Quote:
|
Originally Posted by acidrain
Next, the parts were stripped, de-smut'd, and run at the same CD all together in a mixed batch. Here is the really interesting part... This entire effort began with the goal being a scientific approach to CV anodizing. All the while in the back of my mind I'm thinking that I really want to get away from having to calculate the surface areas of irregular parts, but knowing full well the consistency of the CC LCD method will yield the best results. Well, after studying the volts curves, and trying to come up with the best of two worlds, here is what I did:
I picked a number... 15 volts.
I racked the freshly cleaned parts, checked the temperature, turned on the air agitation, turned the amps all the way up, started with the volts all the way down, and turned on the power supply.
Now, I slowly ramped up the volts (really slowly) to 15 volts. After 5 minutes of the start, I noted the amps (they were steady now), and slowly turned down the amps until they just began to drop, then bumped them back to the steady number. Now I turn the volts all the way up. This move produced a seamless transition from CV to CC. Now I ran the rest of the duration at this setting for two hours. At the end of the process the parts were dyed black with outstanding (normal) results. BTW, at the arrived amps, I reverse calculated the current and known SA, and guess what? The CD was just a tad over my target of 6A CD. YAY!
|
I've been toying with this idea for quite some time as well. But temps have been killing my calculations as well as lack of precision measurements of volts amps and temps. acidrain check your CD at different temps when you make the switch between CV and CC... I'd be real happy to know if you get any drastically different results in terms of CD. I find that when I calculate CD at different times through a constant CV process... The results are too scattered because of temp variation and I have no idea how to compensate for the effect temp has on resistance of the system. I think more testing needs done.. and I'd be glad to help in any way we can. On our next run I may try to keep a thorough log of the variations to see if we can identify something to help.
We're in the process of upgrading the system to a more permanent and larger basis than we currently have and at the same time we want to keep rework to a minumum so we are on the fence about switching to LCD acid concentration and using both CC and CV when applicable. We'd like to use higher concentrations to keep the process time down [it's not helping right now though, we still have to run parts 80-90 min to get a good black.], but I think we'll need more time for study and experience, before we can take that step.
Calculation of surface area for one off or a few parts is too time consuming as this seems to be the most of what we do. So we've been using CV anodizing for quite some time and sacrificing the consistency somewhat of CC ano over shorter times and not having to calculate SA (ever try to calc area of a gun reciever or a trigger housing?)