By Bantam Tools
Courtesy of Bantam Tools
In this tutorial designed for beginners, we'll walk you through all the steps to mill and assemble a light-up printed circuit board (PCB) that displays an image of our favorite bantam rooster! We'll cover all the basics of installing the software, connecting the milling machine to your computer, importing a .brd file into our software, attaching the PCB board to the machine bed, loading the end mill into the milling machine, getting the file ready to cut, milling the board, and then soldering the components onto the board.
The Bantam Tools Desktop PCB Milling Machine comes with all the materials needed to complete this project. The only additional tools you'll need are a soldering iron, solder, diagonal cutters, and (optionally) digital calipers, a multimeter, and needle nose pliers.
Tools, Materials, and Files
- Bantam Tools Desktop PCB Milling Machine
- Flat end mill, 1/32"
- Computer with Bantam Tools Desktop Milling Machine Software installed
- Digital calipers
- Soldering iron and solder
- Diagonal cutters for clipping wires
- Helping hands tool aka "third hand," to hold your circuit board in place while soldering (optional)
- Multimeter (optional)
- Needle nose pliers (optional)
- Printed circuit board (PCB) blank, single-sided, FR-1
- Resistor, 22-ohms (2)
- LED, 3mm, white (2)
- Coin cell battery, 3-volt, CR2032
- Coin cell battery holder
- High-strength double-sided tape Scotch double-sided tape will also work to attach the PCB board to the machine bed, but high-strength double-sided tape is more reliable, especially when milling PCB boards with small features.
FILES TO DOWNLOAD
- EAGLE .brd file Download here.
Step 1: Download the .brd file and install the Bantam Tools Desktop Milling Machine Software
First, download the Bantam Tools Desktop Milling Machine Software and follow the prompts to install it onto your computer.
Next, download the EAGLE .brd file that we'll use for this project.
EAGLE is CAD (computer-aided design) software used to design PCBs (printed circuit boards). The .brd file we'll be milling here was created in EAGLE. For this tutorial, there's no need to modify the .brd file; it's ready to be loaded into Bantam Tools Desktop Milling Machine Software. However, if you wanted to, you could open the .brd file in EAGLE and modify the design. EAGLE has a free version available for download.
Step 2: Connect the milling machine and turn it on
Once you've installed Bantam Tools Desktop Milling Machine Software and downloaded the .brd file, it's time to connect your Bantam Tools Desktop PCB Milling Machine to your computer.
Take the USB cable and plug it into the back of the machine and then to the USB port on your computer. Turn on the Bantam Tools Desktop PCB Milling Machine.
The first thing the software will do is prompt you to home the machine. Homing the machine means the moving parts of the milling machine, called the carriages, will go to their starting point, also called the origin. The homing process tells the software where the parts of the machine are located in space. Without homing, the software wouldn't know where the parts of the mill are located, and it wouldn't be able to start milling your PCB.
Step 3: Set up your job
Now that the software is installed and the milling machine is connected to your computer, it's time to set up the milling job.
First, we'll put a bit fan on the 1/32" flat end mill. While a bit fan is not essential, it's helpful because it helps clear some of the debris, also called swarf, that the milling machine creates when it's cutting your board. Without a bit fan, more debris remains on the board while the board is being milled. As a result, the cutting tool is constantly impacting this debris while it continues to cut the board. This constant friction can dull the cutting tool, cause the motors to work harder than they need to, and create rough edges on the PCB. With the bit fan on the cutting tool, tools typically stay sharper longer, the milling machine has an easier time, and the finish is superior. So, while you don't have to use a bit fan, they're often a good idea!
Be careful not to cut your fingers when installing the bit fan. We suggest putting the flat end of the cutting tool on the table and holding the fan by the blades, with some distance away from the sharp part of the cutting tool. You can then slide the bit fan over the sharp end of the cutting tool.
The bit fan should look like this on your end mill.
The next step is to physically load the 1/32" flat end mill into the machine. An end mill is sometimes referred to as a cutting tool, tool, or informally as a bit. This primer on cutting tools is helpful and differentiates between the various kinds of end mills and bits.
To load the 1/32" flat end mill into the machine, if you've never done this before, refer to the Inserting and Locating a Tool Guide.
Next to "Tool" on our software, click the Change button, select "1/32" Flat End Mill,” click Continue, verify tool position (it should be above an empty area of the spoilboard), and click Locate Tool. The end mill will lower until it touches the spoilboard, pause, then retract upwards. Now the software knows where the 1/32” flat end mill is located in space.
Next to Material, select "Single-Sided FR-1."
Using digital calipers, measure the dimensions of your blank PCB. Width is X, height is Y, and thickness is Z. Enter these values for the Material Size.
While our PCB boards all have similar dimensions, each board can slightly vary in size. Slight variations in board size, especially in the thickness (Z) dimension, can make a big difference when it comes to milling, so it's always a good idea to measure each new PCB board being used.
You'll be using double-sided tape to attach the PCB board to the spoilboard of your machine. Use digital calipers to measure the thickness (Z) of the tape. Enter this measurement as the value for Material Placement (Z). The high-strength double-sided tape is typically 0.007" to 0.008" thick. The Scotch double-sided tape that shipped with your machine is typically about 0.003" thick.
Tip: Most of the time when errors occur in this project, it's due to the thickness measurements being incorrect, so take your time with this step!
Apply a single layer of tape to the bottom of the PCB board. Cover as much surface area as you can, but make sure not to let the tape overlap or wrinkle. If the tape overlaps, it'll make the PCB board stick up higher than the software expects, which can cause rough cuts or even damage the end mill. In our software, click the Loading button to bring the bed towards the front of the milling machine.
Place the PCB board on the spoilboard as shown in the photo below. Be careful to align it as closely as possible with the front left corner of the spoilboard.
Note: The spoil board is often considered to be "sacrificial," meaning it's okay if the end mill accidentally mills into it because it can always be made smooth again in the future. You can read more about the spoilboard in our Dimensions and Diagrams Guide.
Step 4: Set up the .brd file in our software
Now we're ready to bring our .brd file into the software.
In the software, under Plans, Click "Open Files," and select the .brd file you downloaded. If you haven't downloaded it yet, you can get it here.
In our software under Plan, next to Placement, click the triangle, which opens the dropdown menu. In the dropdown menu, for Placement X, enter 0.100", and for Placement Y, enter 0.100". This will take our design and offset it slightly from the edges of our PCB board.
Under Parts to Mill, Traces, Holes, and Outline are already selected. Leave it this way. The Traces, Holes, and Outline buttons tell our software to mill all these features in one job. The machine will first mill the traces and pads, then the holes, and finish by cutting the board outline.
Under Milling Tools, select "1/32" Flat End Mill.
The software will now render a preview, showing the parts of the PCB board that will be engraved and cut, as well as blue lines that show the toolpath. The toolpath is the route that the end mill will take while cutting the file, including when the tool lifts upwards and above the board to travel to the next location where it'll be cutting.
Now take a look at the preview to make sure everything looks correct and doesn't show any red warnings. Here, our software rendering shows you everything that'll be milled.
You can choose to view Preview and Toolpaths together, Preview alone, or Toolpaths alone. You can also select front view, top view, or 3D view.
Notice how under Messages there's a warning: "Marked areas need a smaller tool." Anything covered in red won't be milled. The red warnings indicate that the end mill selected is too large to fit into the shape you're trying to cut. Sometimes red warnings mean you need to go back to your design and change something so that all your features can be correctly milled.
For instance, if there's a red warning between two traces, then the machine won't be able to fit your selected cutting tool between the two traces. If the milling process is not able to separate one trace from the other, your board won't work as designed. For this project, if you zoom in, you can see a small red mark in the letter "S". The red mark is telling us that one corner will be slightly rounded because the end mill can't completely fit into the corner. In this case, the corner won't affect the functionality of this board, so we can ignore the warning.
The image below summarizes all the steps we've finished so far and shows what your completed setup should look like. Check each setting and make sure your software screen matches this image. The only things that might be different are the Material Size and Material Placement sections because you've entered specific values for the PCB board you measured with digital calipers.
Step 5: Mill your design
At this point, we've loaded the 1/32" flat end mill, entered PCB board thickness and tape thickness measurement values, clicked the Loading button to bring the bed towards the front of the milling machine, attached the PCB board to the spoilboard, opened the .brd file, moved the design slightly away from the edges of the PCB board, selected the 1/32 flat end mill, and double checked that our setup looks like the diagram up above.
When you're happy with how everything looks, place all four windows onto the milling machine. Now you're ready to click "Start Milling" and watch the Bantam Tools Desktop PCB Milling Machine mill your board!
It's a good idea to stay close by your machine while it's milling. Never leave a working machine unattended. This board will take about 4 minutes to cut.
Step 6: Remove the board from the machine
When the job is finished, vacuum all the dust out and click the Loading button. Use a scraper to gently pry the PCB board from the spoilboard of your milling machine. If you're using the high-strength double-sided tape, it'll be easier to remove the board if you first apply some 91% isopropyl alcohol to the edges of the board. The alcohol will loosen the adhesive and make the board easier to remove.
Once the board is out of the machine, clean the edges of your board with a scouring pad or by rubbing it against some double-sided tape.
Your board should look like this.
Step 7: Solder the components
Now that we've milled our PCB, it's time to add our components to board. If you're new to soldering, check out Adafruit's Guide to Excellent Soldering for a primer.
Here's an overview of where the components will be placed.
This image shows the components in their proper places and soldered to the board.
First, lay out all the components.
Solder the two LEDs
It's important to bend the 2 LEDs before soldering. If you bend them after soldering, then the act of bending might break the solder joint.
After bending both LEDs, place the short leg in the top hole and the long leg in the lower hole. This placement is important because the short leg connects to ground and the long leg connects to positive.
Remember how we pre-bent the LEDs? This is how the LEDs will look on the back side of the board.
Take a close look at the hole itself. See the circle of copper that surrounds the hole? This circle of copper is called a pad. When we solder the LED to the board, we're actually soldering the leg to this pad.
Solder the legs for both LEDs, four legs total, to the pads as shown here.
Solder the two resistors
Next, pre-bend the resistors as shown here.
Take one resistor and place the legs in the holes as shown. Unlike the LEDs, for the resistors, it doesn't matter which leg goes in which hole. Wiggle it down (flat-nose pliers can be helpful) until the resistor sits flush with the board.
Solder both resistors to the board.
Solder the CR2032 battery holder
Place the battery holder in the holes shown. Then solder the legs to the board.
So far, we've soldered two LEDs, two resistors, and one battery holder to the board.
Next, turn the board to the bottom side, take the diagonal cutters, and snip off the legs.
Next, insert the battery into the holder with the text facing upwards. The LED lights should light up!
If the LEDs don't light up, here are a few things to check.
Take a look at the LED and make sure that the positive leg (longer) is in the lower hole and the negative leg (shorter) is in the top hole. If you've already cut the legs and therefore can't tell anymore which leg is longer, no worries — there's another way to determine which side is positive. Take a look at the rim around the bottom of the LED. Notice that while most of the rim is round, there's one flat edge. This flat edge lines up with the shorter (ground) leg of the LED. Make sure that the leg that comes out of this flat edge is connected to the top hole. If they're backwards, then you'll need to flip the LED.
Take a look at the battery. Make sure that the side that says "+ Panasonic CR 2032" is facing towards you, away from the copper of the PCB board. The side without text should be face down, touching the PCB board directly.
Use a multimeter to make sure all your solder joints are good and therefore allowing electricity to travel through the solder joint. The idea is to test for continuity along the circuit, making sure that things we want to be connected are connected, and things we don't want connected aren't connected. Going into more detail about using a multimeter is a bit outside the scope of this tutorial, but SparkFun has a helpful guide on testing for continuity with a multimeter.
Check your solder joints. A bad, or "cold," joint will prevent electricity from moving through the circuit, meaning the LEDs won't light up as we want them to! Check out Adafruit's guide to common soldering problems. If the issue is a cold joint, usually holding a hot soldering iron to the joint will allow the solder to melt and reform a better joint. If you're new to soldering, it can take some practice in the beginning to get up to speed. Sometimes using flux, a substance that aids solder's ability to flow, can be helpful.
Rework is the act of taking your first attempt at making the board, noticing that there's a problem, and trying to fix the problem. For instance, if you noticed the LED legs were in the wrong holes and wanted to switch them around, this process of removing the LED and installing it again in a different orientation is called rework.
The PCB board we're using is called FR-1, a type of board where there's a 0.001" layer of copper that sits on top of a paper and epoxy-like resin substrate (the center part of the board). This structure becomes relevant when discussing rework because when reheating a solder joint and removing a part, like the LED, sometimes the copper pulls away from the substrate. When the copper separates from the substrate, it's quite hard, if not impossible, to fix. Often the only solution is to move back a few steps, mill out another PCB board, and solder components onto this new board. So, it's worth taking the time to carefully place the parts before soldering them to the board.
As you might've noticed, when you mill one PCB badge, there's still quite a bit of unused space on the right side of the PCB board. You can fit 2 badges on one PCB board. You can also mill them both in one milling procedure.
To place to badges on the PCB, load your first board as shown earlier in this tutorial. Then load the same .brd file again. The second .brd file will show up below the first one in the software. For this second file, change the Plan Placement for X to be 2.600 inches. This will move the plan over to the right so it's placed over the empty space on the PCB board. Next, change the Plan Placement for Y to be 0.0100". This is the same Y offset we used for the first board. It should look like this.
Your setup would look like this.
To mill the boards at the same time, click "Mill All Visible". The machine will proceed to cut the traces in both badges, then the holes in both boards, and finally the outlines.
The finished boards will look like this.
If you have any questions, don't hesitate to contact us at firstname.lastname@example.org. We're here to help. And if you do make the badge, be sure to share it with us. We'd love to see it using #makewithdigikey!
Key Parts and Components