720 rule vs LCD

[sage]

Somewhere along the way in this thread I did metion that I too was wondering what the limits would be. There are other posts in this forum (especially by Fibergeek) that suggests that there are limits to how much (or little) current you can apply and still grow a layer that is both durable and will accept dye. I believe the lower limit is about 3.5amp minutes per square inch my way (or CD of 3A/sqft in the 720 rule) The acid concentration is a huge factor in all of this. If your concentration is too low you will require a high(er) voltage to get the current flowing. Too high a concentration and the acid will destroy the layer as fast as it is produced (disolution).
My biggest complaint with the LCD process is the low acid concentration. I regularly find that I'm at the upper limit of my supply voltage (22v) where my current regulation becomes poor. Therefore I use acid with s.g of about 1100 (around 10% I think) and then I can get a litttle high current for a given voltage. This concentration does not affect the color pickup or the durability as far as I can see.
The ONLY point of this particular thread was just to point out that the 720 rule is really a formula and you are not stuck with 120 or 90 or 180 minutes just becasue the calculator (or the LCD manual) says so. I do advise you still stay in and around the common sense limits it dictates, keeping in mind that it might be possible to half the amount of time by re-calculating.
I suggest you do a search for all the messages by Fibregeek. There is much to learn from him. (I believe it is now the "late" Fibregeek sorry to say).
As time permits I'm going try a few samples starting at the LCD parameters and then a few with 2x, 3x and 4x the current to see what difference it make to both color and durability of the surface. This will take a lot of hours to complete. Stay tuned.

Sage

[mcaswell]

Fibergeek thoroughly researched the figures we use. The lower effective amps is 3 per sf.

We used a lower acid concentration for safety reasons, and to keep the system cooler, so chillers weren't needed.

Please bear in mind that the figures we have quoted are designed for the amateur anodizer, who may be limited in resources for power. The main consideration is that larger pieces can be done with small power supplies, the trade-off is 'time'. So, 3 asf, 4.5asf and 6 asf were chosen to keep things simple, and REDUCE OUR TECHNICAL SUPPORT!!!! Which is an EXPENSIVE part of our operation, taking MANY MAN HOURS per week.
The LCD system is designed to be simple and give consistant quality results, it does that perfectly!

If you want to step outside the limitations of the LCD instructions in the manual, please feel free to do so, and PLEASE report your findings here. BUT, when you have problems and you are outside these limits, PLEASE DON'T ask for tech support. We simply don't have the time to deal with it.

[cameraman]

I've been over this thread several times and a few points bother me.

Rule
5. Mathematics. A standard method or procedure for solving a class of problems.
Source: The American Heritage® Dictionary of the English Language, Fourth Edition

The term is applicable. It's nomenclature: if you want to work with electricity, you use words like ohm, volt, amp. If you want to work with chemistry you use words like mole, titrate, centrifuge, you learn what Avogadro's number is. Math: rule, proof, theorem, postulation. I don't understand why anyone would get hung up on it.

LCD stands for Low Current Density and is defined as 3-6 amps per square foot of surface area. Acid concentration for LCD is 3:1 ratio of water to battery acid. Operating temperature is 60-75 degrees Fahrenheit.

If you are anodizing outside any of these parameters, then by definition you are not using the Low Current Density Anodizing Aluminum System.

The plating manual (please correct me if I'm wrong, MCaswell) is an instruction manual for Caswell's products. It is not intended to be a comprehensive, all-inclusive source for anodizing and plating. That said, I do see value in adding a section on the mathematics of the 720 rule, but it should be in the 'for the technically inclined' section.

However, I think that in its current form, the manual does a very good job of leading the first-time would-be anodizer through the exact steps necessary to anodize a hunk of aluminum. Further, if you follow the instructions exactly, you can't screw it up. I know that for a fact. My very first run, nothing happened. I went back through, followed everything exactly, and wound up with a nice blue flat bar.

Everything beyond the instruction manual is a study for someone who wants to learn more about the craft. This forum is an excellent (but not sole) place for that education. At the top is a sticky to the math of the 720 rule. In it you find that just as the title promises, here's how you calculate your anodizing, and oh by the way, if you don't want to do it yourself here's three ways your computer will do it for you.

I had typed more but deleted it because there's only so much beating a dead horse needs. I find the whole thread very odd.

[sage]

I think I made my point quite a while ago. I also agree with all of your points and I accept them fully.

So, enough said.

Sage