Homebrew PCBs

On Mon, 10 Jan 2005 22:35:57 -0000, Steve <alienrelics@...> wrote:

>
> --- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@y...>
> wrote:
> ...
>> Ok, So lets stick to conventional top side drilling. The problem I see
>> now is the lens system cannot be perpendicular to the plane of the PCB.
>> Did your lens experiment work ok when viewing the PCB at a angle ?
>> What diameter was your lens ?
>> How about just a large diameter lens without worrying about a screen ?
> ...

didn't get that before so i'm answering it now.
The trick is to view from the _OTHER_ side of the drill.
the screen has a target painted on it where the drill will come through.
A lens alone will not work because if you move your head the picture  
moves, making it impossibe to draw a target on the lens that doesn't move  
relative to the drill.
Projection solves that problem.
The goal is to have a magnified picture of the pad, underlying a bullseye.  
Align the two and you have the perfect hole.


> Otherwise, a camera off of perpendicular means the center of the
> screen is only the drill point of the board is the same thickness as
> when it was calibrated and there is no curve to the board. This is not
> a killer, though, as there are only a few different thicknesses of
> boards and it can be "calibrated" for each thickness you use.
> Steve Greenfield


Steve, see above. I do not consider looking off-axis an option, it has  
many drawbacks and almost no advantages. Looking from the other side is  
not prevented in any way, so why not do it that way?
Also, commercial machines all have the viewing apparatus opposite the  
drill, but that doesn't force you not to turn the principle upside down  
and have a normal drill from top viewing from bottom.


The reson i'm doing that now is that carbide drills are just working way  
too good. In the past i used HSS and freehand drilling, which is think is  
as fast and easy as it gets. Of course the drills dull quite fast.
If you etch a small hole in the copper pad the drill will catch easily.  
Now, in a drillstand, with carbide drills, the drill will not self-center  
and it is a tedious process to lign up every hole. My boards are actually  
worse since i have carbide drills and i do not like it, at all.

ST