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  • #16
    Well the good news is I've isolated the problem. My cooling loop was causing too much flow restriction and my aggitation - which was good - wasn't soo good anymore. I've taken the cooling loop out but now i can only do small batches until I get a chiller set up.

    On a side note I'm still haveing problem with the bead blasting and the continuity of finish. Even when very carefull there are still shadows and differences (usually darker). I've got a airline filter on it so I don't think its contamination. I do think though that its the pressure effecting the surface composition in some way. I'm thinking that either a bigger cabinet (so its easier to work on and you can hold the nossel further back) or a conveyor cabinet. Anyone have any thoughts? On one part there is a flat surface area of about 8" x 12" which means the finish has to be perfect for you not to see any differences.

    Another Q i had was with anode placement in the anodising tank. What is ideal placement/material? I was thinking of getting some lead flashing and wrapping that from one side to the other and maybe along the sides but didn't know if that would yeild much more effectiveness then just side mounted ones such as I have now. Thoughts?

    Once again - thats sswee and everyone for your help.


    • #17
      I dealt with the bead blast problem problem when I first started. Blasting @ 90psi gave a gray tint to the parts where they were blasted. I dropped to 40 or 50psi to fix that. My brother blasted some parts for me and after I ran them, I had the same look your describing. Out of the cabinet the parts looked good but after anodizing the parts had light and dark streaks. If you don't hit the part with overlapping passes to get even coverage it shows after anodize. It looks even visually but microscopically the texture is uneven. The larger flat surface is more difficult. I use overlapping passes one way and then again @ 90* to get even coverage.

      Lead is the better material. I have lead sheet wrapping from one side to the other, that covers all but the smaller ends of the tank. As long as you have as much surface area as the part there shouldn't be any problems. More certainly doesn't hurt.


      • #18
        I don't know what the "best" anode arrangement is, but I am under the impression aluminum is generally superior to lead. We normally have cathodes on two side of the tank, 180º from each other. I added cathodes to the other sides once so they were 90º apart and more or less surrounded the work pieces, and couldn't see any gain and removed them. I know cathode size and placement does have a bearing on results, but can't say with certainty what is best. Here is a link to a website that discusses this some: , look under the aluminum cathode link.

        We do mixed part sizes together, and I haven't noticed color variation due to part size. However, different parts may finish differently due to various factors. Rolled sheet seems to get dark easier (in our setup) than machined billet (both parts vibratory tumbled and 6061 alloy), perhaps due to surface hardness.

        I may be wrong, but I can see larger parts being affected by connections, because the higher current would put more demand on the connections and wire size. If the connection limited the current flow the smaller parts may anodize at a higher current density than the larger parts.

        The smaller parts may or may not get darker because of higher surface temperature. Of course, if they were in actuality flowing more current, this would contribute to a higher surface temperature. Unless there were highly contrasting differences in the mass to surface area of various parts, I’m not sure what effect part size alone would do for resulting temperature differences.

        If the small parts were in fact getting darker because of a higher actual current density and/or surface temperature then to me that indicates the increased dissolution is making a more favorable ("softer") surface for dye absorption and retention. Increasing the acid concentration can do the same thing.

        You might run some of the larger parts alone, and increase either the time or current density to find out if they will get darker. Also, on the larger parts two connections on opposing ends might be beneficial.

        I’m nearly certain etching after bead blasting would help to even out the color on the large surface. I would expect anything you can do to blast more evenly would also help.


        • #19
          I think the darker smaller parts where due to surface temp and seemed to have settled out as I got my agitation back up. Its a balancing act right now until i can get a chiller (running with no cooling @ 12 - 20A)

          The beadblasting is whats bugging me most - i have been etching after blasting in some tests and it seems to help but still not perfect. it is a large surface area so is hard anyways. I'm going to try 50psi tomorrow and see if that helps.

          Looking at that link was nicely reassuring as its very similar to what I have set up right now - a horizontal bar with vertical bars coming off of it. I think I would probably keep this configuration anyways. I have found some great agricultural plastic tanks that have nice straight walls which will be perfect.

          Thanks again - i'll see how the beadblasting goes tomorrow.



          • #20
            I had the same problems with streaked/blotchy beadblast pattern.
            I cured it by changing my blast medium to medium sized glass beads, lowered my pressure to 60psi, and held the nozzle at least 4 inches away from the part. I use a back and forth pattern, and move fairly quickly for just a dusting... no overlapping, back and forth one way, then the other way for me. My parts come out perfect everytime now.
            BTW, I always fully etch and desmut to a completely blemish-free surface first, then beadblast, then SP degrease just before ano.
            I do things.


            • #21
              I was wondering if a conveyor bead blaster (if I can find one used and cheap enough) would do the trick. I'm still struggling to get the even finish I want every time.

              There is another thing I seem to have an issue with and was wondering if there was a quick cure for. I am etching, desmuting, rinsing and drying before blasting but when drying I sometimes get water stanes on it. I use pure water to rinse with and force-air dry the part but because its such a large area I sometimes still get marks - any ideas?

              These marks are watermark/residue type things.


              • #22
                Yes, I have that same problem. When it happens, after the beadblast I go back and etch, then de-smut. Sometimes I have to do it a couple times before the water marks come out.
                I'm trying to do a better job of air-blowing, then towel drying all water before it has a chance to dry, but it seems it sometimes happens.
                I do things.


                • #23
                  Okay - current challenge is finding a supplier for some 300 watt Ceramic Heaters or something similar - any ideas where i might get these in the UK? Do they have an industrial name?



                  • #24
                    Okay - here goes - my complete anodising process

                    I've been trying to go over it and over it to see if I've missed anything and I probably have but here it is anyways.

                    There are a couple of things to note - the first is that there will be a separatin between the mechanical (white box's) and anodising (blue box's) of up to a week. I am hoping that this won't be an issue as the etching should take care of any oxidation.

                    Each tank will be polyethylene or PVC depending ( for example). I still need to find all the equipment but I'm planning on using ceramic submersible heaters linked to temperature relays for each heated tank. The only aggitation I have is with the anosing tank - shoudl the dye be agitated and how? I've chosen steam seal as I can pick up a steam oven very cheap and have had fantastic results so far with it - taking the parts out hot means they try without film.

                    For water my plan is a reverse osmosis system with grey and pure water storage tanks. I haven't allowed for any dip tanks in conjunction with the spray ones - should I?

                    I would really appreciate your feed back and thoughts on this - I know its a lot of what we already talked about but I just want to make sure I have everything. Thanks!


                    • #25
                      Looks like a very complete system.
                      I only have these comments...
                      I have had no luck using simple green for any oil or grease removal. I use lacquer thinner, and I'm concidering a solvent still to recycle that solvent.
                      Why the grey tanks? You should rinse into the tank you pulled the part from. This replaces eveporated water, and you end up with zero contaminated water that needs disposal.
                      Finally, you asked about heaters... I use a 3500 watt hot water tank heater (~$12.00) to heat my heat exchanger that I use for my ano tank. The other tanks (cleaner, dyes, de-smut, etc.) are heated double boiler style to temperature with a propane stove and a pot large enough to put my five gal buckets into.
                      I've thought about making a really large double boiler container that is heated by additional hot water heaters, is well insulated, and large enough to house all of my 140F items. That would be expensive to heat for the occasional anodizer like myslf, but may be the ticket for somebody working the system on a daily basis.

                      Will you be racking to a common bus bar, and the whole bar pulled and transfered to the next station?
                      I am using aluminum racking bars (1/2in. sq. bar with 1/4in. holes for the wire, intersected with 1/4in. SS thumb screws for wire attachment) but the continued corrosion has caused me to re-think that. I am going to go with SS bars, and the same holes/thumb screws configuration. I have had no adverse effects to any of my SS periferal hardware.

                      OK, you asked... just my two cents worth!
                      I do things.


                      • #26
                        Thanks for that!

                        Does anyone know of a good degreaser then that I can use in a dip fashon? Does a solvent work like that or do you need to scrub it?

                        I'll change it to rinse into the tanks which i think will work fine for the heated etchant - but where its just the degreaser would the added water not be more then the evaporation?

                        The heating of the anodising tank should be okay as I'm looking for a reversible chiller that heats as well as cools. This just leaves the dying tanks - for this I think any standard immersion heater would work fine as I don't think copper or such would contaminate the dye. I have found some coils that could be placed in the bottom of the tank which might work a treat. Independent cooling is needed as I would tend to do say a week of black - then onto another color the next week most of the time.

                        Yes I was planning on using a common bus-bar - and move that between tanks. SS seems a good idea and something I could weld together to make sure there was never any connectivity problems. Since this is never in the solution I don't see it ever having a problem. The anode bar will be made of rivited aluminium bar on two sides of the tank with vertial risers and maybe some conductive grease between the connections (to avoide corrosion).

                        For the neutralising bath - any suggestions on concentration/makeup?



                        • #27
                          I'm still looking for a better degreaser, but at this time I scrub with heavy concentration of dishwashing detergent and dip in laquer thinner to pass water break test.
                          I read somewhere and it's been working so far, a 1/2 pound baking soda (sodium bicarbonate) per gallon of RO for the neutralizer.


                          • #28
                            What is really the deal with the etch step? I have never used an etch step in my line. Granted 90% of my parts get polished. The other 10% are fresh off the machines and are mostly 6061 alloy. It's my understanding the etch is to make 100% sure your surface is clean of any old oxide right? In a case where parts are being blasted it would seem the etch could be skipped all together. Also what is the cold seal tank content? I have never come across a sealer that is used cold. When I first started anodizing I too used steam to seal but was hooked on a nickel sealer after the first time I used it.



                            • #29
                              I've been rinsing into my SP degreaser, etch, desmut, ano, etc. for months now, and I don't seem to be gaining any materials. As for my nickel based sealer, I typically have to add 1/2 gal or more replacement water after each run due to evaporation (full rolling boil).

                              As for your grey tanks, I also fully submerge into a tank of water after each step, but I first rinse thoroughly into the previous tank to avoid a disposal problem.

                              I'm using 1 cup of Bicarbinate of soda per 3 gal. water.
                              First I rinse into the ano tank, then dunk in the soda water, then rinse into the soda tank, then dunk into fresh water where it remains suspended until ready for dying.

                              I use the etch step extensively as most of my parts are previously ano'd.
                              I also always desmut, no matter what the alloy is.

                              I'm very impressed with your thoroughness and planning. I was not so smart, and ended up changing my entire process as I improved the sizes and methods of opperation. I'm sure with so much planning, you'll have excelent result right out of the gate!
                              I do things.


                              • #30
                                Tim: For me given the bead blasted finish - the etching helps to level out the finish and make it more matt. If I where to skip this then there is more of a chance of a 'shiny' spot on the part. Some of my parts are shipped from Asia so they are in a container with moisture for a few weeks so again - a chance of oxidation there.

                                As for the cold seal tank - its a sealant solution that works at room temp vs. boiling point. Normally you should let the part sit for a week to 'age' and finish sealing but I've had great results steaming them for 10 mins just to close up the pours.

                                Acidrain: So you rinse into the tank and then also dip afterwards? I was a bit worried about getting all the contamination out between steps so this would help - how often then do you change your dip tank?

                                This is what I'm trying to avoid as I'll be spending some (for me) serious money on this to get it right. I'm even building a control panel with temp controllers and such to set everything at constant values. I'm struggling a bit for some parts but I'll get there. Again - I hope if I do it right that I can get it going first time around - instead of 10th