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Jun. 3rd, 2018 09:53 pmThere are baby bunnies.
This guy is all relaxed, on his side, and he's only a little larger than a pinecone.
Last weekend we went to an extension of the local botanic gardens and wandered around admiring a few early roses and a lot of irises. They had bees, too. This lady was all "bees don't bother me" and I guess she must have a way with them, as she's holding frames completely covered in bees, whilst wearing shorts.
Right beside her was a swarm. They didn't know where the swarm was from, as all their hives were full. Maybe the bees recognized this was a good place and were hoping for a vacancy.
I 3d printed a little flywheel in two halves.
Then I dipped it in hot wax to seal it so coating material won't get sucked into its almost entirely hollow insides when I'm vacuum-debubblizing it, and wax-welded it to a casting sprue (in blue) that I also 3d printed. (That was a waste of time and materials: in the future I'll make a mold and cast those.) Wax welding is fairly easy: you dip both pieces in molten wax, stick them together, then stick a piece of metal in the hot wax and drip wax on the joint. After the third or fourth hot droplet you can smooth the wax with a fingertip the same way you do with a caulked joint and get a lovely fillet. (My big sausage fingers don't fit anywhere in this, so I had to settle for the drip weld finish.)
This is a mix of sandcasting and investment casting sprue style. In sandcasting, you have the sprue, that you pour the hot metal into, go all the way to the bottom, so the metal rises up into the mold. This reduces turbulence and debris gets floated to the top, where you have a riser the metal moves into, so your casting only has good metal in it. (The riser is the narrow red round wax thing pointing upwards.) When the aluminum cools it shrinks quite a bit. The riser, being at the top, stays hot the longest, and feeds molten aluminum into the rest of the mold as it shrinks, so the riser ends up both with any debris and with a big sinkhole. That's why you add a riser: so that's not in the top of your shape. In the case of investment casting, you also need a riser to let air out as the metal fills the mold, because the investment isn't very air-permeable. Jewelers do this by putting the investment section in a vacuum, so air is pulled through the investment and the metal is sucked down into the mold fully. (You can also do this with air pressure, but a mold failure in a vacuum chamber means the resulting burst of hot metal is enclosed. With a pressure mold you're likely to get hot metal sprayed all over the room even with an enclosure, because the air will blow the mold out of the enclosure.)
The part of this that's like an investment casting mold is that it's a weird shape at a weird angle. A sand casting mold will be flat so it can be removed when the sand casting is opened in half. With a lost wax casting, removal of the mold is done by heating it up, at which point the wax flows out the holes provided, which is another reason you need two sprues.
Here it is cast in a mix of plaster-of-paris, fireclay, and sand.
(The fireclay and sand are to help it survive the thermal shock of hot aluminum. I'll pull it out of the oven at as hot as the oven can go, and cast immediately, but it's still stressful on the mold material.)
A weird thing: the mix of water and plaster of paris shrinks very significantly. I put the mold in the casting cup, filled it with water, pulled the mold out, and measured the water, to derive the volume of investment I'd need. I then took 1/3 of that volume in water, and 2/3 in investment, and mixed them, and it was half of what I needed, so I made the same amount again and poured it in on top.
Today: Japanese class. It's summer break so we're doing our own class at a friend's house, for two hours. I'm trying to bring some order to it, so it's not just people talking about their last trip to Japan. As such, next class (in a couple of weeks as we're all gone in the meantime) we will show up with a one paragraph Theme about any topic we want, written in Japanese, and then everyone else has to ask one question about the topic and the writer has to answer. We're working on conversational Japanese, as the class focuses on written Japanese.
(I think many language instruction classes come from a background of being taught the way the teacher was taught, which is: growing up speaking the language and having to learn the correct grammar, spelling, and other details of written language. So the class focuses on those topics and skimps on interactive speech.)
After Japanese class, yardwork, dog walking, then over to a friend's for a BBQ and a lot of geek talking. He has a D&D group that have been together for like 25 years, and several of them have branched into software modeling and 3d printing for gaming miniatures, so we spent a lot of time talking about cad software and parts fabrication.
This guy is all relaxed, on his side, and he's only a little larger than a pinecone.
Last weekend we went to an extension of the local botanic gardens and wandered around admiring a few early roses and a lot of irises. They had bees, too. This lady was all "bees don't bother me" and I guess she must have a way with them, as she's holding frames completely covered in bees, whilst wearing shorts.
Right beside her was a swarm. They didn't know where the swarm was from, as all their hives were full. Maybe the bees recognized this was a good place and were hoping for a vacancy.
I 3d printed a little flywheel in two halves.
Then I dipped it in hot wax to seal it so coating material won't get sucked into its almost entirely hollow insides when I'm vacuum-debubblizing it, and wax-welded it to a casting sprue (in blue) that I also 3d printed. (That was a waste of time and materials: in the future I'll make a mold and cast those.) Wax welding is fairly easy: you dip both pieces in molten wax, stick them together, then stick a piece of metal in the hot wax and drip wax on the joint. After the third or fourth hot droplet you can smooth the wax with a fingertip the same way you do with a caulked joint and get a lovely fillet. (My big sausage fingers don't fit anywhere in this, so I had to settle for the drip weld finish.)
This is a mix of sandcasting and investment casting sprue style. In sandcasting, you have the sprue, that you pour the hot metal into, go all the way to the bottom, so the metal rises up into the mold. This reduces turbulence and debris gets floated to the top, where you have a riser the metal moves into, so your casting only has good metal in it. (The riser is the narrow red round wax thing pointing upwards.) When the aluminum cools it shrinks quite a bit. The riser, being at the top, stays hot the longest, and feeds molten aluminum into the rest of the mold as it shrinks, so the riser ends up both with any debris and with a big sinkhole. That's why you add a riser: so that's not in the top of your shape. In the case of investment casting, you also need a riser to let air out as the metal fills the mold, because the investment isn't very air-permeable. Jewelers do this by putting the investment section in a vacuum, so air is pulled through the investment and the metal is sucked down into the mold fully. (You can also do this with air pressure, but a mold failure in a vacuum chamber means the resulting burst of hot metal is enclosed. With a pressure mold you're likely to get hot metal sprayed all over the room even with an enclosure, because the air will blow the mold out of the enclosure.)
The part of this that's like an investment casting mold is that it's a weird shape at a weird angle. A sand casting mold will be flat so it can be removed when the sand casting is opened in half. With a lost wax casting, removal of the mold is done by heating it up, at which point the wax flows out the holes provided, which is another reason you need two sprues.
Here it is cast in a mix of plaster-of-paris, fireclay, and sand.
(The fireclay and sand are to help it survive the thermal shock of hot aluminum. I'll pull it out of the oven at as hot as the oven can go, and cast immediately, but it's still stressful on the mold material.)
A weird thing: the mix of water and plaster of paris shrinks very significantly. I put the mold in the casting cup, filled it with water, pulled the mold out, and measured the water, to derive the volume of investment I'd need. I then took 1/3 of that volume in water, and 2/3 in investment, and mixed them, and it was half of what I needed, so I made the same amount again and poured it in on top.
Today: Japanese class. It's summer break so we're doing our own class at a friend's house, for two hours. I'm trying to bring some order to it, so it's not just people talking about their last trip to Japan. As such, next class (in a couple of weeks as we're all gone in the meantime) we will show up with a one paragraph Theme about any topic we want, written in Japanese, and then everyone else has to ask one question about the topic and the writer has to answer. We're working on conversational Japanese, as the class focuses on written Japanese.
(I think many language instruction classes come from a background of being taught the way the teacher was taught, which is: growing up speaking the language and having to learn the correct grammar, spelling, and other details of written language. So the class focuses on those topics and skimps on interactive speech.)
After Japanese class, yardwork, dog walking, then over to a friend's for a BBQ and a lot of geek talking. He has a D&D group that have been together for like 25 years, and several of them have branched into software modeling and 3d printing for gaming miniatures, so we spent a lot of time talking about cad software and parts fabrication.
