Watch Case Titanium Alloy Lost-wax Casting

o Design and Engraving: Based on the watch case design drawings, a 3D model is created using Computer-Aided Design (CAD) software. Then, a wax model prototype is created through CNC machining or hand engraving. The dimensional accuracy and surface quality of the wax model directly affect the final quality of the watch case; therefore, tolerances must be strictly controlled during the manufacturing process.

o Wax Model Replication: The wax model prototype is placed in a special mold, liquid wax is injected, and after the wax cools and solidifies, the wax model is removed. This yields multiple wax models identical to the prototype. During replication, attention must be paid to the wax temperature and injection speed to avoid defects such as air bubbles.

o Tree Assembly: Multiple wax models are connected together using wax rods to form a wax model group, also known as a "tree." The tree assembly method must be rationally designed according to the shape of the watch case and the casting process to ensure that the molten metal can evenly fill the mold during subsequent casting.

o. Coating: Immerse the wax model assembly in a coating containing refractory materials (such as silica sol, zircon sand, etc.) to evenly cover the surface of the wax model. The coating's function is to form a high-temperature resistant outer shell during the casting process, protecting the wax model from being melted by the molten metal.

o. Sand Sprinkling: Immediately after coating, place the wax model assembly in a sand box and sprinkle a layer of refractory sand, allowing the sand particles to adhere to the coating surface. The sand particle size and material must be selected according to the casting process and the requirements of the watch case. Generally, coarse sand is used for the bottom layer, and fine sand for the top layer to ensure the strength and surface quality of the case.

o. Drying and Hardening: Place the coated and sand-sprinkled wax model assembly in a drying chamber for drying and hardening. The drying temperature and time must be controlled according to the type of coating and environmental conditions to ensure sufficient strength and breathability of the case.

o. Repeated Coating and Sand Sprinkling: To ensure the thickness and strength of the case, the coating and sand sprinkling process needs to be repeated, generally 3-5 times, until the case reaches the required thickness.

o Steam Dewaxing: The prepared wax mold is placed in a high-pressure steam dewaxing kettle. The high temperature of the steam melts the wax mold, allowing it to flow out of the shell. The steam pressure and temperature must be controlled according to the melting point of the wax and the strength of the shell to ensure complete wax removal without damaging the shell.

o Firing: The dewaxed shell needs to be fired to remove residual wax and moisture, improving its strength and permeability. The firing temperature and time must be controlled according to the material and thickness of the shell, generally at 800-1000℃ for 2-4 hours.

o Titanium Alloy Melting: The selected titanium alloy raw material is placed in a vacuum induction melting furnace and heated and melted under vacuum. The vacuum environment prevents the titanium alloy from reacting with oxygen, nitrogen, and other elements in the air during the melting process, ensuring the purity and performance of the alloy. The melting temperature and time must be controlled according to the alloy composition and the performance of the melting equipment, generally at 1600-1800℃ for 10-20 minutes.

o Pouring: After the titanium alloy is completely melted, the molten metal in the furnace is poured through the gate into the preheated watch case. The pouring speed and temperature must be controlled according to the shape and size of the watch case to ensure that the molten metal fills the entire mold while avoiding defects such as porosity and inclusions.

o Cooling: After pouring, allow the watch case to cool naturally within the mold. The cooling rate should be moderate; too rapid a cooling rate may cause defects such as cracks, while too slow a cooling rate will affect production efficiency.

o Case Removal: Once the watch case has cooled to a certain temperature, the outer shell is removed using mechanical or chemical methods to obtain a pre-formed watch case.

o Cleaning and Polishing: The removed watch case is cleaned to remove residual sand particles and oxide scale from the surface. Then, the watch case is polished using polishing equipment to make its surface smooth and flat, meeting the design requirements for size and surface quality.

To improve the mechanical properties of titanium alloy watch cases, heat treatment can be applied. Common heat treatment processes include solution treatment and aging treatment. Solution treatment can make the alloying elements in the alloy more uniformly distributed, improving the alloy's strength and toughness; aging treatment can further improve the alloy's hardness and strength.

o Polishing: Through mechanical or chemical polishing, the surface of the watch case achieves a mirror effect, improving the watch's aesthetics.

o Coating: To improve the wear resistance and corrosion resistance of the watch case, a coating treatment can be applied to its surface. Common coating processes include physical vapor deposition (PVD) and chemical vapor deposition (CVD). Types of coatings include titanium nitride and titanium carbide; different coating materials can give the watch case different colors and properties.

o Anodizing: Through anodizing, an oxide film is formed on the surface of the watch case, which not only improves the watch case's corrosion resistance but also gives the watch case different colors, meeting consumers' personalized needs.

* High Precision and Complex Shapes: Lost-wax casting can produce watch cases with complex shapes and high precision, meeting the diverse needs of watch design. Compared with traditional machining methods, lost-wax casting can reduce processing steps and improve production efficiency.

* Material Performance Advantages: Titanium alloys have advantages such as low density, high strength, and corrosion resistance, making watch cases both lightweight and durable, suitable for long-term wear.

* Good Biocompatibility: Titanium alloys have good biocompatibility and will not cause allergic reactions, making them suitable for people with metal allergies.

* Higher Costs: The price of titanium alloy raw materials is relatively high, and the equipment and process costs of lost-wax casting are also high, leading to increased production costs for watch cases.

* High Process Difficulty: The melting and casting process of titanium alloys needs to be carried out in a vacuum environment, requiring high-level equipment and processes. At the same time, the lost-wax casting process is complex, requiring strict control of process parameters at each stage; otherwise, defects are prone to occur.

* High Quality Control Difficulty: Because the production process of titanium alloy watch cases involves multiple steps, quality control is quite challenging. A comprehensive quality inspection system needs to be established to conduct rigorous quality inspections at every stage, in order to ensure the stability of product quality.