The processing technology for the production of the casing needs to be deeply matched with the selected materials (metal/plastic/composite materials), structural complexity and mass production requirements. The core objective is to achieve the three core requirements of "forming, precision and surface texture". The following is a detailed breakdown of common processing methods classified into four major categories: metal casing process, plastic casing process, composite material process, and general post-treatment process

I. Metal Casing: Emphasizing "strength forming" and "Precision cutting"

Metal casings need to balance structural strength and dimensional accuracy. Common processes revolve around "sheet metal processing" and "precision cutting", and in some scenarios, casting processes need to be combined to achieve complex structures.

Sheet metal processing (applicable to flat/simple curved surface structures such as steel plates and aluminum plates)

Sheet metal is the mainstream process for metal casings (especially in mass production), which is formed through "cold working" without melting the metal. The core steps include:

Stamping forming: By using a press and dies to apply pressure to metal sheets (with a thickness typically ranging from 0.5 to 3mm), the four major functions of "shearing, punching, bending and stretching" are achieved.

For example: the heat dissipation holes on the outer shell of the distribution box (punched holes), the clips on the bottom shell of the laptop (bent), and the metal inner pot of the rice cooker (stretched).

Advantages: Extremely high efficiency (capable of charging 10-20 times per second), suitable for million-level mass production; The cost is low, and the unit price of the mold is controllable after one investment.

Limitations: It is only suitable for thin-walled and simple structures, and cannot be processed into deep cavities or complex three-dimensional shapes.

Laser cutting: It uses high-energy laser beams (fiber laser/CO₂ laser) to perform high-precision cutting on metal plates, capable of processing any complex patterns (such as irregular holes, hollowed-out patterns).

Applicable scenarios: Customized casing (such as special interface holes for industrial equipment), small-batch production (no need to open molds, high flexibility).

Advantages: Extremely high precision (error ±0.1mm), no mechanical stress (smooth cutting surface, no need for secondary grinding);

Limitations: Slower than stamping, and higher mass production cost than stamping.

Bending/rolling:

Bending: Use a bending machine to bend metal plates into fixed angles such as 90°, 135°, etc. (such as the corners of a computer case, brackets).

Rolling: Use a rolling machine to roll metal plates into cylindrical, arc-shaped or other curved surfaces (such as cylindrical equipment shells, pipe guards).

The key requirement is to calculate the "bending coefficient" (metal will rebound after bending, and the dimensions need to be compensated in advance) to avoid precision deviations.

2. Precision cutting processing (suitable for medium and thick plates/complex structures of aluminum alloys, magnesium alloys, etc.

When the casing requires high flatness and complex three-dimensional structures (such as deep cavities, steps, and threaded holes), a "material removal" cutting process should be adopted, with the core being CNC machining:

CNC milling: Through the high-speed rotating tool (milling cutter) of A CNC milling machine, excess material is milled from metal blanks (such as aluminum alloy blocks) to form complex 3D structures (such as the concave-convex texture on the A side of a notebook computer, the sealing groove of an industrial controller).

Advantages: Extremely high precision (error ±0.05mm), capable of processing any complex shape;

Limitations: Low material utilization rate (the raw material needs to be 20%-50% larger than the finished product), long processing time (a single piece may take 10-30 minutes), suitable for medium and high-end, small-batch products (such as high-end drone bodies).

CNC turning: For cylindrical machine housings (such as sensor housings, small motor housings), a CNC lathe drives the workpiece to rotate, and the cutting tool cuts from the side to form cylindrical, conical, threaded and other structures.

Features: Higher efficiency than milling, suitable for symmetrical cylindrical structures.

3. Casting process (applicable to complex cavities and thin-walled metal structures)

When the casing structure is complex (such as with internal ribs or cavities) and mass production is required, a blank can be made by casting first, followed by subsequent cutting.

Die Casting: Molten aluminum alloy/magnesium alloy (at a temperature of approximately 600-700℃) is pressed into a metal mold under high pressure and rapidly cooled to form. It is suitable for complex thin-walled parts (such as mobile phone frames and automotive electronic casings).

Advantages: It can form complex structures (such as integrated clips and screw columns) in one go, and has a high mass production efficiency.

Limitations: High mold cost (hundreds of thousands of yuan for a set of molds), possible porosity on the surface of the castings, and subsequent CNC fine finishing is required.

Sand casting: It uses sand to make molds and is suitable for large, low-precision cast iron/cast steel machine shells (such as heavy equipment bases, large distribution box shells). It has a low cost but poor precision (error ±1-2mm).

Ii. Plastic Casing: Emphasizing "one-piece molding" and "Realization of Complex structures"

The core advantage of plastic casings is that they can be molded into complex structures (such as clips, ribs, and hollowed-out parts) in one piece. The mainstream process is injection molding, supplemented by a few special processes:

Injection Molding: The "absolute mainstream" of plastic casings

More than 90% of plastic casings (such as those of routers, keyboards, and small household appliances) are made using this process. The principle is "pressing molten plastic into a mold and then demolding after cooling."

Core process

Plastic pellets (such as ABS, PC) are added to the injection molding machine barrel and heated to a molten state (180-280℃).

The screw of the injection molding machine presses the molten plastic under high pressure (50-150 mpa) into the cavity of the precision mold.

The mold is cooled by water (10 to 30 seconds), and the plastic solidifies and takes shape.

The mold is opened, and the ejector pin pushes the finished product out, completing one cycle (a single cycle usually takes 30 seconds to 2 minutes).

Key technical points

Mold design: It is necessary to reserve the "draft Angle" (1-3° to prevent the finished product from getting stuck in the mold), "gate" (the entrance for plastic to enter the cavity, which needs to be trimmed later), and "vent slot" (to expel the air in the cavity and prevent the finished product from having bubbles).

Material selection: Plastics with poor fluidity (such as PC) require higher injection molding temperatures and pressures to avoid incomplete filling.

Applicable scenarios: Mass production (after the mold is put into use, the unit cost is extremely low), and it can achieve complex structures (such as one-piece formed clips, heat dissipation fins, screw columns).

2. Special plastic molding process (for specific requirements)

Blow Molding: Suitable for hollow plastic casings (such as protective covers for large equipment and plastic water tank shells). The principle is to make a "tube blank" from molten plastic, then introduce compressed air to inflate it and make it tightly adhere to the inner wall of the mold. After cooling, it takes shape.

Advantages: It can produce large-sized hollow parts at a lower cost than injection molding (no need for complex mold cavities).

Limitations: Low precision and poor surface flatness.

Thermoforming: It is suitable for thin-walled and large-area plastic shells (such as equipment panels and protective covers). The principle is to heat and soften the plastic sheet, then use vacuum suction to adhere it to the surface of the mold. After cooling, it takes shape.

Advantages: The mold cost is extremely low (mostly plaster molds/wooden molds), suitable for small-batch customization.

Limitations: It can only form single-sided structures, and the thickness is uneven (the corners tend to become thinner).

3D printing (additive manufacturing) : It is suitable for sample shells in the R&D stage and customized small-batch machine shells (such as personalized shells for medical devices). The commonly used materials are PLA, ABS and nylon, and the molding is achieved through "layer-by-layer stacking".

Advantages: No need for molds, flexible design modifications (3D models can be printed immediately after modification);

Limitations: Slow speed (a single piece may take several hours), rough surface (requires grinding and post-treatment), and lower strength than injection-molded parts.

Iii. Composite Material Casing: Focusing on "Lamination Forming" and "Functional Enhancement"

Composite materials (such as fiberglass reinforced plastic and carbon fiber) need to be formed through "matrix + reinforcing material composite", and the process revolves around "lamination" and "curing" :

Hand lay-up molding (suitable for fiberglass reinforced plastic shells, small-batch production)

Process: First, apply resin (such as epoxy resin) on the surface of the mold, then lay a layer of fiberglass cloth. Use tools to press it firmly to remove air bubbles. Repeat the process of "resin application + cloth laying" to the designed thickness. Finally, cure at room temperature or by heating (for several hours to several days). After demolding, make adjustments.

Advantages: Low mold cost (capable of making complex curved surfaces), suitable for large parts (such as wind turbine nacelles, ship equipment shells);

Limitations: Relying on manual labor, low efficiency (taking several days for a single piece), and unstable quality (difficult to control bubbles and thickness deviations).

2. Compression molding (suitable for fiberglass reinforced plastic and carbon fiber shells, medium batch production)

Process: Place the reinforcing materials pre-impregnated with resin (such as glass fiber pre-impregnated material, carbon fiber pre-impregnated material) into a metal mold. After closing the mold, heat (120-180℃), apply pressure (10-50MPa), maintain for a certain period of time to allow the resin to cure, and finally demold.

Advantages: The molding efficiency is higher than hand lay-up (10-30 minutes per piece), and the finished product has high density and strength (no bubbles).

Limitations: High mold cost, suitable for flat plates or simple curved surface parts (complex structures are difficult to compact).

3. Winding forming (suitable for cylindrical composite material shells)

Process: After impregnating glass fiber/carbon fiber yarn through a resin tank, it is wound around a rotating cylindrical core mold at the designed Angle. After curing, the core mold is removed to form a hollow cylindrical shell (such as the anti-corrosion shell of chemical equipment or the protective cover of high-pressure pipelines).

Advantages: The fiber arrangement direction is controllable (strength can be optimized according to the force direction), suitable for long-sized cylindrical parts.

Iv. General Post-Processing Technology: Enhancing the "Texture and Functionality" of the Casing

No matter what material the casing is made of, it usually needs to undergo post-treatment after forming to achieve functions such as rust prevention, aesthetics, and protection

Surface coating

Metal parts: Powder coating (electrostatic powder coating, scratch-resistant, suitable for chassis and equipment shells), electrophoresis (forming a uniform paint film, good rust prevention, suitable for automotive electronic components);

Plastic parts: Oil spraying (spraying paint, which can be made matte, high-gloss or metallic colors, such as mobile phone shells), silk-screen printing/pad printing (printing logos and text, such as parameter labels on router shells).

Special treatment of metals

Anodizing (for aluminum alloys) : An oxide film (5-20μm thick) is formed on the surface of aluminum alloys, which can be dyed (black, silver, and colored) to enhance corrosion resistance and wear resistance (such as the aluminum alloy casing of notebook computers).

Electroplating (either metal or plastic) : A layer of metal (chromium, nickel, gold) is plated on the surface to achieve a metallic luster (such as the electroplated keyboard shell made of ABS plastic).

Passivation (for stainless steel) : A passivation film is formed on the surface through chemical treatment to enhance rust resistance (such as the stainless steel casing of medical equipment).

Assembly and auxiliary processes

Drilling/tapping: Process screw holes on the machine casing (for metal parts, CNC tapping is mostly used; for plastic parts, "self-tapping screw columns" are mostly reserved during injection molding).

Grinding/Polishing: Remove surface burrs and scratches (sandpaper/grinding wheel for metal parts, fine sandpaper + polishing paste for plastic parts);

Sealing treatment: Stick waterproof adhesive strips and apply sealing glue (such as for the outer casing of outdoor equipment to prevent rainwater from entering).

Summary: The core logic of process selection

Material matching: For metals, choose sheet metal/CNC/die-casting; for plastics, choose injection molding; for composite materials, choose compression molding/hand lay-up.

Mass production scale: For large batches, choose stamping/injection molding/die-casting; for medium batches, choose die pressing/CNC; for small batches/customization, choose laser cutting / 3D printing/hand lay-up.

Cost and precision: For low cost, choose sheet metal/vacuum forming/hand lay-up; for high precision, choose CNC/injection molding/compression molding.

Structural requirements: For simple planes, choose stamping/laser cutting; for complex three-dimensional parts, select CNC/injection molding; for hollow parts, choose blow molding/winding.