How to Pre Set Stones Using Castable Resins in 3D Printing
Pre Setting Stones with Castable Resins in 3D Printing
Stone setting represents a crucial and highly important phase in jewelry creation. Various stone setting techniques exist, each with specific features and a distinctive design. Consequently, the role of the setter is gaining increasing specialization and is becoming more sought after in the industry. Common methods include claw (prong) setting, grain (bead) setting, pavé setting, bezel setting, and invisible setting.
In recent years, the growing need to optimize production times and increase productivity has led to an increasingly widespread practice: the pre-setting of stones directly onto wax models before the investment casting phase. Simultaneously, the rapid and widespread adoption of 3D printers specifically designed for the jewelry industry has generated a growing demand for castable resins suitable for this stone pre-setting technique.
An ideal castable resin for pre-setting stones before casting must possess specific characteristics: high elasticity to accommodate the stone during setting; an extremely low melting point to facilitate subsequent burnout removal; a burnout that leaves no ash or carbon residues (clean burnout) to preserve the integrity of both molten metal and stones; high dimensional accuracy to ensure a perfect seat for the gem; and the ability to be printed in very thin layers to achieve complex details in the settings.
WHAT STONES CAN BE USED IN PRE SETTING
Thanks to the advent of increasingly high-performance castable resins, 3D printing technology for jewelry now offers a practical solution for companies wishing to produce jewelry with pre-set stones, opening new frontiers in both design and production. However, it is essential to consider that not all types of stones are ideally suited for pre-setting. Among the most commonly used gems for this technique are diamonds, rubies, sapphires, and cubic zirconia.
In this context, selecting stones capable of withstanding the temperatures required for the most commonly used burnout cycles becomes crucial. It is appropriate to consider some data regarding the maximum temperatures not to be exceeded to avoid damage to the stones during the burnout process:
Diamond cast in place temperature: 630 - 650 °C
Rubies cast in place temperature: 640 - 660 °C
Cubic Zirconia cast in place temperature: 650 - 690 °C
Other synthetic stones cast in place temperature: 660 - 720 °C
3D RESIN FOR STONE PRE-SETTING
When opting for pre-setting using castable resins for 3D printers, it is imperative to keep in mind the thermal sensitivity of the stones and, consequently, to select a 3D resin with a low melting point. Resins such as X-One https://www.bluecast.info/x-one and X-Nova https://www.bluecast.info/x-nova are examples of castable materials for jewelry specifically developed for this type of application.
PREPARE THE 3D DESIGN
As usual, creating an accurate 3D model is the first step and of fundamental importance to the success of the process. For precious stone settings created on 3D models printed in castable resin, once the desired dimensional precision has been achieved in the design phase, it is generally not necessary to make modifications or apply compensation factors for material shrinkage. During the 3D file preparation stage, it is essential to consider that during the burnout cycle, the stones must be securely held in place by the investment material and not by the resin model itself, which will be eliminated, creating a void in the mold. Therefore, it is always advisable for the stones to partially protrude from the model and for their girdle (the widest part of the stone) to be fully exposed to be embraced by the investment, thus ensuring stable retention during the casting process. It is also useful to include a small hole underneath the stone, so that it is retained from both the top and bottom by the investment material.
INVESTING AND BURNOUT FOR STONE PRE-SETTING
When preparing the investment material, it's advisable to follow the procedures outlined in the dedicated reference documents. The ratios of liquid to powder, along with mixing durations and vacuum application times, should align with the standard parameters specified for the particular investment compound in use. For castings that include pre-set gemstones such as diamonds, it's strongly advised to incorporate boric acid into the investment mixture, using a proportion between 1.5% and 2% by weight. During the burnout cycle, when peak temperatures are reached, boric acid is believed to form a glass-like coating over the stones. This vitrified layer acts as a barrier, helping to protect the diamonds from exposure to the oxidizing environment of the furnace, thereby minimizing the risk of surface damage or discoloration.
For the burnout cycle specific to stone pre-setting, the following temperature and ramp programming is recommended for X-One and X-Nova Castable Resins:
Synthetic stone burnout
From room temperature to 150 °C with a heating ramp of 8 °C per minute.
Hold at 150 °C for 2 hours.
From 150 °C to 670 °C with a heating ramp of 8 °C per minute.
Hold at 670 °C for 5 hours.
Natural stone burnout
From room temperature to 150 °C with a heating ramp of 8 °C per minute.
Hold at 150 °C for 2 hours.
From 150 °C to 630 °C with a heating ramp of 8 °C per minute.
Hold at 630 °C for 7 hours.
Recommended for X-One V2 resin
It is crucial to note that insufficient flask temperatures—especially when using lower-grade castable resins—can result in several casting issues. These may include traces of incompletely burned resin, poor metal surface finish, and inadequate mold filling. Such problems are greatly diminished, and in many cases eliminated, when employing high-performance castable resins specifically engineered and thoroughly tested for use with pre-set gemstones.
CASTING PROCESS FOR STONE PRE SETTING
There are no strict limitations on the casting method to be used with the pre-setting approach. However, care should be taken to avoid applying excessive force during metal injection, as it may cause metal flashes to extend over the surface of the embedded stones. These metal excesses can typically be removed later using specialized equipment. A broad spectrum of metal alloys is compatible with this technique. The use of a reducing atmosphere during casting is also beneficial, as it helps minimize oxidation of the molten metal. Standard casting parameters—including melt temperatures, flux application, protective gases, and the ratio of fresh to recycled metal—can be managed according to established procedures. Overheating should be avoided; however, raising the metal temperature by approximately 55 to 83 °C (100 to 150 °F) above its liquidus point is usually sufficient to ensure a successful pour for most jewelry alloys.
DEVESTING PROCEDURE
The devesting procedure for castings that include gemstones differs significantly from standard methods. Precious stones, due to the differential thermal contraction between the metal, the investment, and the gem itself, as well as due to mechanical stresses and potential contraction of the metal during cooling, are particularly susceptible to cracking or breakage if subjected to sudden cooling from high temperatures. Therefore, it is strongly advised to allow the flask to cool gradually to room temperature for at least one hour before immersing it in water to remove the investment and the casting tree. This precaution helps minimize thermal shock to the stones and preserve their integrity.
