Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:

> 
> I would not dump it, but first try the method that would result in 
a great  
> simplification of the overall process.
> If it doesn't work you can still go back.
 
You are right, in a sense, one process is an extension of the other. 
Raw copper clad pcb to circuit board in one go looks very attractive.

 
> I think you are right, a defined amount of energy, and thus a 
defined  
> amount of abraded material might be the key to etching down to the  
> laminate. What i see as a potential problem is how to figure out 
the ideal  
> process to position the electrode. One approach could be to treat 
each dot  
> as individual sinker EDM process, but the trouble is when you are 
finished  
> there is solid material after the copper.
> Ideally, one would be able to blast each dot with a single spark, 
but what  
> if you were just advancing and the gap was so large you only 
achieved  
> maybe half a proper spark. What do you do? stop and try more 
sparks?  
> advance?

I understand that Carl does one spark per 0.001in step with his 
machine. I am assuming that the spark is only allowed to occur 
between steps, not during continuous motion. My option would be to 
use the Garden of EDM control to allow as many multiple sparks as 
were required at each step to ensure ablation, perhaps coupled with a 
rotating electrode. Of course, the step does not have to equal the 
electrode tip diameter, half tip diameter steps would ensure that the 
electrode always covered some copper, for example.

Perhaps Carl could give some intial parameters on his spark control 
settings, voltage level, gate duration etc that he has found to work, 
to save duplicating experimental work?

My first trial will be jog steps on the cnc with hand firing a 
selected number of shots in order to judge the quality of the mill.

> I think you might be able to use high power FETs in a very similar  
> fashion, as they have similar gate characteristics.

Yes, I can't see why not, after all we are not talking power station 
currents.

Roger