Home built centrifuge - gold concenrates from IC's

rusty · Jan 20, 2013

Centrifuges used to recover finely divided precious metals from ore circuits have been in existence for years, the one I'm working on will be similar in size to the seven inch Super Bowel shown below the wood pattern I'm working on.

Once the wood pattern is completed my bowel will be cast in aluminum then machined to fine tune the bowel, centrifuges have a great reputation for being able to recover the finest particle of gold from milled or ore. in my case the centrifuge will be used to recover precious metals from incinerated IC's.

The larger pieces of copper and such are screened from the ash with only the fine power left behind being feed into the centrifuge as a slurry, the lighter material gets flung over the top of the bowel while the heavier precious metals become entrapped in the groves located near the upper zone.

Centrifuges are quite, use less water are much more efficient than a shaking table which have more moving parts.

rusty · Jan 20, 2013

Todays progress, the final profile inside and out completed successfully, gave it a coat of linseed oil then some more sanding the pattern for the centrifuge bowel is done ready for casting.

I may have to order a larger crucible to hold the required volume of metal to fill this mold cavity.

The finished aluminum casting will have the required groves machined into it.

butcher · Jan 20, 2013

That is going to be to pretty to put mud in.

rusty · Jan 20, 2013

butcher said:
That is going to be to pretty to put mud in.

Thanks butcher, my small crucible and lack of hobby funds may delay the foundry part of this project.

This evening glued up more wood for another style of centrifuge, this one will be used to polish my waste oil.

Palladium · Jan 21, 2013

I love watching his ingenuity.

rusty · Jan 21, 2013

The gold centrifuge I've posted a picture above is worth an astounding $8820.00 Canadian dollars, is reputed to recover down to 20 microns. The company that sells the machine above also have another 12 inch model that will pull down to 5 microns which is smaller than a human red blood cell.

skippy · Jan 21, 2013

For anybody who wasn't aware, a centrifuge when it fails can be as destructive as a bomb. They have tremendous energy when they get up to speed.

rusty · Jan 21, 2013

skippy said:
For anybody who wasn't aware, a centrifuge when it fails can be as destructive as a bomb. They have tremendous energy when they get up to speed.

For anyone attempting to build a centrifuge they should have a good grasp on kinetic energy and mass.

I'm actually surprised they they use a poly bowel on the gold concentrator. must use some sort of backing to support the plastic.

Once had a Yamaha 650 cruising 120 mph when i came into rain and oil slicked highway i can say for a fact you could not have laid that bike over. The energy in the wheels acting like huge gyros kept the bike upright.

rusty · Jan 21, 2013

The waste oil centrifuge pattern is taking shape.

Jimmy · Jan 21, 2013

I pour aluminum all the time so if you need it poured, let me know.

rusty · Jan 21, 2013

Jimmy said:
I pour aluminum all the time so if you need it poured, let me know.

Thanks for the offer Jimmy, this is a job i prefer to do in house. I use Petrobond which gives a superior surface finish, a fine grain aluminum is required, then I use a commercial degassing tablet.

Any castings showing porosity during the machining phase will be discarded.

I do not think it practical to source this job out especially with the quality control I'm exercising with this project.

Jimmy · Jan 21, 2013

No problem.
I would however recomend Hydroperm plaster over the Petrobond. It is only about $1.00 per pound and will give you a much more superior finish and much less inclusions than Petrobond.
:lol:

rusty · Jan 22, 2013

Jimmy said:
No problem.
I would however recomend Hydroperm plaster over the Petrobond. It is only about $1.00 per pound and will give you a much more superior finish and much less inclusions than Petrobond.
:lol:

If you getting inclusions in your castings using Petrobond your doing something drastically wrong.

The majority of my projects are built on impulse but this will only take you so far with out research, having the right data to work with helps. With what I've learned these past weeks I'm confident that I could now build a large 40 inch centrifuge and not have it disintegrate into pieces.

Because my research tells me a drum that size would turn so slow to generate the required G-Force if you put a chalk mark on it you could count the revolutions, well not quit.

Building a centrifuge that successfully concentrates values is akin to refining precious metals, in the latter you have Hokes and the many tutors willing to assist when a problem arises.

It disappoints me to know how many millions of downloads there have been for Hokes book and how few have actually read the book.

I choose not to participate in a forum contest related to building your own equipment, in fact I do not know even if we have a winner.

Perhaps I should consider my centrifuge my entry.

On a side not Petrobond will no longer be available the North American mines have exhausted their supply of Olivine.

Jimmy · Jan 22, 2013

Ive owned a foundry and have operated it for 30 years. Dont do too much commercial work these days thou.
Cant remember ever using ovaline sand for non ferous work.
Usually I would use alumina sands if I was worried about expansion. And you only need to worry about expansion on thin sections that are created in some types of cores. A thick casting such as that part you are making has no problem with heat buildup. Any potential over heat condition will cause a lot of problems with the oil binder before the thermal expansion of the sand comes into play.
Give the hydroperm a try. No erosion problems as you will have with the petrobond and no thermal expansion problems at all up to 2000F. You will be well below that.
Takes detail too quite well.

rusty · Jan 22, 2013

Jimmy said:
Ive owned a foundry and have operated it for 30 years. Dont do too much commercial work these days thou.
Cant remember ever using ovaline sand for non ferous work.
Usually I would use alumina sands if I was worried about expansion. And you only need to worry about expansion on thin sections that are created in some types of cores. A thick casting such as that part you are making has no problem with heat buildup. Any potential over heat condition will cause a lot of problems with the oil binder before the thermal expansion of the sand comes into play.
Give the hydroperm a try. No erosion problems as you will have with the petrobond and no thermal expansion problems at all up to 2000F. You will be well below that.
Takes detail too quite well.

I apologize - I had no right to jump on you.

If your offer had been closer to home it would have been a pleasure working with you, I could perhaps have learned something new.

I'm capable of doing this small job, as you say the casting is thick enough so there should not be any thermo tearing on cooling.

rusty · Jan 22, 2013

Harold I need some advice, I've never worked with plastic before.

I purchased this a few years back, forgot what type of plastic it is, I can tell you when you try to pull the stringers away they're elastic and it machines reasonably well.

On the small end facing the tail stock, when the bowel is completed this is the end that will mount onto the motor shaft. Something in my head is telling me that I should bore this hole larger then install an insert with the hole reamed out to fit the motor shaft. What is your take on this idea.

The inset would be held in place with roll pins, or flanged on the bottom then secured with screws , drill a slightly larger hole to access the set screw located on the insert which also would have a key way broached in, the maximum RPM is 1500 or slower.

Ok, now I'm thinking that the flange on that metal insert should come from the inside of the bowel with a washer on the bottom side with countersunk bolts topside going straight through

Harold_V · Jan 22, 2013

rusty said:
Harold I need some advice, I've never worked with plastic before.

I purchased this a few years back, forgot what type of plastic it is, I can tell you when you try to pull the stringers away they're elastic and it machines reasonably well.

Looks like it could be polyethylene. Definitely not Delrin, Teflon or Nylon. Most likely has a bit of a waxy smell when being machined, eh?

On the small end facing the tail stock, when the bowel is completed this is the end that will mount onto the motor shaft. Something in my head is telling me that I should bore this hole larger then install an insert with the hole reamed out to fit the motor shaft. What is your take on this idea.

If you have means to install the insert so it is reliable, I agree.

The inset would be held in place with roll pins, or flanged on the bottom then secured with screws , drill a slightly larger hole to access the set screw located on the insert which also would have a key way broached in, the maximum RPM is 1500 or slower.

Ok, now I'm thinking that the flange on that metal insert should come from the inside of the bowel with a washer on the bottom side with countersunk bolts topside going straight through

I was thinking something on the order of flanges as well. I'd consider a large nut, with enough inside diameter to permit the extension portion to be large enough to accept the required bore and keyway for the motor shaft. Sort of like a flange assembly for mounting grinding wheels.

Keeping things concentric is going to be a bit of an issue unless you hold sizes quite close. You may have to balance the entire assembly when it's completed. Castings are notorious for not being homogenous, so it could have a heavy side, even if it's machined on all surfaces, and is concentric.

I most likely would have recommended the bowl be made from 7075-T6 instead of a casting. Much more uniform, and of greater tensile strength. The strength may not be an issue, depending on the velocity of the bowl in operation.

Like to hear how it turns out. I rarely get on the board these days, so please send me an email when you post, directing me to your comments.

Jimmy,
Wish you were near my location. I'm keen on learning more about foundry work. I intend to pour ductile iron in the future. While I never had enough interest to make the foundry my way of making a living, it has held my attention since I was a young lad---used to hang out at a couple foundries. I enjoyed all aspects, from watching cores being made to ramming and pouring molds.

Harold

rusty · Jan 22, 2013

Harold_V said:
rusty said:

Harold I need some advice, I've never worked with plastic before.

I purchased this a few years back, forgot what type of plastic it is, I can tell you when you try to pull the stringers away they're elastic and it machines reasonably well.

Click to expand...

Looks like it could be polyethylene. Definitely not Delrin, Teflon or Nylon. Most likely has a bit of a waxy smell when being machined, eh?

On the small end facing the tail stock, when the bowel is completed this is the end that will mount onto the motor shaft. Something in my head is telling me that I should bore this hole larger then install an insert with the hole reamed out to fit the motor shaft. What is your take on this idea.

Click to expand...

If you have means to install the insert so it is reliable, I agree.

The inset would be held in place with roll pins, or flanged on the bottom then secured with screws , drill a slightly larger hole to access the set screw located on the insert which also would have a key way broached in, the maximum RPM is 1500 or slower.

Ok, now I'm thinking that the flange on that metal insert should come from the inside of the bowel with a washer on the bottom side with countersunk bolts topside going straight through

Click to expand...

I was thinking something on the order of flanges as well. I'd consider a large nut, with enough inside diameter to permit the extension portion to be large enough to accept the required bore and keyway for the motor shaft. Sort of like a flange assembly for mounting grinding wheels.

Keeping things concentric is going to be a bit of an issue unless you hold sizes quite close. You may have to balance the entire assembly when it's completed. Castings are notorious for not being homogenous, so it could have a heavy side, even if it's machined on all surfaces, and is concentric.

I most likely would have recommended the bowl be made from 7075-T6 instead of a casting. Much more uniform, and of greater tensile strength. The strength may not be an issue, depending on the velocity of the bowl in operation.

Like to hear how it turns out. I rarely get on the board these days, so please send me an email when you post, directing me to your comments.

Jimmy,
Wish you were near my location. I'm keen on learning more about foundry work. I intend to pour ductile iron in the future. While I never had enough interest to make the foundry my way of making a living, it has held my attention since I was a young lad---used to hang out at a couple foundries. I enjoyed all aspects, from watching cores being made to ramming and pouring molds.

Harold

Yes it has a waxy smell, you could make miles of fishing line, the darn stuff comes off in one long continuous string and tough to break.

For simplicity I'll go with the flanged insert inside with washer machined to fit below then run some bolts through.

So with the 7075-T6 aluminum this would be billet.

My neighbor has a few machine shops scattered around the globe, next visit I'll ask if he has a dynamic balancing machine.

On the larger centrifuges they roll the iron then weld everything together, but then the larger drum do not turn near as fast as this 7 inches.

Thanks for dropping by Harold.

Harold_V · Jan 22, 2013

rusty said:
So with the 7075-T6 aluminum this would be billet.

That's what they like to call it, but it's just bar stock. The term billet is well overused these days. Sort of a "catch phrase". It's a legal term--most everything comes from a billet--but is further processed to forms. Round bar, rectangular bar, square bar, etc.. You get the idea.

My neighbor has a few machine shops scattered around the globe, next visit I'll ask if he has a dynamic balancing machine.

Certainly worth asking. You might even find it runs fine without balancing---you never know. Velocity is king, here. The faster it runs, the worse it will be.

Looks like an interesting project.

Thanks for dropping by Harold.

Thanks for the invite. Nice to see something different.

Harold

rusty · Jan 22, 2013

Some of the larger machine shops and ship yards must have inventory worth more than Fort Knox, I priced out 1 ft x 8" diameter 7075-T6 aluminum - $200.00 a ft. before tax.

I think Harold is right the plastic i have is Polyethylene same stuff they're manufacturing the new concentrator bowels from. I hope that it works satisfactory as I rather do like working with it, you can take some really big bites bringing your work into shape fast.

Like most of you we're experiencing a major cold spell, the shop floor is freezing cold and its beginning to bother my legs. Had i been prepared would have made a spring board to stand on, in the mean time taking more breaks than usual.

Also did an alignment tuneup on the lathe, tail stock it was out a couple of thou. Now that that job s out of the way I had a chance to hog out the center of the bowel, later machine in the grooves.

Working with an opaque plastic sucks so at this point the pictures are not all that good.

Edit to make correction, re: type of plastic

Home built centrifuge - gold concenrates from IC's

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