Cracking in injection-molded magnets not only affects product usability but also harms the company’s reputation. Enterprises need to optimize all aspects of the process, from material selection to injection molding, to ensure product quality.
Impacts of Cracking in Injection-Molded Magnets
| Assembly: Cracked or fragmented injection-molded magnets will alter the original dimensions and shape of the magnet, making it impossible to properly assemble them with equipment (such as motor rotors).
| Usability: Cracking causes physical structural fractures within the magnet, disrupting the internal magnetic circuit distribution. This leads to product scrapping, rendering it unusable.
| Equipment Damage: If an injection-molded magnet cracks inside a high-speed rotating device (such as a motor), flying debris can damage other precision components within the equipment.
Causes of Cracking in Injection-Molded Magnets
| Stress: During injection molding, if the injection pressure or holding pressure is too high, or if the injection speed is too fast, the melt will experience excessive orientation stress and shrinkage stress within the cavity. The release of internal stress after cooling can lead to cracking, often occurring at the junctions between thick and thin sections. Uneven cooling caused by an excessively fast cooling rate or a low mold temperature can also lead to cracking due to thermal expansion and contraction.
| Temperature and Humidity: Prolonged exposure to high-temperature environments (exceeding the tolerance temperature of the material or binder) can cause material aging and embrittlement. High-humidity environments (such as water absorption) can cause some resins to swell, reducing their strength and leading to cracking. Low-temperature environments make the material brittle, reducing its impact resistance and making it prone to cracking at low temperatures.
| Chemical Media: Under the action of environmental media (such as grease), the penetration of chemical media can weaken the intermolecular forces of the polymer, leading to the initiation and propagation of microcracks. This often manifests as brittle cracking after a period of use.
Methods to Prevent Cracking of Injection-Molded Magnets
| Reduce Injection Pressure and Speed: Excessive injection pressure or speed can cause the molten plastic to exert excessive impact force or localized high pressure on the magnet, leading to crushing or cracking. The injection pressure should be appropriately reduced, and multi-stage injection should be adopted to prevent the melt from impacting the magnet at high speed.
| Consider Environmental Adaptability: If the product needs to be used in humid, high-temperature, or corrosive environments, materials with moisture resistance, high-temperature resistance, or corrosion resistance should be selected, or surface treatment should be applied to improve environmental adaptability.
| Materials: Select appropriate magnetic powder (such as NdFeB, Ferrite) and binder based on the product’s operating temperature, magnetic performance requirements, and mechanical strength needs. For example, a high-temperature-resistant binder should be selected for high-temperature environments, and magnetic powder with a high magnetic energy product can be chosen for scenarios requiring high magnetic performance.
Magnets Manufacturer
At Tengye, we’re thrilled to be early participants in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects. Work with our magnet experts to get the right magnet solution.
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