I cast some brass using the lost foam process some time ago and it was a total failure. The shape worked but the whole part looked as if it was a block of sponge. This time I will try sand casting. I have 3 items that for speed and economy I would like to cast as one. any hint or tips you could give? I am considering filling them from the bottom up, is this a good ides? Thanks
Hello Savarin, Warning: I am more curious than knowledgeable, maybe providing some details will spark others to comment: -How big are they? How big were the sprues in lost foam? -How were the lost foam pieces tooled? -Were they coated? Surrounding sand vibrated? -Was the defect surface finish or porosity in the body of the parts? -Are the bottoms as shown the bottoms to be poured? All in the cope with a flat drag? All the best for the next pour!
I'm not up on the terminology as I dont do much casting and dont have anyone to discuss it with so please excuse my mistakes. The three up there are 2x 70mm dia 55mm high 1x 65mm dia x 80mm high. As they stand is how I was thinking of casting them but with large dia risers. flat on the board, in the cope. The runners in the drag something like this, the blue are the parts the orange are the sprues and runners. The lost foam casting was coated in plaster with large dia drinking straws as vents in loose sand. The resulting cast was so porous it looked like a sea sponge. I actually used it for bearings as it held so much oil in the holes
You have the right idea but your risers will need to be larger to feed the part as intended. You gave up to quickly on lost foam. Best, Kelly
Savarin, thanks for the additional information and the nice CAD pictures. Do you use the CAD to help determine the weight of metal in your melt? The splash basin will not really be a sphere, yes?
that CAD program is a very old 3d solids modelling program called truespace. I still use it on win10 even though some parts no longer work. I've tried a couple of cad programs but cant get this old head around them. That was a very quick and dirty model just for show and to help me visualize the whole. I dont know what shape to make the splash basin but not a sphere.
My guess on the basin is something easy to carve or draw from the drag if using loose pieces or match plate. Your parts are going to be heavy (in my world of flat aluminum emblems). Does this estimate seem about right to you? Figures would be for the entire system and assuming 100mm (4") cope for sprue and risers. General Part Number savarin1 Part Name savarin1 v3 Description Material Name Brass, Soft Yellow Physical Mass 5383.363 g or 5.38kg or 11.87 lb Volume 6.356E+05 mm^3 Density 0.008 g / mm^3 Area 85004.559 mm^2 World X,Y,Z 0.00 mm, 0.00 mm, 0.00 mm Center of Mass -3.369 mm, 2.794 mm, 32.168 mm Bounding Box Length 183.50 mm or 7.22in Width 175.00 mm or 6.89in Height 115.008 mm or 4.52in
Those parts need risers probably comparable in size to the parts, or their will most likely be a shrink voids pentrating the top center of each piece. If these are machining blanks, you will be unhappy with that. Best, Kelly
Thanks, they will be machined, the two will be used on my giant bino as adjusters and the single piece will be a brass hammer head to go opposite the lead head already made. I didnt realise the shrink cavity would be that large in brass.
This was one of my sand cast brass castings some years ago, it was the reducer for an 80mm telescope. The ugly chunk was turned to produce the reducer plus 2 joiner rings for the telescope tubes. The black finned casting is aluminium.
I have been scouring this forum and the interwebs for the pouring temperature for brass to no avail. Everywhere stated around 930'C for melting but no one mentions how hot it should be to pour except "A bit hotter that the melting temperature" Is there a recognised temp to pour at?
Second result Googling 'melting and pouring temperature of brass' https://www.tabletopfurnace.com/blo...temperatures-for-precious-and-ferrous-metals/ Brass melting 900-940 C and pouring 1000-1120 C or melting 1652-1724 F and pouring 1832 to 2048 F
most of my scrap brass is plumbing bits , a lot of which are chromed. Is there anything special I should be concerned about? I am assuming the chrome will be in the dross but am unsure is it floats or sinks.
Well its melted and cast, I didnt use any chromed parts but I did get it too hot but the mold filled. cooled and removed, the underneath with the bottom feeding runners etc The parts I want, they look a bit gnarly. cut all the risers and runners off and it looks solid, the feed sprue shrunk hollow. The middle one of the top 3 was turned down to be the brass head for my lead and brass hammer. However there was a shrink cavity in the middle but I drilled it out and tapped M12x1.25 for a threaded shaft to hold the brass section on. I dont yet know if the other two have any shrink cavities.
As far as your feeder/risers size, they were too small. For them to be useful they need to solidify after the part you need to cast. If they freeze first then they will be drawing molten metal from your part causing greater shrinkage in your part.
As I poured the gout of smoke/steam? and flame made me think it was way too hot as did the enormous amount of powdery dross in the crucible. Too wet sand- I felt it was a large amount of water I had to add to get it to clump, maybe too fine a sand and/or too much bentonite needed the extra water. Larger dia feeders next time. So many lessons to learn. Thanks.
The hammer turned out nice! Is the lead also threaded? The remedy for wet sand it pretty easy, just spread it out in a thin layer on a plastic tarp and let it dry out in the wind and sun a bit then gather it back into its container. My one and only scrap pour was 'chunky' too, looking forward to trying with some bronze sprue stock I got from a forum member.
