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Common Manufacturing Processes for Smart Locks

The industry predominantly employs two forging techniques: die-casting and CNC precision carving. Here's a brief overview of each process:

Die-Casting Method:

1. Design appearance and product structure, then 3D print samples for testing. 2. Select components and establish production processes. 3. Develop molds for the product and its components. 4. Conduct trial assembly and optimize the product.Begin mass production.

Note: Die-cast products typically take 2–3 months or longer to transition from development to mass production.

CNC Precision Carving:

1. Design appearance and product structure. 2. Establish production processes. 3. Create samples using machining and optimize. 4. Finalize optimizations and begin mass production.

Note: CNC-carved products usually require only about one month to move from development to production.

These two methods dominate the industry, though small quantities of copper and stainless steel products are also available.

Key Differences Between Die-Casting and CNC Carving

Die-Cast Products:

Most products use zinc alloy and aluminum alloy. Initially, zinc alloy was favored due to its high-quality finish and durability. However, aluminum alloy has since become the preferred material for cost efficiency. Aluminum products often feature baked paint or powder-coated surfaces, which are more economical but lack the premium feel of electroplated zinc alloy finishes.

CNC-Carved Products:

These products frequently utilize 6063 aerospace-grade aluminum. The process involves creating molds for profiles, which are then machined. The surfaces are typically treated with anodizing for durability and a brushed finish for aesthetics, though the high cost of this process is a notable drawback.

Material Characteristics

The forging materials for smart locks are mainly divided into base materials for the lock body and surface materials. Currently, the common base materials in the smart lock industry include aluminum alloy, aerospace aluminum, zinc alloy, and stainless steel. For surface materials, tempered glass and acrylic are widely used.

The base materials for smart locks mainly include the following:

1. Aluminum Alloy

Regular aluminum is commonly used as a base material for low-end smart locks. Its cost is only one-quarter of zinc alloy. However, it has low surface hardness and weak material strength. It cannot undergo fine polishing and is mostly treated with basic spray painting or glaze sealing. Its characteristics include a rough surface and low hardness. It can also be electroplated to achieve a matte texture on the surface. However, due to the uneven base material, the electroplated layer is prone to fading.

2. Aerospace Aluminum Alloy

This generally refers to 6-series and 7-series aluminum alloys, known for their precision casting, ease of machining, and aesthetically pleasing metal edges. It is lightweight, with high density and strength, but relatively poor toughness. These materials are commonly used in minimalist-style fingerprint locks and ultra-thin fingerprint locks. Surface treatments typically include anodizing (for a matte finish) and brushing (which offers low wear resistance).

3. Zinc Alloy

Zinc alloy is currently the most widely used base material in the industry. It is characterized by high density, strong toughness, and excellent malleability. Through high-temperature melting in a zinc alloy die-casting machine, it is cast into shape, with hole positions and structural designs formed in a single process.

After brushing, it undergoes electroplating for coloring, resulting in a faux copper texture. However, its resistance to lateral abrasion is relatively low. Chrome plating is the most commonly used surface treatment process. The coating thickness is no more than 1 micron, providing extremely high surface hardness, above 8 Mohs hardness, along with excellent corrosion resistance and weatherability.

The vacuum electroplating process involves first plating with chrome, followed by electroplating with gold in an oxygen-free environment (the "gold" here is not actual gold but a chemical liquid). This process requires a complete set of procedures and is more costly. The surface hardness is higher than chrome plating, with better oxidation resistance. Metallic baked paint has a smooth and attractive surface, but it is prone to damage from impacts.

4. 304 stainless steel

Stainless steel has high hardness and is difficult to process. It is mostly made from 2mm steel strips, stamped into shape, and laser-cut for holes. It is challenging to form shapes and cannot be stamped with sharp corners. 

The original color surface material is brushed, with the curved areas polished using water grinding, resulting in a smooth and glossy finish. While there is no risk of color fading, the brushed surface has a micro-burr texture, and the base color is a solid hue, making it prone to staining and residue accumulation, which can affect its visual appearance. After water polishing, the surface is electroplated with gold. However, due to the characteristics of the base material, the color is unstable, and the surface hardness is lower compared to chrome plating, making it more susceptible to scratches.

5. Copper

Due to its high cost, copper is mainly used for villa locks. It is cast and processed through machining.

Surface treatment techniques include oxidation coloring, brushing, and original sandblasting. The coloring of electroplating is unstable. The surface material is relatively soft, with high repairability.

Copper metal is highly resistant to corrosion and does not easily change color. Over time, it naturally oxidizes and becomes more beautiful.

The main surface materials for smart locks include the following:

6. Acrylic Panel

Acrylic material is relatively soft, with low surface hardness and is not resistant to scratches. It cannot be shaped into curves, and corners and holes must be cut to form.

7. Tempered Glass

Tempered glass has extremely high hardness, is scratch-resistant, and has high strength. However, its cost is five times higher than acrylic. It is difficult to process and cannot be bent.

8. 5A Diamond-Coated Screen

This refers to an acrylic panel with an IMD (In-Mold Decoration) surface coating that has a layer of nanomaterial, reducing friction and enhancing abrasion resistance.

Surface Treatment Processes

1. IML In-Mold Labeling

In-Mold Labeling is a notable process where a hard transparent film is formed on the surface, with a printed pattern layer in the middle and a plastic layer at the back. The ink trapped between the layers helps protect the surface from scratches and improves abrasion resistance, while maintaining vibrant colors that are resistant to fading over time.

2. Anodizing

Anodizing is the process in which aluminum and its alloys form an oxide layer on the surface (anode) when subjected to an electric current in a specific electrolyte solution under controlled conditions. If not otherwise specified, anodizing usually refers to sulfuric acid anodizing.

3. Sandblasting

Sandblasting is a process where high-speed sand flow impacts and roughens the surface of a substrate. The abrasive materials' impact and cutting action clean and roughen the surface, improving mechanical properties. This process enhances fatigue resistance, increases adhesion between the substrate and coatings, extends the durability of the coating, and aids in paint leveling and decoration. After electroplating, sandblasting gives the surface of the smart lock a matte finish, strong oil resistance, and a uniform color tone.

4. Varnish Sealing

Varnish sealing involves injecting a high-polymer glaze into the pores of the paint surface, forming a strong, net-like protective layer. This effectively reduces scratches, thereby protecting the paint surface.

5. Polishing

Polishing refers to the process of reducing the roughness of a workpiece surface using mechanical, chemical, or electrochemical methods to achieve a shiny, smooth surface. It involves modifying the surface of the workpiece using polishing tools, abrasive particles, or other polishing media.

6. Brushed Finish

Brushed finishing is a surface treatment that creates linear textures on the workpiece surface through grinding. This treatment provides a decorative effect and highlights the metallic feel of the material, making it increasingly popular and widely used by users.

7. Spraying

Spraying is a coating method where a spray gun or disc atomizer, using pressure or centrifugal force, disperses the coating material into fine, uniform droplets which are applied to the surface of the object. It can be categorized into air spraying, airless spraying, electrostatic spraying, and various derived methods of the basic spraying forms.

8. Baking Paint

Baking paint involves spraying several layers of paint onto a substrate that has been roughened to a certain degree (usually high-density board), followed by high-temperature baking to set the paint. This process requires high-quality paint and offers excellent color visibility.

9. Zinc Alloy Electroplated Enamel Color Coating

This involves electroplating zinc alloy with a twisted branch pattern, followed by enamel coloring. The image (showing a Middle Eastern export model from Meilun Meikai) fails to fully represent the texture, but the actual red base color is very dense, with a glossy outer layer resembling thick glass. This technique was developed in collaboration with a domestic enamel craftsman, and the technical details remain confidential.