Fab Lab ECAE

SRM 20 PCB Milling

Using the SRM-20 for PCB Production: Characterize the design rules for your PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.

Line test:

for the group assignment we did this line test and the png was taken from neil and the reaosn we are doing test because will help us identify if the tool can go between two traces as well as how thin can the traces be. Roland SRM-20 was used in this test with a 1/64 inch mill bit.

and then we used the 1/32 mill bit to do cut the outline :

result:

This was done with a dull milling bit. There were serious burrs because it was not sharp, but we are still waiting for our inventory to arrive which wil allow us to use sharp tools again.

Downloading the PCB files

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You can find the files on this page (PCB files designed by Mr. Brian).

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Milling the pcb :

Since all we have is ATiny45 so I went for brian's ISP because it seems to be working for most people and it is very well documented, I began by downloading the PNG files for both the traces and the outline from brian's page :

we have the roland SRM-20 in our lab and we will be using it for milling pcbs and molds:

To use the milling machine, do the following steps:

First zero the z-axis and zeroing the z-axis is very important and It must be re-adjusted everytime the tool is changed , to zero the z-axis :

change the tool and push it all the way inside in a way only the flute is visible

carefully move it down using V-panel but do NOT let touch the cupper plate because some tools are very fragile , now adjust it manually so it is touching the plate

finally set the zero origin for the z-axis in v-panel

Zero the x and y axis by moving with vpanel but make sure that the tool is not touching the plate otherwise it will break.

Now go to fabmodules.org. this website calculate the tool path and gives you the file that is Compatible with your machine.

Export your files and choose your machine and v-bit you are going to use

Set the cut depth to what you want

Now calculate then save

Start cutting

we used two kind of v-bits:
a. 1/64 for traces with 4 offsets and cut depth of 0.15 mm
b. 1/32 cutting with 3 passes and and total cut depth of 1.7 mm