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BEST METHOD for cleaning coolant-machined Al parts for blasting and anodization??

ianwatts

Plastic
Joined
Oct 14, 2021
Location
Los Angeles, CA
I am looking for the least amount of work to provide no staining (coolant or water) on my high quality/luxury “herb” grinder. We're going for the “Apple” feel so clean, even finish is very important (you can see it here: recreation.community).
Process
  • milling 6061-T6 aluminum with flood coolant (5% concentration)
  • parts cleaned and loaded onto egg crates
  • sit for a few days as quantity is built
  • parts are then bead blasted, acid etched, anodized, and dyed
  • many of the parts sit for multiple days between machining and finishing
Right now my process has two steps: cleaning (remove coolant, prevent coolant stains) and drying (remove water/cleaner, prevent water/cleaner stains). Based off forum posts I have found the following methods (from least to most labor/time intensive):
cleaning
  1. no cleaning, let finishers handle it: given how long my parts sit seems like it would definitely cause staining
  2. rinse off w/ RO water: pretty easy
  3. rinse off w/ soap then water (CURRENT PROCESS): adding soap means I have to wash the soap off after (might be extraneous if I wipe off)
  4. dip rinse in acetone: not ideal given intensity of acetone
  5. ultrasonic cleaning: another tool, don’t want to have to buy a tank
drying
  • air dry: easiest, do nothing (concerned about water stains)
  • blow off: manually intensive, no batching
  • wipe off (CURRENT PROCESS): manually intensive, no batching
  • oven/heat lamp: another tool but hands off & easy to batch
For now I will stick with my current method (more labor intensive than I would like) and test other combinations to see what I can get away with. I will update this thread but would love to hear what combinations others have people used, and to what result?
 

rcoope

Stainless
Joined
Sep 25, 2010
Location
Vancouver Canada
If it's basically about water rinsing and drying, I wonder if running the parts in a dishwasher with no detergent would work. You could make custom racks for a domestic dishwasher pretty easily to hold the parts so they drain properly, and then the drying cycle should work really well. Perhaps you want a degreasing cycle that's gentle in terms of pH, and the a rinse cycle.
 

ianwatts

Plastic
Joined
Oct 14, 2021
Location
Los Angeles, CA
Yeah dishwasher was another common method. Wouldn't want to do it in my regular dishwasher (don't want residual coolant on my dishes) and don't want to buy a separate dishwasher. If I did though would work very well with the plastic egg cartons I have.
 

Wick Craft

Aluminum
Joined
Dec 27, 2013
Location
South Charleston, WV
Right off the mill, place parts in a water bucket, leave them there until next step. Place parts in a heated and agitated tank with 1:3 ratio of simple green concentrate to DI, RODI, or distilled water. Rack your parts, submerge in this tank at 140 F for approx 15 minutes (no, it won't etch your parts, solution is too weak). Rinse parts in tap water. Have a second tank with plain DI, RODI, or distilled water heated and agitated to 190 F; submerge for approx. 5-10 minutes. When pulling out, the parts are squeaky clean and dry almost instantly with no water spots due to the hot DI/etc. water.

If you want a cheap way to get heated/agitation, buy a good Sous Vide cooker and place in a 26 qt SV tank. If you need larger tanks, scale up accordingly using little giant pumps and PVC pipe with drilled holes to use as spargers for agitation and heating elements.
 

Rick_H

Plastic
Joined
Jan 26, 2013
Location
uk - midlands
I am sure I am missing something, but if you are bead blasting what is the worry about light surface staining?

We leave our 6061 machined aluminium parts for weeks to months sometimes without cleaning out of the machine, once they are bright dipped and anodised there are no marks to be seen on any of them, I find it hard to believe there would be any left after blasting unless the staining is actual surface etching.
 

Finegrain

Diamond
Joined
Sep 6, 2007
Location
Seattle, Washington
Another vote for standard dishwasher, rinse cycle, no detergent (your coolant is water-soluble after all), no heated drying -- IME, heated drying exacerbates any water staining.

As for water stains, I should think the bead blast would remove them PDQ.

Regards.
 

Wick Craft

Aluminum
Joined
Dec 27, 2013
Location
South Charleston, WV
A thorough degreasing step must be completed prior to and after the blasting stage for a couple of reasons. The main reason is to avoid imbedding contaminants into the surface of the aluminum, which you won't be able to see with the naked eye. Once the part is dipped into whatever etch or brightener bath, the surface will be "massaged" preferentially which yields a non-uniform surface which isn't visible unless under a microscope. Where it shows up is after the dying process. You run the risk of getting a splotchy finish. The other main reason is to avoid contaminating the blasting media. Also, make sure whoever is blasting your parts only uses media dedicated to aluminum, preferably for a dedicated alloy.....i.e. 6061
 

Rick_H

Plastic
Joined
Jan 26, 2013
Location
uk - midlands
A thorough degreasing step must be completed prior to and after the blasting stage for a couple of reasons. The main reason is to avoid imbedding contaminants into the surface of the aluminum, which you won't be able to see with the naked eye. Once the part is dipped into whatever etch or brightener bath, the surface will be "massaged" preferentially which yields a non-uniform surface which isn't visible unless under a microscope. Where it shows up is after the dying process. You run the risk of getting a splotchy finish. The other main reason is to avoid contaminating the blasting media. Also, make sure whoever is blasting your parts only uses media dedicated to aluminum, preferably for a dedicated alloy.....i.e. 6061

I didn’t think about the process impregnating grease etc into the surface, I would have expected anything like that to be removed in the degrease / etch pre anodise.

I can’t imagine many contract blasters will be so detailed if they operate like many anodisers I have dealt with.

If you are blasting yourself then you can control the process to this level (dedicated and very clean media) - I imagine a quick degrease would still be sufficient prior to blasting though, especially as the anodiser will probably mess something up along the way anyway…

(Can you tell I don’t like anodisers)
 

Houdini16

Cast Iron
Joined
Nov 28, 2017
Dishwasher with spot remover additive and/or DI water, also use a non-staining Aluminum coolant, I use Novamet 910 because I used to get staining on 7075 injection molds when they were machined for 40-70 hours at a time.
2 Cents
 

Rob L

Aluminum
Joined
Nov 5, 2019
Location
Staffordshire, UK
We leave our 6061 machined aluminium parts for weeks to months sometimes without cleaning out of the machine, once they are bright dipped and anodised there are no marks to be seen on any of them, I find it hard to believe there would be any left after blasting unless the staining is actual surface etching.
I do the same although I have started running parts through deionised water in a heated ultrasonic cleaner just before sending them for anodising, mainly to get any gunk out of threads. I haven't noticed any real difference in the quality of the anodising but it can only help if they are cleaner to start off with.

Dish washer on the face of it seems like a great solution however one question, if it isn't legal to dump water soluble cutting fluid down a drain surely that means anything that comes out of the dish washer should be disposed of properly and not dumped down the drain?
 

Houdini16

Cast Iron
Joined
Nov 28, 2017
I do the same although I have started running parts through deionised water in a heated ultrasonic cleaner just before sending them for anodising, mainly to get any gunk out of threads. I haven't noticed any real difference in the quality of the anodising but it can only help if they are cleaner to start off with.

Dish washer on the face of it seems like a great solution however one question, if it isn't legal to dump water soluble cutting fluid down a drain surely that means anything that comes out of the dish washer should be disposed of properly and not dumped down the drain?
We wash all our parts in DI water and dish soap as they come out of the machine regardless, So no coolant would be in the dishwasher.
 

gustafson

Diamond
Joined
Sep 4, 2002
Location
People's Republic
Rinse right off the machine, out of the machine into a bucket of water, water/detergent
MSC used to sell 'Global Aluminum Cleaner' which is mildly acidic

Sitting with coolant will cause staining, period, avoid that

dishwasher works, just make sure for a short cycle, that hot water is at the dishwasher or you will get uneven results. I run the sink next to mine before starting

never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never never let that parts sit in the dishwasher overnight
 

triumph406

Titanium
Joined
Sep 14, 2008
Location
ca
Sometimes I wash parts in buckets with dishwashing detergent added. Parts always come out clean. I've dried in an oven, but mostly wipe with an absorbent cloth

--------------------------------------

My default is do nothing. Maybe put parts in a bucket of water to get rid of excess coolant, then air dry.

Then take to anodizer. Never get any streaks or blemishes in parts, so I can only conclude the anodizer (Danco) is doing a very adequate job of cleaning parts prior to anodizing.

------------------------------------

the parts you have in the video, wouldn't even occur to me to do anything special prior to anodizing, except maybe vapor blasting (at the anodizers)prior to anodizing,
 

ianwatts

Plastic
Joined
Oct 14, 2021
Location
Los Angeles, CA
A thorough degreasing step must be completed prior to and after the blasting stage for a couple of reasons. The main reason is to avoid imbedding contaminants into the surface of the aluminum, which you won't be able to see with the naked eye. Once the part is dipped into whatever etch or brightener bath, the surface will be "massaged" preferentially which yields a non-uniform surface which isn't visible unless under a microscope. Where it shows up is after the dying process. You run the risk of getting a splotchy finish. The other main reason is to avoid contaminating the blasting media. Also, make sure whoever is blasting your parts only uses media dedicated to aluminum, preferably for a dedicated alloy.....i.e. 6061
I'm using Potters glass beads (found here on McMaster) and only using it to blast aluminum 6061 parts, is that what you mean or are there more specific beads for Al 6061 I should look into?

What do you recommend for degreasing? Is DI water and dish soap fine or something more intense?
 

gkoenig

Titanium
Joined
Mar 31, 2013
Location
Portland, OR
Find an anodizer who will do a bright dip.

I've been getting parts anodized for years, and with the exception of one funky batch of material, we've never once had anything but fantastic finishes, with absolutely zero fussing over part cleaning post-machining. The only thing we do? We've always specced out a quick R8 bright dip which acts as a nuke it from orbit cleaning step. Even on bead blasted parts, a quick trip through the bright dip process eliminates every last bit of contamination, with little/no effect on the final surface finish other than to make it perfectly even.
 

ianwatts

Plastic
Joined
Oct 14, 2021
Location
Los Angeles, CA
Find an anodizer who will do a bright dip.

I've been getting parts anodized for years, and with the exception of one funky batch of material, we've never once had anything but fantastic finishes, with absolutely zero fussing over part cleaning post-machining. The only thing we do? We've always specced out a quick R8 bright dip which acts as a nuke it from orbit cleaning step. Even on bead blasted parts, a quick trip through the bright dip process eliminates every last bit of contamination, with little/no effect on the final surface finish other than to make it perfectly even.
Yes, think this is the solution I will go with. In my last batch half of them were bright dipped and none of those seemed to have staining issues (also looked better anyway). Do you know if they're traditionally bright dipped before or after blasting? If before, would I still want to give em a rinse off in water so the blasting doesn't impregnate any contaminants in the metal?
 








 
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