Foundry


Backyard Foundry
Update March 03, 2008 - Sensei coaster
	I've been working on some small patterns on my CNC router for either coasters or small desk ornaments. Since I know a karate instructor I decided to do one with the symbol for Sensei or teacher. I made a simple match plate with two of the patterns.
	The first cast was a bit on the cool side and didn't quite fill. You have to love casting, the mistakes get melted down and recast! The second cast is shown here after the shakeout.
	The left side showing detail.
	The right side detail.
	After some basic cleanup on the belt sander, a quick paint job, and then a bit more sanding to highlight the rim and characters.
	The first two. We'll see if there is demand to make more.
Update August 27, 2007 - Here is the final hitch plate..
	My powder coat gun arrived but no paint. I had to wait a couple of days for the rest of the order to arrive. I hate when that happens! In any case, the powder coating went on well then I used a dry paintbrush to dust off the tops of the letters. Into a toaster over at 400 degrees for 20 minutes after the powder melted and left to cool slowly. The coating isn't too thick on the sides of the letters and it pulled away a little bit from the letters. Plenty of room for learning. I shot a clear coat of lacquer on to give the black a little gloss and it was done.
	I put a piece of foam backer rod around the alignment boss on the back to keep the hitch plate from rattling. Here is a picture of the final plate on the Jeep.
Update August 06, 2007 - I finally finished my match plate for my hitch cover project and after a couple of attempts I was able to pull a decent mold.
	For this project I decided to make a match plate as I will probably cast several of these for other parents in our Scout troop. The base is 3/4" MDF, the background is Beech. The letters were laser cut and then glued on using epoxy. I used a carbide bur to add some more draft to the letters as I was having problems getting a clean release. There is still some cleanup to do on the pattern before the next cast.
	A little better detail shot. I did a bit of hand carving on the fleur-de-lis. The overall size of the cover is about 3 1/2" by a little over 8".
	Here is the back of the pattern. I plan to add some draft to the sprue to make it easier to separate the pattern.
	All the preparation is done, the foundry is warmed up. Just a couple of ingots to drop in and it'll be time to pour.
	What could be more fun than pouring molten metal?
	Shakeout. It looks pretty good so far!
	The back filled out nicely. There is a bit of shrink at the base of the tongue but it shouldn't be a problem.
	A little more sand brushed off and the lettering looks great.
	After a quick wash down, mostly to cool it down so I could handle it.
	After removing the sprue and a quick cleanup on the belt and disk sander. I will most likely paint it in black and then polish the letters and the frame and then clear coat the entire hitch cover.
	The back. Overall I am very pleased with how it turned out.
Update June 17 2007 - The day before father's day I found myself with a full morning to myself. It seemed like a good time to neaten up the side yard.
	The pile of scrap aluminum was growing. The best part was it was all free! I found several aluminum storm doors lying on the side of highway 4 and a camper shell abandoned after a crash. The only problem, it was turning into a real mess. It will all soon feel the heat of the foundry.
	Here is the result: 50 aluminum ingots or about 75 pounds of nice, clean, shiny, aluminum. My next casting project is a hitch cover in honor of my son achieving the rank of Eagle Scout.
Update April 4 2007 - I added some pictures of my first cast item!
	Here is the pattern I made for my paperweight. I turned the aluminum base on my lathe. The letters were cut from maple by Laser Creations, thanks Tracy! I rammed up the mold using J82 sand which is a PetroBond equivalent which is an oil bonded sand. It allows for fine detail and doesn't require as much venting as water bonded sand.
	This is the mold after removing the pattern. The white powder is parting dust (in this case talc) to allow the pattern to be removed without the sand sticking to it. There is a bit of dropped sand but I wasn't after perfection so I dusted the mold with low pressure compressed air, closed the mold up and poured it on March 26th, 2007.
	Just after cracking the mold open. The aluminum is still probably close to 300-400 degrees. You can see how the sand is charred by the heat when poured.
	After a bit of brushing to see how the letters turned out. The technical term for this phase is shakeout. I was pretty surprised at this point since it was my first attempt.
	The completed paperweight. I cut the sprue off with a hacksaw, sanded the bottom flat on a belt sander, and did a quick touch up on the rim with a disk sander. The top was just wire brushed. With any luck the website will be up soon.
Update January 08 2007 - I added some video of pouring aluminum ingots.
Update January 01 2007 - The foundry is complete and I had my first melt! I cast several aluminum ingots a few days after Christmas. Here are some pictures of the completed foundry and the process.
	Here is the completed foundry. The top and center section can be winched up using the electric winch on the lower right side. The top section is lifted to add metal to the melt and both sections are raised to remove the crucible for pouring. The outside of the foundry stays very cool so it is easy to put the lifting pins in place when necessary. In the far background you can see my new Dewalt metal chop saw sitting on my welding table. It has become one of my favorite tools. It positively eats steel! It cuts through the "C" channel I used in about 15 seconds with very few sparks. The blade and the pieces are both cool to the touch after the cuts.
	First attempt at melting aluminum. The burner was plenty hot but didn't work happily with the crucible in place. It would gurgle and backfire, belching nice flames out of the tuyere. Not an optimum setup. A quick trip to the hardware store for some plumbing bits to make a typical "Reil" style burner.
	I picked up this little 12VDC winch at Kragen for $60. It is rated at 1000 pounds but if you read the fine print that is only when used with a second pulley. The top and middle section probably weigh close to 450 pounds so it is pretty close to the limit. It cranks the sections up and down without any real complaint but I would not want to work it any harder. I may try a second pulley to ease the load.
	Here is the gear I made, a lifting handle, pouring hook, dross skimmer, and my small crucible which is heavy wall pipe with 1/4" plate welded to the bottom. I have a second crucible that is 8" schedule 40 pipe about 8" long. Nothing special here.
	The ingot molds are made from a 6" pieces of "C" channel and 1/4" plate welded on the ends. Easy and cheap.
	About 15 minutes into the first melt. I was planning on making a set of tongs when I remembered the fireplace tongs. Sometimes it really is that easy. This is the foundry with the top section winched open and I am adding more aluminum to the melt.
	Here both the center and top sections are winched up and the crucible is ready to be pulled out. The prototype flare fell off of the burner when I removed the burner. The final flare is a much better fit. I still need to make a mounting bracket for the burner assembly so it will stay attached to the center section.
	Skimming the dross, almost ready to pour.
	Woohoo! Molten aluminum, what could be better? Click the links below to see video of aluminum ingots being poured: (broadband) (dial up)
	Pouring the last ingot. Well, there was a little bit leftover. There was more dross than I expected as most of the aluminum was pretty clean, several pieces of pipe and extrusions.
	Here they are, all shiny and still very, very warm. The melt was uneventful, everything worked just the way it was supposed to and the ingots came cleanly out of the molds. Each ingot is almost 1 1/2 pounds.
Update December 2006 - The basic foundry is complete. I am currently finishing the frame that will support the foundry and allow access to the crucible to add metal to the melt. I hope to have it ready for a first melt over the Christmas break.
	The raw material for the foundry shells, two 55 gallon drums from work.
	Lined with 1/8" thick ceramic insulation. The ceramic insulation is used primarily as a thermal break between the barrel and insulating castable refractory. The wire is 3/16" cold rolled steel welded to the barrel. The wire mesh is 1" galvanized mesh.
	Plicast LWI 24 is a lightweight castable insulating refractory. Wow, that is a mouthful! It mixes similar to concrete but the amount of water is much more critical. The manufacturer recommend 6.25 quarts of water and to adjust until a ball squeezed and tossed a foot in the air doesn't break when caught. The difference in water between too dry and too wet is on the order of a few ounces. I found it best to add the water in stages and when close to the recommended amount to test and add small amounts of water until the mix was correct.
	Here is the first batch of LWI 24 being mixed. The mix looks very dry but is almost correct. I added less than a cup of water at this point and it was just right. That works out to adding about 1% by weight, not very much.
	The first batch goes into what will be the top. The mesh was held up until the bottom layer was tamped firmly then more added until the layer was two inches thick. A plastic container was used as a form while the first layer was formed up. Note: the insulation was sprayed with water to ensure the Plicast not having the water drawn out by the dry insulation. If the mix is dried out it will not cure properly.
	The bottom of the barrel, the wooden dowel is the drain in case of crucible failure. Also lined with 1/8" insulation and sprayed with water.
	A two inch thick layer of LWI 24 on the bottom. The top and bottom sections were left to set up for a few hours while I worked on the sheet metal forms.
	One of my neighbors had a leak in his water heater. Cool, free sheet metal. I used the jacket to make the forms for the inner core of the foundry.
	Here is the bottom formed up for two inches of LWI 24 insulation. As the material was tamped into the form the spacers were pulled up until the entire form was filled. The "C" clamp is holding the sheet metal snug against the spacers.
	Here are the top and the bottom with all of the Plicast LWI 24 in place. In front is a plinth that used up the last of the batch. I'm not sure if it will hold up as a plinth block but it was better than throwing the extra material away. The sections were left to moist cure for 24 hours. That is to say they were covered with damp towels which were checked and rewetted as necessary. After curing, I used a concrete stone (you can see it in the lower left of this picture) to ensure the top was level and smooth so it would seal to the middle section. The LWI 24 was actually very easy to smooth with the stone. You can also see what will be one of my crucibles to the bottom right.
	Here is the middle section with 3/16" wire welded to the barrel, 1/8" insulation in place, tuyere and center form in place. Ready to cast Plicast LWI 24.
	Plicast LWI 24 is cast and there was enough left over for another plinth block. The sheet metal looks loose but that is just the free end after I removed the clamp. The refractory is actually a very stiff mix and holds it shape well. I could have probably removed the form at this point.
	I drilled the Plicast LWI 24 for 3/16" steel wire to mechanically couple the insulating refractory and the high temperature refractory. Since the center section will be winched up when hot I wanted to make sure the refractory wouldn't fall out. Ready for Plicast 3000.
	The middle section completely cast. Ready to be moist cured for 24 hours.
	Here is the bottom with a the drain form in place. I sanded the wood dowel on a belt sander to slope down to the center drain.
	Plicast 3000 is a high temperature refractory capable of withstanding 3000 degrees F and also tolerating direct flame impingement. This will be used to make the hot face of the foundry. It is much heavier and significantly denser than the Plicast LWI 24.
	Four inches of Plicast 3000 have been tamped into place and trowel finished for a smooth surface. The outer three inches were left rough to help the bond between the LWI 24 and the Plicast 3000. This was allowed to set up for a few hours.
	Here is the final form for the bottom section. Just four inches of Plicast 3000 to be cast and then it is complete.
	The bottom section is complete. The first time the foundry is fired the wooden form will burn out leaving a drain that I hope will never be used.
	The top section with 3/16" wire and mesh reinforcement in place. The plastic form for the vent has been replaced with a sheet metal form to accommodate the 4" of Plicast 300. The mesh shown is one of two pieces, the second will be added about an inch from the top of the refractory.
	I cast the bottom four inches then added the form and cast the side four inches all in one session. It made it slightly harder to remove the forms but I was able to complete the section faster by not having to wait for the base to cure before casting the sides. The top and bottom sections were left to moist cure for 24 hours.
	The first section set outside on a couple of bricks. It probably weighs about 225 pounds. My son and I tipped it onto a two wheel dolly and rolled it outside. It is sitting on a compacted base of gravel that will eventually be covered in a brick sidewalk. Until then, it is a nice solid base for the foundry.
	The second section was moved in the same way. We put a piece of pipe through the center and then grunted it up on top of the first section. You can see the tuyere on the left side.
	Same drill but more grunt required to get the final section in place. At this point the sections had cured for about a week. Estimated weight is about 650 pounds as it sits here.
	Just for fun I put the burner in place and put a little heat into the foundry. In just a couple of minutes the inside temperature was nearing 300 degrees, even with the burner almost off (hence the yellow flame). The bake out schedule for the refractory calls for increasing the temperature by 50 degrees every hour until operating temperature is reached and then holding that temp for one hour for each inch of refractory. Yikes! It was obvious there was no way to throttle the burner down enough for the lower end of the bake out. My solution was to put a 300 watt light bulb inside, cover the foundry in a couple of moving blankets and let it cook for a couple of days. Over the course of about four days the temperature slowly climbed to nearly 200 degrees inside with plenty of moisture driven out of the refractory. The outside temps were in the low to mid 40s during that time. I put the burner back in and over a couple of hours raised the temperature to the point that the refractory in the center section was glowing a dull orange. No noticeable steam except a little around the joint between the center and the top section. The outside of the foundry never got much above 150 degrees. Next on the agenda is working on the frame that will support the foundry and allow the top and center sections to be lifted for access to the crucible.

Update September 2006 - I've purchased castable refractory and insulation mix for the foundry. Progress is slow at the moment because a few design issues still need to be resolved. This little project is a fallout of a service project our Boy Scout Troop did July 4th 2006. We retired around 1000 American flags during a 23 hour long ceremony. When a flag is retired by burning, the only things that survive are the brass grommets. We gave away a large number of them as mementos of the event but I still have about 6 pounds left over. As I was thinking about what might be a fitting use for them I happened to think about the eagle that sits on our American flag standard. They are cast in a cheap pot metal and are easily broken. I thought it would be neat to cast one from the old brass grommets. A little digging on the web and it turns out that making a backyard foundry is a fairly simple project. Watch this space for updates on the project. In the meantime, point your browser at this site to see what it is about. Backyard Metal Casting