dear all am doting some brass casting .. but i got alot of problems with the final brass model .. i got some airs , or sometimes the brass it getting cold in the pipes ,, so it not fill the model . the idea to make solid model full of brass i was thinking that maybe my wax tree design its not right or the pipes thickness is too low here is a sketch .. showing my wax setup .. and i need you help .. maybe you can show me the best design to cast this model without any problem if someone can draw a sketch .. am attaching some photos for that the goal is .. casting a solid model in brass ,, 1 piece best regards
I vote for 'D' Fat sprue feeds the fattest part. Vents off the smaller sticky outty parts. Pictures of your failures would help. The real issue I see is if that thing is 30cm long, that means the belly of the horse is probably 4inches across??? That's a shitton of metal. This brings up questions of a core to reduce wasting metal and also are you using solid investment or ceramic shell? I've never seen chaplets used on ceramic shell to hold a core in place. I'd like to! If the word chaplet is completely foreign to you, I'd say we need to have a much different discussion instead of how to feed that animal.
Remember the horse pulling the cart. That sun god thingy? That was a great demonstration of how to do the wax and pour. (Yeah, I'm still pissed we lost AA!) All that easily accessed good information flushed down the hole. Really sucks for us.
Yeah that was a good thread. Still might get back the info maybe one day if owner wakes up and realizes. I liked the owl thread too. Was very helpful.
I would only try D. Use a square sprue to reduce turbulence. The metal doesn't swirl around and create gasses. Or should I say it greatly reduces it. All of the vents should be single vents to the surface of the mould, not connected to each other or the pouring cup. If you hit the top of the vent or vents in the cup with molten metal when pouring you can shut off the vents making them useless. Controlling the air and gas flow rate from part to part is tricky. If the volume/flow of metal is increased through the tail of the horse and up the vent as it will, it may reach the left hoof before the metal rising up the left leg causing an air pocket. If the vents are all separate this will not happen. Im not sure I would vent the riders head to the horse's neck. The down force pressure should push any air/gas out of the head if the mould material is porous. This is a very large casting. I am curious how much brass are we talking here. 20-30 lbs What is your mould material and how are you planning to get this up to temp for burnout and casting. Block Casting? You may consider using steam to remove the wax if you are using a plaster type investment. Less pressure in the mould and it stays uniformly moist ready for a pre-heated burnout oven. I only use steam for wax and hybrid wax/PLA castings. Not as large as your horse though. You may have to experiment with how long is long enough. I would think maybe a good hour sprue down in total steam would work. Too much time and it may erode away the inside of the mould.
I bet bill is right, I see 20-30lbs. That's a lot of metal that doesn't need to be there. ON a different note... And you won't pull this off with brASS... Sil-bronze, no problem. THIS is how it's done. I wanted to cast everything solid when I was just learning.... It's just not how it's done and it's the sign of an amateur. (which I still am!) The detail on this horse is incredible!
i didnt take photos phor the old one ,, but here is some photos showing the same problem in another model its 2 kg solid brass
thank you am a beginner i did alot of mistakes ,, lost alot of money ,,, for that am here to learn form professionals it will be great if you share some references showing how to know the right shape to design a wax tree and what is the maximum size to do solid model and avoid the metal shrinking
thank you for all great info .. i did a ceramic shell and coverd by plaster PLA it will be great idea .. i will try it thank you
great casting 100% am sure ill try to cast it in parts but i need to ask you more about casting so i hope you ill be around to answer
You cant tig brass... (well maybe some can, but you and I can't) 200 years ago, hollow pieces were cast and assembled without tig welders. It's much more labor intensive, but it was done. The masters understood casting stuff solid wasn't reliable due to shrinkage and was wasteful. Castings were purposely left with big holes to make them hollow and the pieces to fill those holes in were cast on the tree somewhere. Then it was a matter of shaping those pieces for precise fits by hand and using mechanical methods to hold them in place. When castings had internal cores held in place by chaplets, the chaplets (steel nails) were removed and a small piece of metal was carefully fitted to fill those holes in then filed smooth to hide the plug. Like I said, VERY labor intensive. If you wanna run brASS, then learn to use a torch for this kind of work. My suggestion is run sil bronze and buy a tig welder. Your casting looks pretty good and the expression on his face is priceless. Looks like he got his ass kicked. Those look like small areas to repair to me and being brass, I would get out the mapp gas torch and go for repairing him rather than recasting that one. I suck at repairing brass, but I can get the job done. The trick is not getting the piece too hot and cooking the zinc out of the metal. (because it pops and spits and acts like an asshole) I know I have a thread around here with an adventure of mine repairing a brass lamp. Let me see if I can find it for ya. Remember, there is no perfecting casting, they all will usually need some post casting work. The clowns on youtube would have you believe otherwise.
Got it.. Read this thread. http://forums.thehomefoundry.org/index.php?threads/repairing-cast-brass-i-hate-this-nasty-stuff.861/ HT1 is the brASS king around here, he can make this stuff really sing. I just tolerate the nasty stuff.
I would use a variation of D, rotate the horse clockwise to between 4 & 5 and move the feed to between the hind legs. Not knowing how much weight is in the piece makes it difficult to say for certain if it should be hollow. I did manage to cast a solid horse that came out at around 9 kilo, I had some minor shrinkage within the neck but was able to repair it. I now cast it hollow and without the legs on to ensure a good cast. However I was using Silicon bronze not brass. Good luck.
I think the defects you have aren't from shrinkage they look like they are from the metal being too cold and solidifying before filling the mold completely. One looks like there was a pause in casting and the base metal solidified then more metal piled up on top. One photo has flashing which is made when the shell pulls away from the second ceramic shell layer and metal forced its way into the gap. That is from weak/inconsistent layers or poor slurry mixing and ratios. Lots of different issues. But no shrinkage porosity from the pics above. I agree with Jason you can make a hollow cast with a hole and then a plate that fits into the hole. Then you clean up the parts and hammer the plate into the hole. This binds it in place and then you polish or sand it back so it merges with the sculpture. Or a mig/tog welder. Silicon bronze pours a lot better than brass. Its pretty much night and day. Lancaster foundry supply sells it cheap and they ship small quantities. I'd give it a try via them some day.
I'd go with B with some modification. Extend the main feed so that the cup is maybe 6" above the head of the horse. This would create more head pressure. Take all vents to the mold surface away from the cup. Make the feed into the belly of the horse the same size as the main feed. Also because it's my favorite, I would mold it up in plaster, sand and ludo mix. To me brass is an excellent metal for casting mechanicals which will be further processed. Silicon bronze is the only way to go for sculpture. Watch the heat of your melt and pour as cool as you can to reduce shrinkage or make a large lemon form near the belly so that the belly can draw its metal from that reservoir which should minimize the shrinkage problem. As stated before, avoid the shrink problem by coring the body.
Nearly all my brass animal sculptures I've collected thrifting are hollow castings, split in half and welded down the middle.
