core pin in die casting ???

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DavidF
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core pin in die casting ???

Post by DavidF » Sat Dec 12, 2015 6:01 pm

I was wondering if anyone had any experience with aluminum die casting and pulling a 5.5" long core pin with no draft on it. The thickness of the aluminum would only be 1/16" around the pin so I am thinking it would be possible?? Core pin is .1875" dia

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steamin10
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Re: core pin in die casting ???

Post by steamin10 » Wed Dec 16, 2015 12:42 am

In industry, such a method would be avoided. (AL) Oxides would gather on the surfaces of the pin, and cause scoring in short order, as aluminum is very abrasive in its oxide forms, and has the ability to dissolve iron, in all its forms. AFAIK it is set up for a few thou taper, and a second operation, (If needed) would be a reaming for true size and parallel. Many other die designs of various materials, can be used for production runs, of great numbers. I am thinking of the home guy, where quality may be somewhat variant from standard practice..

For short runs, many things may work, but keep in mind that a pin will have the molten metal shrink in, and grip the pin. Some success with a parting agent like carbon graphite, (candle smoke) can be enough to allow a short press. This may result in crush fractures, or stress defects, where the stripping plates push on the part.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

DavidF
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Re: core pin in die casting ???

Post by DavidF » Wed Dec 16, 2015 10:01 am

Trying to avoid secondary operations. There are 300 holes that would need to be drilled/ reamed that I think would prove very difficult to keep straight. I thought about pulling pins from both sides to cut the pull length in half but then I question how well the pins would meet each other in the center unless I made it so they could align into each other somehow. Im getting the feeling I may be in for a bit of trial and error...Maybe I could use a core material that could be broken out like ceramic or something?

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Re: core pin in die casting ???

Post by OddDuck » Wed Dec 16, 2015 7:10 pm

David, is this in reference to your ROV project? For a hole like that something to consider as a core would be a tube of the correct material and inside diameter that you lay in the mold before you close it up. This would be an easy way to add steel bearing surfaces to an aluminum part, say for caterpillar tracks, and wouldn't have to be removed from the casting, possibly just reamed to size. Hopefully what I'm saying is slightly clearer than mud.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

DavidF
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Re: core pin in die casting ???

Post by DavidF » Wed Dec 16, 2015 8:04 pm

Hi O.D., yes for that project. I considered putting in brass tubes, until i priced them "yikes".
Im considering plastic instead of metal. Bought a small injection molder off evilbay to do some testing.
With the qty i need injection molding might be the best solution, but i may have trouble with putting too much weight on them and bending the link pins. Round and round I go, ill get it sorted eventually.

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Re: core pin in die casting ???

Post by DavidF » Thu Dec 17, 2015 10:52 am

this is the original design, the manipulator and excavator have now been removed and replaced with a suction dredge.

Image

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steamin10
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Re: core pin in die casting ???

Post by steamin10 » Thu Dec 17, 2015 11:11 pm

Eeyou! I LOVE IT>>First if you are going to go woth tracks, I suggest you look at food conveyor chains. they are flat, and commercially produced in plastic and stainless steel, and are a easier path for what you want. Also, reduce the number of carriage bogies, and eliminate moving parts. Look aat some standard tank designs for the M-4 sherman, or the Sheridan track designs for ideas, and work from there. These can be built with common hardware springs (not torsion bar) and be easier to service and 'fix' in the field. Next is it begs for 'canned' hydraulics, that keeps water from the drives. Common auto batteries can be adapted for power, if you keep the air space equalized with a scuba type regulator to adjust the bar pressure for water depth. Old regulator units can be had for minimal expense.


Also consider lawn mower wheels for boggie suspension, with or without sleeve bearings, as water is an adequate lube for light projects like this and inexpensive.

I like the design posted, but have to guess this thing gets to be about 3 ft x 4 ft or so based on the track width of 5.5 inches.

My brain runs on when I see these things, so I will stop here. I would like to converse on what you can do for t his project.
Dave

Just some ideas to explore, form the top hat of an old diver. So why this rig, when a snorkel and fins, or scuba can be fun too....?
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

DavidF
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Re: core pin in die casting ???

Post by DavidF » Fri Dec 18, 2015 12:28 am

. So why this rig, when a snorkel and fins, or scuba can be fun too....?


The beaches open up in the winter, water is quite cold by then.....I hate cold water! Yea, its a nutso project but that's me in a nut shell. Dave,you have hit many of the thoughts I had previously, but you left out skate board wheels :lol: Maybe I have too many visions of grandeur, but since I keep coming back to this project and have been building every thing I do up to it it pretty likely I will "git er done"

Pretty damn close on your sizing BTW.....

rrnut-2
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Re: core pin in die casting ???

Post by rrnut-2 » Fri Dec 18, 2015 6:32 am

Not knowing what the size of this machine is here is my take. Look at the ASV Track truck, track arrangement. The bogies can be made or
bought fairly cheap and yet the setup is robust enough that ASV went on to use them on the multi terrain skid steers. I can even supply
you with pictures as I have two here in the yard.
Attachments
Track Truck 2007.JPG

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steamin10
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Re: core pin in die casting ???

Post by steamin10 » Sat Dec 19, 2015 11:59 am

DavidF: The problem with any roller, aka skate wheel, is their size tends to be too small and get fouled with sand and stones that will lock the tracks. Second the rather cheep bearings wont hold out in water, or salt water, and require extraordinary care to keep them rust free and operable. Stainless pins )axles) and plastic bearings are a better bet, trust me.

These are the same problems you run into with model tanks. I built one with the slow drives of a kiddie jeep. It was too slow for parades and such, but was built with junk, and rubber sheet for tracks with a billion bits of plastic, and push mower wheels. The body was salvaged panels of polycarbonate window glazing, and louan plywood, over a plywood base that carried the mechanicals. No radio, I used a hip box, and phone cord, 6 wire. it would have been neat with radio.

Your project, being in the water would drag an umbilical, that could be floated with bobbers to prevent some fouling. The auto battery problem solved by mating two stock pots into a tank that holds the batts dry, with a paintball tank of N2 for equalizing. I dunno if you can get enough working power for hydraluics, as they are energy hungry for power. No free lunch.

I am a PADI registered diver since the 70's, and have worked around boats and gizmos for the water, so take all suggestions with noted grains of salt. I love the design work and trades to get dreams to work, but in the end, this is your creation. Not to be a know-it-all here, I wish you the best in your endeavers. I used to hunt the 'Washington Park' area in Michigan city. It was a lakefront park that died off and was a Chicago playground, from nearly the turn of the 1900's. I used metal detectors to sweep the grass, and beach, where jewelry and coin could be found, along with a zillion pop tops, and foil wrappers. After many trips, work demands made finding 4 coins in a day just silly. I value my shipwreck spikes more than the coins. There are many wrecks and beach areas here that prove interesting in the cold lake waters. So I really get your motivation.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

DavidF
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Re: core pin in die casting ???

Post by DavidF » Sat Dec 19, 2015 10:53 pm

Good to know someone gets me :D Im a Maui cert diver from 2000, still a baby by all means and have not dove since aluminum tanks went south. Cant say I ever enjoyed diving as I thought I would, hanging on the bottom of a 40'er pulling props in 1' vis 18" from the bottom kills that. (long story) But I have always had a fondness of boats, the ocean, and treasure hunting.
Dave you see alot of the things I looked into as i went about this design. I was planing on running AC thru the tether and running hydraulics, but costs may limit me to DC and steppers although I do have some 90V DC motors and AC to DC drivers. Ill have to hook up my old computer to retrieve some files to show you the bogie sealing arrangement and get your thoughts. The bearing area only has one double lip seal and would be filled with food grade oil, so water intrusion would be minimal at most.
My fleabay injection molder showed up yesterday, it works but the shot size is smaller that what I thought it would be. Waiting on some dom tube to fix things up. Anyone ever encapsulate a steel core into an injection molded part? I used to do it in the composites industry, but its a bit different in injection molding.

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steamin10
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Re: core pin in die casting ???

Post by steamin10 » Sun Dec 20, 2015 12:21 am

I cannot advise on injection machines as I am in open mold, green sand, and poured sand, and ciramic-lost wax methods. The only experience is along the old letter press linotype machines. I do know that metal inserts are added to plastic moldings for various forms, and work well, depending on the plastic.

Using AC in the power cord is problematic with distance. V drop is high and noticeable because of corona cancellation with wires next to each other. It can interfere with control signals if the cording gets long, and fuzz will confuse electronics. Electronics are best capsuled or dunked in Epoxy to seal against moisture, but it is still no guarantee. A hundred foot outdoor extension cord is about all you will get and be convenient, other wise 12 Ga wont be enough, and that means custom cording, and more weight. You might get by, as this is water cooled so heating is not a problem.

I dunno what design weight you are shooting for, ballasting with steel or lead can keep things from moving in wave or current, or the effects of a dredge blast. Weights are offset by the value of water weight. So it must be considered. Underwater sand dredges work best if 50% of the suction volume is used to (fan) blast the sand on either side of the suction nozzle that uploads the cloud of debris. The problem with dredges is anything to be picked up must get close to the nozzle stream. Rocks and debris can easily occlude the breaker bars, and the flow must be cut to clear the stoppage. Think paper wad on a vacuum hose and see what I mean.

I had a busted deal years ago, on a machine taken out of service, bought for cheap. It wound up being a 1 oz shot, well short of the volume promised by the die size. Education can be expensive.

Oil filled operating units neatly side steps the equalization problem, but becomes a nightmare for maintenance. Leaks will cause oils slicks, and internal contamination. Dealing with drain/fill cycles are another step as well as keeping the sealed capsule stable. Again, no free lunch. you will have to work the list of trade offs to come to your design decisions.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

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