In the lock industry, “safety as the bottom line, precision as the core, and adaptation as the key” has long been the core logic of product competition. From lock cylinders and pins in residential anti-theft locks, to sensors and keypad bases in smart locks, and even housings and handles for outdoor locks—the choice of injection molding process directly determines a lock’s anti-theft level, service life, and market competitiveness.
Metal Injection Molding (MIM) and traditional plastic injection molding are not an “either/or” alternative, but rather an optimal combination of “high performance for core safety components + scenario adaptability & user experience for non-core parts.” This article focuses on lock industry-specific scenarios and outlines the best process choices for various lock components from three dimensions: process differences, adaptation logic, and selection techniques.
一.Core Differences Between MIM and Plastic Injection Molding
The core distinction between the two lies in their “molding materials” and “process principles,” which directly define their application boundaries in lock products. The specific comparison is as follows:
| Comparison Dimension | MIM (Metal Injection Molding) | Plastic Injection Molding | Relevance to the Lock Industry |
| Core Material | Metal powders (stainless steel, carbon steel, titanium alloy, etc.) + binders | Thermoplastics (ABS, PP, PC, modified nylon, etc.) | Core lock components need wear/rust resistance; non-core parts require lightweight design and scenario adaptation |
| Process Principle | Metal powder + binder mixing → injection molding → debinding → sintering → post-processing (tolerance as tight as ±0.005mm) | Plastic pellet melting → injection into mold → cooling & setting → demolding (typical tolerance: ±0.05-0.1mm) | Grade C lock cylinders and pins demand ultra-high precision; housings and handles have lower precision requirements |
| Core Advantages | High precision, high strength, wear/rust resistance, ability to form complex metal structures | High scenario adaptability, high mass production efficiency, lightweight, dyeable/UV-resistant | Core safety parts prioritize performance; appearance/auxiliary parts prioritize scenario adaptation and user experience |
| Core Limitations | Longer lead time, slight shrinkage possible after sintering | Low strength, easy aging, poor temperature/wear resistance | Lock cylinders and bolts cannot afford “insufficient strength”; outdoor lock accessories cannot afford “aging and cracking” |
二.Process Selection for Lock Components
The core requirements for locks are “safety & reliability, wear/rust resistance, stable precision, and scenario adaptation.” The functional positioning of different components determines the priority of choosing MIM or plastic injection molding.
1.MIM: The “First Choice” for Core Safety Components of Locks
Core safety components—such as lock cylinders (especially Grade C), pins, bolts, key profiles, metal sensors in smart locks, and keypad bases for combination locks—directly affect a lock’s anti-theft level (resistance to picking and prying) and service life. Their high demands for precision, strength, and wear resistance align perfectly with MIM’s core advantages.
Take Grade C stainless steel lock cylinders as an example: Traditional turning and milling processes struggle to create complex internal serpentine grooves with micron-level precision. Not only are they inefficient, but they also pose risks of “insufficient anti-prying performance.” In contrast, MIM can form complex groove structures in one step. After sintering, the hardness reaches HRC 30-45, with far better wear and rust resistance than traditional processing. Precision errors are controlled within ±0.01mm, fully meeting the industry standard for Grade C lock cylinders: “resistance to technical picking for ≥270 minutes.”
For metal sensors in smart locks and keypad bases for combination locks, MIM ensures precise alignment with electronic components (avoiding poor contact). Meanwhile, the wear resistance of metal materials handles high-frequency pressing, significantly reducing smart lock repair rates (data shows: smart locks using MIM sensors reduce key failure repair rates by 80%).
2.Plastic Injection Molding: The “Scenario-Appropriate Choice” for Non-Core Lock Components
Non-load-bearing, non-core components—such as lock housings, handle covers, decorative plates, and waterproof covers for outdoor locks—have lower strength requirements. They prioritize “design flexibility, lightweight, installation convenience, and scenario adaptation,” making plastic injection molding the better option.
For instance, an ABS+PC alloy housing for residential anti-theft locks offers greater design flexibility and lighter weight compared to MIM metal housings. Molds can create various textures (matte, frosted, metal-like) to match different home styles. Additionally, plastic is lightweight (single housing weight is 40% less than metal), facilitating installation and transportation while reducing wall load after lock installation, indirectly optimizing user experience and overall application value.
For plastic accessories of outdoor locks (e.g., community unit locks, garden locks), UV-resistant modified nylon effectively prevents cracking and deformation after long-term exposure to sun and rain, extending service life to over 5 years. For decorative plates of indoor locks, transparent PC injection molding enables “visible design” to enhance product aesthetics.
3.Special Lock Scenarios: Optimized Combined Process Solutions
Some lock scenarios require balancing “performance + scenario adaptation + user experience,” which cannot be achieved by a single process. A combined “MIM + plastic injection molding” solution is recommended:
- Need for “metal texture + optimal scenario adaptation”: For example, handles of mid-range anti-theft locks use “plastic injection molding + metal coating”—the appearance resembles metal, while retaining the installation convenience of plastic materials.
- Need for “plastic insulation + local metal reinforcement”: For example, plastic housings of smart locks embed MIM metal inserts at electronic component junctions, ensuring insulation safety while improving alignment precision and structural strength.
- Need for “lightweight + core wear resistance”: For example, bolts of portable smart locks adopt a “MIM wear-resistant head + plastic body” combination, balancing lightweight design and bolt wear resistance.
III. Conclusion: Process Adaptation to Enhance Lock Competitiveness
In summary, MIM and plastic injection molding cover all lock scenarios: Choose MIM for core safety components to secure anti-theft performance, use plastic injection molding for non-core parts to optimize experience and adaptability, and adopt combined solutions for special scenarios—achieving the optimal balance between performance and scenario adaptation.
Yibi Precision has deep expertise in the MIM industry, offering one-stop solutions from design consultation and mold development to mass production. Whether for complex groove forming of Grade C lock cylinders, precise alignment of smart lock sensors, rust resistance enhancement of outdoor lock components, or plastic injection molding needs for non-core lock parts, our mature process system solves key challenges such as insufficient precision, high wear, and suboptimal scenario adaptation.
If your enterprise faces challenges in lock process selection or aims to improve product anti-theft levels and reduce repair rates through MIM technology, please reach out to Yibi. We provide free process adaptation evaluations and customized solutions.