Let's Go

What is Milling?
It is designed to cut or shape metal using a rotating tool.
What is PCB Milling
is the process of removing areas of copper from a sheet of printed circuit board material to recreate the circuit according to the design or layout.
Earlier I've tried Making PCB's by Etching process
In etching we take an Impression of our print on the board by some heat treatment and dip it in FeCl3 solution and the rest copper parts are removed only the imprinted part is left.
But this time I was going to learn a new technique for PCB manufacturing. Although this (milling) method is good for personal use not for commercial use.

First Things First

Introduction to Mods-
For the input to the milling machine we have to give it .rml file which is basically composed of G-Codes
G-codes are basically the language that the Milling machine understand it is basically the co-ordinate system x,y,z system.
The work flow is as follows-

1. Making of the PCB design (we omit that this week)
2. Conversion of the design file into .png format file with a high resolution say above 1000 dpi (dots per inch).
3. Converting that .png file into .rml extension by going to fabmodules.org
4. Selecting the input .png file
5. Selecting the output as .rml
6. Now selecting the Process and Machine (SRM-20)
7. Setting some pararmeters (which i'll be discussing further) the calculating the tool path and finally downloading the file.

Testing the Milling traces

For testing the capability of milling traces I downloaded the test file from fab academy archive.

you can check out the files from this link.

I performed the test using 1/64 endmill and it clearly milled to the last of .001 trace in a good manner.
However in making our ISP I used V-Bit because of non availabiltiy of 1/32 endmills and also the pointed edge of 1/64 end mill was blunt somehow fue to some mis-handeling of the bits.
For the group assignment you can go to our group assignment page from this link.

Let's Make the Fab ISP

Step 1-Selecting the Fab-ISP

There are various versiions of Fab-ISP one can choose any one to make I decided to make Brian's ISP.

Source Files

Step 2 - Using Mods

Selecting the output image type, in my case it was .rml.

Step 3-Selecting the Process

Now select the process : Blue circled-Traces to cut the path, Red circled-To Cut the board outline to prey it out.

Step 4- Checking the size of image

On the right hand side toolbar check whetehr the dimensions of the image are correct and then select the Machine. The by default speed is 4mm/sec we don't need to manipulate that.

Step 5-Selecting the Process Parameters

After doing the group assignment and understanding the machine th conclusion of the parameters are displayed I used this settings for milling my board.

Step 5- generating tool path

After sCalculating mods will take some time to generate tool path depending on the process parameters given and after that you can just save your file and it will be saved in your downloads folder in.rml extension.

Understanding Our various parametrs and V-bit

• Just to observe that the tool dimater of a v-bit will increase with the increase in Cut Depth.
  

Understanding Our fabmodules parameters- Optimum Settings Used

• Cut Depth is how deep you want the tool to cut in your PCB. Generally the cut depth shpuld be equal to the thckness of the Copper Film on the FR4 board that we used.
  I used 0.12 as it worked best for out makeshift V-bit.
• Tool Diameter is the diamter if the tip of the tool, For tracing we use 1⁄64 and to cut the outer edge we use 1⁄32. Since in our lab we use a V-bit instead of the 1⁄64 bit, by some trial and error TOOL DIAMTER of 0.35mm to .40 worked best for us.
• No. of Offsets is basically the number of passes the tool will take over the surface, for minimum it should be 4 so that traces aren't short, but if one want's just the traces and all pther copper to be removed then -1 settings should be used(it takes a long time and noisy)
• Offset Overlap so our tool dia is 0.35, now lets assume it mills one line first, then it goes for the next line, Optimally the difference b/w the two lines should be equal to the tool diameter which is 0.35mm. But to be on the safer side we give a certain overlap percentage so that the cutting head goes over the preiously cut path and makes sure there is no residue left.
• Speed- We left the Default speed i.e 4 mms/sec.
• Direction- Climb should be selected instead of conventional settings it gives best results in climb.

Download the traces and outline files from here-
Traces and Cutout

Let's Do the milling

Machine used Roland SRM-20
Software for operating the machine - V panel for SRM-20
The machine consit of a power button and a cable to connect to the PC in our lab a setup is made for SRM so I was saved from downloading any kind of software for it as it was already connected to lab's PC which had the software for it.

Using V panel to operate SRM

The video shows the movement of the tool using the gui of v panel.

Programming the Fab-ISP

Following Steps are there to program the Programmer-


• Install the necessary software for your operating system and download the firmware.
• Then you edit the Makefile
• Set the fuses / program the board
• Verify that the board is working properly
• Remove up the jumpers to make it a programmer.

Here I came to know the down or loss of having a windows system. I felt like for development environment windows can be a bit hard side to get things done. A separate tutorial is given on Brians page for windows system for programming of the ISP.
You can go to the tutorial from this link.

Installation Of Softwares

The bundle of software I installed were-

Atmel AVR Toolchain

GNU Make

AVR dude

Updating My Path

Zadig - for one time Update of Drivers

I was bound to contact my instructor for this all the other prople in Lab were either using mac or linux for which only one command was doing all the magic.
However following the tutorial given the documentation is very neat and I followed the same steps infront of my instructor who was the incharge for my isp board that day.

Editing the Makefile

I downloaded the firmware file from the fab archive and opened the Make File in sublime text and changed the programmer to avrmkii
because we were programming using avr ISP. Basically we were using a progremmer to program a board and make it a programmmer so that it will be used in future as a programmer.
Download the firmfile from here-
Firm Files

Running Commands

Now after that I opened the bash terminal and run these commands-

$make

You'll receive no error

$make hex

You'll see a long chain of Hex code being generated

$make fuse

Setting Fuses so that Board uses external clock

$make flash

Flshing the board means overriding any prev programs etc.

$make rst disbl

And taddaaaaa green leds were blinking too fast showing the date transfer(maybe) and yes the ISP board wos programmed. During the process my laptop was with the instructor and we were having one on one session for this so I could'nt take screenshot of my laptop.
The whole command was typed infront of instructor along with Jay Sir as he was laso stuck in this with me and it was closing lab time we all were in a hurry I could not maaged to take screen capture of my laptop screen's command window.
Now the last process was blowing up the fuse. So i desoldered the fuse.. Now my programmer was ready to program any board.

~Pic taken from brians Page and edited by me

Learning Outcome

• i learned a new technique of making a PCB earlier I was only aware of the etching process of making PCBs.
• I learned to operate mods and also one needs to know the machine before performing any operations on it.
• Handling of so tiny smd components which I've never touche din my life andd soldering it and making my own board was kind of a lil achievement.
• My instructor helped me out in programming the board for which I was so bewildered for days, I learned to deal with problems longer than before.
• I will be using my Fab ISB board in the upcoming week to program other boards. I used my board to help out Jay Sir a fellow Student to program his ISP.