Home setup

[fmahone]

I have been anodizing at my job for five years. The parts were mostly for use on optical tables, bead balsted and deep black dye.
Because the parts were small, sometimes .5 inch diameter and .09375 inches thick, voltage and current were not really a concern, ramp up to 13.5 volts, and monitor the current, time for 30 minutes. I have always had good results. I used a 4000ml beaker for the bath and placed it in a bowl filled with water, wrapped cheese cloth around the beaker and used a fan to blow air across it. Cheap, but it worked.
I now want to set up a system at home with higher capacity. Being and electronic technician, I am looking to build my own power supply. I want the nice features like automated ramping, alarm for voltage/current change and timing.
My question is, how big of a power supply do I need for type II? I have read the various messages and have looked at the 720 rule, etc. I guess I need to know the highest voltage that will be needed and I will have the transformer made to a good current level. I see a maximum of 1500va, lots of power! At present, I am looking at a 2 square foot maximum as I am leary of the amount of hydrogen sulfide gas that will be produced.

[acidrain]

Sounds like you've been anodizing in CV mode. We all use the CC method, and the 720 rule speaks to that.
I personally start out in CV, but then switch to CC after 5min. Each alloy has a different resistance, and only after controlled experimentation was I able to graph out voltage requirements for each common alloy.

I suggest building a CC/CV unit capable of about 20v, and as many amps as you think you will need for your largest run. If you want to add the bells and whistles, more power to you... we'd all love to see that!

When assembling your apparatus, consider this:
*Aggressive agitation of the ano bath is very important to dissipate heat and bubbles at the part surface.
*Heat is generated in the ano bath, and sometimes needs to be dissipated using a chiller.
*Ano bath temperature is critical... 68-70F is what I recommend. The reason is the resistance varies with the temperature, and the anodize layer will become chalky when too warm.
*Acid strength affects the resistance and porosity of the ano layer. We use 1:3 battery acid/water for LCD anodising.
*Strip/etch, de-smut, de-grease, ano, dye, and seal steps all need to be temperature controlled, and RO/distilled water rinse is recommended between each of the steps. I suggest setting up a reverse osmosis tank for this.
*Be thinking of ways to safely heat your chemicals. I use a camp stove and large canning pots "double boiler" style to heat my buckets of chemicals.
*Racking your parts is critical. I've had excellent, trouble free connections using titanium wires bent into make-shift inside and outside clamps. Consider your racking system carefully.

OK, I think that's enough to chew on for awhile.

[fmahone]

The setup at my work usually only hase pieces with less than 2 square inches.
We make a lot of aperature disk for the laser work. the rest is various optical table parts, often with such complex shapes I cannot figure out the surface area. Now, if I could get them to use Solidworks, it will automatically calculate the surface area.
At home, I will be using Rhino 3d, not sure if it will calculate surface or not.
I have been ramping the voltage since the beginning, too easy to punch the voltage and burn the contact area of the extremely small parts. Imagine having to make contact that will not be in the optical path of a .5 in diameter disk!
Automating the ramping is easy, I have designed the same thing for devices here at work. I just need to teach myself programming.
By the way, to show you how deep I get, I mix the sulfuric acid to water by weight ratio as I do not always know what concentration of acid to water is in the stuff I get from supply. Then I take extremely fine aluminum powder (pure)
and weigh it and mix it in! Is that overkill or what!
By the way, I am the electronic technician in the Physics Department at Virginia Tech.