Homebrew PCBs

mpdickens wrote:

> Oh yeah, I forgot to mention that the total estimated
> cost of this device as currently visioned is $110.00
> USD excluding the nozzles, which I think is pretty
> good for a quality spray etcher. But, as with most
> projects, this number could increase by 20% ( And in
> this case, however unlikely, drop by as much as
> 3%...)unless I royally screw the design up.
> 
> As soon as this project is complete, tested and
> working, I'll post pictures, a bill of materials and a
> few notes.
> 

Excellent, Will love to see the finished result. But don't rush 
it  , let it be a rewarding and fun project. The cost will go up 
I'm sure, it never goes down :).

I am making a single sided spray etcher. All construction is by 
welded PVC sheet (mostly gray 4.5mm) There is a sealed lid and 
the PCB enters a raised opening on the lid so the PCB is more or 
less horizontal on the "underside" of the lid. A conveyor spray 
bar having 3 fan type nozzles mounted to it will move linearly 
across the width of the PCB and pray etchant upwards. Below the 
spray bar is room for 12 liters of etchant.

some dimensions;

Chamber (internal)		340 x 360 mm, height 330 mm
PCB panel capacity:		210 x 305 mm
nozzle to panel distance: 	130 mm (?)
nozzle to nozzle spacing: 	110 mm (?)
etchant sump volume: 		12 liters


I have finished building the chamber and lid. Today I finished a 
building a conveyor mechanism using an idea of pulleys and twine 
stretched across the chamber. It doesn't work because of friction 
on the plastic shafts and twine is not steady. Now I'm going to 
use a different approach (throwing away several days of work on 
the old idea). This time I might use two rails mounted inside of 
the chamber walls. A spray bar assembly having wheels will run on 
these two rails. One rail will be a V type fixing its location 
parallel to the rail direction and the other side will be simple 
flat rail configuration. If I can make a sealed housing for a 
stepper motor then the spray bar assembly will have motor mounted 
to it and directly driving one of the wheels. It would make sense 
to use a total of three wheels for the spray assembly so there is 
always contact with the rails.

Tools I'm mostly using are;

Plastic hot air welder
A router bench
Saw bench
small lathe for machining plastic pulleys