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**R-Wells** · 03-05-2005, 05:41 PM

I guess I should mention a few other things here.
I did do standard prep work on the part prior to anodizing.
I have been having reasonable success with the let er rip method for about two years now.

Thanks
Rusty

**sswee** · 03-05-2005, 07:42 PM

1: Surface area What does A/Ft² mean ?
in other words when I figure surface area of a 12" X 12" part is it 288" or 576"

Amps per square foot or your current density. A 12" x 12" part is 144 sq in times 2 sides = 288 sq in. If you want to anodize at 4.5A/sq ft, you would divide 4.5 by 144 giving you .03125A/sq in. Multiply this by your part surface area of 288 sq in, gives you a setting of 9A on your PS.

2: Should I figure the thickness of the material ?
Say I have a peice that is 12" x 12" x 0.250" should I add another 12"?

Yes, you will do better if you get as close as possible to the actual surface area. Normally if you are within 10 to 20% you will be ok.

3: I received a 20a CC power supply from Caswell yesterday , mixed 3 gallons af Napa battery acid with 9 gallons of distilled water , hooked up the power supply to my 13" x13" part (338" =2.34 sqf ? )
turned on the power supply and set the amps to 10.5, heres the question finally .
My volts imediatly went to 10.5 v and then went down to 9.7 over the 90 minutes, the part had a very chalky surface after dying.

First guess would be a bad connection. How are you connected to your part and your cathodes? The peak voltage calculates to 11.25V for the numbers you gave. The chalky residue is from anodizing at to low a current density or anodizing to long and from dissolution.

So I tried it again today, this time the volts imediatly went to 13.3v after about 5 minutes all the smoke leaked out of my new $300 power supply
What did I do wrong?

I am at a loss about the PS smoking. Maybe Fibergeek will help out on this when he reads it.

**Fibergeek** · 03-05-2005, 08:11 PM

The smoke leaked out, huh?

I'm also surprised, they don't build power supplies these days that will allow you to destroy them regardless of how you set the controls, not even Chinese power supplies. You may have gotten a defective one, it happens. I don't remember if there is a fuse or circuit breaker on the back of those, did you check it?

**R-Wells** · 03-05-2005, 08:13 PM

I use three aluminum welding rods, two on the botom corners one on top in the center, all three are tig welded

Thanks
Rusty

**R-Wells** · 03-05-2005, 08:17 PM

Hi Fibergeek,
no I didnt check for a blown fuse, the ps was still working, 10.5 amps/ 13.? volts showing
Everything is working except the cooling fan and the smoke leaking out

Thanks

**sswee** · 03-05-2005, 08:18 PM

How are the PS leads attached to your cathodes and to your wires on the part?

**R-Wells** · 03-05-2005, 08:25 PM

The welding rod is bolted to a support bar, Aligator clip from ps to welding rod.
Caswell 8x8 lead plates for the cathodes, cut and twisted the way they showed in the manuall with an aligator clip from the ps.

Thanks

**R-Wells** · 03-05-2005, 08:31 PM

More info that may be unrelated, but adds to my confusion.
Volts didnt start at 0, they start at 31.5v and 0 amps
as I dial the amps up the volts drop.
from what I think I have read here on the boards, the volts should start at 0 and continue to rise to peak?

Thanks

**sswee** · 03-05-2005, 08:33 PM

Sounds like you did it all by the book, but still sounds like a bad connection somewhere. When you dial your amps up your volts should start out low and climb fairly quick for about the first 20 to 30 min., then start to level off and climb slowly.

**R-Wells** · 03-05-2005, 08:48 PM

I have had lots of conection falures in the past, and I know for a fact that a welded conecttion can fail, but with my old system that just ment that the part didnt anodize.
The part I did yesterday looked just like I left it to long or the bath temp was to high, over anodized?
When I turn this PS on it reads 31.5 volts with the voltage control knobs turned clockwise all the way and the amperage controll knobs turned counter clockwise (anticlockwise like it says in the book).
the voltage dosnt drop untill I conect to the part and begin to dial the amps in.

**sswee** · 03-05-2005, 09:11 PM

Not that it matters, but try making your connections before turning the PS on. The readings your getting with the PS unhooked is normal. I don't think your weld connections are where the problem is. How are the alligator clips attached? Do you have a multimeter to ohm out your connections? Do you use the 720 rule?

**R-Wells** · 03-05-2005, 09:23 PM

Well its not likely that three welded conctions failed , but stranger things have happened.
I havnt checked the Leads for a bad conection, they were just some home made jumper wires that I had in the tool box, fairly new but I would imagine that the aligator clips and eyes are just crimped on.
I will have to check that out.
This isnt likely to have any thing to do with the PS malfunctioning is it,
I mean a bad conection wouldnt cause the smoke to leak out would it.
Could the bad conection be in the PS where the smoke is leaking out?

**R-Wells** · 03-05-2005, 09:49 PM

Oh I forgot, Yeah I kinda loosely use the 720 rule with my old let er rip system.
The part I did yesterday was for the 90 minutes that Caswell recomends in the manual.
The part I was going to do today before the PS failure I was going to do for 60 minutes and see if it came out chalky and then start trying to diagnose the system, but I didnt get that far.

Rusty

**R-Wells** · 03-05-2005, 09:50 PM

Oh yeah I forgot agian, I cant really try it anymore untill I figure out whats up with the PS, it smokes pretty bad.

Rusty

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