All about Metal casting

It seems that several other members are interested in metal casting so here is a spot to share your projects.
I’ll start off with a picture of a recent project.
20190409_122311

13 Likes

Thats cool!
What are you making?

Here is a cast aluminum hopper tube. I am told that aluminum does not corroded in the hopper.
CastHopperTubeCastHopperTube1

6 Likes

What type of pattern did you use?
Rindert

1 Like

I got sick of replacing battery terminals, because even the high dollar one’s break all the time. I made this one out of broke terminals and wheel weights. Jakob DSCN9953DSCN9954

7 Likes

Jakob; The important thing about battery terminals and connectors is to have them totally clean. I know we all over tighten them to get a “good” contact and result in stretching the lead out until it breaks. Now that you can make your own, I don’t suppose you are so concerned about breakage, but time spent cleaning will save time casting. TomC

5 Likes

Andy what do you use to shape Styrofoam for casting.
Jesse

2 Likes

Hi Jesse,
I use a hot wire cutter. Its just a simple wood frame and a piece of nichrome wire salvaged from an old blow dryer. Its powered by a 12 V battery charger. You might need to use a household dimmer switch to adjust the heat… also, its important to have a spring tensioning the wire because it expands when hot.

6 Likes

One thing I will say about lead, caution.

It’s toxic at any level, and has a bad tendency to build up in the body. Even touching lead objects transfers some millionths of a gram to fingertips. But it’s an important material in our world.

Best to practice good hand washing, and clothes washing, treat it like it was pure arsenic, or plutonium…

3 Likes

There are many homemade hot wire foam cutters on youtube. I used a 6 volt battery charger for a power supply and a piece of .035 flux core wire. I used a brake rotor as a weight to keep tension on the wire. I made a make shift table with a hole in the center, and a piece of metal in the hole to isolate the hot wire from the table. I made a slider out of a piece of brass to put electricity onto the wire. It can move up and down to make a longer or shorter path for the electricity. This allows me to control the temperature. If you get the wire too hot it will break. My setup used about 8 amps. Below the table is another slider, but it doesn’t move, it just takes electricity off the wire. I put eight screws in a row in an overhead beam in my garage. The wire gets looped over one of the screws. This allows me to change the angle of the wire to the table. I made several make shift fences and jigs to help me make different shapes. Think about how a table saw and other tools in the shop work. I used foam glue in a spray can I got from a big box home improvement store to stick pieces of foam together. Fill in any holes or gaps with foam glue. The metal reproduces everything exactly the way the foam pattern was, even when you don’t want it to. Be creative, have fun.
Rindert

3 Likes

Andy,

I have some steel 1-1/4" hydronic steam heat pipe with steel fins. I was thinking about making a nozzle by cutting a piece and filling it with aluminum. I would then drill a blind 5/8" hole in the center, and an upward 45 degree nozzle hole near the end. I would remove the fins from the part that goes in the reactor and I would bolt the first outside fin to the reactor body to make an air-tight seal.

If I weld the end of the heat pipe closed and pour in aluminum will there be good thermal contact or will the aluminum shrink and separate from the steel?

1 Like

I think the aluminum would shrink an be loose, based on this video.


Maybe you could get around that by heating the steel pipe red hot when you pour in the aluminum, so the steel would shrink more too.
There was some discussion of completely encapsulating a low melting metal so it could indeed melt but be contained and still tranfer the heat.

5 Likes

Given that aluminum has a greater expansion rate, I suspect that if cast around steel it will hold firmly to the steel. This could get complex when significant temperature variations are involved. Too great of temperature swings and heat transfer and coefficients of expansion could lead to metal fatigue. But with good clean joints and within a certain size range I expect it should work ok.

2 Likes

I watch this guy on Youtube a lot for ideas.

This is an electric furnace he made I am pretty impressed with…

3 Likes

Just FYI Not all blow dryers have salvageable nichrome wire in them. Some have like a solid plate instead. The toaster I scavenged nichrome from had flat wire and it got all kinked.

Is there anything special about flux core or is it, just a that is the wire you had? NiChrome is better, but steel has pretty good resistance as well.

Are you guys just burning out the foam with the metal or are you burning it out after packing it? I assume you aren’t doing the coat in plaster technique…

1 Like

I’m just burning out the foam with the hot metal. I tried the plaster coating but did not work well for me. N this paticular casting i used greensand around the foam because of the complex shape and the size, loose sand collapsed and or blew out. On smaller ittems like my meddalion or belt buckle, loose sand works well.

3 Likes

It’s just what I had handy. I may have made a discovery just by dumb luck.

http://forum.driveonwood.com/t/spiral-path-heat-exchangers/3657/117

My lost foam casting turned out much better than I expected, and I only ever made one. I placed about two inches of loose sand in the bottom of a 5 gallon steel bucket. I placed the foam pattern in the bucket. I covered the pattern with sand. I tapped the bucket with a wooden mallet so that the sand would vibrate into all the nooks and crannies in the pattern. Last I just poured aluminum and the foam burned away as soon as the hot metal touched it.

I have a LOT of experience making castings in green sand. And I have used foam to hold cores in place a bunch of times. But this was the first and only time I used a foam pattern.

Rindert

4 Likes

I kind of wonder if lost foam coated in plaster works better if you vaporize it first. [quote=“r_wesseling, post:17, topic:4595”]
It’s just what I had handy. I may have made a discovery just by dumb luck.
[/quote]

I didn’t know if you had compared it to something else or not. It might work better because the electrons go on the surface of a material, the “hollow” inside seems like it would give it more surface area.

What is the finish comparison to green sand? And are you using commercial green sand?

1 Like

I normally use 120 grit olivine sand, with 2.5% southern and 2.5% western bentonite and 3.5% water. I suppose you would call this commercial sand.
What was used to make the foam casting wasn’t anything that nice, just what we call ‘fines’, a mixture of olivine sand, settled dust and ordinary dirt that people had tracked in from everywhere. It was very dry, and powdery, perhaps 300 grit.
The finish looked like the pattern, Styrofoam beads.
Rindert

1 Like

I think that is a pretty common recipe. I was just trying to figure out whether it was worth it to make a green sand, or whether I should use styrofoam. I want to make like a pencil holder and I don’t want to spend hours trying to clean it up and polish it. which makes using something like k-bond appealing…

This might be of interest to you. It looks like these guys are using mostly western clay with lignite.

2 Likes