8. Electronics Production¶
Here under are the list of information from other instructors during the global session;
* DocumentAs You Go
Unit description¶
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Group assignment:
- Characterize the design rules for your in-house PCB production process: document the settings for your machine.
- Document the workflow for sending a PCB to a boardhouse
- Document your work to the group work page and reflect on your individual page what you learned
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Individual assignment:
- Make and test a microcontroller development board that you designed
Learning outcomes¶
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Describe the process of tool-path generation, milling/laser engraving, stuffing, de-bugging and programming¶
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Demonstrate correct workflows and identify areas for improvement if required¶
Group Assignment¶
Individual Assignment¶
Regarding my week06 Development Board, I had suggestion from my instructor Kae who knows about my final project;
* #### Instruction from Kae
With the current board, wiring is required, but it is possible to combine it with a potentiometer to drive a single servo motor, or to connect an IMU.
Suggested Improvements from Kae;
The following changes may improve usability:
1) Use D3 instead of D1 for the LED
D1 is an analog-capable pin and can be used for sensors, so using it for an LED may be wasteful.
It is recommended to use D3, which has no other specific functions.
Note that this LED pin is also exposed on the header pins. Because the pin carries the LED load, extra care is required when using it as an input or output.
2) If pins are available, it may be useful to connect GND, 3.3 V, and 5 V
This can improve flexibility for future connections.
3) Placing J6 on the left side makes wiring easier
This layout simplifies connections for sensors and I²C devices, and makes it easier to design boards related to input circuitry.
Having those suggestion, I decided to modify my development board by following this.
My previous Development Board was as follows;
Here under are the points my instructor suggested me to design PCB;
Data lines should be as short as possible to minimize the electricity delay.
Power lines should not be too close to other lines to be free from getting short circuit by soldering.
* Make a group for Power and Ground lines with set of pins.
Firstly, I modified the schematics to change the LED connection from D1 to D3 to Keep D1 for other purpose such as Analog input while D3 does not have such function but digital connection only.
Secondly, I modified the distance between each pins and micro computer, and changed the position of switch from bottom to top left.
There is a cross line of +3V3
While I was wondering how to solve this cross line issue, Daisuke suggested me of swapping J2 pin and J3 pins’ position.
Yes, It worked!
Execute “Design Rules Checker”.
Got two errors but for Switch not closed with lines which is not necessary.
PullDown File menu and select “Plot”.
For Lines “F.Cu” and “Edge Cuts” milling,
Select all necessary points as below, then click “Plot”.
Output Messages by Plot comes.
For Hole “B.Cu” milling,
Select all necessary points of which “Drill marks” setting need to be selected as “Actual size”, then click “Plot”.
Holes plot were made.
Open “Mods” and select PullDown menu at top left “Program”.
Select “mill 2D PCB” in SRM-20 mill.
Click “Select SVG file” button in Mods.
Select lines cut “F_Cu” SVG file in you PC.
Check if the shape and size is similar to what you designed.
Be careful that the size might be different sometimes due to the PC system and process.
In such case, you have to try to get exactly the same size as you designed in KiCad drawing.
Actually, this drawing is not the correct one. I should have made “inverse” of this drawing for circuit line milling.¶
Select “1/64 flat” as the cutting tool.
Switch On both “edit info collapse” switches.
Click “calculate” button to make the milling path.
Automatically, below like 3D milling path will appear.
Still I didn’t realize that this milling is wrong at this point.¶
One rml file which is the trace path of milling is made at “Download” folder.
Next I worked with the “Edge Cut” design, which is all black colored square made by KiCad.
Since “Mods” makes tool path at the black color part in the design file such as “png” or “SVG”, you need to draw only cutting line.
Then, open “Edge_Cuts” file with InkScape, and set “Stroke Style” Width as 1.5 mm.
Set stroke color as white, and you will see the white square as follows.
By applying “inverse” of this figure, it will be black frame which will be considered milling path by “Mods”.
Save the file with PNG format.
Select “Edge_Cuts PNG file” in Mods.
Press “invert” button and you get the black framed square as follows.
Choose “1/32 cutout” for Edge Cut.
Same as “F_Cu”, it is very important to set “0” at the x,y,z origin part, and switch On the “edit info collapse” switches.
Click “Calculate” for making milling path.
3D image of “Edge Cuts” is made.
Lastly, I worked with the “B.Cu” (Hole Cutting) design.
Objective of this process is to remain only “inner circle” since outer circle hole is too big for the Development Board.
Change Back Ground Color from White to Black by setting RGB as 0,0,0.
Then, export with “PNG file” format.
You get following design PNG file.
By inverting this color, “Mods” will make hole cut path.
Open B_Cu PNG file by “Mods”.
Apply “invert” by clicking the button.
Select “1/32 drill” for the hole drilling path.
Same as previous other settings, it is very important to set “0” at the x,y,z origin part, and switch On the “edit info collapse” switches.
Click “Calculate” for making drilling path.
You get following 3D view of drilling result image.
Operation of Copper Board Cut¶
Following the group work, I proceeded to cut from the “f_Cu” (lines cutting) with Roland SR20 milling machine.
I used new 1/64 inch End-Mill for “f_cu” cutting.
Cutting with 1/64 inch End-Mill
First cut was done with 1/64 End-Mill.
Cleaned the surface and showed my instructor the cut result, and was tolled “Cut path is opposite!”.
Yes, I made mistake “Not inverting” the path design at the “Mods” for this path making.
Then, I opened the “Mods” and made “revert” of “f_Cu” file and Calculated.
Yes, this appearance must be the correct cut path.
“f_Cu” cut with correct path and surface cleaned for next cut by changing the End-Mill from 1/64 to 1/32 inch.
Hole cutting with 1/32 inch End-Mill
Edge Cutting with 1/32 inch End-Mill
All cut done
Apply seal remover liquid
CNC Cut result
Surface cleaning with a metal fiver
