Week 8 - Electronics Production — Group Assignment

Group assignment:

• Characterize the design rules for your in-house PCB production process: document the settings for your machine.
• This means running test cuts and documenting what your specific machine can actually achieve. You need to find the minimum reliable values for our machines.
• Document the workflow for sending a PCB to a boardhouse
• Submit a design to a board house
• Document your work to the group work page and reflect on your individual page what you learned

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Design Rules for CLS Fab Lab PCB Production Process

Parameter	What to Test
Minimum trace width	Narrowest copper trace that mills cleanly without breaking. We traced a test image as a bitmap and brought it into MakeraCAM, then plotted it on the Carvera. On advice from Angelina, we ran the 0.2mm × 30° Engraving (metal) bit. If that is not small enough, then 0.1mm × 90° chamfering.
Minimum trace clearance	Smallest gap between traces before they short. Use the multimeter to check for a connectivity beep at each location.
Board outline cut depth	Z depth for cutting the board free.

Minimum Trace Width and Clearance Test

Angela and Dorian collaborated on the trace test. Angela imported and traced the PNG file in MakerCAM, while Dorian figured out how to scale it correctly. From there, the team asked Claude about the bit choices. (See Claude prompt below) Then based on their experience trying to follow Claude’s faulty advice, Angela created the toolpaths using the 0.8mm corn bit and a contour cut for the outside and a pocket cut for the interior. The software would not allow her to choose the contour cut so she changed it to pocket. She previewed the toolpaths and exported the files.

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Claude Prompt: So when testing traces do we want pocket or contour?

Note: Claude’s advice was not correct — it would not even let us use contour for the test. We had to use pocket.

Claude’s advice:

For PCB trace isolation milling, you want contour (called Vector Contour in MakeraCAM).

Here’s the logic:

Contour traces a path along the edge of your copper traces, cutting a narrow channel to electrically isolate them from the surrounding copper. It’s precise, fast, and uses minimal cuts — just enough to separate the traces. This is what’s called “isolation routing.”

Pocket would remove all the copper between traces — essentially clearing out every bit of material that isn’t a trace. This works but takes way longer, puts more wear on the bit, and is overkill for a test.

So the workflow for testing your ESP32-C6 traces would be:

1. Import your copper layer (Gerber or PNG-traced vectors)
2. Select the trace outlines
3. Vector Contour — cut along the edges to isolate traces
4. 2D Drilling — for via/component holes
5. Vector Contour again (with a larger bit) — for the board outline cutout

The V-bit depth matters a lot with contour — cut too shallow and traces won’t be fully isolated, too deep and your V-bit widens the channel and can eat into adjacent traces. This is exactly why auto-leveling on the Carvera is so helpful; even a 0.1mm height variation across the board changes your effective cut width with a V-bit.

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Angela went through the setup with the Carvera while Kim recorded the process.

Then ______ used the multimeter to test for connectivity between the milled areas to see when they were too close.

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Board Outline Cut Depth

All of us collaborated on a way to test the outline cuts and decided to make a PCB board test that cut out squares at different depths.

Camille designed a small test area in KiCad. Then she brought it into Makera and set a different cut depth for each square.

Once the cut paths were finished, Camille exported the files, and she and Angela cut them on the Carvera.

Then we ran the auto level during our cut and looked to see which pieces fell out and which did not cut through. All but the far left cut through, so anything greater than 1.57mm cuts through our boards.

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From These Tests We Learned That:

• The narrowest copper trace that mills cleanly without breaking on our machine is approximately ________
• The smallest gap between traces before they short is ________
• Greater than 1.57mm cut depth setting will cut through our boards that measured 1.59–1.6mm with a caliper (but 1.6mm+ was probably a safer bet)

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Other Feeds and Speeds

We used the Aspire Vectric 12.5 software with Makera Carvera ATC to mill our boards. From Angelina’s CLS Fab Academy group site, we were able to find these feeds and speeds.

Speeds & Feeds for Carvera Milling Machine Tools

Tool Size	Spindle Speed (RPM)	Feed Rate (mm/min)	Plunge Rate (mm/min)	Cut Depth per Pass (mm)
1/64” (0.0156”) End Mill	16,000–20,000	100–200	50–100	0.1
1/32” (0.0313”) End Mill	16,000–20,000	200–400	75–150	0.2
1/16” (0.0625”) End Mill	16,000–20,000	400–600	100–200	0.3–0.5
Engraving Bit (V-bit, 30° or 60°)	16,000–20,000	80–150	40–80	0.05–0.1

• 1/64”: Best for fine trace isolation and small detailed cuts. Requires a shallow cut depth to avoid breaking.
• 1/32”: Common for trace isolation and small routing features. Deeper cuts possible.
• 1/16”: Best for board cutouts and large clearances.
• Engraving Bit: Ideal for fine detail work. Cut depth varies depending on the desired isolation width.

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PCB Board House

We chose to try PCBway. We used the simple board that we made in class with one resistor and one diode. Our choices for each item are in bold.

PCB Specification Selection

1. Start by saying what kind of PCB you want. Standard PCB

2. Then how many designs in your file/panel: 1

   

3. Size of your board, qty desired, layers and thickness. Since we were given a file to work with, we didn’t have the KiCad file to get information off of. We used the Gerber Viewer in KiCad to get measurements. 37mm × 22.5mm, 1 layer, 1.6mm thickness

   

4. Quantity — smallest is 5: 5

5. Copper layer, solder mask and silkscreen options: top layer for the first two, but none for the silkscreen

6. Material: FR-4 — they can mill that safely.

7. When choosing FR-4 for the material, more options came up for the TG (Glass Transition Temperature). We chose the default TG 130-140.

   

8. Min track/spacing — default of 6/6mil

9. Min Hole size: no hole

10. Soldermask: white

11. Silkscreen: none

12. UV Printing: none

13. Edge connector: no

    

14. Surface Finish: HASL lead free

    When selecting a surface finish between HASL with lead and HASL lead free for your PCBs, we highly recommend HASL Lead-Free over traditional HASL with lead, as it aligns with global environmental standards and long-term reliability goals.

    Why Choose HASL Lead-Free?

    ✔ RoHS & REACH Compliant — Meets strict international regulations (EU/China/US)

    ✔ Eco-Friendly & Safer — Eliminates toxic lead exposure in manufacturing and recycling

    ✔ Future-Proof — Avoids redesign costs if lead-free compliance becomes mandatory

    ✔ Comparable Performance — Maintains strong solderability with minor process adjustments

    While we still offer HASL with lead for legacy applications, lead-free is the sustainable choice for most modern electronics.

15. Via Processed: N/A — we don’t have any vias

16. Finished Copper: 1oz cu

17. Remove Product No: we don’t mind having their product number: no

    

    

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SMD Stencil

Optional ordering of a stencil to go along with your product. You can uncheck this box. We left it checked to see what the total cost would be. We stayed with the defaults for most everything.

1. Stencil Type: Framework
2. Multilevel / Step Stencil: no
3. Stencil Side: top
4. Quantity: 1
5. Thickness: 0.12mm

6. Existing fiducials: none — we aren’t using a machine to manufacture

   Claude prompt: What are existing fiducials on a PCB stencil?

   Answer: Fiducials are small circular copper marks (usually just a bare copper dot with a clear soldermask opening around them) placed on a PCB that act as reference points for automated equipment.

7. Electropolishing / Electrochemical Deburring: None

   

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Assembly Service

Another option you can opt out of. They will get the parts and make the whole thing.

1. Chose where you get the parts — from them, you supply, or a combo: Turnkey: let PCBway get the parts
2. Board type: single pieces
3. Assembly side: top side
4. Quantity: You would think this would come in from above, but we add the same number here — 5

5. Pay attention to special requirements — we said no to both.

   

You can only choose one or the other — a stencil or an assembly. Makes sense: if it’s already assembled, you don’t need the stencil. So we chose the stencil.

There are many other options, but these were the main ones to get to our quote.

CHOSE CALCULATE

Then save to cart and a special message comes up that you must agree to in order to move on.

Then we had to create an account.

After creating the account, we were asked to upload the file, but it wouldn’t take the .gbr file that we had.

I took screenshots and asked Claude what was going on. It wanted a zip file. It’s getting late — hope this finishes soon.

I got to the next part and I believe this is the end for us — it’s under review.

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Aspire / MakeraCAM Workflow for PCB Milling

After creating a PCB design in KiCad, we uploaded the gerber / svg file into Aspire to make the toolpath.

2D Profile Toolpath Generation (CAM)

This is where you create the actual cutting instructions. For a circuit board, this is almost always a two-part process: a “Roughing” pass and a “Finishing” pass.

1. Select Your Boundary: In the 2D view, click on the rectangular model profile.
2. Toolpaths: Select the 2D Profile Toolpath.
3. Click the 2D Roughing Toolpath icon.
4. Cutting Depths: Set the Start Depth to 0 and the Cut Depth to 0.5. This tells Aspire to only machine the specific depth.
5. Tool: Set the material to Hardwood. Select a 25mm Flute End Mill (3.175mm) under the Carvera Tools subsection. This is also known as a ⅛” End Mill and is set to Tool Number 1 for the ATC.
6. Machine Vectors: Select On the line and the direction of Climb.
7. Do Separate Last Pass: Leave it unchecked.
8. Add tabs to toolpath: Not needed.
9. Name your toolpath (e.g., “2D Profile — ⅛” End Mill”) and click Calculate.

Simulation & Exporting

1. Preview ALL Toolpaths — this is your most important safety check. Click the Preview all Toolpaths button. Aspire will run a full 3D simulation: first the Roughing pass, then the Finishing pass. Check for errors — does it look correct? Did you miss any spots? Click Toolpaths Summary to see the total estimated machining time.

2. Save Your Project File: Go to File > Save As… and save your .crv3d project file.

3. Save Your G-Code (Toolpath Files):

4. Click the Save Toolpaths button (floppy disk icon).
5. Check Toolpaths: Select “3D Rough,” then “3D Finish,” then “2D Profile” → Click Save Toolpath(s).
6. Choose your machine → Carvera Desktop CNC Machine.
7. Choose your Post-Processor → Carvera ATC (mm) (*.cnc) → Click Save Toolpath(s).
8. You will now have the .cnc file ready to run at the Carvera — it will automatically run each toolpath one after another.

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Resources

• Other Fabs:

  • Chaihuo Lab — Week 4 Electronics Production
  • Taipei Lab — Week 4

• PCB Houses:

  • JLCPCB
  • PCBway

• Workflow shared by Angelina

• MakeraCAM Workflow from Mr. Dubick

• MakeraCAM User Guide

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Things for Another Day

Parameter	Description
Minimum drill diameter	Smallest hole the machine can cut
Minimum annular ring	Copper remaining around a drilled hole

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Last update: March 25, 2026