In this Instructables you will learn how to cast using a DWS550 3D print from the Ember printer.
Step 1: Design
When 3d modeling a piece of jewelry many variables should take place in the design process to insure a successful print, casting and finished functional object. The most tricky part of jewelry is planning out the process to insure less work down the road.
1. Geometry- What are you trying to achieve from your model? In this case I wanted to create a simple ring with a tube setting to incase a 6mm Diamond.
While designing the geometry of a piece its important to keep in mind the interaction the object has with the body. In this case a ring was sized to fit a 7.5 size finger.To size your finger you can easily buy a ring sizer like the one below from Otto Frei/ Amazon/ Rio Grande, and other jewelry suppliers to measure the size of your finger. To size your finger simply take the finger you wish to size and try a variety of metal rings on that finger. The one closest to fit will be one that passes over your knuckle, not easily, but is removable (You want to be able to remove the ring, but not have it too loose as well).
2. Thickness- One of the beautiful characteristics about casting is the ability to achieve fine detail and texture. My advice is to push these perimeters as far as you can, while still achieving successful castings, and functional adornment. With that being said as thin as you can print on the printer is as thin as can cast. Silver will flow better than bronze, and gold better than silver. We were able to get successful castings from as thin as we could print on the Ember (0.10mm) in both silver and bronze castings.
The first ring we are testing is a simple ring which could be hand carved from wax or fabricated in metal. the difference is the time it takes to achieve maximum perfection in design is very minimal, sizing can be manipulated instantly both for the stone and ring band size, making this a desirable way to create production designs and pieces. WORK SMARTER NOT HARDER!
3. Feeder Gate- When designing a piece its important to keep in mind how to attach the sprue/ feeder gate (piece of material that will allow for your metal to flow to your object during the casting process that will attach to your mold and wax tree)
-When adding texture to a piece this is a very important variable that should be taken into consideration when your designing. Depending on the complexity of the piece and factors such as thinness/thickness, scale you may need multiple feeder gates, or one placed in a spot you might not expect.
The ring designed has a 3.5mm feeder gate positioned into the interior of the ring shank. I placed the feeder gate their for multiple reasons. First, for production if you want to make lots of these little guys its much easier to finish, grind the interior of the the ring than it would be to create the half round surface of the exterior. When you remove material from the rounded area you risk taking away to much materials easily or not removing enough. Secondly, this part of the ring will be on the bottom and inside of the ring away from the stone which aesthetically will be the drawing point from the eye. Basically, you want to keep your Mona Lisa as your main attraction and not obstruct it from any inconsistencies if possible.
Step 2: Keeping in Mind Your 3D Print for Casting
This ring was printed on our very own Spark printer. For detailed printing Instructables Click HERE (https://www.instructables.com/editInstructable/edit/E6OWVKJIBRRWX41)
1. Orientation- When adding the orientation of the ring its important to keep in mind certain variables while printing. For instance for Finishing later we want the top part of the bezel to be as perfect as possible so we have that positioned to print first and not end up on the printing bed.
2. Supports- Think in perspectives for finishing later. Removing Supports can be challenging, and you want them to be positioned in places that they can be easily removed and not interfere with the construction of your piece.
Step 3: Preparing 3d Models for Casting
Its important to examine your 3d printed models before preparing them for casting. If anything is included in your model IT WILL CAST.
1. Removing Supports- The easiest way to remove supports is using a scapel blade. I have found that a very high quality scalpel blade to cleanly remove supports can eliminate pitting in pieces and be easiest to clean up post casting.
2. Adding in Material- It has taken me lots of time to refine this process but it is possible to attach castable Resins to wax. If for instance you remove too much Resin from your model of something accidently cracks or brakes you can re attach the pieces, or add in wax filler material. Using a wax pen to heat hard wax (microcrsitaln works wonders) you can heat the wax to fill it on/ into your 3d printed model. often you have to blow on your piece and be patient for the wax to cool during this process.
3. Refining- Make sure that models are one hundred percent ready to cast before attaching them to tree. What I tell students is for every 5 minutes you spend in wax work post processing metal work you could spend 5 hours.
Step 4: Prepping Mold
Now that you have your final pieces you are ready to attach them to your tree for molding.
1. Orientation- Specifically an important variable for different types of casting. I will be explaining the techniques for both Vacuum and Cintrifigual casting. Positioning your piece on your tree is important. First, in case you are attaching multiple pieces lets start some ground rules. Work from thickest pieces on the bottom up to finest delicate pieces on top. Its important to keep in mind that this tree will be flipped upside down. The part which you are attaching to the main feeder gate and sprue base will be the bottom and button of your model, and the parts furthest from the sprue base will be at the tippy top.
2. Gravity- Use the element of gravity to your advantage even though you are vacuum casting. Gravity will pull the metal downwards first. So, the delicate fine pieces at the bottom will be filled with multon metal and then will fill up as the metal is poured eventually filling the button of your mold.
3. Vacuum/ Cintrifical- These elements will both add to producing a detailed casting. Using these techniques allow you to achieve supreme amount of thinness and texture. The ability of what you can get away with in casting by controlling temperatures of metal, flask and force is vast. A safe rule of thumb is .8mm in thickness can normally cast with ease using the formulas I will give you. The most important factor is always to test a piece first before making multiples.
-the ring we designed is a simple test so we can easily decipher which variables could easily be flawed to see which part of the process was done incorrectly. starting with a simple piece first is key to make sure that your casting/printing variables are on point.
4. This ring will have the sprue attached to the feeder gate at a 45 degrees angle with the tube setting positioned upward. This way when the model is flipped around when we are casting the metal will first flow toward the tube setting of the ring and then up through the ring shank back into the main feeder gate.
5. By heating the main feeder gate with a hot knife or wax pen you can heat the wax enough to melt it and place your sprue gate into the feeder gate. Its important to melt in wax around your resin object to insure no gaps can be found from the sprue gate to the main feeder gate. Any gaps or air cavities could result in pitting or miss casting your pieces.
Step 5: Cast
For casting you have two options:
1. Cast yourself
- If you will be casting yourself you can use any methods that you feel confidant using. Thousands of techniques exist and each caster will tell you a technique that is "the best" . Using your own equipment the best idea is to test your own vacuum, centrifugal and kiln to get best results.
a. FLASK- Depending on the type if casting will decipher the type of flask you use. If you are vacuum casting the perforated flask with holes works best (flask with holes). The flask with holes be sure to add tape around the outside before pouring in your investment! If you are doing centrifugal casting the non perforated (no holes) work best.
b.INVESTMENT: Many different investments exists for 3d printed plastics. Be sure to read the PLATICAST document before starting the process. Wear PPE such as respirator while mixing and safety glasses.I have found Ransome and Randolph (the casting Gods) have made a really awesome product called Plasticast. This investment has great results with DWS products. For best results test your plastics with the investment on a singular piece to insure you get good results before casting a whole tree. Attached in the Kerr Cast document that has water to investment measurements which is consistent to the Plasticast but is not included from the vendor.
-When your mold is ready to go mix up proportional investment to water ratio (kerr cast chart page 21) be sure to mix for at least one minute and make sure all investment is mixed in water and its not lumpy before vacuuming.
* This investment is VERY different from traditional investment because of its expansion. When you pull the vacuum on this investment to remove bubbles take caution that it raises 45% more than KerrCast and other investments. This investment is able to take heat and expansion more than others so its properties are much different from other investment types.
c. BURN OUT-let your flask set for at least an hour before touching or moving it.
-Regular Burnouts have proven to be successful (attached is the KerrCast burnout cycle with detailed suggestions and methods Page 23) I have gotten perfect castings using these burnout methods from Kerr Cast. I have noticed that the 8 hour burnout leaves less damage on the molds using the plasticast as opposed to the 10 hours.
d. CASTING- Once your kiln is fired up and completed its burnout cyle and depending on the type of metal your pouring will decide the holding temperature of your flask. Also, the thinness of your piece will also make a factor of that as well. If your piece is a very thick solid object your flask should have a lower holding temperature at about 900 degrees F before casting. If it is a very thin web like 3d printed piece 1,025 F is a great temperature for your flask. Each mold and object will completely change this factor. So test pieces individually if you can.
e. METAL CONVERSION- Because DWS does not have a conversion chart like wax to metal type then Fusion 360 has an awesome option in its settings where you can change the object to the type of metal. This will give you the correct metal weights. Multiply that number by 10% to give yourself enough room for extra wax and feeder gates that you had attached in your mold.
NOTE- if you use a lot more feeder gates weigh out the wax ahead of time to be sure to add this weight in to your mold weight. Each casting grain has a different volume of weight. If you buy the metal it will come with a volume weight which is what you will multiply your wax weight by to get a close estimate of how much metal you will need to pour.
f. POURING METAL-
VACUUM- If you are casting using a vacuum be sure to quickly and carefully transfer your flask from the oven to your vacuum surface. Make sure your vacuum is pulling a complete 20cfm and that it maintains that before you pour metal. If it is not DO NOT POUR YOUR METAL. check your flask seal and make sure that its completely on your vacuum. If it still is not pulling a good vacuum check the bottom of your flask for a blow out of your flask. If this happens DO NOT POUR METAL, your mold is not worth wrecking your equipment.
-Metal casting temperatures will all come from your supplier. Rio Grande has casting temperatures on each type of casting metal if they are your metal supplier or for reference. Be sure to clean old metal completely of investment using a sand blaster and ultrasonic. You can use 50% old to new metal as long as you add a flux to your metal. All metals will have different flux which will help them pour better.
CENTRIFUGAL- If you are casting using centrifugal you will need to make sure your metal is ready to cast and quickly pull your flask from the oven. When heating your metal a good visual way to tell your metal is hot enough if seeing the way it is moving in your crucible. Carefully tap or shack your crucible to see the liquidness of your metal. You want it to be watery and past the slump stage so it will flow into your mold.
2. Find a local jeweler/ casting company near you. This will eliminate an extensive investment in equipment. Be sure to tell your caster exactly which resin you are printing with because some resins will burnout and some won't.
Difficulty casting? -
With resins many variables could be affecting perfect casting. If your casting has a lot of porosity often the resin is negatively interacting with your investment during the burnout process. Here is an awesome chart that shows some casting complications and why they might be occurring. http://www.ransom-randolph.com/defect-analysis.ht...
Step 6: Post Process Cleanup/ Finishing
g. QUENCHING- after you poured your metal start a timer for 5 minutes and have a deep bucket of cold water ready to go. Take your tongs around your flask and completely submerge your flask in the water. Maker sure that you shake it around under the water. It will feel like a fish out of water in the tongs. Once it is completely done moving and steaming with CAUTION you should be able to grab your cast piece! By quenching your piece under water you have removed most the investment.
h. INVESTMENT REMOVAL- if some investment is left on your piece you can place your piece in the ultrasonic to remove the rest or if you have access to a sandblaster you can use it on your piece. Alumina silica works best and be sure your pressure is at PSI if you have a delicate piece.
i. SPRUE/GATE REMOVAL- Once your piece is clean, now you can take of your objects form the feeder gate. By using metal gate cutters you can easily remove your pieces. For more accurate removal you can use a jewelers saw. The closest you remove and most accurate now, will be easier to clean up your pieces in the long run.
j. SANDING- Before designing your piece you thought about the feeder gate so cleanup should be minimal. to round surfaces and remove any signs of a feeder gate I like to use a belt sander attachment that can be put on your flex shaft or dremel. If your doing production or larger pieces I highly recommend getting a belt sander to help remove signs of your feeder gate. If your sanding your piece start with a lower grit sand paper (80)grit) and work your way finer 1000 grit. Dont skip from lowest to highest because it will be clearly noticeable in your piece especially when you take your piece to the buffing wheel. Scotch brite (red or green) both work really well to achieve a brush finish to your piece as well as a 3M spider wheel, which can also be attached to your flex shaft or dremel.
k.TUMBLING- Many different tumblers exist. To work harden your pieces a rotary or vibratory tumbler with ceramic media work really well. Cast pieces are less strong so this will help harden them. NOTE: If you have fragile thin pieces they could bend. Also, often times the beads depending on how complex your piece will get trapped inside your piece. you can remove them by hand or using an ultrasonic.
l. POLISHING- If you want to achieve a high polish or mirror polish for your piece be sure to sand your piece completely first. Use a muslin wheel and buffing compounds to shine up your piece. Start with Tripoli compound, and then use Rough. 3D printed piece dont need more compounds most of the time because of the high quality and resolution on the Spark printer.
I cant wait to see what you all come up with now! Good luck! Remember the most important part is the process. Its important to test all methods multiple times if need be and keep going back to the drawing board.