Newbie here, some sandblasting/finishing guidance needed! - Page 2
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  1. #21
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    I didn't mean the possibility of corrosion after wet blasting as a critique, just something to be aware of and how to deal with it

    and yes, I had that powder on the parts as well after tumbling, especially in holes and similar features, but it came off during etching, didn't cause any issues at all, undyed or black dye, didn't see any traces of it, I'll visit the customer I processed those parts for on Friday, will try to remember and take some pictures of the ugly tumbled finish

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  3. #22
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    3 cold water rinses, hang to dry immediately after coming out of the tumbler gets all the dust off. Let them dry, even a little bit, before rinsing and the dust will have to be wiped off.

    Soft water seems to work best. Hard water leaves visible residue.

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    "Tumbling" or "Vibe Bowl" ?

    There is a difference, but I have no knowledge to convey.

    Can the people recommending such please clarify ?

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    Quote Originally Posted by digger doug View Post
    "Tumbling" or "Vibe Bowl" ?

    There is a difference, but I have no knowledge to convey.

    Can the people recommending such please clarify ?
    In my experience 'tumbling' and 'vibratory finishing' are terms that seem to be used mostly interchangeably. I agree it can cause some confusion if you've seen the 'rock tumbler' style machines that are sometimes also used for finishing.

    My understanding is the rock tumbler style machines and vibratory finishing machines produce approximately the same results, but vibratory machines are much faster, and are probably better at finishing small IDs and so on. One other style is the 'high energy centrifugal finishing' machines where multiple 'rock tumbler' style barrels are whirled around a central axis while also rotating so that the centrifugal force adds energy to the 'rockslide' motion happening inside the barrels, those produce results much faster again than a standard vibratory bowl or tank.

    I run a medium sized vibratory finisher (Mr Deburr from CM Topline) as the step before my blasting process and for the most part it's a pretty hands off process. It definitely takes some tuning to get the correct media for the job though!

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    Thank you for that 'splaination.

    Yes, I see the actual tumbling devices allow the parts
    to hit one another.

    I see some vibe bowls (or rectangular troughs) indicate they
    keep the parts away (somewhat) from each other.

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    Yes, the bowls are the best for parts separation.

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    forgot to take the pics on Friday, here they are now

    to be fair - the chemicals I use for etching and desmutting do not include stuff that might solve the Si contamination issue - HF acid, for safety reasons I don't want to deal with that stuff, but there can be shops out there that could prep those glass bead blasted parts better than I could

    both parts are anodized, the brighter part is vibro tumbled with coarse plastic media, the darker one is glass bead blasted (high pressure to make process quicker)

    tumbled part is much more comfortable to hold, smooth to the touch compared to blasted part that feels like sand paper
    notice the dark shade near the edge on the blasted part, never had that defect with tumbled parts, not quite sure what was going on there
    20191217_140900.jpg20191217_140903.jpg20191217_140909.jpg

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    Quote Originally Posted by jz79 View Post
    forgot to take the pics on Friday, here they are now

    to be fair - the chemicals I use for etching and desmutting do not include stuff that might solve the Si contamination issue - HF acid, for safety reasons I don't want to deal with that stuff, but there can be shops out there that could prep those glass bead blasted parts better than I could

    both parts are anodized, the brighter part is vibro tumbled with coarse plastic media, the darker one is glass bead blasted (high pressure to make process quicker)

    tumbled part is much more comfortable to hold, smooth to the touch compared to blasted part that feels like sand paper
    notice the dark shade near the edge on the blasted part, never had that defect with tumbled parts, not quite sure what was going on there
    20191217_140900.jpg20191217_140903.jpg20191217_140909.jpg
    They look great! I guess the etch really smooths out the appearance of the tumbled part!

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    Quote Originally Posted by as9100d View Post
    Tumbled finish on aluminum is ugly. Glass bead however is not....

    All Apple products are glass bead before anodize
    My understanding is that Apple products are polished, then bead blasted. They're not relying on the bead blast to get rid of tool marks.

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    Quote Originally Posted by DanielG View Post
    My understanding is that Apple products are polished, then bead blasted. They're not relying on the bead blast to get rid of tool marks.
    Garnet blast to remove oxide then glass bead at a low pressure.

    Sent from my Pixel 3 using Tapatalk

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    Quote Originally Posted by aarongough View Post
    I run a medium sized vibratory finisher (Mr Deburr from CM Topline) as the step before my blasting process and for the most part it's a pretty hands off process. It definitely takes some tuning to get the correct media for the job though!
    Several of the abrasive media manufacturers will run sample parts for you and help you figure out the correct media/solution combination for a given part. Haven't done this personally, but it might be worth looking into.

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    Quote Originally Posted by jz79 View Post
    the darker one is glass bead blasted (high pressure to make process quicker)

    tumbled part is much more comfortable to hold, smooth to the touch compared to blasted part that feels like sand paper
    notice the dark shade near the edge on the blasted part, never had that defect with tumbled parts, not quite sure what was going on there
    One thing worth noting from this: the reason the blasted part is so much rougher is because it was blasted with high pressure. Low pressure bead blast will produce dramatically different results.

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    Alkali Etch your aluminum parts.

    Roger

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    Default Alkali Etching

    Quote Originally Posted by rogertoolmaker View Post
    Alkali Etch your aluminum parts.

    Roger
    The other day I suggested Alkali Etching your aluminum parts. I thought I needed to expand on the information so you may be able to setup in your own shop.

    Alkali tanks each have a capacity of 23 gallons.

    Materials:
    Water
    Sodium Hydroxide 23Lb.
    Sodium Carbonate 23Lb.

    Operating Temperature 140 deg. F

    Specific Gravity at operating temperature 12 Be

    The concentration of this solution shall be determined by means of tests for specific gravity. Test shall be made once a month and additions of equal parts of sodium hydroxide and sodium carbonate shall be made to replace drag-out losses. Loss dur to evaporation shall be replaced by the addition water to maintain a uniform solution level. Discard the solution once a year.

    Before dumping into the sewer contact your local fire department.

    Roger


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