LSR Overmolded Magnet Rubber Protective Sheath

At Xiangchu (Hubei) Rubber Co., Ltd., located at No. 54, Neihe Lane, Fankou Sub-district, Echeng District Economic Development Zone, Ezhou City, Hubei Province, China, we specialize in custom LSR molding for industrial and consumer applications. Our LSR overmolded magnet sheaths are manufactured via precision liquid injection molding, ensuring a seamless, gap-free bond between the LSR outer sheath and the inner magnetic core that eliminates delamination under continuous use. We can produce custom sheaths to match your specific magnet dimensions, magnetic performance requirements, and application-specific environmental constraints, with consistent quality controlled through our ISO 9001-certified quality management system.

Unlike dip-molded or post-assembled rubber magnet covers, our overmolding process integrates the LSR and magnet core in a single production step, resulting in tighter dimensional tolerance and more reliable protection. This product line caters to low-volume prototype development and high-volume mass production, making it suitable for a wide range of project scales.

Technical Specifications

Material Properties

Our LSR overmolded magnet protective sheaths use food-grade or industrial-grade raw liquid silicone rubber as standard, paired with customer-specified or commonly available permanent magnet cores (neodymium iron boron (NdFeB), samarium cobalt (SmCo), alnico, and ferrite magnets are all compatible for overmolding). Key material properties are as follows:

• LSR chemical composition: 100% solidified high molecular weight polydimethylsiloxane, no added plasticizers or low-quality fillers that cause leaching or aging
• Temperature resistance range: -40°C to 200°C (continuous operation), with short-term peak resistance up to 230°C
• Chemical inertness: Resistant to water, common detergents, mild acids, alkalis, oils, and most organic solvents
• Bonding performance: Covalent bonding between LSR and magnet surface pre-treatment, 100% gap-free encapsulation to prevent moisture or contaminants from penetrating to the inner core
• Compliance: Standard industrial grades meet ROHS and REACH environmental requirements; food-grade options meet FDA 21 CFR 177.2600 regulations for indirect food contact

Physical Performance

*Note: Magnetic performance parameters are determined by the inner magnet core specifications. We can adjust magnet grade, size, and magnetic flux output to meet your application requirements.

Process Parameters

Our production uses precision horizontal liquid injection molding, with controlled process parameters to ensure consistent product quality:

• Injection pressure: 8 MPa to 15 MPa
• Mold temperature: 160°C to 190°C
• Curing time: 30 seconds to 120 seconds (depending on sheath wall thickness)
• Post-curing: 4 hours at 150°C to eliminate residual volatile compounds
• Surface finish options: Matte, semi-gloss, and glossy, as requested by customers

Product Advantages

1. Comprehensive protection for magnetic cores

Exposed magnets are prone to chipping, cracking, and corrosion when exposed to moisture or harsh chemicals, which degrades magnetic performance over time. Our seamless LSR overmolding creates a fully waterproof, chemically resistant barrier that prevents oxidation and corrosion of NdFeB and other corrosion-prone magnet alloys, extending the service life of the magnetic component by 3–5 times compared to unprotected magnets. The elastic LSR outer layer also absorbs impact and vibration, reducing the risk of magnet breakage during handling and operation.

1. Customizable design and tight dimensional control

We support full customization of sheath dimensions, wall thickness, LSR hardness, and magnet specifications to match your application requirements. Our precision injection molding process maintains consistent dimensional tolerances even for complex geometries, such as curved profiles, through-holes, and mounting notches. Whether you need small, precision sheaths for consumer electronics or large overmolded magnets for industrial machinery, we can adapt our production to your design.

1. Non-marking, non-slip performance

The LSR outer sheath has a low surface energy and non-abrasive texture that prevents scratching of contact surfaces, unlike exposed hard magnetic cores. It also provides excellent non-slip grip, making it ideal for handheld tools, mounting components, and consumer products that require secure handling. Unlike thermoplastic overmolding, LSR maintains its elastic and non-slip properties even at low temperatures, eliminating brittleness in cold operating environments.

1. Biocompatible and food-safe options available

We offer food and medical-grade LSR formulations that meet global regulatory requirements for indirect food contact and short-term skin contact, making our sheaths suitable for food processing equipment, medical devices, and consumer wellness products. The LSR material is non-toxic, odorless, and resistant to repeated cleaning and sterilization (autoclaving, alcohol wiping, and UV sterilization are all compatible).

Applications

LSR overmolded magnet rubber protective sheaths are used across a wide range of industries, with common use cases including:

1. Household and consumer goods: Magnetic knife holders, refrigerator door seals with embedded magnets, curtain weight magnets, shower door magnetic strips, and handheld magnetic therapy devices. The LSR sheath prevents surface scratching on countertops and appliances, while blocking corrosion from high-humidity bathroom and kitchen environments.
2. Industrial automation and manufacturing: Magnetic sensor protective covers, conveyor system magnetic positioning components, robot end effector magnetic grippers, and motor magnetic core encapsulation. The vibration-absorbing LSR reduces signal interference for sensors and extends the service life of moving magnetic components.
3. Outdoor and marine equipment: Magnetic mounting bases for navigation lights, boat cover fastening magnets, and offshore equipment positioning magnets. The fully sealed LSR encapsulation prevents saltwater corrosion, which is the leading cause of failure for exposed magnets in marine environments.
4. Medical and wellness devices: Wearable magnetic therapy components, medical device magnetic closures, and diagnostic equipment magnetic positioning parts. Our food and medical-grade LSR options meet biocompatibility requirements for skin contact applications.
5. **Automotive industry: Door seal embedded magnets, trunk lid magnetic positioning components, and sensor magnetic core protection. The LSR material withstands the wide temperature range of automotive engine compartments and interior environments, maintaining performance from cold winter start-ups to hot summer interior temperatures.

Selection Guide

Hardness Selection

LSR hardness can be adjusted based on your application requirements:

• 30–40 Shore A: Soft, high-flexibility applications, such as curved seal components and wearable devices, requires high conformability
• 40–60 Shore A: General-purpose industrial and consumer applications, balances protection, flexibility, and structural stability, suitable for most magnetic mounting and positioning use cases
• 60–70 Shore A: High-wear applications that require higher structural rigidity, such as industrial conveyor components and high-frequency use magnetic grippers

Size Specifications

We offer two production options to meet different project needs:

1. Standard stock sizes: For common round, square, and rectangular magnet dimensions, we maintain limited stock of ready-to-ship sheaths for small-batch emergency orders. Contact our sales team for current stock availability.
2. **Custom size manufacturing: For non-standard dimensions and special geometries, we accept custom orders based on your drawings or sample specifications. We support minimum order quantities starting at 100 pieces for prototype development, and scale up to 100,000+ pieces for mass production.

Material Grade

Select the appropriate LSR grade based on your application:

• Industrial grade: Suitable for general industrial applications that do not require food or medical contact, offers cost-competitive performance with consistent quality
• Food grade: Compliant with FDA 21 CFR 177.2600, suitable for food processing equipment and consumer products that require food contact
• High-temperature grade: Formulated for continuous operation above 180°C, suitable for industrial high-temperature processing environments

Quality Assurance

At Xiangchu (Hubei) Rubber Co., Ltd., all production processes follow the requirements of our ISO 9001-certified quality management system, from raw material incoming inspection to finished product outgoing testing. Our quality control processes include:

1. Raw material inspection: Each batch of LSR raw material is tested for hardness, tensile strength, and purity before production, and all magnet cores are inspected for magnetic flux output and dimensional accuracy to ensure they meet specifications.
2. In-process quality checks: We conduct dimensional and visual inspections every 2 hours during production to identify and correct process deviations in real time.
3. Finished product testing: Each batch of finished overmolded sheaths undergoes performance testing, including water penetration testing, adhesion strength testing between LSR and the magnet core, and dimensional verification, to ensure no defective products are delivered to customers.
4. Traceability: We maintain full production batch records for all products, enabling full traceability from raw material to finished product shipment.

For inquiries, custom development requests, or quotations, contact us at:

• Address: No. 54, Neihe Lane, Fankou Sub-district, Echeng District Economic Development Zone, Ezhou City, Hubei Province, China
• Phone: +86 18071171144
• Email: churubber@163.com