WEEK 4

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WEEK ·4·

ELECTRONICS PRODUCTION

INDIVIDUAL ASSIGNMENT

1. make an in-circuit programmer by milling the PCB, then optionally trying other processes

LEARNING TO USE THE MODELA MACHINE

I've never made a copper clad board. This is why Gonzalo (our Fab Academy instructor) taught us step by step to use the Modela Machine. First, place double-contact tape on the back of the copper clad board. This will prevent the board from moving while the machine is milling.

It has to look this way. The double contact tape should cover the largest area of the copper clad board.

Then the copper clad board is placed on the support of the Modela machine. The support or "bed" has a grid that will allow us to indicate coordinates of the location of the copper clad board.

The copper clad board should be stuck properly. It is important NOT to place your fingers on the board because we will fill it with fat. Hold the copper clad board by the sides.

We will use two drill bits for this work. The 1/64 drill bit is good for milling the board. The 1/32 drill bit serves us to cut the board. Then carefully position the drill bits so that they do not break.

Then in the program place the coordinates and load the image of the traces to start milling. I’ll explain the setting steps of the program later.

The machine starts milling the card.

Once the process is finished, we suck the dust. Repeat the process with 1/32 drill bit.

This is how the PCB looks like in the end.

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MILLING AND CUTTING THE PCB

Now it's my turn to do the process by myself. First I organized my tools. The copper clad board and the two drill bits. 1/32 SE 2FL and 1/64 SE 2FL

The first thing to do is to pin up the board to the platform using double contact tape. 1/64 SE 2FL drill bit is used for milling the board. It has to be placed and adjusted with care. Manually we will have to lower the machine head to an ideal height to start the milling.

A copper board with a good milling looks like the one in the photo. Check that the copper part is well defined.

The 1/32 SE 2FL drill bit is used to cut the board. The chips that comes out of this process are thicker, as seen in the photo. This is also a way of seeing that the machine is cutting to a correct depth.

Finally it will look like this. The cut must allow to remove the board easily. Re-vacuum for cleaning.

My first copper clad board was very good. I decided to make two more boards because the next step is welding so I wanted to have some “back up” boards.

Here we see the milling process on the second board. The chip is thinner.

As seen in the photo this was not a good milling. This happened because the board or the base of support were a little curved and when passing the drill bit, it easily took some areas and others not. I had to do the milling again.

I decided not to make the cut immediately to test if making a third board could ruin the second one. But it was not ruined, the spindle works with different coordinates for each board.

The milling of the third board came out very well.

I started cutting the second board.

The cut was not made. I forgot to change the setting option from milling to cut.

I thought it was because the drill bit was not very deep so, manually, I lowered it two more points and as you see in the photo when moving the machine head, it made a diagonal cut to the board.

The cut of the third board came out very well.

I wanted to make a third board but I didnt properly secure the drill bit and as we see it didn´t milled well. The drill bit broke.

11 - 15

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SETTING UP THE MODELA MACHINE

Here I will explain step by step the settings that I use for the Modela machine. The first thing is to have in PNG the files you want to mill or cut. The image on the left shows the traces, the middle image the cut box and the image on the right is the diagram for welding the components.

The first thing is to start Linux, open the terminal and type sudo fab to find the program of the Modela machine.

In output process we look for: Roland MDX-20mill and then appears the box to place the settings.

First I loaded the png image. The preview of the image appears on the left side. Then I clicked on: make path to see the route that the machine will make. In the configurations we place the following: error 0.1

In the upper box we put "mill traces 1/64" as it is the first indication that we will give the machine. We place the start coordinates of the copper clad board. We click on: make.rml and then on: send it. A box like the image appears indicating the time the process takes and the status bar.

Once the process is finished all the traces become red.

Then (having already changed the drill bit) I loaded the image of the cut box and chose the option: cut out board 1/32. Error is still 0.1 and I placed the source coordinates then clicked on; "make rml" and on: "send it". The progress bar will appear.

I repeated the process for copper clad boards # 2 and # 3

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SOLDERING THE COMPONENTS TO THE PCB

The first thing I did was to order the components that I would have to solder, then stick them in my notebook next to their names (so as not to confuse them as they are really small).

I cleaned the soldering station. In the image we see a cautious that when heated and placed tin would do the soldering. It is important to have wet the sponge that is seen under the cautil since there we will clean the rest of tin of the cautil.

I used the copper clad board # 2 to practice welding since I have never soldered anything before. A good weld must shine and care must be taken not to join traces with the weld.

After the practice I took the copper clad board # 1 and start soldering the most complicated components. I started with the IC (integrated circuit) and the diodes. These components have a specific way of being placed, otherwise they will not work.

Here we see the first well-soldered components.

Then I continued with the resistors, capacitors, jumper and pins.

It is necessary to have good illumination direct to the board, good pulse not to place crooked components and to have on hand the diagram that will guide us during the process.

Here we see my copper clad board completely soldered.

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PROGRAMMING THE PCB

The first thing was to prove that the plate is well welded. I tried it by connecting it to the computer, the green lights mean that the computer recognizes the board so it is well welded.

The next step was to program the board. For that i opened the terminal on Linux and write: make clean

The next step is: make hex

After making Make fuse, the process concludes

Then we write: lsusb and we see that the board is being recognized which indicates the term of the programming.

To be able to record on the board you have to remove the jumpers. The copper clad board ends up looking like the image.

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