Mini drum de-plater

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Kilroy2k1

Active member
Joined
Jun 4, 2008
Messages
28
Location
Canada
I finally got around to building a mini drum de-plater to process the pins from the telecomm boards from my previous posts. Thought I'd share a picture of it for anyone interested in building their own.
Its built from a very fine pitch stainless steel screen, copper strips for strength and some misc photocopier parts.
I have not run it yet but will be this week. I hope to be able to process 1/4-1/2lb of pins at a time.

http://picpaste.com/drum-Uw17dJ6G.jpg

Any and all comments welcome.

Tom.
 
Currently its spinning at about 15RPM, I feel its a little fast yet so I'll be fine tuning that to slow it down with some form of motor control.
I will be testing it with water today.

Tom.
 
How are you making electrical contact to the basket?

The screen may act similar to a Faraday cage and prevent current from throwing to the parts inside it. Also, if the solution gets too hot from high current and/or the sulfuric becomes too dilute, the basket could be attacked. It's pretty thin material.

Were it me, I would make the basket of perforated plastic (available in sheets with holes as small as 1/16") and use an internal contact, such as an electrified center axis (stationary axis and rotating basket) or danglers.
 
There will be a lead cathode on the edge of the container such as what you would normally see in a cell and on the left side of basket on the shaft I made a spring loaded slipring so the whole basket will function as the anode.
I have used that screen material as a basket in the cell already and it seems to hold up well so far.

Tom.
 
Tom,

As GSP mentioned, if you put your cathode outside your basket, the current will try to flow directly from the basket to your cathode. It won't have much effect on the pins tumbling around inside. What you want is for the current to flow through your pins on its way from the anode to the cathode. This can be accomplished by including danglers inside the basket instead of outside.

Dave
 
Another problem is the danger of sulfuric acid drops flying out as the tumbler is turning. With your present arrangement, I think this will definitely occur no matter how slow the tumbler turns. I, for one, wouldn't want to be near that while it is tumbling. A way to solve this would be to use a plastic tank deep enough to be above the top of the tumbler. Slots could be cut in the tank for the axle. See pdf attachment. I sketched this hurriedly without labels. The horizontal line represents the solution level. To make it more safe, you could put a lid on top.
 

Attachments

  • Tumbler Tank.pdf
    228.9 KB
Oops, Sorry I missed GSP's Post.
GSP I saw your recommendation on another posting about the faraday cage effect and did some research online. I found some commercial drums made of different metals so I suspected it was possible to do with a metal drum.
I then did a small scale test and enclosed some pins in a tiny cage made of the same material and dipped it and it stripped the pins quite well. I didn't do a timed test so not sure if the stripping time is the same or not but it was very effective. It gave me enough confidence to try a lager scale, if it doesn't work out well enough then I'll try something else.
Cyanide would be ideal for the 24lbs of pins I have but I'm not confident or educated enough to properly handle that process alone.

Tom.

(edited to add) I like the idea of cathode danglers inside the drum, I'll look for some hollow 5/16 shafting and I believe I can modify the rig for that easily enough.
 
I've also thought about, instead of danglers, hanging several short lengths of fairly heavy chain (3 or 4 links each, say) from the center shaft. The chain would have to be loose on the shaft and some type of stops used on the shaft to keep the chain from sliding horizontally - maybe very snug thick plastic washers or metal washers welded on or short lengths of thick snug plastic tubing.
 
GSP
You raised a good question on the splashing so I ran downstairs and mocked up the tub with just water in it and set it spinning. At the RPM it is running there is no splash at all, not even a sloshing noise from the water, but I still think it will be too fast for deplating. I'm thinking it should use less then 5 RPM to give the current a chance to work. I'll either add a motor controller to slow it down or locate a different lower speed motor. As it is it is a 24V motor running on 5V from a small wall wart.

Tom.
 
Kilroy2k1 said:
GSP
You raised a good question on the splashing so I ran downstairs and mocked up the tub with just water in it and set it spinning. At the RPM it is running there is no splash at all, not even a sloshing noise from the water, but I still think it will be too fast for deplating. I'm thinking it should use less then 5 RPM to give the current a chance to work. I'll either add a motor controller to slow it down or locate a different lower speed motor. As it is it is a 24V motor running on 5V from a small wall wart.

Tom.
Click to expand...
I wouldn't expect much splashing from the drum itself turning. Did you load it with some of the pins you plan to run? As the drum turns pins will be carried up the ascending side. They may not "flow" as a liquid, but tend to stick together and then drop down in "clumps" because of their irregular shape. Either way, you might want to consider a cover for the system to contain any tiny droplets that might make it through the basket.

An alternative is to turn the drum on an angle of maybe 45°, with the whole drum sitting in a bucket that is taller than the width of your drum. You'd have to redesign the support system for the drum, but the whole drum would be in the bucket, so any splashing would be fairly well contained, especially if you cut a small hole in the lid of the bucket for the shaft of the drum to pass through. By placing the bucket lid loosely in place, any splashing or droplets would be contained inside the bucket.

Any type of cover, whether it be a cover over your current design or a bucket, will also help to keep the concentrated sulfuric acid from absorbing moisture from the air. As the acid begins to dilute it will start to attack your metals more vigorously.

Dave
 
I'm adding one more stage of step down pulleys to it to slow it down some more. With pins in it you can hear them rolling down but no splashing using water to test, the screen is very fine so it would take a pretty aggressive splash to pass through and the sulfuric I currently have has a higher viscosity then plain water.
I can easily add a shielding cover to it but it would not be wise to completely enclose it without ventilation to let the fumes dissipate. When I get to the first run I'll know if any cover is necessary.

Tom.
 
I read a few threads where you recommended keeping the temp low to reduce base metal etching and its been in the back of my mind while building this jig and have an idea or two on the table.
I purposely made the basket sit higher then what is needed for the tub I intend to use so there was room for some extra cooling rigs. I have an old water cooler that still has functioning refrigeration but all the plastic valves and seals are shot and it leaked like a sieve. Rather then put it in ice water my plan was for a refrigerated cooling setup. My first idea was a chilled sand bed. Not the most efficient thermal transfer medium but safer then sitting it in a tub of water. I could also add a large piece of copper in the sand to act as a better thermal mass directly under the sulfuric container.

As far as power supply goes I did some light searching for plans for a regulated rectifier with poor results. I would much prefer to use that over a battery charger but I have to use what I have on hand for the moment. Once I get the rotational speed to where I want it I'll sharpen up my googleeze and see if I can find something I can build.

Tom.
 
While tumbling, the tumbler would be out of the solution about 2/3 of the time and would be exposed to oxygen in the air. This combination of sulfuric and oxygen could oxidize and degrade the stainless much faster. Just thinking out loud.
 
If it lasts long enough to do this 24lbs of pins then it'll have served its purpose. I don't foresee me ever getting a deal like this anytime soon.. lol

Tom.
 
as long as the acid is concentrated and cool, copper will hold up better than stainless steel (in my opinion).
 
goldsilverpro said:
While tumbling, the tumbler would be out of the solution about 2/3 of the time and would be exposed to oxygen in the air. This combination of sulfuric and oxygen could oxidize and degrade the stainless much faster. Just thinking out loud.
Click to expand...

I believe oxygen is actually what passivates stainless steel. As long as the acid stays concentrated O2 shouldn't accelerate the corrosion at all.
 

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