Homebrew PCBs

Stefan Trethan wrote:
> On Tue, 07 Jun 2005 09:34:46 +0200, Stefan Trethan <stefan_trethan@...>  
> wrote:
> 
> 
>>>Most small chemical pumps do not have the pressure required for optimum
>>>nozzle performance, which is > 1 Bar (100kPa). These include magnetic
>>>drives. Yea sure you see magnetic drive pumps in professional pray
>>>equipment but take note at the size/price of these pumps. I've did a LOT
>>>of research on pumps when building my hobby CuCl2 spray etcher and the
>>>best (only) pump I've found suitable was the 12V Flojet brand pumps sold
>>>for caravan use.
>>>Adam
> 
> 
> 
> Say Adam, i saw by chance they are selling shurflo pumps at ebay germany,  
> but no Flojet.
> I think to remember you had something to say about those. Since i have  
> lost all my mail in the harddisk failure i can't look it up. (well, i  
> could use the archives but yahoo frightens me these days...)
> 
> If you know the shurflo, please comment.
> I'm not actively looking for a pump right now, but i'd rather keep my eyes  
> open than buy one expensive when i want to have another go at the sprayer.
> 
> thanks
> 
> ST


No probs, I'm glad to help someone else avoid having to go through all 
the trial and error I did. I found two main brands of 12V "on demand" 
diaphragm pumps for water supply in caravans. Diaphragm pumps are more 
efficient, and more suited to high pressure/low volume than centrifugal 
impeller pumps. This means for our "small" sized pumps a diaphragm type 
is a better choice. The two brands are Shurflo, and Flojet. 
Unfortunately all the Shurflo's are built the same and are not FeCl3 
resistant only because they use stainless steel screws to hold the 
little plastic pistons on the diaphragm. The Flojet apparently does not 
have this drawback with all materials are resistant. Here is a copy of 
the reply I got from Flojet customer support when asking about chemical 
compatibility.

"The wetted materials are:

- Polypro/galss plastic for the housing and check valve assembly
- Poly/glass inner piston
- Santoprene diaphragm
- EPDM check valves
- EPDM switch diaphragm
- Santoprene seal ferrules

Rgds,
Roy"


I bought a Shurflo pump over the Flojet because at the time I didn't 
know better and they had more details on the datasheet. Considering the 
Shurflo flaw, it lasted a good 3 months before the SS screws finally 
gave way in the CuCl2. Luckily for me, only the ball bearing was 
damaged, so I was able to remove the last remaining threads of the SS 
screws and replace them with plastic coated machine screws.  I managed 
to save my Shurflo pump and its been in operation for a few months now. 
The Flojet should be ok.

http://www.flojet.com/prodInfo/overview/81000-233_ds.pdf

There are more powerful models than this one but the price doubles 
because they are considered "industrial". I can't see any major 
differences between them that would justify the price jump. In any case, 
you have to choose the right nozzles to get the best performance from 
your pump. Mine is operating at 200 kPa (2.0 Bar) , which was chosen for 
maximum power transfer without overloading the pump motor. Electrical 
power = 12.5V @ 6.5A. Running time approximately 1/2 hour before case 
temperature rise reaches 60\ufffdC. Etching time normally is only a few 
minutes however.

For your nozzles, see http://www.spray.com  Considering I'm in Australia 
it only took two weeks to order three nozzles via their Australian 
representative ( A$10/nozzle). I was surprised to learn that the spray 
nozzle business is setup for selling small quantities. The factory had 
to especially make my nozzles because they didn't have them in stock, 
anywhere.

Adam