Have you ever wanted your 3D printed object to be more than just a chunk of plastic?
This Instructable will show you the necessary steps to turn any 3D print into a solid piece of cast bronze or another molten metal of your choice. While the process can be time-consuming and making metal molten to be quite challenging without the proper equipment, it is a very rewarding and fun project to do. You use a multitude of skills and disciplines to do this project and it really teaches you a lot about 3D Design and casting and just using your hands in general.
In my case, my class designed and built bells that were 3D printed and then cast in bronze. While your 3D printed bell does not have any noise, a properly designed bell has a beautiful ring after being cast in bronze. Stick around and you'll learn really how easy and doable this is!
3D Design Software
Rhino Cad - All 3 of these programs work great for designing a Bell
Wax for Gating and Vents or Carving
Scraper for Wax
Casting Plaster Mix
5 Gallon Bucket
2 Gallon Buckets
Kiln for High Temperatures
Foundry for Melting Metal
Angle Grinder or Dremel
Drill and Bits
Drill Mixing Attachment
Clamp-on Fishing Weight
Various Tools to Clean Cast Object
Die Grinder is helpful
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Designing Your Bell and Clapper
There is an infinite number of possibilities when it comes to designing your bell and the clapper.
For starters, I will show you an easy way that can work in almost any CAD program.
For Tinkecad, there is already a shape that can be easily made into a bell but since it is the thin shape it will not cast the best and the sound is lacking but it is an easy way for beginners.
For other more complete programs like Rhino or Fusion 360, there is also an easy way that makes a complete and great sounding bell.
Starting with the cross-section I attached to this step, you will use this to trace and get a simple outline of the shape of your bell.
In Fusion 360, start a 2D Sketch and then trace around the cross-section. After finishing the sketch, you want to revolve the sketch 360 degrees. After, you should have a complete bell with the shape of the cross-section around the whole way. Your bell is ready to be decorated to your liking. You can see I added some simple circles with a rounded edge on them and revolved them around.
In Rhinocad, the process is really quite similar. You will import the cross-section, trace it and then revolve it. I would recommend using the software your most comfortable and if you need help with any of them feel free to reach out.
I made two sized sphere clappers which will be seen later. I made two sizes and matched the design to my bell. If you do not want to design your clapper, you can use a scrap piece of bronze from the casting process and that works well too. Keep in mind when you design your bell, you want a way to attach your clapper. There are a couple ways to get this done. You put in a ring at the top of your bell which allows your clapper to be tied around it and held up. I opted to drill a hole in the top of my bell because tying knots in small areas would be hard with my larger fingers and small string. Later, I'll reveal my easy secret for holding your clapper in the right and bell in the right spot without tying a knot.
The casting method really can show all the details, so be as crazy as you like. I made my bell around 3 inches tall as it is easily fit in the 3D Printer and helped not use as much bronze. I would not go much smaller than an inch because it can cause the casting of it to fail. This can cause is to fill solid if the mold is not perfect or it can be thin and not cast in every spot leaving holes. You can go bigger though, the only downside is that you use more bronze and filament. In the end, it is your call but the 3-inch size works well and does not have any issues.
Step 2: 3D Print Your Bell
Every 3D Printer can run a little different but all have the same basic settings.
Don't forget to level your build plate and use the right size nozzle. Filament color does not matter as it will eventually be melted out and not matter in the end.
For my print, I flipped my bell model upside down to prevent supports from being created on the inside. I thought it would be easier to remove supports from outside. I used a raft to make sure my print was stable and made sure that supports would only come from the build plate or the raft for that matter. You can see I had a lot of supports but in the end, it paid off, there was no damage to my bell. It does use more filament but the results come out great.
To remove supports I used some cutters and my fingers to help remove most of the supports. After there were only small pieces left, I moved onto some pliers and just wiggled back and forth until it was all done.
Step 3: Gate and Vent Your Bell Using Wax
To get the bronze to your bell, it will need a path. The path that we will make is made of wax. To better illustrate what is going on, I have attached a diagram found on Google that makes it a little easier to look at and explain. In our case, we do not need to worry about the core pins, core vents or If you were doing just your bell, you can see that the gates and vents could be very simple. As long as there is a place where the bronze can go in and the air can go out, you should be good. You generally want a larger piece of wax to send the bronze and small thinner wax for the vents where any air and impurities can be pushed out as you pour. You can see that on the wax tree, it is not only bells. There are 3D models of people and some other geometric objects. This process can be applied to almost anything.
Gating and venting can look challenging but the process is quite simple. You want enough support that your objects do not fall or move when the mold is poured around the objects. You must gate and vent everything so that it all faces an area where the mold can be poured into and filled or else the object will be completely solid. You learn that the hard way... To attach the wax to wax and the 3D Prints, use a propane torch to heat the wax and simply stick it together and hold for a few seconds. Once the wax is cooled, it should be stuck. Always give it a small tug and make sure the gates and vents do not break off or else bronze could not go into your mold. If you have issues with the wax not sticking, you can use the torch so heat a small scraper to apply to the ends of the wax and quickly remove the scraper and push the wax on to the 3D print or another piece of wax. Be sure to not apply the torch to the 3D prints as they could easily deform. Building with your cup on a board of wood or melamine allows for easy transportation and makes a good base for when your working on the tree.
Another important note is that you must be sure to pay attention to where you place your gates and vents on your piece. On my finished project, the design was half there and not so there. This was due to the gate being placed over my design. Well, I tried to grind everything smooth, there were holes where the wax followed my design and therefore not making the top uniform. This can be fixed if you fill it in with more bronze or know someone who can weld bronze. In my case, I did not think it was worth and frankly, it adds character. Just pay attention to where your gates and vents go and be aware that a complicated design could be covered up, like mine.
Step 4: Build Your Wireframe and Wrap in Paper
Attaching the wireframe and paper is a rather easy step in this process. This will act as a support and dam for the plaster mold as it gets poured in.
Chicken wire works great for the wireframe and if you have something on hand as we did use it. Chicken wire is cheap, easy to cut and allows the edges to bend over when you form the full circle. Be careful to not cut your fingers on the chicken wire as it is very sharp when it is cut. You want about an inch of space around the edge of all your objects on the wax tree. Too tight makes it harder to pour your plaster in and you risk having an issue with the mold. If you go much bigger, your wasting the plaster and making a larger mess later. For the top of your wireframe, you want two or three inches over the top of your objects being cast.
The paper around the wireframe is only temporary for the mold pouring process. It simply holds on the water and plaster and sand in place while the plaster hardens. You want this paper to go about three inches about the wireframe to insure nothing spills over. Duct Tape works great to fasten the paper in the cylinder shape. You're ready to mix and pour your plaster!
Step 5: Mixing and Pouring Your Plaster
This step has the potential to make a huge mess, hence the tarp for easier cleanup. Measurements for this mixture do not need to be super precise but the closer the better. We will mix sand, molding plaster and water and then pour the mix into the molds made in the previous step. For your measurements, I use about an inch and half lower than the top of a 2 gallon bucket. In order to make your measurements easier, you can use spray paint once your sand is your bucket and make a line to go every time. Let it dry and move your sand to another bucket and mark the same line. Repeat this until you have three 2 gallon buckets ready for measurements.
To mix, first, start with water and plaster. The water goes in first and then slowly add the plaster while the drill and mixer are spinning. Once the consistency is even, add the sand in the same manner. Once all three elements are consistent, you're ready to pour.
Your first bit of the mold will be used to form a dam around the base of your paper and wireframe. Just pour on the outside of forms wait. It will take some time for the mixture to set up and cure if you are working in the shade but the sun can accelerate the process if you want to risk it. Once it thickens up the consistency of melted ice cream or a milkshake, you can push it up to form a dam and wall so the plaster can not leak from the inside out.
After the dam is made, you are ready to pour inside the wireframe and paper. Start with a small mixing cup and pour it into the bottom of the form. The smaller cup allows for precise pouring and can help prevent from pouring onto the bells and dislodging them from the gates and vents. Be sure to fill up every bell with the mix to ensure it does have any pockets in it. Once the bucket is a little lower to pour easier, you can start carefully pouring and filling in the wireframe and paper. You could need more than one pour so be ready to mix more if needed. Once your form is filled, let it sit and cure. The cure time has a lot of variables so be ready to wait a little bit of time. During this time you could start to clean up some and get organized.
You know the molds are ready to remove the paper from when the top of your mold is hard and there is no standing water left. If you watch the curing process, you will notice the water is slowly sucked into the plaster and sand.
Step 6: Put Your Molds Into the Kiln
This is another waiting process in this project. Now that your molds are solid and hard, they are ready for the kiln. The kiln will melt all the wax and 3D printing filament from the mold leaving behind our plaster mix as the mold.
The kiln should be set at about 300 to 400 degrees to start the melting of the wax and PLA Filament. The molds should be at that temperature for about a day for most of everything to melt out. After this day's time, we will increase the temperature to 1000 plus degrees to ensure that every little impurity is gone because we do not want something where are bronze will be poured. This is a super important step but makes sure that anything inside your mold is gone and allows for everything to correctly chemically bond inside the plaster. Once this is done, you are ready to pour your bronze.
Thank you to IronSmiter for a comment on this section and for a more detailed summary of a proper plaster investment process used in both jewelry making and larger pours like this. Here is what Iron Smiter said:
"Normal" quick burnout cycle for investment goes something like this.
Put the mold in a cold burnout over, bring it up to 300 F, and hold for 2 hours. most wax, and many plastics will melt/burn at this step.
Ramp temp up to 700 F for 2 hours This should completely burn out all organics, including leaves, and plastics.
Up the temp again to 900 F for an hour. Mainly to avoid thermal shock Set temp to 1350 F for 3-4 hours. This is the temperature at which the chemically bonded water is released, and converted into it's final form.
If you want to get persnickety, this is often followed by 30 min to an hour at casting temp (for bronze, this should be around 2200) I would skip this step, if using straight plaster. Anything over 1500 may negatively affect a pure plaster mold.
Step 7: Pouring the Bronze
This is the most exciting process of it all.
After setting our molds in a sandpit and making sure that they are stable, you can pour your bronze. Before the pour, use a shop vacuum to suck out anything else that could have dropped into the mold. This is just for safety.
The foundry will heat the bell bronze up to around 2,000 degrees. Bell Bronze is unique for instruments as it contains bronze, copper, and tin. I do not know the specific science behind it but it is better. Pouring bronze requires very special equipment and safety gear. If you do not know what your doing, find someone who does. Bronze will instantly melt through any normal clothing and is not for everyone. If you feel unsafe, do not do it.
After the pour, let it cool some and then you are ready to break your cast free in a couple of minutes. It is cool to see it go so fast.
Step 8: Break Open Your Molds
Breaking open your molds is very easy, just take your time and no damage will be done to your projects in the mold.
The first step in opening the molds in using a reciprocating saw to cut the wire mesh supporting the plaster. Once this is cut, it falls open.
After this is done, use a small hammer and pry bar to slowly remove the plaster from the bells. Once most of the plaster is off, you can move on to a more thorough cleaning.
Step 9: Clean and Separate Bells
After becoming free, dunk your new bronze tree into a 5 gallon bucket full of water. Letting it sit in the water not only lets it cool off in the water but it also gets rid of some of the plaster. When picking up your bronze tree, it will still be very hot so be careful. Use pliers or a shovel to move it into the bucket.
Be sure to replace the water in the bucket if you are doing more than a couple of trees because the water will actually become very hot because the bronze was just poured.
The final step for cleaning the tree is to pressure wash what is left of the plaster. It is easier to do it when it is in a big bunch as they do not move around as much. You can see large chunks still come off even after soaking. This process can take time but it pays off in the end.
Using an angle grinder with a cut off wheel, you can slowly cut the tree to separate the bells for their own cleaning. Don't forget your hearing and eye protection!
Step 10: Clean Your Cast
As you can see, the casting can be rough in areas and clean in others. While this casting process is somewhat crude, it really shows the details down to the layers of the filament.
For cleaning your cast, I would suggest leaving some chunks of the bronze tree on your bell. This allows for you to have a handle on your bell where you can clamp to a vise or hold in different angles while your working on it.
To clean my bell, it was rather hard, to be frank. I went with a very complicated design which resulted in a harder time cleaning. Since I do not have access to a sandblaster, it was hard to get in the small areas of my design. It did form a unique contrasting pattern with the light and dark areas of the bronze. If you do use an abrasive on your cast, start light and go heavy. It could be very easy to clean your less complicated design. The ground areas do you show a true bronze color. As you can see, I chose to flatten the pipe structure of my bell. While it was different than what I truly wanted to do, it came out well and I was able to get a fairly uniform finish.
Take your time and your bell could be far better than mine.
Step 11: Finishing Touches
The finishing touches are all dependent on your own bell but I do have an easier way to hang both your bell and your clapper if you decide to do the string method instead of the ring method.
First, I used a 2ft to 3ft piece of string to hang my bell. The length depends on your situation but I decided to go longer than shorter. To attach the clapper, I first drilled a hole through the clapper. I did mine with a 7/64 Drill Bit and a hand drill but depending on your string size, it could vary. I also put a hole directly in the center of my bell in order to hang both it and the clapper.
At the end of the line, I tied two half hitches in order to secure the end of the line and stop the clapper from falling through. Next, I ran the line up through the hole in the bell with needle-nose pliers because my fingers were having trouble fitting. Burning the end of the string makes this much earlier to run through. Next, find the height of where the clapper will hang inside your bell. I laid my bell on its side and pulled the clapper to the desired area of hanging. I marked the height with my finger and pulled the string back done. At this point, I took a clamp-on fishing lure weight and pinched it on the same spot as the mark. Not only does it make the spot adjustable in the future, but it also makes it so you do not have to keep guessing your knot location or having to tie more than one knot because one slips through the hole. Once you have done this, you are ready to hang your bell. If you followed the directions, it should have a good ring to it. The design and thickness are factors to the ring but in general, the base shape works great.
Step 12: Thanks for Viewing
Thank you if you made it this far. This was a really fun project and definitely a different way to use 3D printing. It does not have to end with the filament, you can go above and beyond.
If you have any questions or comments, leave them down below.
Participated in the
1 Person Made This Project!
SuperRistopaha. made it!