Characterize the design rules for your in-house PCB production process
Submit a PCB design to a board house
Individual assignment:
Make and test a microcontroller development board that you designed
Extra credit: make it with another process
Using mods CE for cutting PCB on Carvera
Layout of Mods CE
Note: use Firefox to run this! The other browsers cause problems.
Proceedings:
Prep your files: I took a screenshot
right click - programs - open programs - machines - Carvera - mill 2D PCB
In the menus within the green rectangle, upload svg files. Upper one: svg of actual traces. Lower one: svg of outer contour
Examples for pictures to upload in Mods CE. Left: png of actual traces. Right: png of outer contour
Change settings to match Carvera in Calculate (black) menu. Click on "Calculate"
Preview CNC process in View (blue) menu. This will automatically download the gcode/ nc
Preview nc. The outer edge is missing.
Vocab:
Traces: the layout on your PCB
Exterior Image/ EdgeCut: outside line where PCB can be cut.
Tool Diameter: diameter of the tip of the tool. Typically we use 0.4mm for the traces and 0.8 for cutting. Always double check
when starting to mill.
Tabs: the stencil thing one can use for securing cut pieces do not move. If ignored, the PCB might not work.
DPI: according to this source,
DPI stands for "During Production Inspection". The machine will monitor the milling process and correct if necessary.
Weirdly enough, the first error we did on the lab is not setting the DPI. This resulted in the scale of the PCB increasing by the 100.
ASK QUESTION IN GLOBAL/ REGIONAL LECTURE
What we call gcode is actually nc (numerical control) or tip (only generated in fusion) file type
To review gcode use "gcode to english"
Good gcode visualizer is "Camotics
For milling PCBs use the 0.2mm, 0.4mm, and 0.8mm metal drill bits.
Step down: 0.14mm
Whenever the measuring laser is on or the machine moves: keep fingers away!
Hardstop: when end switches signal the end is near. Softstop: software knows the dimensions of machines
and signals end through relative position.
Do measuring with glass rules (bc glass does not have thermic expansion).
Fab Mods:
Program to generate gcode from pics developed by FAB Academy. We use it to mill PCBs.
How to use: Open in browser (firefox works best) then OpenPrograms-Mill 2D PCB Program -
On the left side input t2 pics: one for the outer cut and another for the PCB drill itself.
Always check the preview. It's available in the "View" card. Change tools in main card.
Proceedings using Carvera Controller Software:
Turn on CNC mill (button behind machine right side) and connect to computer (yellow button in Fig1).
Home machine manually.
Upload files
Upload Files
Select uploaded file
Make sure the right bits are in the right slots.The order of the bits is written next to the bit slots.
The wireless probe is always on the far back slot.
There are 2 parts to connecting the bits: the collet (to fasten bit) and the bit itself. For changing bits:
Check if the right collet is in. If not, use big cylinder bit to unscrew it.
Fasten the new collet by turning it with the fingers.
Make sure that the bits are placed correctly in their slots:
the circle has to be fully hidden and the bit placed vertically.
To place them correctly, press on the circles on the bits.
Fixing the material (if it moves, it breaks)
Check if material is perfectly straight like shown in the picture. If it is not, bent it accordingly.
Measure in every direction.
Measuring straightness of material
Attach the double sided ultra thin tape to the bottom of the plate.
Make sure to leave a bit of overlap to avoid wrinkles or dirt from touching it. Furthermore, this helps when
removing the tape. Check the pic for an example:
How to attach double sided tape correctly
Stick it as far front left as possible.
Press down softly when sticking to plate with a cloth or sth.
If it does not do a proper job: let it finish and restart operation with an extra 0.1mm step down in the beginning.
Setting the working coordinate system within the machine
Fig1: Layout of Carvera Controller
Z-Axis: change the bit to the wireless probe one in Carvera controller. Use the auto probe function.
Manual check if correct: use controls to move closely to the plate. Keep decreasing step down dimension the closer you get.
You'll know you reached when the setup from the pic makes a sound:
Measure if connection is establish.
Set multimeter to make noise when electricity is flowing. Power to plate, GND to bit.
x/y-Axis: drive where you want to go manually using the Carvera Controllers. Smaller steps the closer you get (set with the orange buttons).
Right click on x/y buttons and make Zero (dark blue menu). For really precise measuring: use "edge finder" bit. Flick it, it will wobble.
Move it closer to material until it stops wobbling. It will then make a jump. That's how you know half a radius ago was the zero.
Carvera Controller control.
Manually home machine.
Importing the files: (see Fig1 for layout)
Open the light blue menu -> "import file" -> close
Reopen light blue menu -> "select file
Unselect the two options. Start machine. Stay close and keep hand close to emergency stop button.
First result. Do not go smaller than 0.001inches distance!
Follow instructions from the group assignment. Check the images there. Apart from that, we ran into the following problems:
The size of the PCB was scaled. My instructor figured out that we had to increase the DPI. Then the size was correct.
By then we tried another board: the Fab-Xiao
Download link to .nc file: Download: Fab-Xiao NC
We wanted to use the same plate to mill the PCB as other people as well. We changed the XY origin.
Inside the traces, some leftovers remain. These might cause shortcuts or other issues. Use a cutter knife to remove them and a metal sponge to sand it down.
We were missing SMD mae headers. We bended some through holes to 90° and them soldered them on.
The machine gave an error warning whenever we got close to the origin. We just got as close as possible.
Files for the Hello Xiao
Post-processing:
Sand it down and clean up traces
Leftover traces (black) need to be removed.
Prepare the components: bend and cut the headers however it's needed. Collect components.
Collected components. Advice: use double sided tape to not loose them
Solder the components
Final result of PCB
Soldering instructions/ safety precautions:
Tie back your hair.
If sth falls, let it fall.
Do not touch the tip.
Touch the soldering iron to the solder wire to melt it. Add the component to it. Remove it to let it cool/ harden.
Try to not to inhale the fumes.
Everything the soldering iron touches gets hot. Be careful when holding it in place.
Board for the Pico H/ Standard Pico
The Pico H is a static sensitive module and therefore should best be handled on a non static surface.
Knowing myself, I will do precisely that very soon. As such, I designed a breakout board around it.
