certain amount of time. |
| Feed Rate | The speed that the spindle moves along the X and Y axes |
| Cut depth (trace/outlines) | How deep into the material the machine cuts for the traces and outline of a design. |
| Tooling | The tools and mechanisms used to do the miling process, such as the bit and the spindle. |
| Diameter | The diameter of the bit being used. |
| Flute Length | The length from the end of the bit to where the flutes (i.e. the slots along the bit) end. |
Characteristics for Specific Bits¶
We used the 1/64”, 1/32”, and 1/16” Flat End Mill bits and their respective values.
These characteristics were obtained from the Bantam Tools software.
Constants:
These values were the same for each of the 3 bits.
Plunge Rate: 381mm / min
Spindle Speed: 27500 rpm
Number of Flutes: 2
Trace Depth/Outline Depth:
We set the trace depth to 0.15 mm for our desired board (this does not depend on the bit used). The depth of the outline is approximately the same as the depth of the material, since we wanted the board to be fully cut out.
Variable:
These values changed between the 3 different bits.
Feed Rate:
- 1/16”: 1650 mm / min
- 1/32”: 1100 mm / min
- 1/64”: 688 mm / min
Since smaller bits have to be more precise, they have to move slower.
Pass Depth:
- 1/16”: 1 mm
- 1/32”: 0.8 mm
- 1/64”: 0.4 mm
Diameter:
1/16”: 1.587 mm 1/32”: 0.794 mm 1/64”: 0.397 mm
Flute Length:
1/16”: 5.09 mm 1/32”: 1.59 mm 1/64”: 0.79 mm
Finding Trace and Gap Limits for 1/64” Bit¶
To test these measurements, we cut out the line test design provided by Neil in this week’s presentation. We used the 1/64” bit to cut the design.
Here is the milled line test and video of the process:
We found out that for the 1/64” bit, its limit for trace size is roughly between 0.008-0.010 in. We can also conclude that the minimum gap width is around 0.016 in.
Some other groups did measurements for other bits as well. The group that did the 1/32” bit found that _. The group that did the 1/16” flat end bit found _. The final group, which did the V-bit found ____.
Conclusion¶
The data shown by our own milling process shows that there is a greater threshold for the 1/64" bit to create space between materials than for taking away material around a specific trace. While the bit was able to create a line of the material all the way through, it was only able to create a gap around 0.016in. This shows that this bit is not fully suited for gaps but is very capable of creating individual traces.
Sending PCB to Board House Workflow¶
Several sources were used to make this workflow. You can find some of them here and here.
Workflow¶
- Design a circuit board schematic in your desired electronic design program (our lab uses primarily Kicad and Autodesk).
- Test the board by milling it in-house to see if it has all the necessary features and there are no errors with the design.
- Select a PCB house, and check its cost and the different types of cuts they do to figure out which best suits your desired design.
- See what type of files they accept - this will generally be a Gerber (.gbr) file.
- Once the schematic is designed, export the file as the house’s accepted design file.
- Some manufacturers will also do a DFM (Design for Manufacturing) check on your file to lower manufacturing costs and ensure that there are not any problems with the design.
- A DFM check by the manufacturer usually happens before payment for the primary design but may require an additional fee.