power supplies

[mh]

i am using a ten gallon tank and my power supply, rated at 15 volts, 40 amp seems to max out on voltage if i dont have many piece of material in the bath. im doing alot of natural finish pieces for the engineering market, hence dying qualities r not an issue. i would like to get up to 12 ASF if not higher and was wondering if voltage is dependant on bath size and surface area of work pieces. i would like to go up to a larger bath as i am having a hard time keeping up with demand. i have 2 power supplies offered at the moment
30 volt, 20 amp or a 15 volt, 60 amp

i believe the second would allow me to use a 12 ASF and fit more surface area per bath but am worried i will max out on voltage if only doing small pieces

i dont really want to back off to 6 ASF again as i cant do enough in the day

any help would be greatly appriciated as i dont want to pour money down the drain ......

[-AAPB-Eric]

15 volts is a bit on the low side if you want beefier power.

Yes, I do LCD method in CV now, and at 6-7 ASF and I do approx. 1-2 square feet in surface area. The voltage has much to do with the amperage. From what Ive learned (and hopefully its right), a higher voltage = more amps the parts will draw out. If your high on both your good. If you high on amps but the voltage rating is low then you wont hit that high amp.

If you ask me, and if this is correct, then the 30 volt one is better. Again, when anodizing I find my voltage is the higher value of the two.

[acidrain]

Acid ratio will affect the power requirements.. a stronger acid will make it easier for the current to flow (less resistance).
If you are set on anodizing at higher CD's, you might try increasing your acid bath strength to 2:1.

[M_D]

There are many factors that will determine voltage needs: electrolyte temperature, alloy, current density, and connection quality. Also, acid concentration will affect volts needed, and dissolved aluminum content is very influential too. The higher aluminum content will required more volts.

To expand on the electrolyte temperature factor, the part temperature is often higher than the surrounding liquid, and depending on the agitation level the difference will vary between the part temperature versus liquid temperature. The better the agitation is, the closer the part temperature and liquid will be. A higher bath temp will decrease the volts required to achieve a given current density. If the agitation is very good, you can run a higher bath temperature and keep the part temperature reasonable, often lower than a cooler bath with poor agitation. We are only talking a 1-2 volt potential difference here under most circumstances.

Keep in mind that the more current you pump into a tank in a given time, the higher the cooling capacity has to be.

I believe 15 volts will limit you to about 6-7 amps CD, for 10 amps CD we run around 17-18 volts and 12 amps CD is often 20 volts. In any case, it is good to have some reserve capacity on volts if using CC mode, as the voltage requirements can vary for a given CD.

I don’t know if you have tried the higher CD yet on the clear parts, but in general the lower CD will provide a clearer finish. Depending on the alloy, you may need to cut back on the thickness with a higher CD to avoid getting a tinted color.

The 60 amp 15 V power supply will anodize more parts per hour than the 20 amp 30 V power supply, but you will be limited to a lesser CD.

Voltage isn’t too dependent on tank size or part size (assuming current is correctly calculated to suit the part).

What kind of racking are you using?