Copy Cad power requirements "problem"

[lintmann]

I posted about a year ago about problems I was having with my little 3A power supply? Well I ended up getting a bigger one, 30A-30V because I figured that that was what I needed. Well it was better but still had some of the smaller PS's problems. I did a little experiment the other day plating some heater hose sized tower clamps(4-5 sq" max") and this is what I found...

Bath Temp 90 deg. (1.5 gal solution)
Plating volts 1.5V
About 1" of the 4x8 sheet of anode in the solution.

With the clamp in the solution I was pulling about 2.5A with the anode and
clamp at opposite ends of the tank. With the clamp next to the tank I was
pulling 4.5A.

Then I lowered the whole 4x8 anode into the tank and it pulled 3.3A with the
anode and clamp at opposite ends(almost 1A increase due to the increased
anode surface area I guess). Now the funny part and what my old 3A unit
would do... As I brought the clamp closer to the anode the current increased
to 5.5-6A and then kicked off! The voltage light went out(voltage dropped to
.4) and the current light came on(current dropped to .7). If I moved the
clamp away from the anode the PS would kick back in and voltage and amps
would be restored to 1.5V and 3.3 amps. I then tried this same experiment
with a larger rad hose clamp and it would kick the PS out when the clamp
was only half way across the tank

Have you ever had this happen in any of your plating?

I'm not quite sure what is going on but the best way I seem to be able to
control the current is by the amount of anode and part that is in the
tank(of course increasing the voltage will also increase the current). I did
manage to plate my vacuum actuators(about 120 sq") but that was only because I held the majority of it out of the tank, constantly rotating the part much like a water wheel contacts the water. If I let too much of it contact the solution the current would increase too much and the PS would kick off. Not the most time efficient way to do plating but it worked in the end.

As far as smaller plating jobs I pretty much have them figured out and they turn out great everytime but this bussiness of the PS kicking off has me scratching my head, I mean after all it is a 30V-30A power supply!

Any thoughts or ideas are appreciated.

[seanc]

Originally Posted by lintmann

I'm not quite sure what is going on but the best way I seem to be able to control the current is by the amount of anode and part that is in the tank(of course increasing the voltage will also increase the current).

It seems that you're still stuck on the idea that the voltage has to be 1.5v. Voltage will be different for every different size part you try to plate. Ignore the voltage. Make your adjustments to get the appropriate current, and voltage will be whatever it needs to be.

In the case of the hose clamp, 4-5" should be plated at .3-.5 amps (old formula still?). At this amperage you'll only see about .5v.

but this bussiness of the PS kicking off has me scratching my head, I mean after all it is a 30V-30A power supply!

The size of a power supply has nothing to do with it's quality.

One of two things may be happening here:

1) Your power supplies are tripping because they think they're in short circuit. As you move part closer to the anode, the current increases, and they hit their "trip" point.

A well designed power supply will deliver it's current into a dead short. Lower cost supplies will have a circuit breaker to prevent supply burn out.

or ....

2) As the current increases, they reach the constant voltage/constant current switch over point.

Tell us more about the new power supply. Do you have a current control knob, or only a voltage control knob?

Sean

[lintmann]

Hi seanc....so I guess you remember me Actually I learned a lot from you and last time with your help I overcame most of my problems including the 1.5V thing. I've plated parts at lower and much higher voltages with really nice results but this time to keep a constant I chose 1.5V. I'm actually done plating everything that I have to for my car and this was a little experiment before I put it all away for the winter. If it's safe to do in the kitchen then I might bring it out to try a couple things otherwise it will stay stored until it warms up outside.

Still though my volts and amps don't jive do they? It still seems like I need way more current than others do for some reason and I did confirm with Caswell last year that I did in fact receive the old solution. I guess I should have turned the voltage down to get the .3-.5 amps that you say it should only need but as it was I think the clamp was on the edge of a nice bright plate job. From what I've learned so far with other parts I have plated, had I lowered the voltage much more it probably would have turn out quite dull and would have required buffing.

Here is my power supply...
http://cgi.ebay.com/Variable-DC-Powe...QQcmdZViewItem
I bought it new and only used it twice so far but it seems to work pretty good. I went with this brand because that was what my 3A one was and the reason that I chose it then was because it looked like the one Caswell sells but they were all out at the time. For what it's worth, when I was having problems with my original 3A one I borrowed a top of the line 3A one from the avionics shop at work and got the same poor results of "not enough amps".

Like I say, I'm all done the parts for my car now but I really did like the whole plating experience and since I have two more cars to do and a long list of new "friends" I'd like to be able to nail down the method.

One thing I never did mention is that my plating time is really short compared to what others have said. For example each hose clamp would be nicely, brightly plated in a minute or two and not 10-15 like others have mentioned.

Any other thougths?

[seanc]

Originally Posted by lintmann

....so I guess you remember me

only remotely . I had to go back and read your last posts, and realized there were still some "loose ends"

... but this time to keep a constant I chose 1.5V.

Well, a "constant" is good, but it should be the current, not the voltage.

Your new power supply is the right type, CV/CC. It will operate in either constant voltage, or constant current mode, but not both at the same time. You must choose which mode to use, and CC is the one to use for plating.

Turn the voltage knob half-way up, then use the current knobs(s) & meter to get the current you want based on the part size. There are LEDs on both the voltage and current side, you want the current LED lit all the time. That indicates it's in "CC" mode. Don't let the voltage distract you!

The 30A Mastech is just like it's little brother, has short-circuit breaker built-in, and I suspect that's why it's tripping. It's just not capable of operating at extremely low load resistances, and our plating tanks are very low resistance.

You may want to try the dummy load workaround we've talked about before:

My power supply has me confused

3A power supply

How do I calculate voltage ...

One thing I never did mention is that my plating time is really short compared to what others have said. For example each hose clamp would be nicely, brightly plated in a minute or two and not 10-15 like others have mentioned.

That is to be expected. The more current you use for any given part, the faster it will plate.

Plating deposit thickness is directly proportional to current density. To achieve any given thickness will take twice as long at 50 ma/sq-in as it would at 100 ma/sq-in.

In your test, plating the 4-5" clamp at 2.5A, gives a current density of about 500ma/sq-in. That will plate 5 times faster than at 100.

What I don't understand is how you're getting "good" plate at that density (it should be burning badly), unless your surface area calculations are way off.

Sean

[lintmann]

Thanks for those links sean they have a lot of really good info in them!!!

As far as the clamp that I plated, I double checked it and at the absolute most it would be 7-8 sq" so you see my current is still "high". And yes it does plate very nicely with no burning at all. I could even plate higher with no problems if I wanted to...

I'd like to try it again with this new info but I am getting low on brightener and don't really want to waste it on experimenting. Do you know if the current brightener will work with the old solution? I asked Caswells tech line this days ago and still haven't heard back...