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cleaning parts after tumbling

Sorry in advance for the length of this post.. but I will try to be as specific as possible.

I have a 3 cubic foot vibratory tumbler, in which I use plastic cone shaped media. The liquid soap solution is from the same company as the media. The parts I am tumbling are Zinc die cast carburetor parts, in preparation for Di-Chromating.

I have a gravity feed tank which trickles the soapy mixture ( 3 ounces to 4 gallons water) into the tub while the machine is on. It uses about 4 gallons per 2 hours. Then I put in 4 gallons of pure water for a rinse cycle lasting another 4 hours.

The operation of burr removal and polishing is working as expected, but I have trouble with a film of some sort accumulating on the part when it is blown dry. This film can be easily wiped away with a cloth, or just a finger. If the parts were in the shape of a box, or if all the surfaces were flat... it would be a simple wipe down pre - chromating operation... but there are countless little crevasses for the film to hide out in. If left on, the film will effect the di-chromating quality.

I have tried a few things, and am reaching out for more info on this topic. At one point I was using the well water here on the acreage we reside on for the soap solution. Today, I used clean rain water from our reservoir we water the trees with. This seemed to help quite a bit, but it is not perfect. I then thought about putting a few samples in the dishwasher (while the wife was out) to see if the hot water and spray would work... no such luck... still comes out with a film... and once again a cloth will take care of it. The residue left on the cloth is pretty dark, so I am assuming part of the material coming off the parts is not just some soap.

Is this a common problem, with a simple solution? I have zero technical knowledge of the tumbling trade, so it is very possible I am missing something fundamental here... and have put my thick skin on.

Thank you,

RB

Reply to
Ryan
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There may be a few things contributing to the problem. A gallon per hour is a mighty small amount of liquid IMO. In my Torex I use plastic media and VF-77 solution, about the same ratio as whatever you are using. But, I have a sump and an aquarium pump set up for constant flow through a small sprinkler. I don't know offhand what the flowrate is, but way more than 1 gph. I would not run with plain water as the media breaks down quickly and it will adhere to the parts, as well as embedding back into the media, along with powdered aluminum and whatever impurities are along for the ride. You need the detergent to keep the media and parts clean.

Do the parts have ANY grease, dirt, or oil on them? If so, they should be washed in hot soapy water and rinsed beforehand. When finished in the vibe they should be washed again, won't take much, a soapy dunking and clear rinse should be fine. Don't let the parts start drying before the final wash. If I have a lot of parts to remove, I will put them in a bucket of water to keep them wet during that period.

I'm thinking the time in process is quite excessive, I have never run anything more than 45 minutes, and that usually cause I'm a lazy bastard and don't want to go do the removal until I'm ready.

I have had more than one plater mention how they like seeing my parts come in, they save time and solution because they need only a bare minimum of etching. They are already "clean" and don't have any grease, oil, etc on them. If you have any ???, contact by email with proper topic in subject line.

HTH

michael

Reply to
michael

The media is most likely to blame. Ask your supplier to provide a media that does not soup up as much. We run AL in ours and use lots of fluid but it is run through a filter before being sprayed into the tub. I used a house water filter rig that costs $ 40 at your Home depot / Lowes using a 5 micron filter. Big difference after adding filter. I change the filter every few days if running

10 hour days. Use a good fluid VF-77 is great.

Pete

Reply to
Pete

Do your dishes have spots on them after they dry?

It sounds like you have hard water. Rain water is better, but still not good enough.

You probably need to rinse them with distilled, or reverse osmosis, or deionized. The film is probably "hard water" deposits. Calcium/Magnesium carbonates.

Water softener water might be good enough, depending on how good it does to remove the "hardness".

You should give your parts a final rinse in the pure water before they are allowed to dry. You might not get the film off by rinsing them after they are dry.

If a final pure water rinse does even better, but still not good enough, you might have to use pure water during the tumbling/washing cycle.

Dave

Reply to
David A. Webb

Great ideas!

I should clarify a few things:

The parts are beadblasted then into the tumbler. I am using VF-77T soap. Using 3/8 x 3/8 cone shaped V-Preplate media (green) from Vibratoryfinishing.com, this is the finest grit in plastic they offer that I am aware of.

To reduce tumbling time, I am strongly considering purchasing media in the next step up in abrasiveness... the stuff is just so darn expensive... But that would be a welcome change, as it takes a few minutes per part to pick out the media from some of the little ports and holes so I would change the media shape at the same time.

Keep the ideas coming!

RB

Reply to
Ryan

Try clean water.

The price of consumer type RO systems has dropped to about $200. You can get a few gallons per day of pretty darn clean water with a small RO system.

RO water makes for a very clean rinse.

Another clean rinse agent is liquid nitrogen. We used to use it to clean off some optical equipment. Thermal shock and a strong need for specks of dust to start bubbles means you get a very clean surface.

Naturally the use of liquid nitrogen in this way is very dangerous.

Reply to
frank

When you put the rinse water in, not all of the old water has been eliminated from the tub. This means that you are still using the soap at a much diluted ratio. As others have mentioned, hard water does make the problem worse. One thing to try is doing the work without any soap and see if it is any better. This probably isn't what should be but it should work. I'd also use compressed air to blow out all of the passages when removing the parts to assist in the removal of the small chips.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

Reply to
Bob May

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