Summary for dc power supply for anodizing Discussion
focus_keyphrase: dc power supply for anodizing. The thread centers on choosing a DC power supply for anodizing and understanding basic setup limits. Jeffrey Holmes asks whether there is a practical aluminum surface-area limit for a tank, what ripple means, what rectifier size and voltage are appropriate for Type II anodizing, whether voltage or amperage ramps during the process, and whether controls are built into the rectifier or sold separately. In the answer, the respondent says the shop sounds close to ready and stresses that learning from books is more efficient than relying only on forum posts. He recommends Wernick, Pinner and Sheasby’s The Surface Treatment and Finishing of Aluminum and Its Alloys as a worthwhile reference that can prevent costly mistakes. The excerpt shown does not include direct technical answers to the power-supply sizing questions, but it clearly points the reader toward authoritative reference material for those details.
Q. All right folks, excuse me if this sounds quite elementary, however, I am unable to determine the answer to the questions which are to follow.
First, here is some background information on my shop setup so far. My tank’s internal dimensions are as follows : 36″ length x 12″ width x 18″ depth which calculates to approximately 33.7 US liquid gallons per tank.
This tidbit of information brings me to my first question. As a general rule of thumb, is there a maximum amount of aluminum surface area which may be processed in a given tank size? I guess to simplify my question, is there a standard “aluminum surface area to amount of electrolyte” ratio an individual should consider when anodizing or is the sky the limit? Can I cram as many parts as possible in the tank and as long as I maintain an anode:cathode surface are ratio of approximately 3:1? (I realize that tank overflow is a potential hazard. I am searching for a hypothetical answer here).
Secondly, I am currently in the market for an anodizing rectifier (DC power supply) and really want to make sure that I purchase the correct thing the first time around. Since I find it difficult to believe some sales representatives and feel that they are more often than not, looking out for their own best interests (excuse me if you are in sales, I realize that not all sales reps are the same and I was simply generalizing from my past experiences). I can’t afford to make a mistake in this department. As I know nothing about DC power supplies, perhaps somebody can bring me up to speed – a crash course perhaps. In several places I have read that minimal ripple is best suited for anodizing. Often I read that 5% ripple is just right. Can somebody explain to me what “ripple” is and what affect is has in the anodizing process?
I feel that a rectifier with an output range of 0-24 volts and 0-400 amps will be adequate for my needs given my tank dimensions. What is the highest voltage output that one would recommend for type II anodizing? Would anyone here care to advise me on my rectifier output size, knowing my tank dimensions? Keep in mind that this power source is not going to be utilized in your average, everyday garage setup. I will have adequate power to run this unit.
The next question which stumps me is ramp control. I am not exactly clear on which ramps up during the process of anodizing. Is it the volts or the amperage? I currently believe that the voltage does the ramping, however, I just read somewhere that the amperage ramps up. Perhaps it was a typing error – I just want to clarify this. The VOLTAGE ramps up – correct?
Having said that, how does one calculate the ramp up speed?
Last question and this may be really dumb, bear with me. I have looked at many different used DC power supplies on the internet. It seems to me that most of these units are simply big boxes without any means of control (no dials, gauges or knobs – just electrical hookups). Would an industrial sized rectifier normally come with a control of some sort or is this commonly a separate purchase? If indeed that two are sold separately, which makes up the bulk of the overall cost, the power supply or the controller?
Thanks to all who have aided me in the past and to those who will direct me today. Without you people my journey to understand the previously understandable would have been far too great a task! Cheers all!
Daniel DeGueldre
anodizing shop entrepreneur – Ste. Anne, Manitoba, Canada
A. Whew! That’s a lot of questions. I’ll try a few of them
-You can pretty much crowd as much work into your tank as you want. Shielding isn’t much of a problem in anodizing, but stay a few inches away from the cathodes.
The maximum voltage you will need for type II will probably never be more than about 19 volts.=, maybe less.
400 amps is plenty for your size tank.
You can ramp up manually over a period of about 5 minutes. Most T-II won’t require any ramp up at all.
Ripple isn’t a major concern in anodizing. 5% or 10% should work okay. yes you need voltage/amperage control. I suggest you buy from a reputable manufacturer of plating rectifiers. they will help you select what is correct.
The biggest problem you’re likely to have is cooling. Budget at least as much for a chiller as you do for the rectifier.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004
A. Hi Daniel,
I’ve been reading the questions that you’ve been posting for a while now and it sounds like your shop is almost ready to go. It seems like you want to make sure that your setting things up correctly and that you are willing to do a little research to make sure that you don’t make any errors that are easier to avoid in the beginning – that is a very good thing.
That being the case, and I’m sure that someone (probably Ted) has said in the past in response to one of your letters, trying to learn EVERYTHING from posting questions on the Internet CAN work – but it is a lot more efficient to crack a book for a lot of the information. Get a copy of “The Surface Treatment and Finishing of Aluminum and Its Alloys” by Wernick, Pinner and Sheasby and you will agree that it was the best investment that you could make. It will more than pay for itself (and the time it takes to read it all the way through – it’s about 1000 pages) just in preventing mistakes.
It has, for example, detailed sections describing the effects that voltage, amperage, ramping times and the manner in which the power is turned off after anodizing is done have on the finish. If you already have a copy, check out pages (fifth edition page numbers) 380, 387, 398, 421, and 969-971. I checked my notes and those pages should have some really relevant information to some of your questions.
Good luck!
Jim Gorsich
Compton, California, USA
2004
Thank you so much for that Jim. I have already indeed looked into purchasing this pair of text books. It is without a doubt an investment as much as it is an aid I’m sure. Unfortunately, as dollars are spread thinner and thinner every day while purchasing equipment and supplies, these books are forever pushed to the back burner. To date this entire operation has been built on our own dollar, no bank loans or grants have been issued here. This of course calls for strict budgeting as I am sure you can imagine.
You were correct in assuming that my shop was nearing completion. It may be for this reason that I procrastinate on purchasing these texts. I realize this may in fact be my downfall as I to believe that no single resource should ever be one’s sole center for knowledge. For this reason I have been dabbling within our local libraries and speaking with others in the field. I must admit, however, I do find www.finishing.com to be a tremendous help and even perhaps a crutch. Should I find myself misunderstanding something I read or confusing something I hear, I can always come here and have myself straightened out. For that I am very appreciative – you have no idea the progress that I have made here in the past few months. Though I realize I have many more struggles ahead I am willing and able to overcome them – particularly if Ted and people like you are behind me! Cheers all!
Daniel DeGueldre
anodizing shop entrepreneur – Ste. Anne, Manitoba, Canada
2004
A. Hi Daniel,
I can definitely understand not wanting to drop the full price on the book – the $500 typically asked for it is pretty steep. However, every once in a while you can find it on sale and it becomes a lot more affordable (not to long ago I picked up a copy of the 5th edition through the ASM website for $200).
That being said, if my notes are correct you may want to look at questions 51573 and
12130 – the first deals with sizing a chiller and the second deals with sizing a rectifier.
Also, if you haven’t yet, you may want to check out the “100 Q and A” at the Anodizer’s Plaza reached through the “WWW links of interest” link on the home page. It has some very informative and interesting information that helped me a lot before I bought my copy of “The Surface Treatment and Finishing of Aluminum and its Alloys”.
Good luck,
Jim Gorsich
Compton, California, USA
Ed. note Nov. 2013: Unfortunately, “Anodizer’s Plaza” is long gone.
April 14, 2009
Q. Mr Daniel DeGueldre I have been experimenting with anodizing, and just like you I want to open an anodizing business in Malta. What do you plan on anodizing when you’ll open your shop? Do you think it is worth the money invested? and is there enough work to keep you going?
Every one can feel free to reply.
Thanks in Advance.
Alan Vassallo
– Malta
2004
Q. Regarding anodizing rectifiers big and small, can somebody set me straight on what exactly constant volt/amp control is? Secondly, what makes it so important?
Thanks so much everyone and please excuse my ignorance.
Daniel DeGueldre
anodizing shop entrepreneur – Ste. Anne, Manitoba, Canada
October 23, 2013
Q.
My question is for hard anodizing, what is the mechanism of supplying the amperes, like we have to supply at one time or by gradually? Like 2 amp to 5 amps for 5 min then increase? So kindly provide the amps supply mechanism. And for hard anodizing why we choose the amps mechanism instead of voltage?
Aijazullah Tajir Attari
– Abu Dhabi, UAE
A. Hi, Aijazullah. Ramp control for anodizing can be as complex as you want to make it. I’ve been to shops which use very complicated digitally controlled voltage/amperage profiles in their belief that it makes for hard anodizing that is better in some fashion, and that may be.
But the basics are simple: Ohm’s Law tells us that I=E/R, that is, Current equals Voltage divided by Resistance. The hard anodizing film is a very good electrical insulator; that is, it creates a very high Resistance. If Resistance is very high, we need a very high Voltage to drive Current to continue to build the anodize film. However, when you start anodizing, Resistance is very low, so if you apply a high Voltage, then a very high Current will result and the parts will fry/burn. So you must slowly ramp up the voltage, in proportion to the thickness of the anodizing to maintain a reasonable current throughout the cycle. Or, more simply, just control the process with constant current.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
November 11, 2013
Q. Hi friends,
Yes I understand that for hard anodizing we have to apply the amps gradually; I want to know what is the meaning of gradually? Considering an example like I have to supply say 20 Amps for a set-up, then how should I start it with how many amps in the beginning and then at what interval shall I need to increase the amps?
Aijazullah Tajir
– Abu Dhabi, UAE
A. Hi Aijazullah. As I said previously, the answer can be as complex as you want to make it. If you want to make it complex, the answers depend on the alloy being processed, what temperature you can truly hold at the work surface, which additives (if any) you are using, and several other factors which take many pages of graphs and tables to present. Jim Gorsich described on what pages in the industry’s most important reference book to find all those charts and tables and research answers to your particular situation. On top of that, some specialists have implemented additional proprietary current-time profiles they use which they feel are superior, and which they can’t be expected to share.
But on the other hand, I think you may not be taking the time to carefully read and truly understand the very simple and important concept that has been explained, i.e., that in lieu of complex current-time profiles you can simply anodize at constant current. Hold your 20 Amps per square foot from start to finish and see how your hard anodizing works; then try again at 30 Amps per square foot. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.