3 Technical Challenges of Embedding Magnets in Silicone Products

The battery cap problem encountered by German customers

In January 2025, a German energy storage equipment manufacturer urgently contacted us. They were searching for a specialized silicone Battery Terminal Cap for their newt-generation battery cabinets. However, three previous suppliers had failed to resolve technical issues. The client stated in their email that this project had been in development with other suppliers for six months without success, and this was their final opportunity—if the issues remained unresolved, this project would be terminated.

To address this problem, we immediately convened a team of engineers for a video conference with client. During video meeting, client demonstrated the flaws in their existing battery cap and shared their 3D design files. After collaborative analysis by our engineers, production managers, material suppliers, and magnet technicians, we identified three critical challenges:

Three Critical Challenges

Challenge 1: Conflict Between High-Temperature Vulcanization and Magnet Demagnetization

Silicone requires vulcanization at 160–200°C, while common neodymium magnets (e.g., N52/N54) begin to lose magnetism above 80°C. According to Rubber World 2023 statistics, 32% of magnet-embedded silicone products fail due to high-temperature demagnetization.

Challenge 2: ±0.1mm Precision Positioning

Magnets tend to shift during silicone vulcanization, leading to misaligned magnetic poles, uneven adhesion, or inconsistent placement. In silicone products, a 0.1mm error can cause critical failures—for example, a medical device manufacturer once recalled an entire batch due to a 0.3mm magnet misalignment triggering sensor errors.

Challenge 3: Balancing Softness and Functionality

Overly Hard Silicone (70–80 Shore A): Difficult to insert into battery cabinet ports, prone to tearing, or impossible to remove once forced in.

Overly Soft Silicone (20–30 Shore A): Insufficient structural support, causing magnet displacement due to deformation.

Solutions

After analyzing above three problems of battery cap, Grandshine’s solution to this issues is as follows:

Overcoming the “High-Temperature Deadlock” with Process Innovation

Magnet Material Upgrade: Switched from traditional N35 magnets to nickel-plated N54UH magnets (rated for ≤150°C), using non-magnetized blanks during production to reduce defect rates from 32% to 2%.

Post-Magnetization Process: Magnets are embedded in non-magnetized form during molding and magnetized only after vulcanization, eliminating high-temperature demagnetization risks.

Achieving 0.01mm Precision with Dual-Stage Tooling

Primary Mold: Hydraulic locking + infrared calibration ensures ±0.05mm magnet positioning accuracy.

Precision Mold: Modular vulcanization design eliminates shrinkage and deformation.

AI-Powered Quality Control: Coordinate-measuring machines (CMM) combined with AI models validate batch consistency at ±0.01mm tolerance.

The Golden Balance: 40 Shore A Silicone

After testing five silicone formulations (30–80 Shore A), we found:

After conducting a series of tests, we identified the optimal silicone hardness: 40 shore A flame-retardant silicone achieves a perfect balance between insertion force (≤5N) and retention force (≥15N). Additionally, we implemented a reinforced rib design across the entire battery cap to prevent collapse while ensuring longitudinal tear resistance.

After resolving all three challenges, we delivered T1 samples to the German client. Their feedback: “You are experts in solving complex, high-difficulty products!” The project was successfully approved.

Universal Solutions for the Industry

Whether designing medical seals, industrial shock-absorbing components, or consumer electronics, these methodologies apply:

Magnet Demagnetization: Post-magnetization + high-temperature-resistant magnets (e.g.,SmCo), magnetization strength ≥3,000 Gauss.

Silicone Shrinkage: Modular segmented vulcanization + vacuum pressure forming, thickness tolerance ≤±0.3mm.

Softness-Function Balance: Dynamic Mechanical Analysis (DMA) for rebound curves, insertion/extraction force ratio = 1:3–1:5.

In smart wearables, medical devices, pet supplies, consumer electronics, and renewable energy sectors, the fusion of magnets and silicone is pushing technological boundaries. At Grandshine, our commitment extends beyond technology—we obsess over every 0.01mm of precision.

If you are facing challenges such as magnet positioning failures in flexible materials, conflicts between silicone hardness and functionality, or material stability issues in harsh environments, Grandshine engineering team will provide you with professional production services. If you need to design a new product, Grandshine offers comprehensive supply chain management services spanning from design to production. We look forward to work with you.