Jewellery and 3D Printing: Jewel Casting Revolution

The art of jewellery crafting has been with us for thousands of years. With mould casting the manufacturing process of choice, it requires skilled artisans to manage every single detail with refinement.

On the other hand, 3D printing is revolutionizing the way we do manufacturing. Jewellery is not the exception, on the contrary, it is one of the industries that have beneficiated the most out of this. And even when talking about small entrepreneurs and designers, desktop 3D printers are becoming more accessible each year.

Investment Casting

Out of all casting methods, investment casting or lost wax casting is the choice for jewellery. Since accuracy and surface finish are indispensable requirements for jewellery making, other casting methods like sand casting, wouldn’t be enough to achieve this.

On the other hand, materials used in jewellery like platinum, steel or tungsten require high melting points that can’t be handled with plaster casting, for example. It is also a fast and easy method for achieving the final product.

Investment casting consists of creating a mould from a wax figure known as a pattern. Then submerging it in refractory material or investment, which hardens to reproduce the shape. During the process, the wax evaporates to leave the hollow cavity where molten metal is cast.

Traditional investment casting requires a meticulous hand made work to create a pattern, which is time-consuming and requires an exceptional skill for details. With CAD modelling and 3D printing, this is a thing of the past.

An Alternative to Traditional Sculpting

To produce a pattern there was a need for sculpting a master pattern of hard materials like wood, clay and plastics to create a mould where the wax pattern would be created. Thanks to CAD modelling you can skip the sculpting process to get a master model.

CAD software allows you to modify your model for your needs and ensures dimensional accuracy. Experimenting with complex geometries wouldn’t need exceptional skill, which means creative freedom for experimentation on design.

With 3D printing, you can create a wax pattern with the same quality on resolution and surface finish as traditional wax patterns. It’s important to clarify that what is referred to wax, isn’t wax in the strict sense, but any resin that satisfies the requirements for the investment casting process. Thankfully, castable resin exists for 3D printing. So, you can skip all those steps that involve pouring wax on a mould.

Taking into account how digital technologies would alter the jewellery market:

• A 3D model eases how you preserve, modify and experiment with your design, saving up time and costs.
• Jewellery production is tied to customization. The jeweller has to adapt his design to customer wishes. Digital technologies improve communication on the design process and prototyping. Customer feedback is more present than ever.
• Even with the best craftsmen, some details are exceptionally difficult. 3D technologies can achieve beyond what the human hand can do.
• 3D models allow spread ability. You can easily send and replicate your model for casting anywhere in the world. Moreover, with just one printing, many wax patterns can be made.
• With high-quality desktop printers being more accessible than before, independent jewellers can benefit from this business. This would mean, the jewellery business is inevitably decentralizing.  

Workflow

Direct investment casting has a workflow that is reduced in the first steps with the help of 3D technologies. The rest of the process hasn’t changed. The following are the steps for manufacturing a piece of jewellery.

Modeling

Every CAD software can create a jewellery design, but there are some made specifically for the matter. CAD allows for different design and evaluation options in order to guarantee smooth and precise results.

Sprues, which are feed channels that improve mould filling, can be designed directly from the software. They also work as support for intricate parts.

Printing

When 3D printing a wax pattern, there are two main considerations to take:

• Printer accuracy and resolution for small delicate parts
• The material has the properties needed for investment casting

For this objective, stereolithography (SLA) is the method of choice. Since SLA printers are one of the most precise methods, also there are photocurable resins that are able to cast. We recommend the Formlabs Form 3. Not just because is the market leader for desktop resin printers, but because of its friendly relation between cost and quality.

Depending on the resin of choice, the process will vary. Some are easier to work with than others. Each resin reacts differently to how thick supports must be and how they are applied. Both washing and post-curing steps depend on the resin.

While some resins harden fast and easy without the need for a post-curing light, some require more skill to avoid failure. Even for a sanding process, there are better castable resins than others.

Since Formlabs has lead development on 3D printing integration into investment casting, two very reliable options for resins have come out of this: Formlabs Castable Resin and Formlabs Castable Wax Resin.

In the end, what’s most important is that material evacuates efficiently without damaging the investment or leaving residue during the burnout.

We are currently printing a motorbike carburettor using the castable wax resin on the Form3 printer, which you can see in the video below

Wax tree assembly

Before preparing the mould, patterns must be connected to the main sprue bar through branch sprues. With the help of sticky wax and a heat pen, connections must be made in a smooth way to guarantee optimal casting material flow. The main sprue must be firmly attached to a rubber base. This assembly is called a sprue tree, because of its final shape.

One of the main concerns of investment casting is bubbles sticking to the wax surface. To avoid this issue, wax patterns must be dipped in a surfactant coating solution before investment.

Apply investment

The investment comes in powder form, then mixed in water. Too much water into the mix involves a weaker mould, but too few will make the mix more viscous and harder to degas. Recommended proportions are often provided by the manufacturer.

At the same time, a flask is tightly adjusted to the spur base. While pouring the investment solution there should be special care for bubbles, we highly recommend using a vacuum chamber.

After that, just let the mould rest until it gets hard and dry, then retire the rubber base.

Burnout

After the mould is dry enough, the flask goes into the oven to completely vaporize the resin. This is arguably the most delicate step, as heating requires optimal temperatures, times and rates for everything to work nicely. In other words, there is a need to establish a burnout schedule before heating. It may vary depending on the following:

• Flask size
• Investment properties
• Resin type

After heating for some hours, the mould should be ready.

Casting and Finishing

Finally, molten metal is poured into the cavity. Manufacturers must make sure the mould surface is hot enough for the metal to flow without solidifying. Fastening the flow is important to make sure the material fills the cavity, a centrifuge promises a nice result. After hardening put the mould on the water to retire the casting. After cutting the spurs, the only thing left is to clean and polish the surface to get the finishing details.

Solid Print 3D are here to help you make the right decision with your next 3D Printer purchase. For more information, please call Solid Print3D on 01926 333 777 or email on info@solidprint3d.co.uk