Week 8 – Electronics Production

Group Assignment

In this week’s group assignment, we evaluated the minimum trace width and the minimum spacing between tracks that can be reliably achieved using our PCB milling machine Roland Modela MDX 20, Vinyl Cutter Roland CAMM-1 and Leaser cutter X Tool.

Group Assignment

Test with Roland Modela MDX 20

Test with Roland CAMM-1 Vinyl Cutter

Test with XTool Leaser Cutter

PCB Design - Verifying Constrains

Below is the design from my Electronics Design Week that I’ll be producing this week. I made a few small tweaks to improve the layout and usability. I added a right-angle sliding switch (highlighted in the green box) to easily turn the battery ON and OFF. Since the PCB size was originally 50 mm × 70 mm, I adjusted the component placement, bringing them slightly closer in the Y-direction. For the next iteration, I plan to include a push-button with a latching circuit for power control.

Test with XTool Leaser Cutter

Based on our Group Assignment, we verified the design rule constrains that we gave during Electronics Design Week.

Design Rules Constrains

I asked AI to explain above constrains and made a table for my future reference. Prompt : can you please help me to understand each of these constrains in the attached image?

As our drill bit size is 0.8 mm, we need to update the DRC constrains. And increase the hole size of XIAO pad holes to 0.85 mm. first, I update one pad property and then copy that updated pad property then selected remaining XIAO holes and used paste default pad property to selected. Click any of the XIAO hole pad >> Right click >> Properties >> Diameter : 0.85 mm >> click Ok >> again right click same hole pad >> copy pad property to default >> select all the remaining hole pads >> paste default pad property. By doing this all the XIAO pads will be updated with the 0.85 mm dia drills.

Right click on pad >> Pad Properties >> Update Diameter : 0.85mm >> Ok

Copy pad property to default

Select all remaining pads >> paste default pad property

Track and Via hole, as I wanted to use battery my instructor Saheen guided me for adding the via hole becasue the VIN and GND for battery connection are on the back side of XIAO thus after soldering, I will not able to excess it. Thus, we need to a via hole. Select Place Vias >> Place the Vias on the VIN and GND pads >> double click the placed Vias >> update via diameter : 1.4 mm and Via hole : 0.85 mm >> Click Ok.

Place Vias >> Place the Vias on the VIN and GND pads

Double click the placed Vias >> update via diameter : 1.4 mm and Via hole : 0.85 mm >> Click Ok

After updating all and before preceding for gerber generation it is very important to perform DRC - Design Rule Check and verify the update the 3D viewer.

Design Rule Check

Now, I generated the Gerber files. They are considered as instruction files that machine understands, this is very important when the PCB is sent to the factory for fabrication. The Gerber file contains information about PCB layers for example Copper layers (tracks and pads), Drill information, Edge cut / board outline information etc. The steps to generate gerber files is documented in my week 6 - Electronics Design Week.

Gerber Files Generation

Gerber Files Information

For my future reference and understanding, I am adding a video of PCB making process in a factory.

Gerber to PNG generation (FABLAB Kerala Plugins) & Interactive BOM Generation

In our case, PCB MIlling in FABLAB, we usually need PNG/SVG of Top layer, Bottom layer (if applicable), Drills and Border line.

I used Gerber to PNG plugin made by FABLAB Kerala to generate the PNG image of my Traces Top layer, Drill Top Layer and Outline Top layer. More details about Gerber2Png. Later in my documentation these images, I will open in modesCE for PCB milling in the FABLAB

Gerber2Png Plugin

Gerber2Png Plugin

Now, I clicked on Gerber2Png plugin icon >> a new window will open in the browser >> Click Generate PNG >> Download All .

Gerber2Png file generation

Gerber2Png file generation

Traces_Top_layer

Drill Top Layer

Outline Top layer

At this stage, using online modesCE, I check the toolpaths in 3D and 3D and get the idea of final PCB outcome. Here I pats are appearing to near then we can go back and rearrange the components and re-draw the paths.

Online Modes - Carbide Nomand PCB

2D Toolpath

3D of PCB

X,Y and Z-direction Toolpaths

Next, I generated an interactive BOM (Bill of Material) by using from a KiCAD plugin - Interactive HTML BOM. To generate the BOM Click the HTML BOM icon >> set the Directory / BOM Destination >> Generate BOM .

Interactive HTML BOM

Click the HTML BOM icon >> set the Directory / BOM Destination >> Generate BOM

Later after Milling the PCB, this BOM will be very useful in collecting, organizing and soldering the components onto the PCB.

HTML BOM

PCB Milling

We have Roland Modela MDX-20 milling machine in our lab. It is a is a 3-axis desktop milling machine.

Roland Modela MDX-20

To mill my PCB I need to perform three major operations - Traces Top layer, Drill Top Layer, and Outline Top layer.

Milling the Traces Top layer

The first thing that I did is I opened the offline modes in the PC and opened the Traces Top layer PNG file of that I got from Gerber to PNG plugin.

Open the modesCE

Open the Traces Top layer PNG

We are going to use V-bit 0.2 mm End mill for milling the Traces. We are using this end mill instead of 1/64 end mill because the 1/64 tip is very fragile and we need practice to use it, thus initially we are using V-bit 0.2 mm End mill.

Selected the End Mill to mill the Trace

Now I entered Offset numbers, offset stepovers ant then Click Calculate doing this will calcualte the vector toolpath for milling the top layer traces.

Offsets nos.: 4, Offset stepovers: 5, calculate

Then, I moved the clicked the Position to Change Bit.

Position to Change Bit

We need to be very careful while changing the tool but always keep your one hand under the tool bit so that it does not fall on the bed and break its tip. And attach the bit key back to the magnet.

Changing the Tool Bit

After this, I pressed the view button on the console of the machine so that the bed will come forward and I can stick my copper clad PCB on the bed.

Important always clean the bed using brush and vacuum before sticking the PCB on to the bed.

Then, using scale I measure the approximate X and Y distance of the object from the bed origin (0,0). This values I entered in Modes.

X distance of PCB from the Bed's origin

Y distance of PCB from the Bed's origin

I entered these X = 4 mm and Y = 6 mm values in to modes and press Move to Origin.

Enter values in the mode >> press move to origin

Now in below image, we can see that the End mill bit moved to the entered location, but its x coordinate is exactly on the top of the edge of the PCB, thus I increased X distance from 4 mm to 6 mm, so that the milling start point / workpiece origin is set at x = 6 mm and y = 6 mm. It is very important to remember the origin point.

The bit is exactly on the top of the edge of the PCB so I need to move it futher inside the PCB

X=4 and Y=6 >> X=6 and Y=6

We can calculate and see the trace and tool path by clicking on the view button and finally click send the milling process will be started.

Send to Machine for Milling

Milling Operation

Milling the Drill Top Layer

Now I moved the bit to position to change bit because to perform drill operation on top layer, I need to use 1/32 (about 0.8 mm) drill bit.

Change the Bit

Now I uploaded the PNG of Drill Top Layer and selected the Drill Bit 1/32 in the modes and then calculated the toolpath move the bit to origin and send the path to the Machine to start the Drilling process.

Open PNG of Drill Top Layer

Select 1/32 Drill Bit

Move to Origin

Calculate and Send

I sent the file to Machine and it started the drill operation.

Drill Top Layer

Milling the Outline Top layer

This operation will be perform my drill bit do I do not need to change the bit, I uploaded the PNG of Outline Top layer and keep the Drill Bit 1/32 as it is in the modes and then calculated the toolpath move the bit to origin and send the path to the Machine to start the Outline cutting process.

Cut Outline

Then I used the scraper tool to take the PCB out from the bed.

scraper tool

Sanded the PCB

I used the cutter knife to remove the copper and separate the traces. They were not connected in 2D vector file and 3D File, however the actual PCB was having joint traces.

Two Traces were touching

Component Soldering / Assembling

Using the FABSTACH, viewed and add the components from our FABLAB inventory. I printed the component list and used the double side transparent tap to stick the components on it.

FABSTACH

LAB's Inventory

Sources and sticked the components

Soldering Station

Here, while soldering the interactive HTML BOM is very useful to locate the component placement, and orientation mark it placed after soldering. The hovering feature over list can help locate the components.

Interactive HTML BOM

Understanding the direction of polar components such LED is important. In below image the direction of green aero shows the anode or the green lines on the top shows the cathode of the LED.

SMD 1206 BLUE LED

SW2818B Neopixel

While soldering SMB components, always heat the pad first then touch the solder wire to the pad not to the soldering iron. Then place the component using tweezers and heat the pad/component leg so that they will get connected. Now the component is placed properly aligned with other remaining pads. I soldered the remaining pads with the component legs.

Heat the pad and touch the solder wire to the pad

Hode the component with tweezers and solder its leg with the pad

Another important thing is to solder small and tiny component first and solder the big and the tall component in the last. Following this I soldered all the components of my board.

Final PCB

Inspection and Testing

The first thing that, I did was to clean the PCB with the pcb cleaning isopropyl alcohol.

Cleaning with isopropyl alcohol

Then, I used the multimeter to Test the continuity for any short circuit or open connection, It is good to refer the schematics and Gerber file while doing continuity test. I also checked the continuity from each XIAO EXP32C6 Pin to the Female Socket header using jumper wire.

Test the continuity for any short circuit or open connections

Last, I tested with USB Digital Tester (Model : J7-C) to check the Power on current consumption.

Power-ON Current Consumption Check

Next, I tried to program and tired to Blink LED.

          const int BlueLED = D7;         // the Pin number of Blue LED pin

          void setup() {
            // initialize digital pin BlueLED as an output.
            pinMode(BlueLED, OUTPUT);
          }

          // the loop function runs over and over again forever
          void loop() {
            digitalWrite(BlueLED, LOW);      // change state of the LED to LOW level
            delay(100);                      // wait for a 0.1 second
            digitalWrite(BlueLED, HIGH);     // change state of the LED to HIGH level
            delay(100);                      // wait for a 0.1 second
            digitalWrite(BlueLED, LOW);      // change state of the LED to LOW level
            delay(100);                      // wait for a 0.1 second
            digitalWrite(BlueLED, HIGH);     // change state of the LED to HIGH level
            delay(700);                      // wait for a 0.7 second
          }
          

Last, I tried to program the Push_Button and tired to Blink LED based on Push button Input.

          const int BlueLED = D7;         // the Pin number of Blue LED pin
          const int PushButton = D8;      // the number of PushB Button pin,
          int ButtonStatus = LOW;         // Variable for reading the pushbutton status
          int i;                          // counter for for loop

          void setup() {
            // initialize digital pin BlueLED as an output.
            pinMode(BlueLED, OUTPUT);
            pinMode(PushButton, INPUT);
          }

          // the loop function runs over and over again forever
          void loop() {
            ButtonStatus = digitalRead(PushButton);   //read the digital status of Push Button 

            if (ButtonStatus == HIGH)                  //if Push Button Status in HIGH then flash LED 
            {
              for (i = 0; i<10; i++)
              {
                digitalWrite(BlueLED, LOW);      // change state of the LED to LOW level
                delay(100);                      // wait for a 0.1 second
                digitalWrite(BlueLED, HIGH);     // change state of the LED to HIGH level
                delay(100);                      // wait for a 0.1 second
                digitalWrite(BlueLED, LOW);      // change state of the LED to LOW level
                delay(100);                      // wait for a 0.1 second
                digitalWrite(BlueLED, HIGH);     // change state of the LED to HIGH level
                delay(700);                      // wait for a 0.7 second                      
              }
            }
            else 
            {
              digitalWrite(BlueLED, HIGH);        // change state of the LED to HIGH level        
            }
          }
          

Downloads and references

• Gerber Files
• PNG Files
• CNC 3018 Router Engraver
• Spindle Kit for 3018 CNC Machine