< <br>
2. [Fablab Leon Adrian's group assignment](http://academany.fabcloud.io/fabacademy/2020/labs/leon/leon-group-assignments/) <br>
3. [FabAcademy Adrien Bracq](https://fabacademy.org/2019/labs/lamachinerie/students/adrien-bracq/assignments/week05/linetest/) <br>
4. [FabAcademy Kannai 2022](https://fabacademy.org/2022/labs/kannai/Weekly_Group_Assignments/week04/) <br> <br>
5. [FabAcademy Nadieh 2021](http://fabacademy.org/2021/labs/waag/students/nadieh-bremer/blog/week-4/) <br><br>
--------------------
## Task I. Design Rules for in-house PCB Production
### The Machine - STEPCRAFT 420
<img src="https://www.stepcraft.us/web/image/product.product/3694/image_1024/STEPCRAFT-3-D.420%20CNC%20System%20%28DIY%20Kit%2C%20No%20Spindle%29?unique=7c12bab" width="480" />
<table>
<tr>
<th>Property</th>
<th>Specs</th>
</tr>
<tr>
<td>Working Area</td>
<td>300 x 420 x 132 mm</td>
</tr>
<tr>
<td>Control Board Combatibility</td>
<td>TBC</td>
</tr>
<tr>
<td>Kress Spindle</td>
<td>800W 6A, 10,000- 29,000 RPM. </td>
</tr>
<tr>
<td>Max speed</td>
<td>3000mm/min</td>
</tr>
</table>
<!---Jon to insert labelled picture of PCB machine
Jon to label labelled picture of the plates.--->
### Material & Bits
- FR1 Board, Copper layer 35um
- EndMill Shank diameter 1/8"
- 1/64" = 0.4 mm flat end drill bit for milling surface ie traces.
- 1/32" = 0.8 mm bit to mill the outline of board.
Refer to Jon individual link for more details.
<br> <br>
### Recommended StepCraft settings from instructor
We set the rotary tool to be at roughly 10,000-12,000rpm.
<table>
<thead>
<tr>
<th style="text-align: left">Operation</th>
<th style="text-align: center">Endmill size</th>
<th style="text-align: center">Cut Speed</th>
<th style="text-align: center">Cut Depth</th>
<th style="text-align: center">Total Depth</th>
<th style="text-align: center">Offset</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left">Traces</td>
<td style="text-align: center">0.4 mm flat</td>
<td style="text-align: center">50 ~ 60 mm/min</td>
<td style="text-align: center">0.04 ~ 0.05 mm</td>
<td style="text-align: center">0.04 ~ 0.05 mm</td>
<td style="text-align: center">2 ~ 4</td>
</tr>
<tr>
<td style="text-align: left">Traces</td>
<td style="text-align: center">0.8 mm flat</td>
<td style="text-align: center">60 ~ 80 mm/min</td>
<td style="text-align: center">0.04 ~ 0.05 mm</td>
<td style="text-align: center">0.04 ~ 0.05 mm</td>
<td style="text-align: center">1 ~ 2</td>
</tr>
<tr>
<td style="text-align: left">Traces</td>
<td style="text-align: center">0.1 mm 10 deg V-bit</td>
<td style="text-align: center">50 ~ 60 mm/min</td>
<td style="text-align: center">0.04 ~ 0.05 mm</td>
<td style="text-align: center">0.04 ~ 0.05 mm</td>
<td style="text-align: center">1 ~ 2</td>
</tr>
<tr>
<td style="text-align: left">Board Outline</td>
<td style="text-align: center">0.8 mm flat</td>
<td style="text-align: center">50 ~ 80 mm/min</td>
<td style="text-align: center">0.42 ~ 0.45 mm</td>
<td style="text-align: center">1.65 ~ 1.70 mm</td>
<td style="text-align: center">1</td>
</tr>
</tbody>
</table>
Here are some images of the tools we used
<img src="./0.1mm_20deg_vbit.jpg" width="480"/>
0.1mm 10 deg V-bit -> tracing <br/> <br/>
<img src="./0.8mm_tool.jpg" width="480"/>
0.8mm flat bit -> outlining <br /> <br />
<br> <br>
### Precision Test
<img src="http://academy.cba.mit.edu/classes/electronics_production/linetest.png" width="480" />
Picture above is the Test file used was [linetest.png](http://academy.cba.mit.edu/classes/electronics_production/linetest.png) downloaded from fabacademy's electronics page.
The numbers shown are in inches.
The raw file is imported into mods from instructor Steven's [link](https://skeatz.github.io/mods/)
<img src="./Bryan_CNC_pic.jpg" width="480" />
<img src="./Tooldiameter.JPG" width="480" />
<img src="./Linetest.jpg" width="480" />
<img src="./linetest_on_ncviewer.jpg" width="480" />
Blow is the result of milling the gcode generated above:
<img src="https://fabacademy.org/2022/labs/singapore/students/bryan-tee/images/week04/burr.jpg" width="480" />
From the result image, we have a few observations
1. By setting the tool diameter at 0.4mm, a gcode generator can only generate up to 0.4mm toolpath (0.016 inches). We could set it to be less than 0.4mm, but the cut diameter is limited by the tool diameter.
This means that if we set the tool diameter to be 0.001mm, we can generate all the paths on the linetest image file, but it will not result in the correct size.
2. Always secure the PCB firmly on the sacrificial board. This is important as the machine has vibrations during operation, which can cause an unsecured PCB to vibrate out of place. In the image provided, the
linetest vibrated out of place when cutting with the outline tool toolpath, but we deemed it as "still acceptable" as no traces within the PCB were damaged.
<br/>
Below illustrates how to generate (almost all) paths for the image, albeit it will not appear correctly on the actual PCB (hence no point to running the file itself).
<ul>
<li>convert 0.001inches to mm -> approx. 0.00394mm</li>
<li>set the tool diameter to be larger than the value indicated above -> 0.00394mm to purposefully avoid generating the last 0.001inch line (demonstrates understanding of how to generate path)</li>
<li>generate the toolpath and view on ncviewer</li>
</ul>
It will generate the following. Note that this is a hack, which might be useful if we need the path to be generated instead.
<img src="./mods_generate_vsmall.png" width="480"/>
<img src="./vsmal_linetest.png" width="480"/>
**Updates to Global Evaluator**
The goal of linetest is to ensure the correct dimension is milled, and this is determined by comparing the gap size and the line size below (they should be the same size).
We did not test further as from the linetest above, we feel that the width between the top portion and the bottom portion roughly corresponds and is at its limit (0.016mil).
Our local instructor Steven provided some images to illustrate going beyond the limits of a milling tool (the same tool was used). Writing this here to show that we have learnt how to determine the
limits of the tool. The following was generated by changing the tool diameter from 0.4mm (0.016mil) to 0.3mm (0.012mil), and the line was generated up to 0.012 mil (9th from the right)
<img src="./grp_demo_milling.jpg" width="720"/>
<img src="./grp_demo.jpg" width="720"/>
From the (clearer) image, you can see that from the 7th or 6th gap from the right, the gap on the top does not match the line on the bottom. The 6th corresponds to 0.15mm and 7th corresponds to 0.14mm. This means that this
tool has a limit of roughly 0.016mil, which tallies with our results.
**End update**
]]>