8. Electronics Production - Girls¶

Overview¶

Assignment	Name
Feeds and Speeds	Amalia and Angel
Plunge Rate	Zaina
Depth of Cut (traces)	Jenna
Depth of Cut (outline)	Elle
Workflow for sending a PCB to a boardhouse	Kathryn

Feeds and Speeds – Amalia and Angel¶

Speeds & Feeds for Othermill 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.

Boardhouse Workflow - Kathryn¶

The reason you would send a PCB to a boardhouse is to get professional fabrication with high precision. Instead of manually etching or milling, you upload design files, and the manufacturer handles printing, drilling, and finishing. Some boardhouses, like JLCPCB, also offer assembly services, soldering components directly onto the board.

Assuming you have your design finished, perform a final Design Rule Check (DRC) to detect any errors
Open the Gerber Export tool in your EDA software
Generate Gerber files for the following layers:
Top & Bottom Copper Layers (GTL, GBL)
Top & Bottom Solder Mask (GTS, GBS)
Top & Bottom Silkscreen (GTO, GBO)
Board Outline (GKO or GBR)
NC Drill File (Excellon format, .TXT or .DRL)
Open the Gerber files in a viewer
Check that all layers are aligned correctly, verify hole placements and sizes, and confirm that any silkscreen text is legible and positioned properly
Select all Gerber files and the NC Drill file and compress them into a .zip archive. Double-check that all necessary layers are included before proceeding

Go to the website of the boardhouse you want to send your PCB to and select the type you want by clicking “Quote Now” (I went with JLCPCB)

Upload your .zip file where it says “Upload Gerber File”

Configure the PCB Specifications by going through the rest of the page
Choose the PCB quantity and size (JLCPCB automatically detects dimensions)
Select the number of layers (1-layer, 2-layer, or more)
Choose the PCB thickness (default: 1.6mm)
Set the copper weight (default: 1oz/ft²)
Pick a solder mask color
Choose a surface finish (default: HASL, or ENIG)
etc.
Review and confirm the final settings

Choose PCB Assembly (Optional). If you want your components soldered as well, there’s another option to toggle below called “PCB Assembly”
Upload a BOM (Bill of Materials) and Pick & Place (CPL) file
Select components from JLCPCB’s parts library
Confirm placement and approve the assembly preview
Review the order summary to ensure everything is correct.
Upon arrival, inspect the PCBs for defects (check traces, silkscreen, and hole alignment)
Use a multimeter to check for continuity and short circuits. Power the board with a regulated power supply and check voltage levels. Test individual components and signals with an oscilloscope if needed.

Depth of Cut¶

The Traces - Elle Hahn¶

To test the depth of cut on the otter mill desktop milling machine, I used the following image. I got this image from last years group page.

To turn this into being able to cut out in the milling machine, I used corelDraw. I imported it into corelDraw as an image. And then I traced the bitmap using the trace bitmap tool. Than I used the detail logo options. Under this I made the details as high as possible and the other two options low.

It is important that when making the bit map, you choose the selected color to remove box. If you don’t select this then it wom’t come up. Then the color to remove is the white. Technically the image has shadowing, therefore you need to merge all the colors together that arent black under the colors table. To merge them, just select the first color then hold the shit button as you select the others and then right click and merge or click merge. This will make it easier to remove the white. When you remore the white It will mill out everything but the numbers.

Once I did that I exported it to the computer. Then on the desktop work I added the file like normal. We ued the PCB Engraver 0.005”. This was the smalles bit and I could do more than the other sizes. Once that I did change any of the other settings and I generated it. Then I did the file set up as usual then went ahead and milled it. This took about an hour.

This is what my cut looks like. As you can see the engraver can go up to 0.004”, however if you want a secure trace, I recommend using 0.008” and above for your traces.

The Outline - Jenna Chebaro¶

I milled directly from the trace and exterior image that Dr. Gershenfeld gave us.

I converted the png to svg through online image converter. I used a 1/64 bit, re-doing the trace section for convenience but focusing on the outline.

Plunge Rate - Zaina¶

What Is Plunge Rate?¶

The plunge rate is the speed at which the cutting tool moves vertically into the material, usually during the start of a cut or when milling a pocket.

Units: Typically in mm/min or IPM

Why It Matters¶

Going too fast = tool breakage, chatter, excessive heat
Going too slow = inefficient machining, tool wear

It is especially important when:¶

Milling deep pockets
Drilling down into solid material
Using a CNC router or mill
Plunge Rate = 10% to 30% of Feed Rate

Example:

Feed Rate = 1000 mm/min
Safe Plunge Rate = 100–300 mm/min
- This is because tools are less efficient and more stressed when moving straight into material.

Factors That Affect Plunge Rate

1) Soft (wood/plastic) = faster plunge 2) Hard (metal) = slower plunge 3) Tool Type 4) Center-cutting end mills can plunge straight down - Non-center-cutting tools should ramp in, not plunge 5) Tool Diameter - The bigger the tool, the more it can handle faster plunge speeds 6) Material

Last update: April 10, 2025