gwynlaredogranger

perhaps you are conflating investment casting with (cope and drag) sand casting

i wrote some huge thing but really, you arent going to have much luck getting a foundry to sell you a mold. the molds that we make in foundries are for us to use, the customer usually just wants teh metal casting that comes out of it. ask your BF what other things he may need aside from molds ( he most likely will want to make his own molds as that is part of the 'fun' of foundry) and try to get him something that he can use over and over...best of luck!

The cool thing about jewelry casting is that most if not all waxes are solid and not large. Not to say that jewelers haven’t cast big pieces , but not usually. I dig the set up for your burn out schedule , I’m sure you have that dialed in. When I started casting I first learned large investments . These would be 2-5 ft tall range moulds made from ludo, pottery plaster, #200 mesh silica flour. After setting up we would load a hand built soft brick kiln around them and face it with hard brick, rig up a burner and camp out for a three day burn. Taking them out of course was also surgical because they’re friable. When the moulds get big the flasks get heavy , be sure to seal the bottom to its coddle board.We used hardware cloth around the interior of the flask so that it was about a half inch beneath the exterior of the mould. That protects the galvanized from direct flame exposure ,also pre burn any metal reinforcements so they don’t create vapor that will hurt the moulds.When the scale increases so does the amount of weight the investment has to bear so structure becomes important . Careful for leaks while pouring ( we bedded the moulds under loose sand when pouring) take care not to get sand In the cup;)

Most wax patterns need to be hollow. Also the runners and gates are hollow core. Nobody can make a statement about casting that applies to all castings. Most foundries that are burning more than 150 pounds of wax at a time need to use an autoclave . That I’m no way means that you should always use an autoclave. Plus most people aren’t going to have a device like that. The best way to burnout shells is the right way for each shell/pattern. If you’re casting the same part over and over and over you tailor the burn to that . If you’re burning a large solid piece , then you need an entirely different approach. There’s no one size fits all really. Plus no matter what shells break from time to time, doesn’t mean it’s from the heat. The manufacturer recommends dewax at 1000 degrees and for anything above 150 lbs you’ll need a lot more gas and an afterburner ( I built a dewax that is 8ft x8ft x 5 ft for my shop and it has an afterburner and internal plumbing that is sealed from air so the wax doesn’t flame up) . It’s piped into a rubber mold with ingots so I can remelt. When you use an autoclave you’ve also got to reclaim your wax and separate the water back out in another melt operation. I could on and on but you get the idea . The thing about casting that’s tough is knowing when to do what for each individual shape, they all have different rules but at the end of the day they all are the same rules.

yeah i wouldnt do any of that steam stuff ,especially without an autoclave, and even that is usually in large process ceramic shell facilities where youre dewaxing 150 lbs or more of wax. most foundries stopped doing that since the breakage is much higher with uncured shells or green investment mixture. jewelers usually use a small fired kiln. if your investment mixture is silica flour and plaster it stands a better chance, but still the steam breaks down ceramic shell before it's cured (it gets vitreous at 1000º). you want a fast hot kiln that can get to 1000º in under ten minutes if possible. if youre using investment mixture then you want to get through the 212º range long enough to drive out steam but not so long that the plaster calcifies easier. i usually cook investment mixture for a few hours, whereas with shell, they can burn in under a half hour...

im sure youre right about graphite needles,also has terrible shear value, but do you mean ledeburite? i know that doping the iron with Si moves those graphite needles around a bit. ive seen this in castings in areas that cool slower than the rest of the casting due to thickness.

investment casting, cool, i have a shell department. they sell that stuff that doesnt need to be in a slurry tank nowadays. how will you be dewaxing? i have burnout oven that i can reclaim my waxes with. Aluminum bronze is tough to weld and super hard, harder than some steels even. great for wear plates. i have large opinions about dewaxing, it can get sketchy. plus the shell needs to be cured a certain way...aw man so much to cover! yeah the peeping is great out here too, ive come to feel fine wearing tons of safety gear all day in the heat, that way when you take it off ,it actually gets cooler, even if its 95 out, it feels cool ,compared hahah!

gadget- copper is a challenge to melt, requires a decent temp of around 2000º f -2100º . that gets it hot enough to flow but not too hot as to cause porosity and other defects. its a lot trickier to melt than bronzes that is for sure, but you will love the way it pours out, it will fill in a similar way to aluminum, but its heavier and has better head pressure when poured. be sure to not disturb the melt surface and to skim all slag thoroughly. it is MUCH hotter than aluminum when you are pouring so you wont even be able to stand near the crucible without trousers on. i prefer pouring Al because its lighter and lower temp, and still fills really well. but i mostly pour non ferrous alloys.

whole other game than cans.

Daniel interesting that sweet spot of fast enough but slow enough is a difficult one to nail down for sure. is this anything like spherical graphite iron? do you use a % of silicon in this alloy? outside of the dendritic patterns ,what are the forging characteristics of the alloy youre making ? im asking because i dont know too much about the families of iron/steel outside of ccasting them. i only have to deal with the alloy,its flow ,shrinkage, porosity and ductility. i dont know enough about forging to know if this alloy is better or worse in its physical working properties, i do get that its look is beautiful and also probably difficult to homogenize,thanks.

do have a sense of how long your nucleation cycle actually is? its a shame about that porosity in the previous attempt, its definietly a result of long nucleation, and also the thickness, i wonder if the shape can be changed to avoid thicker castings? im sure you know a lot more about that, but from a metallurgical standpoint that short cycle crystallization is key in making a void free casting. very cool thread and interesting results. i love the glass as parting agent trick too!

are you saying that i'm completely wrong in my suggestions? or are you saying that if something seems to make sense, that it doesnt actually make sense? or are you saying that because you dont like me that youre trying to find something to disagree with me about? or are you totally discounting my experiences of the past because i have osha certification ? im not sure i follow what youre posting about, can you clarify? also id like to get back on topic since the person who posted this thread is looking for good input on their set up and melts, not listening to two old guys yammer back and forth

i have a 30 hour osha card and a lot of the stuff i had to learn made very good sense. even if it seemed over the top ,its better to assume the worst than to not. i guess what i meant by my statement wasnt that silica fibers werent important, but the immediate threat to me was the lack of awareness of surroundings, and of the proper PPE and also piping safety. that was all i meant, im very sorry i didnt say that well, and in no way was i downplaying the threat of silicosis or of silica fibers. its my biggest fear persoanlly, since i work around silica in at least five forms daily. from fumed silica, silica flour, caobo-sil, colloidal silica, to crushed glass, lead crystal powder, etc. i deal with it on a daily basis ten to twelve hours a day. therefore its way more of a risk for someone who is working in that capacity, than it is for someone who is having occasional exposure, and since its cumulative it seems to make sense that it is dealt with in order of threat, but i realize now that i am in the minority in the sense that not everyone posting here is that involved daily. i stand corrected. looking at what others have posted they are suggesting that check valves arent important, this is incorrect. the purpose of a check valve is two fold, it allows the gas to flow in one direction only, and it stops combustion from entering a flammable gas ,such as acetylene for example. with propane set ups like this the real concern isnt the tank blowing up, its teh gas line being melted, stepped on and cut, or wearing out from time becoming brittle etc. so when i see an uncovered rubber hose carrying 5 psi of LP i get nervous XXXXX just one drop of molten aluminum can weaken it to bursting temps, or even radiant heat formt eh body of the furnace. now thats all well and good if youre in a foundry with a sand floor and are wearing safety gear, but wearing shorts in a backyard next to a wood pile and im going to focus on that as the most likely thing to go wrong here. thats more what im saying. flashbacks and checkvalves are never installed on propane lines for gas grills, stoves etc. thats becasue they have flame safety for in home use and for camping gear its assumed that youre outdoors where gas has no chance to build up uncombusted like it woudl inside. I use fluid power valves that are normally closed for my furnace lines and i at least cover the hoses (if im not hard plumbed) with a flame resistant sleeve like i use on my TIG lines.

any!

Glenn-i always err on the side of caution. i run every deice in the shop with one way valves, my glory holes have triple lockout safety sytems with relays, fluid power gas actuators etc. if im using a janky set up in a backyard then why woudlnt i take every conceivable precaution? if im in a residential neighborhood ten feet form a wooden scrap pile why wouldnt i take that extra step to ensure that the tank can never blowback? im sure its not necessary ,it may be ' just an opinion' (isnt everything these days? are facts dead?)but its always better to overdo safety than to under estimate waht 'could go wrong'. i mean ,i dont know what youre driving at Glenn and i realize that my anecdotal experiences are irrelevant ,but if i had to chose between rigidizing wool, that i may encounter a few hours a month in fornt of, vs. putting a check valve on a tank running to a home meade foundry, id chose the latter all day long since it is a more immediate threat. threat assessment is par to fsafe shop practice as you know, i know you have a ton of experience and knowledge too, so you know what im driving at. even if i have ten degrees in engineering and years of experience with combustion systems, annealers, automated control systems , ultra violet sensors, flame control etc, i can still be worng, (i dont have any engineering degrees, just took classes in college) and i can know nothing about al of that and still be correct in suggesting that a flashback arrestor ( or checkvalve) is usefull for anyone using buringn propane, a gas grill int eh back yard isnt the same thing as a high temp burner. why would i demand the same safety set up for two different devices? just saying...