WARNING! SOME OF THE PROCESSES IN THIS INSTRUCTABLE ARE DANGEROUS (MOLTEN METAL..ETC..) DO THIS INSTRUCTABLE AT YOUR OWN RISK!!
Ever wanted to Make some cool Item whether functional or art, out of metal? Is it too complicated to make out of simple foam? or Did you simply want to make more than one of the item? This instructable, while rather small, will tell all about the things needed to achieve said task. Most items in this Instructable will be made and comprised of research I have done on most parts, walking you through the Basics of each Task.
we will start off with your options of 3D modeling. and then move on to the most important parts of the whole setup:
- 3D printing options
- Pre- Molds
- Building or buying the appropriate Foundry with applicable tools.
- Building molds along with their different types and casting methods
- Choosing metal types
- and Finally casting the items and cleaning them up
Step 1: Designing Your Item
As we start off, we need to understand what necessary software you're going to work with to make your Files that go to print. Now while there are many to choose from, I myself have only worked a few different types, Sketchup, AutoCAD inventor, and a little blender. There are many that you pay for and some that are free. If you are a student look at inventor as it is the one I prefer since they give it away to students for usually free. And the fact that it's one of the best softwares for this. Now as for this Instructable we will be looking at just what you'll need to design into it .cause you know, that's just how it is.. :D, and the fact that there are lots of tutorial on just that , that I would never be able to explain it well enough.
Now for Demonstrative purposes I have shown a simple parts that I have made that will fit our purposes, Now to learn from my mistakes.... DO NOT FORGET TO ADD SPRUES AND AIR EXHAUST HOLES TO YOUR MODEL. you may ask " what are sprues?" They are essentially the part of the mold where the metal enters the mold from. Now as for me I have forgotten about doing that , so for me I had to make some out of clay which complicates things farther down the road. If you can now, I would advise you try to 3D model it in first. To make your model capable of being cast you will want to pay special attention to:
- flow of metal/Air bubbles
- Mold strength
- Room to machine and sand.
- Slag and junk reservoir
Soo... Flow of metal.that is one of the most important parts in designing your model.. The more separate high points you put into the mold, the more exhaust points you will need to release the bubble so that the metal can flow. Here in the picture Shows an examples of how you should orient something like a Crown. For each case Shown there are their own advantages and disadvantages.
A is just totally wrong, with too many areas for air to get trapped. (RED AREAS)
B is an example of how you could get away with having it faced up that way, it's just that it has a lot of wasted material....
C, the best option, shows use of minimal Sprues and exhausts to give it the best result, for that one there is only one maximum height to be filled.
D might work, but the issue with that one is not having a lot of space for all the material to flow.
Mold strength, referring to how small the details are... you don't want to your parts to be too small otherwise it makes it really difficult to fill later...and sometimes your molds break, which I have done a number of times. as far as the rest goes Detail is not easily achieved in casting metals often it's more "get it close and machine/sand the rest off.
This leads to my next point, room to work... when you go to cast your model you'll notice that the surface is not by any means perfect. It usually needs a lot of work and elbow grease to whip it into model shape. so from this you may want to make some surfaces thicker to accommodate sanding and polishing.
And now with all of that... with your finished model. We Now can move on to 3D printing!
Step 2: 3D Printing
Whether you're versed in this already and have a 3D printer, or just don't have one, you'll need to know your options.
For those of you who don't have 3D printers or any kind of machine to make your master part, like me... you will very much want to look into where you can bring your beauty into reality. Without that you would have to sculpt it yourself and that is much harder and a well conditioned skill. If you're good at that then have at it! you can make one... But with the right process you can make multiple cloned parts.
SOoo.. your options are current as it stands:
Of these I have used both 3D hubs and Shapeways , both good options depending on what you want to do..
For our purposes I used 3D hubs because often enough I can have something printed for a price that I can afford, and in the material we need.
One large thing to pay attention to is material of your print... some might be strong and cheap, some might be detailed and expensive. For the best results I would use ABS plastic in highest resolution doable, Because well.... pesky printing lines show up in your model.
when you you choose ABS, this gives you the option to sand and or Acetone smooth your item, which I'll explain next.
Step 3: Acetone Smoothing (safely) SKIP to Bottom IF LARGER OBJECT
With some materials that you 3D print you can use acetone vapors to smooth out print lines. One of the easiest methods I have used Is fairly easy to do and doesn't require you to put acetone anywheres near a large ignition source. Of course there are a few things we need to pay attention to.. cautionary things.
Know this :
Acetone is Explosive! corrosive to certain materials and drys out your skin really bad. PLEASE PLEASE be carefull with it. Its not terribly dangerous as long as you just treat it right.
Put gloves on (ones that don't dissolve in acetone)
Be in an open area ( outside or well ventilated)
Be no where near any ignition sources
Respirators and Goggles are preferred but as this stuff is what they use in nail polish remover its not terribly necessary
But over all just be carfull.
SOO.... Past the Pre-cautionary statements we move on!
This method needs:
- Stove to boil water
- Mason Jar with lid or other acetone safe semi-sealable container
- a few paperclips or stiff wire
- cotton string (polyester will probably melt...)
- and a few containers of to put it in...
with all of that together, we prepare the Jar for the parts by either magnetizing a hook to the top of the lid or physically attaching it with a screw.
once you have that setup you can start preparing your 3d model to be hung in the jar, For me I just Took a piece of wire, formed it into a hook, heated it up, and then stuck it in a place out of sight (bottom)
From there you just string it up so that it is suspended above the liquid being placed in the jar.
Now just boil some water, and while your waiting place maybe a little bit of acetone in the jar, Just enough to cover the bottom with a few millimeters of liquid. Now just place your item on the hook and close the jar up. MAKE SURE TO NOT SCREW ON TIGHT. The acetone will create pressure and create issues.. for you and your part.
Now just place the boiling water in a larger tub and place the jar in with it.. within a few minutes you will see the inside of the jar start to condense liquid on the walls. wait about 30 seconds to a minute and then pull it out, the part should look a little wet meaning it was slightly coated with the vapors. This will be a little sticky at first so just hang it up somewhere for it to completely cure.
Now that you're part is nice and finished in plastic you can move on to The first Molds!
FOR BIGGER OBJECTS:
for the larger items sometimes acetone smoothing really is not easy to fit in a container. so.. you must sand it!!
try to to start with some lower grits to get most of your lines off, then work your way up till it is mostly smooth, remember. the item cast will not really come out as a perfect surface anyways!
Step 4: PRE-casting Molds
For your item to properly come out of the final cast mold it will need to be made out of a material that melts out !
Lost Casting waxes, like mine above, work great for our purposes. But first we must make our molds to match our 3d printed item. First we must consider the possible routes.. Silicone, Vacuum forming, and green sand molds.
silicone works great for most Jobs as all you have almost all of the details captured. and its very flexible.
Vacuum forming is reserved those items that have a small amount of details that a sheet of warmed plastic can be dropped onto and then then suctioned to the surface. Hence Vacuum Forming.
Green sand molding is on of most common methods for doing this as all you need is the sand, but as is it typically can be a pain to setup correct.
For my regular models to be cast I went the silicone route because its not easy to do Vacc form on it. I might try again later.
Now my silicone skills are far from perfect, so I will just point you towards a better tutorial on that:
Testeds lightsaber casting mold...: https://www.youtube.com/watch?v=DEVi0mEaJJQ
In this case all you have to do differently is ,after you make the mold , cast it out of the casting wax.
Of course some of you wonder " how do I melt the wax for the mold?", all you need to do is get a cheap (sacrificial) steel bread loaf pan from dollar store. Then you warm up your oven according to the waxs temperature specified by the dealer. Mine was around 200 degrees fahrenheit. Just warm up the oven to the temp, and warm it till the wax turns into a pool in the pan. when it is fairly thin you can then pour it into the mold. And before you know it you are pulling out a completed Burnout copy of your print ! and now for the Foundry (Metal melter) !!!(after these messages)
Step 5: Side Note: GEM Casting (plastic)
This is now where you can apply the earlier skills and add in just a few more steps to make clear parts for jewelry.
All you do different here is work up all the way upto and including the making of the mold. making sure during this time to get the best surface as possible on the jem prints, everything you miss will show up in the surface.
all you do is fill the molds with clear acrylic plastic resin. and then after, you sand them under water with wet sand grade sand paper. Do this with as many steps of sandpaper as you can tolerate. all the way up to 1200 grit.
Then after all is said and done you take a special spray pictured above.... and then follow said directions to finish them with a nice glossy finish.
By this time you should now have a fully finished gem for whatever you intend to use it for!
Step 6: Metals and Your Foundry (melting the Metal)
For this step you can either buy or build your way to molten metal, Of course for most of us the bought option is just too easy or just too darn expensive ( $500 +++). I built mine based mostly on the one Grant Thompson built his tutorials from. For some people, parts may have to vary based on availability of certain materials. So mine will look a bit different. But overall you'll need to know what metals you want to work with first
Given the Properties of metals and our cast items: I would advise not even thinking about steel/Iron really any metal with over 1900 degree melting point. Any metal of that range will start to make things really difficult to do...
So if you work with Grants setup you can work with:
- maybe Bronze (Not going to touch on this yet , I have not used it yet, I suspect it's similar though))
- other low temps you could do with just a torch. like Gold, silver, lead, and so forth
Out of these my favorite one to work with is brass due to the ease of getting flux. Flux being an additive that prevents the zinc from boiling off. Also the metal looks cool and cleans up nice with its low porosity (Bubbles). For brass to work, you can use Dollar store Roach killer (Boric Acid) as flux. The temperature that brass needs to melt will determine what kind of foundry we'll use. Based on a melting point of 1652-1724 fahrenheit we will need 2 Propane powered Jets with which Grant shows how to do very well here:
The Main part of the foundry built in his video here:
when you got to do the plaster in the foundry be sure to use cold clean water, any dirt will speed up the plasters curing from the 15 min. to 1 min.
If you want to work with aluminum cans,being cheap and all, It works, but don't expect it to be much of a clean cast. pictured above is 2 ingots cut in half and sanded to show porosity of two different grades of aluminum, if you have gotten this far don't skimp on your metal.
where I got my brass from is my local scrap yard, they were more than happy to sell it to me. and if you can make sure to get Cast brass scrap instead of extruded. Extruded has different properties that make it kind of messy to work around. Scrap pipe components work best.
Parts that I would pay particular attention to is getting a hold of :
Graphite crucible for your Foundry: These may cost a bit, but they last fairly long and are much less polluting to the metals you melt. Mine is an A2 size crucible with a holding volume of 12 lbs of Brass. When storing the crucible be sure to not let it near any WET areas, Water is a Big problem for crucibles, as it can cause it to fail.
Crucible tongs: in Grants video You see the use of some regular steel tongs, which work... but if you are willing and able I have built a pair that can be welded up with a few bits of mild steel that work extremely well and is much more reliable pictured and videos above.
The crucible tongs pictured above are built so that one person can pick up the crucible by squeezing the two handles together and then simultaneously holding the third smaller handle to tilt and pour out the contents of the crucible.
If you end up deviating from the designs you see here for the foundry, pay attention to your spacing of air in between the foundry walls and the crucible , if there is too much space, the propane will not burn properly.
Step 7: Metal Ready Molds
Now that you have a mold that has produced a wax model duplicate you can now make that piece usable.. Normally with a lost foam mold you build it out of foam and just bury it under some sand, its pretty much the same for us here, but we add a step that more assures the metal to get to every part. We now use Lost wax!
To do this we take our lost wax part and spray them down with a light coat of spray glue so that the compound doesn't wick off after we then dip it in a watered down solution of Sheetrock brand drywall-joint-compound. This being half of the bucket of compound mixed with 10 lbs of water. Once enough of the part is coated you let it dry and then dip it again and again till it's a fairly rigid structure. This came from an article that explains it a bit better than I do here: (experimental: dip it once in the diluted solution then smear on the thick unwatered down compound for significantly faster results)
Like my parts above which are ready to be evacuated of their waxy counterparts. All you do for this is place your coated cast into the oven and melt the wax out. leaving a tray underneath to collect the melted wax. If you at any point used foam parts in the making of your part under the coating, you will need to acetone those parts out before going to the oven.
Now with the cleaned Hollowed Mold. you can get ready to cast!!
Before you set up you will need to bury your item in the sand, being careful not to get any sand inside!! with the item fully buried you will need to form a cone around the tops of the holes so that you can pour metal into the mold, and not let it leak away and destroy your container. when you fill it you will have some parts that you will need to cut off later. Make sure you fill it a little over the hole so you have enough "head pressure" to have the mold completely fill.
with this completed you now have a rough casted part !!! :D On to finishing!!
Step 8: Last Task: Finishing Your Part.
Now that your part is made of metal you start the process of sanding and polishing which is fairly explanatory as is.
You start by removing the rough layer on the piece by starting with a simple file or Bench grinder and your part preferably mounted to a vise or other secure object. Other usefull tools can be drill with a flapper disc sander, a wire brush, and not on the drill, a bench belt sander. The more secure the piece the less work needed to sand. and From there you can work it from 60 grit up till 2000 grit sand paper where you can then either call it finished or go a step further and use Red Jewelers Rouge and a polishing wheel to shine it to a mirror finish. If you were careful during the whole process you should make off with a beautiful piece of Brass. as you can see here, I am still working towards the perfect mold...
currently I am working on a experimental mold attachment so that the part can have a reservoir. Reservoirs give the part a place to put the less than perfect parts! All of this mostly being slag and other heavier bits that end up giving you those nasty blemishes you see up in the photos....
Now stop listening to me talk! you're DONE!!!