Overcoming Smart Bracelet Screw Corrosion: A Targeted Solution

 Recently, a smart bracelet designed and manufactured for an Italian client with stringent quality requirements underwent a critical reliability test—metal screws embedded within the plastic housing exhibited signs of corrosion during actual use. Although seemingly minor, this defect not only compromises the product’s aesthetic integrity but also raises concerns regarding its long-term durability and functional reliability.

Screw corrosion is not an isolated issue; it represents a common challenge in plastic-encapsulated electronic devices, particularly wearable consumer electronics exposed to complex environmental conditions. The root cause typically stems from the interplay of multiple factors:

First, as a wearable device in constant contact with human skin, smart bracelets are inevitably exposed to sweat. Sweat contains water, salts, and weakly acidic components that continuously attack the most vulnerable points of metallic fasteners.

Second, early design iterations often employed carbon steel screws with electro-galvanized coatings for protection. However, if the plating layer contains micro-pores, exhibits uneven thickness, or sustains minor damage during manufacturing or assembly, moisture and electrolytes can penetrate through these defects, initiating localized corrosion.

Third, during the insert molding process, molten plastic at high temperature encapsulates pre-placed metal screws. Due to the mismatch in thermal expansion coefficients between metal and polymer, residual internal stresses develop upon cooling. These stresses can degrade the inherent corrosion resistance of the metal components.

Our Solution

1. Mold Structure Optimization  

The mold design was refined by improving the positioning mechanism and encapsulation method of the inserts. This ensures more uniform and complete coverage of the screws by the surrounding plastic, thereby minimizing the surface area exposed to humid environments.

2. Material Upgrade to AISI 304 Stainless Steel  

Superior Screw Material: We replaced the carbon steel with AISI 304 stainless steel, which has a self-repairing protective oxide layer that resists sweat and corrosion.

3. Selection of Enhanced Engineering Plastics  

Concurrently, we evaluated and implemented engineering plastics with superior chemical stability, lower moisture absorption, and reduced tendency to decompose into corrosive byproducts. This mitigates one of the key environmental contributors to metal degradation.

We thank our client for their valuable feedback. This solution underscores our commitment to continuous improvement and delivering durable, high-quality products.

Precision Advantages of a CNC Machining Center with Automatic Tool Changery

 Our new CNC machining center with an Automatic Tool Changer (ATC) is a significant upgrade.   Its key precision advantages are not from the tool change itself, but from how ATC enhances process stability and guarantees final part accuracy.

Here are the core benefits:

1.   Eliminates Human Error for Consistent Tool Setting

Manual vs. ATC: Manual tool changes introduce variability—inconsistent tightening force, potential contamination, or operator error—all leading to tool runout and inaccuracy.

ATC Advantage: The ATC performs every tool change with identical, programmed motions.   It ensures perfect, repeatable tool positioning in the spindle by consistently cleaning the taper, gripping, and locking each time.   This removes random human errors, guaranteeing superior tool-holding rigidity and minimal runout.

2.   Enables "Complete Machining in a Single Setup"

Manual Bottleneck: Complex parts requiring milling, drilling, and tapping must be interrupted for manual tool changes, introducing potential errors from machine thermal shifts or part stress relief.

ATC Advantage: The machine can automatically change tools and complete all operations in one continuous cycle without removing the part.   This is critical for precision because it:

Maintains a Single Datum: The workpiece remains fixed, avoiding cumulative errors from re-fixturing.

Guarantees Geometric Relationships: It reliably ensures high positional accuracy between features (holes, slots, surfaces) on a part.

3.   Ensures Batch Consistency and Process Stability

ATC Advantage: For batch production, ATC ensures the entire process, including tool changes, is perfectly repeatable from the first to the thousandth part.   This guarantees high consistency in dimensions and tolerances across the entire production run, which is difficult to achieve with manual intervention.

4.   Supports Optimized Machining Strategies

ATC Advantage: ATC allows for dedicated "roughing" and "finishing" tools.   The finishing tool remains sharp and unaffected by roughing wear, directly producing better surface finish and tighter tolerances.   It also enables in-process probing and automatic tool compensation for adaptive control.

In summary, the key precision advantages are:

High Repeatability: Consistent tool positioning.

Low Error Accumulation: "One setup" machining prevents error stacking.

High Process Stability: Removes human variables.

Superior Process Capability: Enables optimal finishing strategies.

This new machine will provide customers with more precise mold manufacturing services

Rotary Secondary Injection Molding: Characteristics and Applications

 Rotary secondary injection molding is an advanced manufacturing process that enables the production of integrated dual-material components in a single operation.  This technology combines two different plastic materials—typically a rigid substrate and a soft elastomer—into a seamless, high-quality product.

Process Overview

The process begins with the injection of the first material (usually rigid polymers like ABS, PC, or PP) into cavity A, forming the product's structural base.  The mold then rotates 180 degrees, aligning the substrate with cavity B. A second material (such as TPU, TPE, or silicone) is injected to encapsulate designated areas of the base component.  Finally, the completed part is ejected, ready for use without additional assembly.

Key Advantages

1.  Enhanced Product Quality: The immediate bonding between freshly molded materials ensures superior adhesion, while mechanical interlocking features prevent delamination.  This results in durable components with seamless transitions between materials.

2.  Increased Efficiency: By consolidating two manufacturing steps into one automated cycle, the process eliminates intermediate handling and significantly reduces production time.  This automation allows for higher output with minimal operator intervention.

3.  Design Flexibility: Engineers can create products combining multiple material properties—such as rigid structural elements with soft-touch surfaces—enabling innovative designs that improve both functionality and user experience.

Applications

This technology is widely employed across industries:

- Consumer electronics: Protective cases, wearable device bands

- Automotive: Steering wheels, control buttons

- Medical devices: Ergonomic instrument handles

- Household products: Tool grips, kitchenware handles

Economic Considerations

While requiring higher initial investment in specialized equipment and mold design, rotary secondary injection molding becomes cost-effective for high-volume production.  The reduction in assembly steps and improved product quality contribute to long-term manufacturing efficiency.

This advanced molding technique continues to gain popularity as manufacturers seek to create sophisticated products that combine multiple material properties while maintaining production efficiency and consistent quality.

CNMOULDINGs: Professional Two-Shot Overmolding Mold Manufacturer

 CNMOULDINGs is a high-tech enterprise specializing in the design, production, and machining of two-shot overmolding molds. With years of industry experience and advanced manufacturing technology, we are committed to providing high-quality, high-precision two-shot injection mold solutions for industries such as consumer electronics, medical devices, automotive parts, and home appliances.

Core Business: Two-Shot Overmolding Molds

Two-shot overmolding (also known as dual-material or multi-material molding) is an advanced injection molding process that combines two different plastics or colors in a single production cycle, enhancing product functionality, aesthetics, and durability. CNMOULDINGs excels in this field with the following advantages:

Precision Design & Engineering

Utilizes CAD/CAE/CAM software for mold structure optimization, ensuring stability and accuracy in injection molding.

Supports complex two-shot designs, including soft/hard material bonding, multi-color combinations, and transparent/opaque integrations.

High-Quality Materials & Processes

Uses premium mold steels (e.g., S136, 718H) with heat and surface treatments to extend mold lifespan.

Strict control of injection parameters to eliminate weld lines, air bubbles, or delamination.

Diverse Applications

Consumer Electronics: Phone buttons, earphone casings, wearable devices.

Automotive Parts: Dual-color buttons, seals, interior components.

Medical Devices: Non-slip grips, soft-touch housings.

Household Items: Toothbrush handles, tool grips.

Technical Advantages

Two-Shot Molding Machines: Compatible with rotary plate, core-back, and other two-shot molding methods.

Rapid Prototyping & Mass Production: Short lead time from design to trial molding, accelerating time-to-market.

Strict QC System: Ensures dimensional and functional accuracy via 3D scanning, CMM, and other inspection methods.

Service Commitment

CNMOULDINGs prioritizes customer needs, offering one-stop solutions:

Mold design consultation → Production & machining → Trial molding → Mass production support.

Flexible customization for both small batches and large-scale manufacturing.

Contact Us

For professional two-shot overmolding solutions, CNMOULDINGs is your trusted partner! Visit our website or contact us directly for technical details and case studies.

CNMOULDING: Professional Insert Molding Manufacturer – High-Precision, High-Strength Insert Molding Solutions

 CNMOULDING is a high-tech enterprise specializing in the design, manufacturing, and production of insert molding (Insert Molding) molds. We are committed to providing global customers with high-precision, high-stability insert molding solutions for applications in automotive, electronics, medical, home appliances, and industrial components.

With advanced machining equipment, extensive industry experience, and a strict quality control system, CNMOULDING has become a long-term partner for many renowned companies worldwide, offering one-stop services from mold development to mass production.

Key Advantages of Insert Molding

Insert molding is an efficient process where metal or non-metal inserts (such as nuts, screws, terminals, or sensors) are pre-placed into the mold and then encapsulated with plastic. Compared to traditional assembly methods, CNMOULDING’s insert molding technology offers the following benefits:

1. High-Strength Bonding: The plastic encapsulates the insert with high strength, ensuring superior pull-out force and torque resistance, thereby preventing any loosening or detachment.  

2. Cost Efficiency: By eliminating post-molding assembly processes, this method reduces labor costs and minimizes assembly errors, thus significantly enhancing production efficiency.  

3. High-Precision Molding: Precision-engineered molds guarantee accurate positioning of the insert and uniform encapsulation of the plastic, meeting stringent engineering requirements.  

4. Wide Insert Compatibility: This technology supports a variety of materials for inserts, including metals (such as copper, aluminum, and stainless steel) and non-metallic options, addressing diverse industry needs.  

5. Material Versatility: It is compatible with both thermoplastics (e.g., ABS, PC, PA, POM) and thermosetting plastics (e.g., phenolic resins), fulfilling various performance requirements across applications.  

CNMOULDING’s Core Competencies

1. Advanced Mold Design and Manufacturing  

CAD/CAM/CAE simulation is utilized to optimize the mold structure, ensuring stability and enhancing the accuracy of insert positioning.  

High-precision CNC machining, EDM (Electrical Discharge Machining), and mirror polishing are employed to guarantee mold durability and superior product surface quality.  

2. Mature Insert Molding Process  

Automated systems for insert placement improve production efficiency and maintain consistency in manufacturing processes.  

Rigorous process control over parameters such as temperature, pressure, and injection speed effectively prevents issues like insert misalignment and insufficient plastic filling.  

3. Rigorous Quality Inspection  

Advanced inspection methods, including 3D scanning, pull-out tests, torque tests, and others, ensure that the bonding strength of inserts complies with industry standards (ISO 9001, IATF 16949).  

4. Wide Industry Applications  

Automotive: Sensor housings, connectors, gear assemblies  

Electronics: PCB inserts, switch components, heat dissipation modules  

Medical Devices: Surgical instrument handles, disposable medical inserts  

Home Appliances: Buttons, fasteners, structural parts  

Why Choose CNMOULDING?

🔹 30+ Years of Experience – Successfully served 500+ global customers in insert molding.

🔹 Rapid Response – Efficient project support from mold design to mass production.

🔹 Cost Optimization – Process improvements reduce scrap rates and save costs.

🔹 Custom Solutions – Tailored services including multi-cavity molds, hot runner systems, and automated insert placement.

Contact Us

If you are looking for a reliable insert molding supplier, CNMOULDING is your ideal partner! Contact us for customized solutions, professional technical support, and high-quality service.

CNMOULDING: Professional Soft Rubber Product Solutions Provider

 As a company specializing in soft rubber product design, mold development, and manufacturing, CNMOULDING leverages extensive industry experience and technical expertise to provide one-stop soft rubber product solutions, including customized production using various materials such as silicone, TPU, and TPE.  

CNMOULDING’s Core Advantages  

one. Diverse Material Options to Meet Various Needs

We offer a wide range of soft rubber materials, including:  

Food-grade silicone (FDA/LFGB compliant, suitable for baby products and kitchenware)  

High-elasticity TPU (wear-resistant, tear-resistant, ideal for sports gear and industrial components)  

Eco-friendly TPE (recyclable, low hardness, perfect for medical devices and electronic accessories)  

Special-performance soft rubber (custom options for high-temperature resistance, flame retardancy, conductivity, etc.)  

two. Precision Mold Development Ensures Product Quality  

High-precision CNC machining and 3D printing mold flow analysis optimize mold structure  

Support for multi-cavity and stack mold designs to improve production efficiency  

Capable of producing ultra-thin soft rubber parts (as thin as 0.2mm)** to meet high-precision requirements  

three. Advanced Manufacturing Processes Guarantee Performance  

Liquid Silicone Rubber (LSR) Injection Molding—Ideal for high-precision medical and electronic components  

Solid Silicone Compression Molding—Suitable for high-temperature kitchenware and seals  

TPU/TPE Injection Molding—Used for anti-slip grips, sports protectors, etc.  

Overmolding (Two-Shot Molding)—Combines hard and soft rubber for enhanced functionality  

four. Strict Quality Control Complies with International Standards  

ISO 9001 certification ensures standardized production processes  

RoHS/REACH compliance testing meets export requirements  

Physical performance testing (tensile strength, tear resistance, temperature resistance, etc.)  

Why Choose CNMOULDING?

End-to-end support from design to mass production—DFM (Design for Manufacturability) analysis optimizes product structure  

Rapid prototyping and small-batch production—Shortens product development cycles  

Cost-optimized solutions—Material selection and process improvements reduce overall costs  

Global logistics support—Stable supply chain for markets in Europe, America, Asia, and beyond  

CNMOULDING—Your Trusted Soft Rubber Manufacturing Partner!

How to Address the Issue of Thin and Easily Broken Ejector Pins in Injection Molds

 1. Optimize the Ejection Process  

Adjust ejection parameters to minimize stress on delicate ejector pins.  

Reduce ejection speed: Excessively high ejection speeds generate significant impact forces, increasing the risk of breakage in thin ejector pins. A moderate reduction in speed can mitigate this risk.  

Implement multi-stage ejection: Utilize the multi-stage ejection capability of the injection molding machine. Initiate the first stage at a low speed and short stroke to release vacuum adhesion, followed by standard ejection in the second stage. This approach effectively reduces peak impact loads.  

Verify ejection stroke: Ensure the stroke is precisely calibrated to fully eject the part without over-extension, which may cause the ejector pin to lose guidance support and become unstable.  

Maintain proper lubrication: Regularly apply high-temperature mold release oil to the ejector pins to minimize friction between the pins and the mold core.

2. Revise Mold Design  

The most effective and long-term solution is to replace fragile, undersized thimbles with larger-diameter counterparts.  

This modification requires adjustments to the hole positions in both the mold core and the ejector plate. Although this involves higher initial costs, it provides a durable and reliable resolution.

3. Modify Ejection Methodology  

When spatial constraints prevent increasing the pin diameter, alternative ejection mechanisms should be considered.  

Use flat thimbles: In narrow regions such as rib areas, flat thimbles offer a greater cross-sectional area and superior resistance to bending compared to round thimbles.  

For boss columns with high shrinkage forces, employ stripper pins, which provide a broader and more uniform ejection surface.  

For deep cavities or thin-walled parts, consider air-assisted ejection systems. These introduce compressed air from within the cavity to disrupt vacuum formation, significantly reducing demolding resistance.  

Apply push plate ejection: For large, deep-container components, push plates offer full-surface contact, distributing ejection force evenly and minimizing localized stress compared to point-contact ejector pins.

4. Enhance Mold Structural Integrity  

Incorporate guide pillars: Install guide sleeves on the ejector plate to ensure precise alignment and smooth movement of the ejector system, thereby preventing lateral shear forces due to misalignment.  

Polish ejector pin bores: Inspect and refinish worn pin holes to reduce friction and improve operational smoothness.  

Inspect for and correct undercuts: Conduct a thorough mold inspection to identify any unintended undercuts that may contribute to excessive part retention force, and rectify them accordingly.