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Unlike a PCB order from a normal [PCB house] PCBs on the PCB Mill are made by isolating the desired trace from the plate of copper (known as the "copper clad"). This can cause problems because according to your design there is only a thin trace of copper between any 2 points amongst a sea of essentially nothing (more specifically nothing conductive that would get in the way). With the isolation method that the PCB Mill uses, you have to make sure that your layout program of choice knows that there is copper everywhere else. Otherwise components will end up shorted together.
| Warning |
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Always mill BOTH sides of the PCB layout. Even if you have only 1 signal layer. If you leave the "other" side of the copper un-milled, the leads of your components will be shorted together by the large, unisolated copper plane that is on the back. ALWAYS isolate the pads on the reverse side of your PCB....it may not look like the leads will short but they inevitably come into contact with the un-milled copper plane. |
Dealing with no Plated Through Holes
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The easiest way to verify the correct drill depth is to
- insert the drill into the collet all the way up the collar (the little brightly colored plastic ring that should be on all the drills, should have the drill size marked on the same ring in white).
- Use the jog function of the mill to move the head so that the drill bit itself is just to the left of the copper clad board but the foot of the head is still squarely on the copper clad.
- Use your hand (NOT the head down command in the jog window) to gently lower the head until you either reach the bottom of the head stroke or the drill touches the material.
- If the drill touches the back of the
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- mill before the head bottoms out on the copper clad you need to:
- adjust the Up/Down adjustment ring on the head until the drill just barely grazes the aluminum sacrificial board.
- Now adjust the lower limit of the head so it will go down just a little a more into the sacrificial board. Ideally you want the conical section at the top of the drill head to be fully embedded into the sacrificial board so that only the uniform section of the drill goes through the copper clad.
Once you believe that you have set the drill depth correctly, jog :
- Jog the drill head to a spare spot on the copper clad
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- Turn on the drill spindle to reasonable speed and
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- then
- Activate the "head down" command in the jog window
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- Inspect the hole to insure that it has fully and cleanly penetrated the entire copper clad, but has not gone too far (more than 1/4 of the way) into the sacrificial board.
Go ahead and run through all the drills that you need to do on the entire board. Since the drill bit collars are gaurenteed guaranteed to all be at the same height, you do not need to readjust the drill depth for every new hole size you have to drill.
| Warning |
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If you ever switch to a mill bit or carbide router or for ANY reason adjust the drill depth you will need to run through the drill depth procedure before drilling another (set) of holes. |
If your drill does not have a collar (AKA you got it from ELEC 342 or the likes...grrr....) then you will have to re-adjust the drill depth for every drill that you use or insert all the drills all the way to bottom of the drill collet (or get the bits from the OEDK).
Mill Depth
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Always mill the traces AFTER you drill the holes, doing it the other way may result in the drill pulling up an etched trace and destroying the work of the milling process. |
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