Kelly, we're on the same page as far as what we're calling a leaker....there were what looked like aluminum sand grains on the surface. Could well have been from insufficient mold packing too, but blaming it on the coating because I could still see the color of the foam through the coating in places...yeah....THAT thin. In part, seeing how far the process can be pushed before it fails/learning what I can get away with. I poured one of the trigger housings with the wheel and scope rail and when it turned out as good as it did...I reset and poured the other two. The air vibrator needs some work...or at least mounting it does. Held against the pail such that the rotating ball bearings path is vertical and perpendicular to the pail, it moves the sand. Bolted flat to the side of the pail...not so much. Likely too much flex in the joint...ie just wobbling around on the mounting bolt. Does make my hand go numb pretty quick so at least it's doing something. Thinking to cobble together a vibrating "platform" that I can set my pails on as I fill them. See what I can scrounge up. Al
That's what I did. It works well and has the added benefit of being able to prep multiple molds and if you make a screened sieving hopper to sit on top your buckets, you can use is to filter and reuse your used mold sand. I suggest four casters instead of three. Mine can be a little tipsy but being on casters also allows it to rattle around a little better. A 5-gal bucket of sand is North of 50lbs so it takes some energy to excite that mass. You're right about mounting the vibrator to something rigid. Otherwise the flex of the wall absorbs the energy and localizes the affect. If you think you're a little under powered, vibe while you fill. http://forums.thehomefoundry.org/index.php?threads/lost-foam-process-and-my-rig.145/ Best, Kelly
I went through most, if not all of your threads, not sure how I passed over that. Simple and effective...I LIKE it! Thank you, Al
Thinking I've got my wheels for the furnace. Double dipped these and no leakers, but I did get some bubbles on the back side of the rim where the coating was dripping off after dipping...trapped air bubbles seem the likely culprit. Need to check out some non foaming or low foaming soaps....or use less Dawn. Sprued these straight off the back as in the test wheel, and gave them a spin while pushing lightly into the sand...had sand coming up between the spokes...then filled and rapped the pails to settle. Shut the furnace down @ 1550F, skimmed in the furnace and poured straight away. Al
I made some wheels for a rail. They are clunky, but with lost foam, typically no shrinkage issues. Thin to win on the mud. Seeing color is no problem. Fresh and hot See how flat the blank face is? (I picked the one on the right a little green and the cup came off) Chucked over spacers to register on the working face. 5 degree taper on the inside of the flanges. Not much porosity, this is all extruded, window frame and soda can scrap.
...That brings me back to making all the pulleys and guide wheels on my big furnace lift. Nice to be able to put metal where you want it. http://forums.thehomefoundry.org/index.php?threads/furnace-cart-and-lift-build.278/#post-5125 Best, Kelly
I need to give ganging patterns a try at some point...would save me a bunch of metal I'm otherwise using for sprues. Have another project I want to get after as well...so many going on...as usual lol. Need some 2" hose barbs to hook up the bead blaster and small paint booth to a dust collector blower so they can be ducted out the wall. Currently using a large shop vac, it's LOUD, vents inside the building and takes up floor space. Dust separators on both items and a bag in the shop vac so the dust isn't an issue but the fumes and noise certainly are. Not perfect, but ultimately usable. The defects were all at the top when pouring....longer sprues may have helped. Another scope rail too, which came out pretty darn good...now I just have to figure out how I'm going to hold it to machine the radius for mounting on the tube....might need to make a 2piece table vise. Read somewhere about using a 50/50 mix of toilet ring wax/paraffin for filling defects and have been using that. I also used it to attach the gates/sprues to the parts this time. Wax needed to be hot for gluing but wasn't melting the foam. Al
Sometimes just casting a set of custom shaped jaws for your existing vise will do. I cast (lost foam) these fixtures to use as drill fixtures to hold my water neck casting. They were awkward to hold without them. Toilet ring wax works ok. Tends to be a little soft in the warmer weather. If you have not already done so you need to invest in a hot melt glue gun to attach the sprues and pattern pieces. They can be had for $10 at hobby and big box stores. Best if you get one with a low and high temp range and use low temp glue sticks. It burns out very clean but is a bugger to machine or sand through. Instantly sticks parts together but also instantly loads cutting bits and sanding belts/sleeves. Best, Kelly
Have a hot shmoo gun that I've been using as well...just wanted to try the wax. The mix seems to attach the sprues solidly...will see what happens when this "warmer weather" thing you speak of arrives in 4-5 months. Al
More lost foam? Were will it all end? You need something - hot wire it out, glue it together, seal, coat, dry and the next day you have your part. Did the runner on the scope mount fail to fill? Seems it may not be necessary. For the hose adapters, it would seem attaching the sprue to the flange may have worked better. Worth a try if you do any more. You might try pouring a little hotter, I've been at 1,650F with no ill effects. I got a low temperature hot melt glue gun for under $5. It has worked well for a long time and has been left on overnight by mistake a few times. I use 50/50 toilet ring/paraffin mix as well but my next batch is going to be 75% toilet ring wax. I damage the foam trying to scrape off extra. I mainly use it to seal cracks at joints. It looks like you switched to metal cans to get more head. I think you lose heat in them. I'm still using Kelly's method of making a foil pouring cup but I use a piece of doubled aluminum foil. My cups are a bit small sometimes, about 1-1/2" diameter. In the photo above you can see where I missed and spilled a lot. I pour into 5 gallon buckets and if I need more head I just make a longer sprue and bury it deeper. I routinely remelt sprues and runners (from sand casting) and really don't see excessive porosity. I don't do any porosity control except fast melt, minimum stirring, and put get it out of the crucible as soon as it is skimmed. I've not had any leakers of what I could air test, and structural like the wheels it's just not an issue. Kelly: Thanks for the post above, I remember your vise fixtures above now. I need to be more aggressive at making fixtures. Two half rings would have been great for holding the flanged wheels in the lathe. The key stock looked a little iffy and I think I got lucky on that. Aluminum is usually a good soft material for chucking up steel as well so I've got to keep thinking "lost foam" in everything I do.
LoL. I've done that too. I've left my hot wire on over night several times......must put an indicator light on that thing. I've always had that pattern makers wax fillet stock and swear by it.......but, if you want a little more control with the toilet ring wax, try this: Buy yourself some disposable plastic syringes. They're cheap and you can get them from McMaster Carr. The chamber on mine are a little under 1" diameter and 4" long. Melt the toilet wax and fill up the syringes. Let them cool. When you want to use them, just place them in a glass of warm water in an insulated travel cup. At the right temperature you can precisely apply the wax with the syringe and then wipe it with a ball fillet tool or radiused scraper. They do take some heat...no doubt. I think it's pretty small and easily accommodated with pour temp. Can't argue too much with a spent soup can accept I had to cut and chisel them off which took to much time. A smooth piece of muffler pipe can be pulled off the cup stock when it shrinks and they build up a nice oxide layer with reuse. Just don't ding them up cuz they wont pull off if dented or out of round. When I was researching that moldable ceramic fiber for my low mass furnace project, guess what they said one of the uses was.....yup, lost foam sprues. Here was there picture. I'm going to paint some on a my favorite long snout funnel and see how it does. What you did with the spacers looked practical. Once you get a true face and OD to grip on, you're pretty much home free. On wheels, I learned not to cast in the center holes (even though you can) under 3/4" or maybe even an 1" if you plan to just drill and ream. They'll never be concentric cuz the drill just follows the hole.....unless your mounting them on an inside mandrel or bolt stub. If you are going to use a boring bar it doesn't matter. Best, Kelly
Lost foam end?....well I am almost out of propane....but I do have about 10gal of used oil so...no time soon. Plenty of foam yet too. The piece attached to the scope rail isn't really a runner. I think of it as more of a support to help keep the pattern flat while coating and embedding in the sand. The one poured without had some minor issues with straightness, this one as cast was eyeballed at around .005" from being flat/straight. Might be a fluke and I won't know till I try another couple but that's VERY acceptable as it gets machined top and bottom anyways. May add some material to the top and try cutting a picatinny rail right into it too...or CAST it in....kind of doubt that would have the desired precision, but it's only time and foam and like dad always said..."your time is 60minutes and hour". When I've been pouring, I get enough smoke from the top of the foam cups to obscure the view so thought I'd try the cans. May see about some exhaust tubing, but have some heavy wall pipe and was thinking to make a kush head tool or two. We'll see. Al
I've got a foam cast iron pour in the works. The last foam aluminum Kush head stuck in the can, so it's easy enough to grab another from the recycle bin. I doubt there is any significant heat loss and I prefer the strength as opposed to the foils. I started out with just a sand basin, but have had better results with the additional head and reservoir of metal. I have salvaged some 3" Pneumatic tubing from a demo project and use it for higher value pours. The interior is super smooth and as Kelly mentions slips right off if there are no dents.
I only use foil tape to form the conical transition from the Kush Cup to the foam pattern button/sprue. Best, Kelly
So are those disposable sprues since they wind up filled with metal? I guess I'll have to try a Kush Cup to see if it affects my pours.
I'd have to think the ones pictured are disposable and you just cut them off.....unless the they were tapered and smooth enough they could be removed without damage. Wont know until I try on that. Not sure I'd put a great deal of effort into them unless they were really quick and easy to make or I had a special need with a sprue and pouring cup. Cup and foil tape cone seem to have been working well for me. Best, Kelly
I treat soup can kush tools as disposable one use items that most often must be cut off the top of the sprue in order to remove them, although in a pinch I've managed to tape them back shut again and reuse them once or twice. The smoke and fire coming out of the can makes it impossible to see how full the can is most times. For cans being used the first time, sometimes you can get an idea by watching for the discoloration on the outside of the can that happens when the metal starts to fill them up. I think it was evlwhtguy (sp?) on the AA forum who suggested using a big box fan to suck the smoke away and improve the visibility of the top of the sprue; sound reasonable, but I have never tried it. Jeff
