Using 3D Printing to Create Custom Jewelry
Access 3D Services is able to utilize 3D printing to create custom jewelry and other small items by using 3D printed models to create castable molds. Molding a 3D printed model creates a silicone mold containing a cavity that retains all of the surface details of the original model which will then be transferred to whatever material is used for casting. The silicone mold can be cast with various resins or even some metals, or can be cast with wax in order to create a model for lost-wax investment casting. This process would allow one to recreate the 3D printed model in a variety of materials, from castable plastic up to gold and other precious metals. Let’s take a look at the process of turning a 3D model into a cast epoxy resin pendant that can be reproduced multiple times and has a smooth, glossy finish.
1) First, a 3D modeling program is used to design an object. I took the basic shape from a piece of existing jewelry I liked and turned the 2D shape into a 3D object in Tinkercad, however more serious designers will want the vast functionality of a real 3D modeling program like Solidworks, Audodesk Fusion 360, OnShape, Blender or other 3D design software. Once the design is complete a flat plate is added to a flat surface of the object which will be the pouring opening in the mold. Two piece molds or cut molds are different and require a sprue hole for filling, however our heart pendant has a large flat surface for pouring.
2) Once the model is completed a mold box is designed around the model, encasing 5 sides with a 2mm wall with a few mm of space around the object in every direction and at least 5mm of space above the object. For example, a 5mm tall model should have a 12mm tall mold box (2mm base, 5mm object height, 5mm additional space).
3) The completed 3D model and mold box are exported as solid mesh files in the STL file format. The small and precise jewelry model will be 3D printed on a DLP 3D printer, whereas the mold box will be printed on a FDM 3D printer. A DLP printer uses a projector to cure UV reactive resin and is able to create small objects with much greater accuracy and precision than a FDM 3D printer, which melts thermoplastic and applies it one layer at a time to a flat surface.
4) Once both the custom pendant and the mold box are 3D printed any extraneous zits, dots or other imperfections are removed and the pendant and the interior of the mold box are treated with Smooth-On XTC-3D resin coating. This coating is brushed on and is a self-leveling resin that will fill any layer lines or other imperfections in the print leaving the printed object with a perfectly smooth, shiny surface. Because silicone molds will pick up the surface finish of the object being cast this step is essential in being able to create glossy resin objects like this pendant.
5) Once the resin coating is fully cured the pendant is placed in the mold box and the volume of the space in the box is measured with water and an industrial syringe. The pendant and mold box are then dried and the pendant is taped or glued into the mold box with the flat surface secured to the bottom. A two part silicone is mixed up, in this case Smooth-On MoldStar 20T, and is poured into the mold box and surrounds the 3D printed model. The silicone is filled up to the top of the mold box, completely covering the entire model, and is allowed to cure for the designated time for that silicone (30 minutes for MoldStar 20T). MoldStar 20T is self-degassing and does not require vacuum degassing. Although it does retain some small bubbles within the silicone the bubbles are isolated to solid silicone and always migrate away from the surface so they have no impact on the surface quality of the cast material.
6) Once the silicone has cured the mold is pulled free from the mold box. Any extraneous silicone is cut free with a utility knife and the mold is cleaned with soap and water. The mold is then ready for use for casting various resins, wax or even chocolate!
This mold was created for our affiliates at Resin Wares who work exclusively with Epoxy Resin, however in order to continue the process to create a pendant out of gold you would pour wax into the silicone mold and continue the investment casting process. Investment is a type of plaster that is resistant to heat and can be used to cast metals including silver and gold. Each investment mold is used only once then is broken to extract the metal casting, so a reusable silicone mold of an item allows for the fast reproduction of investment casting molds and the resulting items.
Using the above process Access 3D Services can take a 3D design and turn it into a 3D printed item which we can then create a silicone mold out of. The cast item will retain the glossy surface of the printed item thanks to a coating of resin, so the finished piece will retain this same glossy surface finish. This process allows for the rapid reproduction of items that require a consistent surface finish or for the production of investment casting molds and this process has revolutionized the way custom jewelry is made!
Article by Joe Eckert, Operations Director, Access 3D Services
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