Trying to understand my CC PS

[Countryboy1966]

I am having trouble understanding how to properly set my powersource. I am going to describe a situation I am running into and hopefully it will lead to something. For the sake of the conversation, I have a Caswell CC PS 15v 25A.

Say I need to anodize approximately 147 In Square. This calculation takes the aluminum racking into consideration. Using the equation anodizing at 4.5 amp, I need to have 4.59 amps. When I start up the system, I start it with the voltage all the way up, amps all the way down just like the manual states. I also have all the connections made and correct. When I go to adjust to the 4.59 amps, all I can adjust to is 3.5 amps at 15.5V. Over the course of the next sixty minutes, the amps increase to approx. 4.1amps.

Anyone have any ideas? I am going to get a meter on it the next time I run, but I wanted to to check with you guys to see if I am missing something. The annodizing is turning out good, but I feel like my process control is lost because I do not know what it going on in the process. I know something is wrong because I have a powersource that can anodize upto 5 sq feet and I am at one.

Another thing I might be missing is that in the CCPS manual, it states to set the amperage before connecting, then turn back off, connect, then turn on and complete the annodizing process. Is this how everyone else does it?

Thanks in advance.

[sswee]

What is happening is the resistance in the circuit is high enough that at 15.5 volts it will only push 3.5 amps through the circuit. The resistance for some reason is declining slightly allowing the amps to increase. You need to find the connection problem.
You said you are using aluminum racking, how do you connect to the part? How is the PS hooked to the racking?
SS

[gcdrummer02]

are you stripping your racking everytime you use it? Is it turning funny colors?

After you mount all your parts, use a multi-meter to check your connections.

[Countryboy1966]

Yes I am stripping the racks between uses. I need to get the multimeter on the job, but I had the same issue the first time I used the rack and since the beginning of anodizing. I chalked it up to me being a rook. If you recall my statment in another thread regarding varying amperage comment related to Square footage which is false.

I have a horizontal bar that lays across the top of the tank. Then I have downward facing bars that go into the solution. These bars are fastened to the bar on the top of the tank with 10-32 316 SS Bolts. Then I have clamping mechanisms that is pretty much a piece of spring loaded aluminum fastend the the vertical bar with 8-32 aluminum bolts. I've been having this issue since the beginning before I built this racking so I am thinking that the issue is elsewhere. As far as my annode and cathode connections, I use aligator clips and the wires are 14 or 16 gauge.

[Countryboy1966]

Originally Posted by gcdrummer02

After you mount all your parts, use a multi-meter to check your connections.

I searched the archives and could not find anything on this topic. What is the best method of checking the connections? I know enough to get in trouble, but not enough to understand what to do from scratch.

Thanks for any help.

[sswee]

Set a multimeter to ohms(upside down horseshoe), touch the probes together to check meter function. It should read 0 ohms or no resistance. Touch 1 probe to the PS connection and the other to your rack bar. The resistance should be minimal. Probe the rack bar and the part to check the part connection. You can probe each side of any connection in question.
You can get a cheap digital multimeter(DMM) at most auto part stores for about $10.
SS

[acidrain]

Could be acid strength too low, or acid temp too low. What is the acid ratio, and temp during the run?

[woodjames]

The problem is you only have a 15v power supply!!! Over voltage protection is kicking on, and is reverting to voltage limitation rather than current control. Voltage and amperage will increase proportionally, due to ohm's law. The power supply has a 15v max and you're already beyond that (you said 15.5v) to achieve your correct current density. I'm guessing that resistance changes in the bath increases the current (3.5 to 4.1), usually heat increases conductivity in electrolytes.

Check your approximations!

Originally Posted by Countryboy1966

I am having trouble understanding how to properly set my powersource. I am going to describe a situation I am running into and hopefully it will lead to something. For the sake of the conversation, I have a Caswell CC PS 15v 25A.

Say I need to anodize approximately 147 In Square. This calculation takes the aluminum racking into consideration. Using the equation anodizing at 4.5 amp, I need to have 4.59 amps. When I start up the system, I start it with the voltage all the way up, amps all the way down just like the manual states. I also have all the connections made and correct. When I go to adjust to the 4.59 amps, all I can adjust to is 3.5 amps at 15.5V. Over the course of the next sixty minutes, the amps increase to approx. 4.1amps.

Anyone have any ideas? I am going to get a meter on it the next time I run, but I wanted to to check with you guys to see if I am missing something. The annodizing is turning out good, but I feel like my process control is lost because I do not know what it going on in the process. I know something is wrong because I have a powersource that can anodize upto 5 sq feet and I am at one.

Another thing I might be missing is that in the CCPS manual, it states to set the amperage before connecting, then turn back off, connect, then turn on and complete the annodizing process. Is this how everyone else does it?

Thanks in advance.

[dmiom]

Originally Posted by woodjames

The problem is you only have a 15v power supply!!! Over voltage protection is kicking on, and is reverting to voltage limitation rather than current control. Voltage and amperage will increase proportionally, due to ohm's law. The power supply has a 15v max and you're already beyond that (you said 15.5v) to achieve your correct current density.........

What James is alluding to is "the final straw" that is drawing your attention to the problem - but its not the root cause.

As the original poster described, he is wishing to anodise at a current density of 4.5 ASF. Using the LCD process, at 4.5 ASF, the typical peak voltage required is only 11.25 volts IF everything else is in order, and even with a safety margin, it IS within capacity of that power supply (although it would be marginal at 6 ASF where the predicted peak voltage is 15v).

The root cause is likely to be related either to tank temperature (too cold?)/chemistry and/or imperfect connection (if you're using Al clips/wire it may be better to switch to Ti for the immersed racking) and/or workpiece estimation

Have a look at an identical thread on power supply issues.

Dave

[Countryboy1966]

I have a 4 gallon acid bath. 3 gallons of distilled water and 1 gallon of acid purchased through napa. I am agitating. My bath level has not decreased. Short of titrating, which I am going to learn to do, I should have correct concentration. I've done a maximum of maybe 8 trails through the tank.

My anodizing manual states I need to be between 60-75°F, but it seems 68-72° is ideal? I've anodized all over within the 60-75° parameter, but never exceeded 72°.

My clips are the cheap steel alligator clips you would buy at wally world or a parts store. I'll get some Ti clamps.

I am going to check connections and change a few things out and then trial again to see what happens.

Everyone's input has been greately appreciated. Thanks!