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Usually, I stick to single sided layouts whenever possible.
Sometimes, you can not avoid a second layer. For every via in the circuit, overlapping to the associated
counterpart is essential.
A tolerance of more than 0.1mm is not acceptable...
One day, I had a "great" (...) idea of how to overcome the alignment problems.
Built as a temporary solution, this cheesy thingy has proven to be a reliable, fantastic solution for
precise overlapping. I milled hundreds of PCBs with this...
First side:
- Make sure you have positive x and y coordinates for top of PCB!
- Move your milling tool into the left, small hole and null x and y axis.
- Carefully bend your PCB to the top (x ynd y).
- Use your milling tool as a stopper and push your PCB up against it (from right to left, aligned to bottom).
- Move milling tool to your PCB-origin and note the traverse paths (*1*).
- Null and mill ;-)
- ...
Second side:
- Make sure you have negative(!) x and positive y coordinates for bottom of PCB!
- Carefully bend your PCB to the bottom side (x ynd y).
- Flip the board over in x direction
- Move your milling tool into the right hole and null x and y axis.
- Again, use your milling tool as a stopper and push your PCB up against it (from left to right, aligned to bottom).
- Move milling tool to the inverted position you noted before (*1*)
- Null and mill ;-)
- ...
Six screws are sufficient for holding it down, assumed you bent the PCB right (corners up)
Two guide rails for T-slot table adaption.
The PCB adapter should have a fixed, marked position on your machine.
The milling zone is lowered and the edge can be used for precise y-alignment.
Just a stupid idea, but it works pretty well ;)
ASkr 4/2006
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