Developing a refrigerator prototype model requires a precise CNC machining process to validate design feasibility, test component fit, and evaluate aesthetic performance. Unlike small appliance prototypes, refrigerators have complex structures (e.g., box, door body, refrigeration system mounts) that demand strict control over dimensional accuracy and surface quality. This guide breaks down the full workflow—from preliminary preparation to post-processing—with key parameters, material selections, and practical tips to ensure prototype success.
1. Preliminary Preparation: Lay the Foundation for Machining
The success of CNC machining starts with thorough preparation, including 3D modeling, material selection, and equipment/tool readiness. This stage ensures the subsequent process is efficient and error-free.
(1) 3D Modeling: Define Prototype Details with Precision
Use professional CAD software (e.g., SolidWorks, UG) to create a detailed 3D model that covers all critical structures of the refrigerator. The model must balance design requirements, assembly logic, and machining feasibility.
| Structure Category | Key Design Details | Precision Requirements | Purpose |
| Main Body (Box) | Inner cavity size (e.g., 500mm×600mm×1800mm), partition slots, refrigeration system mounting holes | Cavity dimension error ±0.2mm; hole position tolerance ±0.1mm | Ensure fit for insulation layers and refrigeration components |
| Door Body | Frame size, observation window cutout (if applicable), hinge mounting slots | Frame parallelism error ≤0.1mm; cutout edge smoothness Ra ≤1.6μm | Guarantee tight sealing when closed; match hinge assembly |
| Functional Components | Handle shape (ergonomic curve), control panel slot, drawer slide rails | Handle surface roughness Ra ≤0.8μm; slot depth tolerance ±0.05mm | Improve user experience; ensure smooth operation of moving parts |
Model Optimization Tips:
- Layered Design: Split complex structures (e.g., door body with inner liner) into separate machinable components to avoid tool interference. For example, machine the door frame and inner liner separately, then assemble them.
- Process Marking: Label key machining features (e.g., “no tool marks on visible surfaces”) and reference datums (e.g., box bottom as the origin) to guide CNC programming.
- Interference Check: Use software to simulate component assembly (e.g., door closing, drawer sliding) and eliminate overlapping or collision risks (e.g., ensure 2–3mm clearance between door and box).
(2) Material Selection: Match Performance to Component Roles
Different parts of the refrigerator prototype require materials with specific properties (e.g., strength, transparency, gloss). Below is a detailed comparison of suitable options:
| Material Type | Applicable Parts | Key Properties | Machinability Advantages |
| ABS Plastic | Box body, door frame, handle | Good impact resistance (Izod impact strength 20 kJ/m²), easy to color, low cost | Low tool wear; can be machined at high speed (10,000–15,000 rpm) |
| PC Plastic | Observation window, control panel cover | High transparency (light transmittance ≥88%), impact-resistant (10x stronger than glass) | Precision cutting achievable; minimal chipping on edges |
| Acrylic (PMMA) | Exterior decorative strips, logo plates | Excellent gloss (60° gloss value ≥90%), vivid color expression | Smooth surface after polishing; suitable for aesthetic-focused parts |
| Aluminum Alloy (6061) | Drawer slide rails, refrigeration mounts | High rigidity (tensile strength 276 MPa), good corrosion resistance | Fast machining speed; suitable for load-bearing structural parts |
Material Blank Preparation:
- Cut blanks according to the maximum size of each part, reserving 5–10mm machining allowance on all sides. For example:
- A door frame with a final size of 600mm×800mm×50mm requires a 610mm×810mm×60mm ABS blank.
- An aluminum alloy slide rail (100mm×20mm×5mm) needs a 110mm×30mm×15mm blank to accommodate roughing and finishing.
(3) Equipment & Tool Preparation: Ensure Machining Accuracy
Select CNC equipment and tools based on material properties and part complexity to avoid defects like tool marks or dimensional deviations.
| Equipment/Tool Type | Selection Criteria | Recommended Specifications |
| CNC Machining Center | High-precision 3-axis or 5-axis models (for curved surfaces like door handles) | Positioning accuracy ±0.005mm; spindle speed range 8,000–24,000 rpm |
| Milling Cutters | Solid carbide tools for plastic; high-speed steel (HSS) tools for aluminum alloy | – Plastic: Φ6–Φ12mm flat-bottom mills (for roughing), Φ3–Φ6mm ball-head mills (for finishing)- Aluminum: Φ8–Φ16mm end mills (for roughing), Φ4–Φ8mm face mills (for flat surfaces) |
| Drills & Taps | Twist drills for holes; machine taps for threaded mounting holes | – Drills: Φ2–Φ10mm (match hole size requirements)- Taps: M3–M8 (for hinge and handle mounting) |
| Fixtures | Vacuum suction cups (for flat plastic parts); precision vises (for aluminum components) | Vacuum pressure ≥0.8 MPa; vise clamping force ≥5 kN to prevent workpiece displacement |
2. Programming & Setup: Translate Design to Machinable Code
This stage converts the 3D model into actionable CNC instructions and prepares the machine for operation—critical for ensuring machining accuracy.
(1) CAM Programming: Generate Machining Code
Use CAM software (e.g., Mastercam, PowerMill) to convert the 3D model into G-code, and optimize parameters based on material and part structure.
| Machining Stage | Key Parameters | Optimization Tips |
| Roughing | – Cutting speed: 10,000–12,000 rpm (ABS); 12,000–15,000 rpm (aluminum)- Feed rate: 1,000–1,500 mm/min (ABS); 800–1,200 mm/min (aluminum)- Cutting depth: 2–5mm (ABS); 1–3mm (aluminum) | Use “layered cutting” to remove 90% of excess material; leave 0.3–0.5mm allowance for finishing |
| Finishing | – Cutting speed: 15,000–18,000 rpm (ABS); 18,000–22,000 rpm (aluminum)- Feed rate: 500–800 mm/min (ABS); 400–600 mm/min (aluminum)- Cutting depth: 0.1–0.3mm | For curved surfaces (e.g., handle), use “spiral cutting” with a step distance of 0.05mm to eliminate tool marks |
| Hole Machining | – Drilling speed: 8,000–10,000 rpm- Tapping speed: 500–800 rpm (M3–M5 taps) | Use “pecking drilling” (drill 3mm, retract 1mm) to clear chips; apply cutting fluid for aluminum to prevent thread stripping |
(2) Machine Setup: Install Tools & Secure Workpieces
Proper setup ensures the machine, tools, and workpieces are aligned to the same coordinate system—avoiding dimensional errors.
Tool Installation & Calibration:
- Mount tools into the tool magazine and use a tool setter to measure tool length and radius. Record data in the CNC system to compensate for tool wear.
- For example: A Φ6mm ball-head mill for ABS finishing needs its length calibrated to ±0.001mm to ensure consistent cutting depth.
Workpiece Clamping:
- Clean the machining table to remove debris, then fix the blank using fixtures:
- For ABS box blanks: Use vacuum suction cups to cover 80% of the blank’s bottom surface (prevents warping during machining).
- For aluminum slide rails: Secure with a precision vise, ensuring the blank is parallel to the table (error ≤0.01mm).
- Set the workpiece origin (e.g., use a touch probe to detect the blank’s edge) and input coordinates into the CNC system.
3. CNC Machining Execution: From Blank to Prototype Structure
This stage divides machining into roughing and finishing to balance efficiency and precision—critical for complex refrigerator structures.
(1) Roughing: Shape the Prototype Foundation
Roughing removes most excess material to bring the blank close to the final shape, prioritizing speed while avoiding tool damage.
| Component Type | Roughing Focus | Key Operations & Parameters |
| Refrigerator Box | Machine outer frame and inner cavity; mill partition slots | Use Φ12mm flat-bottom mill (ABS); cutting speed 11,000 rpm, feed rate 1,200 mm/min; cavity depth cut in 3 passes (5mm each) |
| Door Body | Mill door frame and observation window cutout; machine hinge mounting slots | Use Φ10mm end mill (ABS); cutting speed 10,000 rpm, feed rate 1,000 mm/min; cutout edges left with 0.3mm finishing allowance |
| Aluminum Slide Rails | Machine rail profile and mounting holes | Use Φ8mm end mill (aluminum); cutting speed 14,000 rpm, feed rate 1,000 mm/min; holes pre-drilled with Φ3mm twist drill |
Post-Roughing Inspection:
- Use a digital caliper to check key dimensions (e.g., box cavity size, door frame width) and ensure they are within ±0.5mm of the design value.
- Clean chips from the workpiece surface with compressed air to avoid interfering with finishing.
(2) Finishing: Achieve Precision & Surface Quality
Finishing refines the workpiece to meet final design requirements, focusing on dimensional accuracy and surface smoothness.
| Component Type | Finishing Focus | Key Operations & Parameters |
| Box Inner Cavity | Smooth cavity walls and partition slot edges; ensure flatness of mounting surfaces | Use Φ6mm ball-head mill (ABS); cutting speed 16,000 rpm, feed rate 600 mm/min; wall roughness Ra ≤1.6μm |
| Door Observation Window | Smooth cutout edges; ensure parallelism with door frame | Use Φ3mm ball-head mill (PC); cutting speed 18,000 rpm, feed rate 500 mm/min; edge chipping ≤0.1mm |
| Handle | Polish curved surface; machine ergonomic grip contour | Use Φ4mm ball-head mill (ABS); cutting speed 17,000 rpm, feed rate 700 mm/min; surface roughness Ra ≤0.8μm |
Finishing Quality Checks:
- Use a surface roughness tester to verify Ra values (e.g., visible surfaces require Ra ≤0.8μm).
- Use a coordinate measuring machine (CMM) to inspect critical features: For example, hinge mounting holes must have a position error ≤0.1mm to ensure door alignment.
4. Post-Processing: Enhance Prototype Performance & Aesthetics
Post-processing improves the prototype’s appearance, functionality, and durability—bridging the gap between machined parts and a realistic refrigerator model.
(1) Surface Treatment: Refine Texture & Appearance
Tailor treatment methods to material type and part function:
| Material/Part Type | Surface Treatment Steps | Expected Outcome |
| ABS Box/Door Body | 1. Sand with 400# → 800# → 1200# sandpaper (remove tool marks)2. Wipe with isopropyl alcohol (degrease)3. Spray matte paint (50μm thickness, color matching design) | Paint adhesion ≥4B (no peeling); surface gloss 30–50 GU (matte finish) |
| PC Observation Window | 1. Polish with 600# abrasive paste (remove cutting marks)2. Polish with 1200# paste (enhance transparency)3. Clean with lens cleaner | Light transmittance ≥85%; no visible scratches or haze |
| Acrylic Decorative Strips | 1. Sand with 1000# sandpaper (smooth edges)2. Polish with acrylic-specific polishing paste3. Apply UV protective coating | Gloss value ≥90 GU; no yellowing after 100 hours of UV exposure |
| Aluminum Slide Rails | 1. Degrease with alkaline cleaner2. Anodize (form 8–10μm silver-gray oxide film)3. Sandblast (matte surface) | Corrosion resistance: No rust after 48-hour salt spray test; friction coefficient ≤0.15 |
(2) Assembly & Debugging: Validate Prototype Functionality
Assemble machined components and test key functions to ensure the prototype meets design goals:
Assembly Steps:
- Pre-Assembly Check: Verify that all parts meet dimensional requirements (e.g., door frame fits box body with 2–3mm clearance).
- Component Installation:
- Mount hinges to door and box (use torque wrench to apply 5–8 N·m force to avoid thread damage).
- Install handle onto door (ensure alignment; no wobble when pulled).
- Attach slide rails to drawers and box (test sliding resistance ≤5N).
- Sealing Test: Place a thin paper strip between door and box, close the door, and pull the strip—resistance should be uniform (indicates tight sealing).
Functional Debugging:
- Door Operation: Test opening/closing 100 times—door should stay closed without manual locking; no squeaking.
- Drawer Sliding: Open/close drawers 50 times—no jamming; slides smoothly throughout the stroke.
- Component Fit: Check that simulated refrigeration system mounts (e.g., compressor brackets) align with holes (position error ≤0.1mm).
5. Quality Control & Optimization: Ensure Prototype Reliability
Strict quality control identifies defects early, while optimization reduces costs and improves efficiency for future iterations.
(1) Key Quality Control Standards
| Control Item | Acceptance Criteria | Inspection Method |
| Dimensional Accuracy | – Box cavity: ±0.2mm- Door frame: ±0.1mm- Hole position: ±0.1mm | CMM (for critical features); digital caliper (for general dimensions) |
| Surface Quality | – Visible surfaces: Ra ≤0.8μm, no tool marks/scratches- Hidden surfaces: Ra ≤1.6μm | Surface roughness tester; visual inspection (under 500lux light) |
| Assembly Fit | – Door-box clearance: 2–3mm (uniform)- Drawer sliding resistance: ≤5N | Feeler gauge (for clearance); force gauge (for sliding resistance) |
| Material Performance | – ABS impact resistance: ≥15 kJ/m²- PC transparency: ≥85% | Izod impact tester; spectrophotometer |
(2) Process Optimization Tips
- Material Saving: For large parts (e.g., box body), design hollow structures (with 3–5mm thick walls) to reduce blank size—saves 20–30% material cost.
- Machining Efficiency: Combine roughing and semi-finishing for simple parts (e.g., decorative strips) to reduce tool change time by 15–20%.
- Post-Processing Simplification: For non-visible parts (e.g., inner partition slots), skip painting—saves 10–15% of post-processing time.
Yigu Technology’s Perspective on CNC Machining Refrigerator Prototype Models
At Yigu Technology, we believe design-machining integration is the core of efficient refrigerator prototype development. Many clients face issues like door sealing failure or drawer jamming due to disconnected design and machining. Our team optimizes models for manufacturability: For example, we add 0.3mm machining allowance to door frames to ensure sealing clearance, and design self-lubricating structures for slide rails to reduce post-processing. We also select materials strategically—using ABS for main bodies (cost-effective, easy to finish) and PC for observation windows (high transparency, impact-resistant). For large-batch prototypes, we use multi-cavity fixtures to machine 2–3 parts at once, cutting production time by 40%. Our goal is to deliver prototypes that accurately reflect mass-production effects, helping clients shorten product development cycles by 25–30%.