F.A.Q.

Spin casting is a casting method that uses centrifugal force to distribute molten metal into a mold. The process starts by heating the metal until it becomes liquid. The molten metal is then poured into a silicone rubber mold, which is pressed between two plates of a special centrifuge that rotates it rapidly. The centrifugal force pushes the metal towards the outer walls of the mold so that the metal takes on the desired shape. After the metal has solidified, the mold is stopped and opened to extract the finished part. This technique is particularly useful for creating small, detailed objects such as buckles, buttons, costume jewellery components or model parts.

Spin casting is used in various industrial applications, exploiting its ability to produce detailed, high-quality parts. Here are some of the main applications:

• Buckles: Used extensively to produce belt buckles, where precise details and a good surface finish are required.
• Clothing accessories: Widely used to create unique, customised clothing accessories, such as buttons, clasps and other decorative elements requiring fine detail and heating elements.
• Costume jewellery: Suitable for creating costume jewellery components, such as necklaces, bracelets and earrings, which benefit from the property of reproducing fine details.
• Model-making components: Ideal for small model parts, such as model train, car and aircraft components, which require high precision.
• Promotional items: Medals, badges and commemorative coins are frequently produced by spin casting, due to the superior surface quality and precise detail.
• Furniture components and hardware: The technique is used for handles, knobs and decorative hardware for furniture and doors, enabling the faithful reproduction of complex designs.
• Toy parts: Small metal toy parts, which often have high aesthetic requirements, are effectively produced through spin casting.

Metals with a low melting point, such as zamak and tin alloys, can be used in spin casting. These materials are ideal because they can be melted at temperatures that allow silicone rubber molds to be reused several times.

Spin casting offers several advantages:

• Reduced tooling costs: The silicone rubber molds used in spin casting are less expensive to produce than the metal molds required by other casting techniques.
• Flexibility in production: It is ideal for small production runs or prototyping, allowing rapid and low-cost changes.
• Detail and precision: Centrifugal force helps fill the mold completely, allowing for fine detail and high fidelity to the original model's features, making it perfect for creating small, complex objects such as jewelry and model components.

Spin casting is generally not ideal for creating large components. This method is more suitable for small, detailed objects because of the physical limitations of silicone rubber molds and the technique itself. Rubber molds may not withstand the weight and pressure of molten metal needed for large parts. In addition, managing the centrifugal force required to properly fill a large mold may be technologically demanding and less efficient.
 

In centrifugation, efficient management of materials is critical to minimize waste and environmental impact. During the process, sprues, which are the excess solidified metal, can be easily recycled in subsequent production cycles. This means that almost all of the metal used can be reused, and waste is mainly limited to the collection of impurities from the surface of the molten metal. These impurities are removed with a skimmer before the metal is poured into the mold, thus ensuring that the final product is of high quality and that waste material is minimized.

Our customers can count on more than 50 years of experience in spin casting. We offer specialized consultations both at the plant start-up stage and at customers' sites. We also provide remote support to quickly and accurately resolve major issues, offering detailed technical advice and guidance. Our goal is to ensure that you get the best possible results, maximizing the potential of spin casting.

Two silicone rubber discs are used to make a spin casting mold. Models of the object to be produced are placed radially on the lower disc, then the upper disc is overlaid. The assembly is closed with a molding box and inserted into a vulcaniser, a thermal press that hardens the rubber. After vulcanisation, the mold is cooled and opened, the models are removed and the feed channels connecting the centre of the mold to the negative impressions are made.

Determining the most appropriate rotation speed and pressure to be applied to the mold in spin casting is essential to ensure the quality of the parts produced. Here is how to proceed:

Rotational speed:

• Analysis of part geometry: The shape and size of the part influence the required speed. Fine details and fine structures may require higher speeds to ensure that the molten metal completely fills the mold cavities.
• Material properties: More viscous materials, such as zamak, may require higher speeds to effectively fill the mold, while more fluid alloys, such as tin alloys, may be processed at lower speeds.
• Mould diameter: The diameter of the mold plays a key role in determining the speed of rotation. A larger diameter requires an adequate speed to generate the centrifugal force necessary to distribute the material uniformly through the mold without compromising the details or causing imperfections.
• Practical experimentation: Theory must always be backed up by practice. The production of test parts is essential to refine the rotation speed. By adjusting the speed according to the results obtained and the imperfections observed in the parts, the optimal configuration can be arrived at.

Pressure to be applied:

• Leakage control: The pressure must be sufficient to prevent molten metal from escaping from the mold edges.
• Avoid deformations: The pressure must not be so high that it deforms the negatives of the mold, as this would cause crushing on the finished parts.
• Balancing: It is important to find a balance that keeps the metal inside the mold without causing deformation, thus ensuring the quality of the finished parts.

By following these principles, the ideal combination of rotation speed and pressure can be determined, ensuring high quality parts and minimising defects and rejects.

Spin casting is particularly effective for small- and medium-series production. Although it is generally not the best choice for very high volumes, such as those handled by pressure casting techniques, it offers significant advantages for limited runs:

• Cost reduction: Silicone rubber molds are less expensive than metal molds, making it cost-effective to produce moderate quantities of parts.
• Speed of setup: Molds can be prepared and modified quickly, allowing great flexibility in production and experimentation with brand new designs without major investment.
• Quality and detail: Spin casting allows for parts with very fine detail, which is ideal for specialized markets that require high quality and precision, such as the jewelry or precision model industry.