Homebrew PCBs

mpdickens wrote:
> --- Adam Seychell <adam_seychell@...> wrote:
> 
>>It just so happens my current project is building a
>>spray etcher. 
> 
> 
> Obviously, I am also building a spray etcher. I
> searched through the message archives and I found
> references to a couple of pumps (One was even
> recommended...). However, upon examination of these
> pumps (Using spec sheets published by the manufacturer
> or by talking to manufacturer tech support) it became
> obvious that they were not suitable due to either the
> materials used in thier construction or not enough
> pressure (GPH is never the problem). If anyone bought
> those pumps, the etchant most definately destroyed the
> shafts (Stainless 316) or the impellers (Delrin) or
> both. 
> 
> I have been looking at centerfuge pumps and diaphram
> pumps (Just as you have). However, I have not looked
> at the Shurflow or flowking lines (Although I'm gonna
> take a look based on your recommendations). 
> 
> I have found one pump that has suitable materials used
> in the construction and produces the desired pressure.
> However, it's a submersible and I'm not thrilled with
> that (So, I'm not going to purchase it...). It was
> $36.00 USD at my local hardware store. 
> 
> Well Adam, it looks like you and I are breaking new
> ground (At least for this list). 
> 
> 

What you describe is similar to my findings. Centrifuge pumps are 
great for high flow rates, but the pressures are relatively low 
compared to other pump architectures. Commercial spray machines 
use anywhere from 50 to 150 nozzles and so the ratio of flow rate 
to pressure is high making centrifuge pumps very suitable. For a 
home built etcher using a low nozzles count, the pressures 
requirements ideally should be the same as commercial etcher but 
the flow rate is a lot lower.
The diaphragm pump is the best choice for home build spray 
machine as it can produce suitably high pressure at low flow rate 
and is reasonable priced.
The Shurflo 2088-444-142 I mentioned earlier will do 180 kPa at 
6.1 L/min (measured with cupric chloride Sp.Gr 1.30).
I plan to use three fan spray nozzles from Spraying Systems Co.

Nozzle part number:

Veejet Kynar HVV-KY
angle=65\ufffd
Capacity size=08
thread=1/4 BSPT
price=AUD $10 each

see link
http://service.spray.com/catalog/pdfmet/catalog60BM/kynar_flat_sm_std.pdf


The 65\ufffd was chosen because it is apparently the typical angle for 
fan nozzles used in commercial PCB etching machines.
The choice of nozzle capacity and number of nozzles was 
calculated based on the pump capacity and maximum width of 275 mm 
PCB to etch.