Announcement

Collapse
No announcement yet.

Analyze this(not a movie review).......

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Sid03
    replied
    Fibergeek- You dont think the lower piece in that picture looks VERY dark?The piece above it is what it started out looking like. I think it may have been cast aluminum. I will run some stuff that i KNOW is 6061 and see if everything turns out good again

    Leave a comment:


  • Fibergeek
    replied
    Agitation promotes an even coating, the lack of it shouldn't prevent any coating or by itself make the coating thin.

    Be careful about creating two variables in your experiments. Attack one variable at a time, you will make things harder to figure out if several things are allowed to change in the same experiment.

    Different alloys or even small differences in prep. can cause the raw anodize to have different shades, so does current density.

    Your description "scratches easily" is disquieting. although anodize doesn't achieve full hardness until it dries out completely, it shouldn't scratch easily. What do you mean by "easily". Coatings grown at way too low a current density (under 2A/sq.ft.) do this. Can you reproduce a good electrical connection? Unless you are using a real CC mode power source (the current is held constant, regardless of resistance and voltage) you will be at the mercy of any connection resistance. CC can compensate for this, up to its max voltage capability. This is called "voltage compliance". However; even with CC, the coating resistance (PAR) you calculate from current and voltage figures will be wrong if the connection resistance is high, or even worse, changing as you anodize. Anodizing beyond PAR may help this situation, but it doesn't fix the actual problem. Problems like this will return unexpectedly and will haunt you. Please take connections seriously.

    BTW, the same evil effects occur with the "old method" no one was aware of it because they weren't trying to measure anything. Bad results were blamed on the aluminum alloy type, chemical reactions, etc. You still hear that alloys like 7075 are hard to anodize, no they aren't.

    We've had some posts here lately describing the pains and expense pros endure to get good connections (racking) ever wonder why?

    Leave a comment:


  • NeoMoses
    replied
    Here's the picture that Sid sent me.

    Leave a comment:


  • NeoMoses
    replied
    Most cast alloys that I have anodized have turned very dark gray. The only color that takes well is black.

    Leave a comment:


  • Sid03
    replied
    no, it was machine finished. It was either 6061 or MIGHT have been cast then machined. Would cast aluminum react like that? How can I post pics? Thanks

    Leave a comment:


  • NeoMoses
    replied
    Sid, I believe you calculated PAR correctly. The high value of PAR indicates a very thick anodized layer. This sounds like a higher current density than 4.5 A/ft^2 was achieved. I have achieved finishes like that when I was going for higher current density anodizes. I usually don't see a dark gray layer formed until my current density is over 15 A/ft^2 or so... I'm not sure exactly why your part reacted as it did.

    By chance, was your part bead blasted? I notice that my bead blasted finishes always appear more gray than a gloss finish.

    Please post your pictures, I'd be interested to see them. I'll post some of my pictures later on today.

    Leave a comment:


  • Sid03
    replied
    I think caswell should mix up some of their red dye and see what it measures new. Id be surprised if it is in the range that their dye supplier states it should be.


    Today I ano'd another part to test things out again.....see if it would still work as it did yesterday. I ran a larger piece, and ran into something strange. After anodizing the part was very dark. Instead of a yellowish tinit, it was almost grey/black. I actually had to go get a camera to take a couple pics! Any ideas why something would get so dark? IT's suppose to be the same series of aluminum as I have been using also. It's dark enough that just sealing and having it look silver would be totally out of the question. Any ideas?

    It's late, but if I did the math right PAR turned out to be 4.29ohms.

    Leave a comment:


  • M_D
    replied
    I have noticed that running past PAR usually makes dying easier. I have done a few parts lately that were run past PAR at equilibrium for 10-20 minutes and dyed solid black in 2-3 minutes. Blue hasn't been a problem, I have found if the blue doesn't take then it is a bad anodize job. Red seems to dye best if run past PAR. I have anodized to PAR, and the red wouldn't get dark, so I have pulled parts back out of the dye, rinsed and anodized more. Sometimes, just a few more minutes in the anodizing tank makes a big difference, and the red dye takes.

    My red PH is high too, 7-8. I noticed when I mix a new batch of red, it will not work as well untill it ages a day or so. I have read that distilled water will drop in PH as it is exposed to air, because it absorbs CO2 which is acidic. The red dye concentrate seems to be fairly high on the PH scale.

    Leave a comment:


  • Sid03
    replied
    It may look like a small difference on paper, but the difference is an easy to scratch ano that barely takes the dye compared to a good hard to scratch ano layer that takes the dye as it should. I have been doing the 90 minutes thing since I started LCD with unsatisfactory results, and this is the first time I have got results even close to the old method previously used. I have done that same sample piece about 4-5 times at 90 minutes, and this is the only time it took the red dye and didnt scratch VERY easily. Maybe I NEED to let it run at the peak voltage for awhile....maybe thats the key. Im simply trying to figure out the problems I was having, and if you say the time difference wasnt it.....im left wondering why it worked this time and not before. There was one difference, I used air agitation this time and havnt thus far with LCD since the bubbles during ano are hardly noticeable. Maybe that was the thing that made everything work this time? It would simply amaze me if that was the case.

    Leave a comment:


  • Fibergeek
    replied
    The difference in measured voltage between 13.40V (1hr. 40min.) and 13.50V (1 hr. 53 min.) is less than 1% (13.40 / 13.50 = .9926).

    The difference in voltage between 13.16V (1 hr. 23 min. = 83 min.) and 13.50V is about 2.5%. Your are actually very close to my times, but your anodize is thicker. PAR at this point is 2.93 Ohms per sq.ft. For any practical purpose, this should yield results just as good as what you had at 3 Ohms per sq.ft.. You could have stopped here.

    Differences as small as these look like normal experimental error.

    Try it again. If you can do this consistently you're doing real well.

    Leave a comment:


  • Sid03
    replied
    well, it looks like I didnt hit that equilibrium until 15-20 minutes after the "normal" 90 minutes were up. I was just wondering why it took longer for me?

    Leave a comment:


  • Fibergeek
    replied
    It may be your red dye is working in spite of the too high pH. The pH values you were given are from the dye manufacturer, it may work better (or faster?) if you use the recommended pH.

    It probably wasn't necessary for you to continue the process for that long after equilibrium, but it didn't seem to hurt anything. Anodizing for say 10 minutes after PAR stopped changing could have been enough.

    I don't think you are doing anything "wrong". I was able to get an equilibrium condition several times at 3 A/sq.ft. current density. One time I let it run for an extra hour, another time I stopped shortly after it occurred, the dyeing was great both times. I have noticed that equilibrium occurs more easily if the work is very small for the volume of the tank. I have not seen it at all when the work was around 0.5 sq.ft. in 3 gallons of electrolyte, conditions don't stay uniform enough I guess.

    If what you saw really is prevalent among other users I haven't heard about it.

    Leave a comment:


  • Sid03
    replied
    Thanks for the replies. So whats your thoughts on my red dye? The Ph is MUCH higher then the dye manufacturer told Caswell it should be, yet it seems to work now. Also, im not sure that you have addressed the issue of it taking at least 30 minutes longer to achieve a decent ano layer. Im guessing that something im doing must be "wrong", or it would be done anodizing closer to 90 minutes. I realize there are variables, but if the effects of such variables can chage the timeframe so drastically im wondering how many others that purchase caswell's kits using the new LCD will have similiar experiences given the supplied instructions of 90 minutes ano time in the LCD instructions. IF it's working for everybody else closer to 90 minutes, why is it taking longer for me? Any thoughts? Thanks again

    Leave a comment:


  • Fibergeek
    replied
    To say what Neilfj and I said yet another way:

    Setting PAR = 2.5 Ohms/sq.ft. is an average value that is useful in predicting how much voltage will be required for a given current density. You can adjust this value to suit your circumstances if you like.

    It has turned out (to my suprise) that explaining a good connection is actually harder than making one. Neilfj had one heck of a time with this until he figured it out. Now you know how to do it too. This means you get to help us explain it to others who may be having trouble with it. Everyone is the product of their own experiences, adding your way of explaining this can only help.

    To further explain "PAR is high but dyeing sucks"; like Neilfj said, some extra resistance caused by the connection degrading can fool you. You can't tell if all the resistance you see (calculate) is real or just the bad connection. There is a way to get around this; it's called in electronics a "Kelvin Connection". It involves adding another connection to the work to sense the resistance only, it carries no anodizing current. This is typically operated at very low current, like 1 microamp. Since V = I x R, if I is very small, V will also be very small for a given R. The degradation of the connection caused by the anodization will be vanishingly small, if there is even any at all. But this is another wire; and you will probably also need some amplification, we can avoid this with good connections.

    BTW, you don't have to reach equilibrium to grow a layer as thick as you did.

    Leave a comment:


  • neilfj
    replied
    The PAR of 2.5 ohm/sq ft was the approx. value that Fibergeek obtained in his testing. If you look at his document, you'll see his PAR value ranged from 2.2 - 2.8 ohms (or there about). The determination of PAR is dependent on a number of variables such as temperature and the thickness of the anodized layer, as well as to some extent the aluminum alloy being anodized.

    If the PAR value was high AND had you had poor dyeing it is most likely because of poor connections which increases the resistance in the electrical connection (only true if you have eliminated other reasons for poor dyeing..ie..contamination, spent dye, dye temps, etc). If you have a high PAR value with good dye qualities, it is because the layer is thicker...where the thicker layer also equals higher resistance.

    The PAR value and the voltage is variable, depent upon your setup and circumstances and everyone will have different readings. The point is to detect the slow rise in voltage to its peak, then the slow drop. As Fibergeek mentioned, you probably reached equilibrium in that the coating was being eaten away by the acid at the same rate it was being grown. I've run into the exact same situation where the voltage stayed relatively constant for a long period of time and never actually dropped and the dyeing was excellent.

    Leave a comment:

Working...
X