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diy aluminum investment casting using a 3d printer.

by:Max Apparel     2020-09-16
Hello everyone, I will share with you my method of converting 3d printed parts directly into aluminum castings.
When I need to make a custom pad and a 3d printed plastic pad for my car, I learned this because it won\'t be under pressure.
Having it CNC machined out of my price range, so I got things in my hands and came up with this.
Traditionally known as investment casting, this process is a black art for some people, and due to the need for luxurious tools, it is seen as something that is not feasible for your standard DIY people.
As I have proven here, getting good results is not necessarily an expensive investment!
I soon realized that the opportunities for this process could be endless, so I thought I would share them with you.
Material: print parts as usual.
If you need a precise part, then you have to consider the extra shrinkage of the material you cast, in my case it\'s aluminum, so I enlarged the part by about 2%, because the metal is shrinking, the holes actually get bigger when the parts change hours, and there are holes everywhere
The size of 040 \"or at least 1mm is insufficient, allowing shrinkage and defects.
I plan to drill all the holes out because they have to be exact fit anyway.
These values vary according to many factors, but 2-
The 3% shrinkage of aluminum is a safe range.
You can also print with as little padding as possible, as these parts will not bear any load and can melt faster with less material.
I also printed the gate and vents, which also helped to ensure the parts in the investment tub.
I \'ve learned that these plastic parts have a lot of buoyancy in terms of plaster investment, so it\'s nice to hold them firmly.
In my experience, it\'s hard to put too many vents on you, and I\'ll put a vent on each high point opposite the gate and on the larger size vents.
The gate is the part of the big pyramid you see in the picnic, where you pour in the melted metal.
If your section has a long and flat section, put a vent every few inches.
Vents will allow the metal to flow into areas that otherwise will be occupied by air that cannot escape, and with the solidification and shrinkage of molten aluminum, these vents will also allow the metal to be pulled into the thicker part of the part.
The vents can be designed as parts or printed after the fact occurs and glued together with melt.
In case I decide to increase or decrease the number of vents used, I prefer to stick to it later.
If the parts you are going to cast are small enough, about the size of the grapes, the vents may not be necessary as your gates will provide you with enough space for your pouring to escape the air.
The location and size of these components is a science in itself, but in general, a good large gate is used to help the pouring and metal shrink and a lot of vents are used.
For a bathtub, I used a standard plastic dry wall mud plate because its side wall has a nice cone and it is easy to release the mold after pouring.
I made a temporary wall with cardboard so that there would be less plaster needed to fill the mold and you don\'t want any No
A certain amount of plaster is needed if you can help, because the drying time will be longer and it will be easier to crack.
If I can, I try to keep 1/2 to 1 plaster material around the part.
As you can see in my example, I made several vents with the top of the drywall pan so I can glue pop-
The sickle sticks to them and when I pour the plaster and wait for it to dry, it can be used as a way to fix the part.
I fixed all the parts together with hot glue because it would melt cleanly and it would easily fall off the mud pan later.
Once the investment is dry, the stick is removed and can be reused if you wish.
At this step, I will show you my hybrid investment method, which is an easy way for a typical home workshop without a vacuum pump or any fancy dedicated investment casting equipment.
I know you can buy a professional investment pre-
Made on the Internet, may get better results than I did in this homebrew version.
But I will say I have tried it.
Professionals like me, I don\'t see any difference, so look at it with its value.
I used some fine silica sand from your standard hobby grade plaster and local material suppliers to keep everything cheap and easy.
For the investment mixture, I use 2 parts of gypsum to 1 part of silica sand, I heard that someone used the 1:1 mixture, but I tried it and the investment was very fragile when the investment dried up, it just crashed on me.
This is also useful to me.
The purpose of the silica sand is to help the mold break more easily and to help the plaster resist high temperature.
Investment powder mixture: 1 part of 2 parts of gypsum silica gel Sandi starts with 8 cups of gypsum, puts in a dedicated dry solid bucket, and then puts 4 cups of silica into a solid bucket, stir well so there will be no lumps or anything.
No water yet.
Now, when we mix the investment powder with the water.
This will be two parts to one part of our powder mixture of water.
You want to use cold water, which will slow down your curing process.
Final mixture: 2 part investment powder 1 part cold water is a key step in time, so make sure all your tools and casting are nearby and ready.
Add powder to the water instead of the opposite.
So I \'ve got my last mixing bucket with 6 cups of cold water inside, \"12 cups of investment powder to 6 cups of water\" pour the powder into the water and start stirring, make sure you scrap the bottom while stirring and keep breaking down any lumps and keep stirring for 2 or 3 minutes.
It should be a good cream consistency that does not block or thick.
Once fully mixed, I run the track Sander on the side of the barrel, helping to coax all the bubbles to the top, and then stir quickly before pouring into the mold.
Don\'t wait to pour after stirring because all the sand will fall to the bottom.
When pouring the mold, I try to pour along the inclined side to prevent the formation of the bubbles, if possible, until the bubbles overflow, and then, when the mold is full, I run the track Sander on the side of the mold for 30 seconds to a minute to remove the bubbles and put the investment into all the small details and make sure that the mold falls off after it is resolved at the top.
At this point you have done everything you can and now you have it completely unchanged for a few hours.
This is an example of the failure of the investment mix experiment.
The amount of powder is much larger than the amount of water used.
This step is by far the most tedious and time consuming part.
This is also the most likely place I have learned from experience to mess up the mold.
If you can get into the kiln then I highly recommend that if not you can do it the way I do it!
First remove the mold from the mud Pan, at which point the mold is still very wet and heavy.
When my wife is not at home, I start the drying process in my kitchen oven \", which is an important part; )
\"Put the mold on the tray in case the plastic drops down, start at low heat, lift the mold 50 degrees around an hour until about 350 degrees.
At this point, the plastic begins to sag and melt.
You don\'t want to get much hotter than this when you\'re at home, or it really starts to stink in smoke, trust me, or no, but I \'ve learned the hard way.
At 350 degrees, I lit the casting furnace located outside to heat it in a low setting.
As you can see, I stacked a pile of cast bricks to make it higher and allowed me to install two molds at the same time.
After my Foundry reached about 500 of the temperature, I put both molds there and the plastic started to melt and I slowly raised the temperature every hour.
As I said, patience is needed for this step.
I continue to raise the temperature for about 6 + hours to make sure I see that they start to go red, which means it is very hot over 1000 degrees.
If you heat it too fast, it breaks, too slow and takes forever.
Even with the kiln, the professional will burn out the investment casting of this size for 14 hours.
I noticed that there are cracks in different sizes on the outside of almost all molds, which may be due to this burn out step, but it hasn\'t caused me any major issues yet, so, don\'t let this stop you from going on.
Once the mold is completely dry and burnt out, I take it out and blow out any residue from the mold with compressed air, which is an important step to ensure that all carbon is removed from the mold, so you can get all the details.
I ruined some pretty molds because I didn\'t remove all the residue from them.
Gently handle, be careful, because these are red hot plaster blocks, so you want some very good fire-resistant gloves and the pieces blown out with compressed air will also be very hot.
After cleaning the molds, I buried them in a large box of sand. I use cut-
Open the cans to cover the opening to make sure there is no sand inside the mold.
When the molten aluminum is in contact with the aluminum, these thin aluminum scraps are easily separated by combustion.
I make sure the sand is wet but not too wet, you want it to stick together when you pack it, when working with molten aluminum, you don\'t want anything to get wet, it can be a dangerous situation where water quickly turns into steam and can cause blowing
This sand box is meant to ensure that small cracks in the mold do not blow open on the ground and leak molten aluminum, and it also supports and isolates the mold so that they do not cool too fast.
So I made the sand a good flat base for mounting the mold first, and then, I put the flat aluminum sheet on top of the mold, so I don\'t accidentally shovel the sand into the mold.
Then slowly use a small garden shovel to encircle the whole thing with sand.
You can blow out any small piece of sand if you need it, you just need to be careful not to put too much in it.
Keep all the aluminum sheet and round cans in the sand all the time, you can pour the aluminum sheet directly into the sand, I didn\'t notice any problems.
I\'m going to add a safety disclaimer here, and if you\'re not working around molten metal before you do some research, please do some research first because I can\'t possibly reach the danger of all this.
Obviously, this is very hot and liquid metal flows into some strange places if it spills.
So please wear steel toe leather boots on the outside, including the mask, and you can\'t see the bare skin.
Since my Foundry is still getting hot because the mold is burnt out, it becomes my favorite part of the project. . .
Melt the metal!
I used the luggage rack of the Ford Mustang and broke it with a hammer, \"faster and more fun than with a saw,\" and then I melted it.
Once melted, I make sure the burner stays longer until the material reaches the pouring temperature.
Make sure you melt enough of the metal, which will take more time than you think, and it\'s really bad just to have the whole project destroyed by what\'s called partial dumping.
Speaking of this, I am not very scientific, I have heard from an old timer that once the aluminum is hot enough, you should pour the aluminum and do not stick to the steel bar when immersed.
So, once the weather is so hot, I must skim the surface and remove the scum or slag.
I do this with some steel bailing lines and it has nothing but leaving beautiful shiny molten aluminum on it.
After skimming the scum, pour the metal as soon as possible, and when you pour it, make sure you have a solid gesture and a stable hand, as you want to pour it quickly and thoughtfully, and most importantly, don\'t Stop pouring even if you miss the target a little, just re-adjust and keep the metal flowing until you see it coming out of the vent.
Then pour the rest into your cupcake jar or any container you have to use.
Let the mold cool for a while, I sat my mold for about an hour, and since the mold is still hot, I still use pliers to remove the mold!
It\'s fun/stressful part for me, just start breaking the plaster and you can see the part you hide in the mess perfectly formed!
Cut the watering way and vents with a hacksaw, the rest looks great, the details are crazy, you can see every layer of 3d printing, now I wish I could add more details to the model like some text.
Be careful because this hobby is very addictive and uses are almost endless!
Good luck and safety.
Thanks for reading.
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