Calculation Help

[Monkey2674]

Ok im using a LCD setup with a CC power supply. I want to go by the 720 Rule. Im looking for a .5 thickness so I think that means I need to run it for 80 min. But I am confused on the furmula to figure out surface area and how many amps to set it at.

Im anodizing a paintball barrel that is 12in long. I wrapped a piece of tape around it and figured its about 3.5in around. Thats as far as I got. How do I figure out how many amps to use. And I know I have to calculate the inside as well. Any help would be great.

I tried using 2.5 amps and the volts starting climing. And after about 5min it was at my PS limit (13volts.). So Aparently I dont know how to calculate very well.

[Monkey2674]

Oh ya I wanted to run it at 4.5 asf.

[sswee]

Monkey2674,
No problems. Check out the sticky on the 720 Rule calculator. It makes things alot faster and you can pop different numbers in to see the changes in times and settings.

On the SA question,
To figure SA on a tube - Diameter x Pi = C(circumference)
C x length = SA in inches square
With a circumference of 3.5" divided by 3.14(Pi) gives you a diameter of 1.12". This is just under 1-1/8" diameter. Does that look right?
3.5" x 12" = 42" sq for the OD.
You figure the bore diameter the same way then add the two together. Are you sure you want to do the bore? From reading on those guns, the bore size effects the way they shoot. It won't be much but the bore diameter will be smaller. If the bore was .75", you would do
.75 x 3.14 = 2.355"
2.355" x 12" = 28.26"
42" x 28.26" = 70.26" sq

720 rule
720 amp min * desired thickness = min / CD = anodize time
720 * .5 = 360 / 4.5 = 80 minutes

Amps to set
CD/ft sq = amps per in sq
4.5 / 144 = .03125A
Amps per in sq x SA = Amp setting
.03125 x 70.26 = 2.19A

These numbers are only an assumption since I don't know the actual OD and bore sizes. You should not be to far off with your settings. Sounds like a weak electrical connection may be pushing the voltage up. If you can get some more accurate sizes, we can double check the figures. If you need more help just holler

[Monkey2674]

WOW! Thanks alot. I wanted to use the 720 Calculator but dont have excel.
Ill have to get it.

You said a weak electrical connection. Such as the wires from the PS not being big enough, or as in not a good conection to the part.

[sswee]

Electrical connection to the part most likely.

[Monkey2674]

ok thanks ill try a better connection tommorw. If thats it ill have to order a sput welder, those look so nice.

[sswee]

Just got my sput welder. It made a big difference. Took some practice to get it down good though.

[sswee]

After thinking about it for a while if you have checked your hook up to the part, the next thing would be old anodize still on the part causing a high resistance. How did you strip your part? SS

[Monkey2674]

I used Ano Stripper purchased from Caswell.

[Monkey2674]

heres my steps.

1. Strip with stripper
2. Rinse
3. Degrease
4. Bead Blast
5. Rinse
6. Degrease
7. Rinse
7.5 Attach Wire
8. Ano
9. Rinse
10. Dip in Baking Soda Formula
11. Rinse
12. Dye
13. Rinse
14. Put in LT Sealent
15. Rinse
16. BE SAD AT RESULTS.

Am I missing anything that is nesessary? I use gloves thru everything. Checked temps.

[R-Wells]

Hi
Whats the temp of your ano bath?
I have been strugelling with my peak voltage as well .
using 4.5asf , at 68 degrees I was peaking at 13.5v at 70 I peak at 12.1
at 72 I peak at 11.3.
I dont know if this is some anomally with my system or what.


Rusty

[Fibergeek]

R-Wells,
When the electrolyte get warmer, its conductivity gets better. This means that you should expect your peak voltages to decrease as the temperature increases. What you describe sounds about right.

[Monkey2674]

My bath was at 68*.

[R-Wells]

Try heating your bath to about 72 .
I feel really silly, the first thing I do is heat my bath, then turn on the AC unit to keep it cool

Rusty

[sswee]

Besides your voltage limiting out your PS, what problems do you have with the part. I ask this because I have had parts limit out my smaller PS and start dropping amps. The parts still dyed and looked good. My peak voltage has been varying +- 2V of caculated voltage depending on electrolyte temp. I have had the best results at 65* to 68* to slow down dissolution.



Rusty,
I have a heater in my tank for the same reason. Shop has no heat, so I have to heat up the solution to start. Then turn it off to keep the temp down.