My New Lost Foam Casting Rig

I was doing a little reflecting. It’s been a little more than 2 ½ years (May 21st, 2016) since the maiden heat of my furnace and ~2 years since my first lost foam pour. I’ve gotten a lot more out of the lost foam process than I ever anticipated, especially since initially I never intended to pursue it at all. Though I certainly do see other casting processes and metals in my future, lost foam is here to stay for me. Since my original lost foam molding rig was pretty much a throw-together,

https://forums.thehomefoundry.org/index.php?threads/lost-foam-process-and-my-rig.145/

I thought I’d build a more permanent piece of equipment to incorporate some things I’ve learned along the way, further improve the ease of use, and maybe even take the casting capabilities a little further.

I still have some work to do on pattern coatings too, but I envisioned the potential improvement areas to be speed/ease of mold preparation, increased packing density and mold stability, cleaning & storage of mold media, and enhanced vacuum assisted casting to hopefully further expand the casting envelope and reduce pour temperatures. Beyond this, since I can pour up to 60 lbs of aluminum, I’d like increased flask and mold capacity to handle bigger parts.

So all this gave rise to building my new lost foam rig. It’s based on 30-gallon steel drum. I bought five of these a couple years ago from a guy for $15/ea. I used one of them for the shell when I built my first furnace. They’re pretty darn nice for dry storage but I decided to cut another one up for this build instead of rolling one up from scratch.



First task was resizing the barrel. I seldom need the entire depth of the barrel. It would weigh over 350lbs filled with sand and I wouldn’t want to shovel that much sand every casting cycle. So I cut a section out of the lower portion, rolled up some hoops from scrap on my slip roll, tacked them in place on the floor for the vacuum plenum, then welded the base back onto the shortened barrel. The barrel is only 22ga so it was a little tricky migging it back together. I added an 18 ga hoop to reinforce the thin walled barrel to accommodate mounting provisions and also the vacuum port.



Packing lost foam molds is already quite fast but would be even faster with a “sand shower” type distribution system. Prior to vibration, this more evenly distributes sand in the mold and around the pattern as you fill the flask which also reduces the chances of foam pattern deflection due to uneven sand weight/pressure. It may provide some enhanced packing benefit as well. I have taken to just dumping the flasks on my concrete driveway to demold the parts, letting the sand cool, and then sieving it back into buckets through a screen for reuse or storage. I don’t enjoy cleaning up so I thought I’d just combine all that into one step.

The removable top portion of the flask is a clamp on sieving barrel and flask extender. I made a buck and used the lip on the barrel with some light hammer work to shape the bottom of the left-over barrel section, so it would clamp onto the top of the flask.



Next, I rolled a hoop from tubing in my slip roll, tacked it in place, and did some more light hammer and planishing work to form the lip over the hoop so it could be sealed with the lid and clamp from the original barrel, and seal up the smelly sand for storage.



The sieving plate lifts out and when removed, the additional barrel section serves as a clamp-on flask extender for increased depth and flask capacity. With the sieving plate in place, spent sand can be shoveled into the sieve, turn on the vibration as needed, and the sand is filtered, showered, and evenly distributed across the next mold or stored in the flask.



There’s some bits and pieces that go into the pedestals that suspend the flask on springs.



The base is a bit of over kill but I had the material and along with the casters, it enables me to use the outriggers I built for my furnace. I used the piece parts to fixture everything up for welding



The flask pedestals with trunions are mounted on springs to suspend the flask and mold mass enabling the vibrators to provide a higher level of excitation for a given flask mass and lower compressed air usage. The suspending die springs are 6” long free length and there is about 2 ½” of spring travel when fully loaded with sand with the flask extender. The entire flask assembly can lift on/off the base and suspension springs.



There are set screws in the support pedestals that can be adjusted to limit and tune the total lateral movement of the suspended flask.



Instead of one turbine vibrator under the base like my old rig, there are mounts for four smaller turbine vibrators. Each vibrator can be tuned by the axis/attitude in which it is mounted. The intensity and frequency can be varied through the exhaust port or air supply control valves. I’m hoping for improvements in packing density and better packing of complex shapes, undercuts, and blind voids.



The new flask is 16” in diameter and 18” deep, and holds 235lbs of sand fully loaded.



The flask extender adds 9” of height and another 120 lbs of sand for a total 355lbs. This all will reduce demolding, sieving, and clean up to a few minutes. The clamp on lid seals tight for storage so no lingering lost foam odor.



I need to mount the manifold, plumb flexible lines to the turbines, and apply some paint. More to come.



Best,
Kelly

 

Build Update 11-17-2018

After a long wait, the stainless steel, 200 mesh, screen I ordered from overseas finally showed up. I guess for only $4 instead of $40+ it was worth the wait. I completed the filter floor by stretching it over the perforated plate and applying this high temp wiper edging. Besides fit and finish, the seal enables it to be removable and serviceable. I added a couple lifting eyes in case I ever need to pull it out to clean or modify the plenum.



After mounting the manifold and initially routing the plumbing, it started looking a lot more like one of my contraptions than a piece of foundry equipment. It’s a long way from your Mama’s 5-gallon plastic bucket but I think I’m going to like it.



Before I started the build, I vacillated about whether to mount the vibrators directly on the flask or on a separate base the flask merely sat on. Mounting the vibrators on the base would have better isolated flask heat and accommodated the use of multiple flasks but I didn’t foresee needing multiple flasks of this size and mold sand insulates well. Even so, I’d still have to be able to manipulate a 350 lb fully loaded flask. I wanted to transfer as much vibratory energy as possible to the flask because the four smaller “G8” turbine vibrators together consume about 15scfm of compressed air which is just under the max flow rate of my compressor. I have a phenolic insulator under the turbine bases to reduce heat transfer and I think the flask will remain cool enough 90%+ of the time and only see significant temperature rise with very large (>20lb) castings. On the biggest parts I can use the vacuum system to draw cooling air through the flask.

For good measure, I decided to add a fifth turbine vibrator on the bottom of the flask. The mount can accommodate either the smaller G8 or a G25. I mounted an extra G25 I had from a previous purchase.



A single G25 is what I used on my previous smaller rig. It uses 4x the compressed air compared to one G8 but produces 2x the vibratory force. I don’t have enough compressed air to continuously operate all four G8s and the G25, but I could power them all for 5 minutes or so with the 80-gallon compressor tank fully charged or, and with the selector valves, could potentially run a combination of the G25 with a couple of the G8s active continuously. -Plenty of vibrating options. Pneumatic vibrators are compact but tend to be power pigs.

Anyway, it’s done.



One unique feature of this rig compared to my previous set up is the ability to install a lid and lock the flask in different positions during vibration. In addition to the multi-axis vibration, this might come in handy for packing complex hollows and undercuts.

Now for the details.....

Pneumatic Manifold and Hose Looms: The plumbing might be a tad bulky for the little turbine vibrators but I already had the 5/16” OD line and push fittings. They should flow well with little pressure drop. To help tidy things up a bit I made the manifold from a piece of 1” OD - 1/2” ID tube, drilled & tapped the ports, and welded it to the flask support pedestal. Each vibrator station on the manifold is numbered and valved to keep track of which ones are rattling. A pressure gauge sits on top the manifold to monitor supply pressure. The hose looms were inspired by automotive spark plug wire looms.



Positionable Turbine Vibrators: They can be mounted in any one of four positions at each station.



Steady Rest: It’s positionable in height and location, with or without the flask extension, and should help with accuracy and control of the larger pours, especially when dealing with that initial hesitation in lost foam pours. It won’t be needed for anything except brim full A20 and bigger pours. The A20 gets a little awkward brim full and held high.



Splash Guard: I was a little concerned about splashing molten metal on the plastic tubing and pneumatic components. Having to replace a plastic tube here and there wouldn’t be a tragedy but just in case I fabbed up this hinged splash guard that quickly installs/uninstalls for pouring. The guard can be left installed to dump the mold unless the steady rest is in place. Then one of the two needs to be removed in order to dump the mold.



Outriggers: I had previously built these for my furnace lift and use them as levelers on a couple other pieces of machinery I have built. With the flask extender installed, it looked a little top heavy and I wouldn’t want to see the whole rig topple over while demolding after a pour so these will add stability when using the tall flask.



Vacuum Port: 2” port with magnetically stored plug to seal the port when not in use. I have a 5ft section of hose to connect it to my portable pressure/vacuum source.



Ejector: Need to make a magnetic mount for my pocket blow gun so I can use it for blowing smoke away from the pouring cup for better visibility when pouring.



I have to use my larger ½” ID, high volume, compressed air hose and G-style quick disconnects to run this machine. My standard utility compressed air lines can only muster about 40 psi delivery pressure with all of turbine vibrators active. With the larger air hose I can mainline or regulate directly from my 80-gal compressed air tank and achieve 80+ psi supply pressure and that makes the turbine vibrators sing along quite well. My big hose reel is a beast….50ft of ½” ID hose.



I Dub Thee: I think the rig deserves a name and at some point in the future, a cast plaque. I sort of liked Shake and Bake (Please pardon me Kraft Foods). With all the vibrators Steely Dan could be in the running……but Lil’ Smokey seems a little more fitting. Maybe the American members can remember “Smokey the Bear”. Non-US members….you’ll need to search it.



I have a couple other accessories planned for it. I’m really looking forward to using it. I think I need to make a video.

Best,
Kelly

 

Wow! Can't wait to see it in action!

Jeff

 

Yes, my old rig has a copper coil under the floor and uses compressed air for that. I have to plug the vacuum port. This new rig is also capable but I never use it because I always need to dump, cool, and filter the sand after each use. Could potentially use it for the first cast after storage.

I have a companion build started for my pressure/vacuum source for this rig. It uses two 3-stage central vacuum motors that can be pneumatically connected either in series or parallel. In series it can pull a 1/2 atm of vacuum and in parallel can deliver 200cfm for fluidizing! I'll post the build but need to finish this one first.

Best,
Kelly

 

Cant wait to see the castings that come out of that sucker!!

Something tells me that the spot reserved for completion is going to include a new conveyor system that catches the sand after it is dumped from the flask and carries it up dropping it through a sieve into a hopper for the rain shower system..
Or maybe Kelly will do something more elaborate.. LOL

 

Here's my new conveyor system.........



Best,
K

 

Looks like it might take some work to automate....

 

Thanks for the comments and likes fellas. I completed the build and updated post #2 above.......with sort of a monster edit to the former place saver post.

Best,
Kelly

 

I used the rig for the first time this weekend.



I mentioned back in post #2 that I can’t continuously power all of the turbine vibrators but can feed them temporarily from the compressed air stored in the 80-gallon tank. I also installed a ½” ID hose reel and a new pressure regulator on the tank. My old regulator was fine for powering hand tools but this rig is an air hungry beast. So, some time ago I purchased and installed a high flow regulator.The regulator turned out to have a spring that limited the regulated pressure to <60 psi. It was supposed to be 125psi. I’m waiting on the higher range spring I ordered from the manufacturer that enables 125psi regulated pressure. The result was I could only feed the vibrators on my new rig at about 40 psig.


All that said, it still seemed to buzz along pretty well even at the low supply pressure but I ‘m really looking forward to being able to use it at design pressure. Not the greatest quality but here’s a video while I was prepping the mold for my automotive upright casting. I’ll post up again when I can power it at >80 psig.



Best,
Kelly

 

I like my big molding rig a lot but it’s a lot of sand to throw for smaller parts. An A-10 crucible and 5-gallon flask will take care of most parts I cast. When it comes to vacuum assisted casting, I either need to use my larger unit that is the subject of Post #1 of this thread, or my original flask made in Oct of 2017 from a spent 5-gallon can of water seal. It had a little “side-car” attached to the side where a vacuum motor sat on top.



That build thread is here:

https://forums.thehomefoundry.org/index.php?threads/lost-foam-process-and-my-rig.145/

It worked just fine but the “side car” was a little awkward and I have since built my vacuum motors into this Vacuum/Pressure cart:

https://forums.thehomefoundry.org/index.php?threads/vacuum-forced-air-cart.810/#post-18387

I’ve been using my 5/6-gal flasks (aka lock-ring steel buckets) on that original vibe cart so I decided to upgrade my smaller 6-gal flasks to include vacuum capability and build a new vibe cart to include some of the features of my larger rig.

The 6-gallon steel buckets are little taller but otherwise the same dimensions as the fives.



That allows a little more room for the screen and plenum at the bottom so I used those to make the vacuum capable flasks. I had enough of the perforated plate, 200 mesh stainless screen, and edge gasket leftover from the build of the larger rig to build plenum screens for two flasks similar to the previous build.



Then it was just a matter of punching a couple holes in the bottom of the flasks…....



The flasks just sit on a platform with a gasket that seals on the bottom of the flask when it is placed on the vibe cart.

I’ll spare you the blow-by-blow of the build, but after a little work on the saw and welder, here’s how it came together.



Completed and assembled…..



This sealing plate registers with a couple locating pins and the silicone gasket seals the bottom of the flask to the vacuum port on the vibe cart.



Flask positioned on vibe cart.



Like with my larger rig, I cut the center out of a lock ring lid and bucket, and welded them together to make a flask extender to accommodate taller molds. It has a removable perforated plate that classifies (screens) used sand as it is shoveled back into the flask for storage.



Flask extender installed…....



Classifying screen in place.



Since I called the larger rig "Ole Smokey", maybe this one is "Lil Smokey" ..........but I don't get much if any smoke any more.

I can hardly wait to christen it!

Best,
Kelly