Yihui Casting | Common Defects in Jewelry and Precious Metal Casting: Incomplete Shape/Large Void Causes and Professional Solutions

In the production of precious metals such as gold, K gold, platinum, etc. in jewelry casting, incomplete casting shape (insufficient pouring, cold insulation, lack of flesh, etc.) and large voids (shrinkage, porosity, sand holes, etc.) are two common and far-reaching core defects that directly determine the dimensional accuracy, structural integrity, and finished product qualification rate of castings. They are also the most concerned process difficulties for overseas jewelry brands and custom studios in mass production and single piece production. Yihui Casting has been deeply involved in jewelry and precious metal casting for 20 years. Combining overseas market process requirements with its own mature technical experience, it systematically sorts out the core causes and targeted solutions of two types of defects, supplements directly applicable prevention points, integrates Yihui's exclusive process details, and helps global customers efficiently avoid defects and stabilize production quality.

The core logic behind the formation of two types of defects is clear: incomplete shape is mainly caused by insufficient filling ability of the metal liquid and interruption of the forming process, commonly seen in complex style jewelry castings; Larger voids are mainly caused by the solidification shrinkage of molten metal, gas accumulation, or mixing of molding sand/core sand, and are prone to occur in the thick walled castings of precious metals. Two types of defects often occur simultaneously due to improper process control, especially in overseas jewelry customization and small batch production scenarios. Deviations in process details are more likely to cause batch non conformities. Therefore, it is crucial to accurately identify the causes and implement scientific solutions.

1、 Core causes of casting defects in precious metals for jewelry

Based on the 20 years of overseas customer service experience of Yihui Casting, five core process issues have been identified, all of which are frequent occurrence scenarios in overseas jewelry casting, directly causing incomplete shapes and large void defects. The specific analysis is as follows:

1. Improper operation of wax tree planting (core cause: incomplete shape)

As a key prerequisite for wax loss casting of precious metals in jewelry, the deviation of wax tree planting process is the most easily overlooked problem in overseas small-scale production. If the water outlet branch is too thin or too long, and the auxiliary water outlet connection is not in place or there are blind spots, it will directly increase the flow resistance of precious metal melt, block the filling path, and ultimately lead to insufficient casting and insufficient watering, especially for complex hollow out and delicate textured jewelry styles popular overseas, the impact is more obvious.

2. Low temperature of casting metal liquid (core cause: incomplete shape)

The precise control of temperature parameters of precious metal melts (gold, K gold, platinum) is the core prerequisite for the quality of overseas jewelry casting. Insufficient temperature of the molten metal will significantly reduce the fluidity of the molten metal, making it difficult to smoothly fill complex cavities, especially in small patterns and thin-walled parts of jewelry castings, which are prone to incomplete filling. At the same time, it will increase the probability of cold insulation defects, resulting in gaps at the joints of the castings, which does not meet overseas jewelry quality standards.

3. Low mold temperature (core cause: double defect superposition)

Inadequate pre-treatment of mold temperature is one of the main reasons for batch defects in overseas mass production scenarios. According to the exclusive process standards of Yihui, the temperature of K gold casting molds must be ≥ 700 ℃, platinum casting must be ≥ 900 ℃, and sufficient insulation must be provided; If the temperature of the mold is insufficient or not insulated, the low-temperature mold will quickly absorb the heat of the molten metal, reduce its fluidity, and cause shape defects such as lack of flesh and cold insulation; At the same time, residual wax and moisture in the mold can generate gas and form air resistance, which can lead to defects such as pores and sand holes, directly affecting the quality of the casting.

4. The wax mold is not completely burned out, and the mold baking is insufficient (core cause: large voids)

The negligence in the pre-treatment process of the mold is the core cause of void defects. In overseas jewelry casting, some customers simplify the mold baking process in order to shorten the production cycle, resulting in incomplete burning of wax molds and incomplete burning of molds - residual wax materials will produce a large amount of gas at high temperatures, forming gas barriers. Unburned molds will absorb heat from the metal liquid, hinder flow, and easily cause incomplete casting. They can also cause large-sized voids such as pores, affecting the structural stability of castings.

5. Surface roughness inside the mold cavity/insufficient metal feeding amount (core cause: double defect superposition)

The rough surface inside the mold cavity will increase the frictional resistance of the precious metal melt flow, resulting in the inability of the molten metal to quickly and completely fill the mold cavity, which is prone to shape defects such as unclear contours and local lack of flesh, especially affecting the presentation of delicate textures in overseas jewelry; However, the deviation in the calculation of metal feeding amount cannot meet the requirements of cavity filling and solidification shrinkage, which will directly cause the casting to be partially unfilled. At the same time, due to insufficient metal liquid shrinkage, it will exacerbate cavity defects such as shrinkage and looseness, which will double affect the qualification rate of finished products.

2、 Yihui Casting Exclusive Solution

In response to the five core causes mentioned above, Yihui Casting combines the characteristics of jewelry and precious metal casting with the production needs of overseas customers to launch exclusive solutions that balance process feasibility and cost control, helping overseas customers quickly solve defect problems and improve production efficiency:

1. Standardize the operation of wax tree planting and optimize the structure of the water outlet

Core optimization: Prioritize connecting the metal inlet to thicker parts of the casting to eliminate dead corners; In response to the complex styles of castings popular overseas, multiple auxiliary water outlets have been added to solve the problems of thin, long, and poorly connected water outlet branches. By diverting and reducing pressure, the flow resistance of molten metal is reduced, ensuring all-round filling of the mold cavity, avoiding incomplete shape defects such as lack of flesh and insufficient pouring from the source, and adapting to the casting needs of complex jewelry styles overseas.

2. Accurately increase the temperature of the casting metal liquid

Targeted solution to the problem of poor fluidity caused by low metal liquid temperature: Based on the characteristics of different precious metal materials (gold, K gold, platinum), the temperature of the metal liquid is precisely controlled to reduce the viscosity of the molten gold, enhance its filling ability, effectively reduce incomplete shape defects such as cold shut and unclear contours, and ensure that the delicate texture and fine structure of jewelry castings can be fully presented, meeting overseas quality requirements.

3. Standardized mold temperature control (Yihui exclusive parameters)

Core solution: Raise the oven temperature and strictly follow the 20-year process parameters of Yihui - K gold casting (excluding wax inlay) to raise the oven temperature to 700-750 ℃, platinum casting to 900-980 ℃, and maintain insulation for more than 1 hour before cooling to the pouring temperature. The insulation process can ensure that the wax mold is completely burned out and the mold is fully burned through. Cooling down to the pouring temperature can avoid the influence of high-temperature molds on the formation of the metal liquid. It balances the smoothness of filling and the dimensional accuracy of the casting, and simultaneously solves the dual defects of incomplete shape and voids.

4. Optimize the mold baking process to eliminate wax mold residue

Optimize the mold baking process based on overseas production cycle requirements: reasonably extend the baking time to ensure that the mold is completely burned out and the wax mold is completely burned out, avoiding the formation of gas barriers caused by residual wax materials; At the same time, the exclusive baking process of Yihui is adopted to reduce residual moisture in the mold, solve cavity defects such as air holes and sand holes from the root, and balance production efficiency and quality control to meet the needs of overseas fast reverse production.

5. Optimize the quality of the mold cavity and accurately calculate the amount of metal feeding

Two pronged solution to dual defects: 

① Using fine and smooth casting powder to significantly reduce the surface roughness inside the mold cavity, reduce the frictional resistance of molten metal flow, ensure fast and smooth filling of the mold cavity by molten metal, and avoid unclear contours and local lack of flesh; 

② Taking the weight of wax trees as the core, accurately converting the amount of casting gold not only ensures that the molten gold completely fills the mold cavity, avoiding incomplete shape defects, but also provides sufficient compensation for the solidification shrinkage of the metal liquid, reducing large void defects such as shrinkage and looseness, and reducing the loss of precious metals.

3、 Summary:

In the casting of precious metals in jewelry, the five core processes of wax tree operation, metal temperature, mold temperature, mold cavity quality, and metal dosage directly determine the molding effect and structural integrity of the casting, and are also the most prone to deviations in overseas customer production. Strictly implementing the targeted solutions mentioned above by Yihui, standardizing the process operations in each link, and accurately controlling key parameters such as temperature and size, can effectively avoid common defects such as incomplete casting shape and large voids, stabilize production quality, improve product qualification rate, and reduce production costs.

Yihui Casting has been deeply involved in jewelry and precious metal casting for 20 years, focusing on the core needs of overseas jewelry brands and custom studios, optimizing iterative process technology, and providing exclusive process adaptation solutions according to the production scale and style complexity of overseas customers. We help global customers solve casting defects and create jewelry castings that meet international quality standards.

Yihui Casting Technology Co., Ltd. was established in 2003. After more than 20 years of accumulation, Yihui has now developed into a national high-tech enterprise that integrates research and development, production, sales, consulting, installation, and training of lost wax casting equipment, and provides one-stop solutions for metal casting. Yihui Casting Technology products include metal casting equipment, casting wax, graphite products, quartz products, etc., which are exported to Southeast Asia, the Middle East, Europe, America and other regions. The company has its own R&D team, which independently develops and produces automated vacuum die-casting machines, G20 vacuum bead scattering machines, and intelligent system D3 vacuum pressure casting machines, breaking the industry's long-standing dependence on imported high-performance jewelry equipment.

For more information about Yihui Casting Technology Co., Ltd., please visit our official website or contact our team.website: www.yihuicasting.com      email : info@yihuicasting.com     whatsapp : +86-13802830498