Overmolded Magnets — Sealed, Precise, Automation-Ready
Injection-molded polymer fully encapsulates the magnet — corrosion-proof, dimensionally stable, and shaped for snap-fit or press-fit into your product. The cleanest solution for pumps, medical devices, and food-grade equipment.
For Procurement
MOQ, lead time, packaging and commercial terms — go straight to a quotation.
Request a Quote →For Engineering
Grades, drawings, process data and design support for your DFM review.
Magnet Design Guide →For Quality / SQE
Certificates, inspection planning, traceability and PPAP / FAI support per project.
Certificates & Documentation →
Why Overmold?
Bonded NdFeB or sintered magnet + engineering polymer = the best of both materials.
- ✓Complete corrosion protection — polymer barrier is thicker and more durable than any coating — survives salt spray, steam, and chemicals
- ✓Net-shape precision — molded features: snap-fit tabs, locating pins, gear teeth, threads — eliminating machined components
- ✓Automated assembly ready — consistent molded geometry feeds vibratory bowls and pick-and-place systems without special tooling
- ✓Food & medical grade options — PPS and PEEK overmolding meet FDA and USP Class VI requirements
Applications
| Application | Typical Spec | Why This Material |
|---|---|---|
| Circulation Pump Rotors | Bonded NdFeB ring in PPO | Wet rotor designs — no seal needed, magnetic drive |
| Medical Pump Components | SmCo in PEEK | Autoclavable, biocompatible, no coating to degrade |
| Automotive Sensor Targets | NdFeB in PA66 | Survives 150°C engine bay + road salt |
| Food Equipment Sensors | Ferrite in PPS | IP69K washdown rated |
| Flow Meter Impellers | Bonded NdFeB in PPS | Dimensionally stable, corrosion-proof |
Overmolding Materials & Capabilities
Polymer and magnet combinations matched to your environment.
| Parameter | Options | Notes |
|---|---|---|
| Polymers | PA6/PA66, PPO (Noryl), PPS, PEEK, TPE | Food/medical: PPS, PEEK |
| Magnets | Bonded NdFeB, sintered NdFeB (coated), SmCo, ferrite | Sintered requires coating before molding |
| Max size | Up to 150mm diameter | Insert molding press capacity |
| Tolerance | ±0.05mm molded dims | Critical features can be post-machined |
| Temperature | PA: 120°C / PPS: 180°C / PEEK: 250°C | Combined with magnet temp rating |
| Sealing | Up to IP67 / IP69K | Tested per IEC 60529 |
Magnet Selection for Overmolding
The molding process constrains magnet choice:
- ✓Bonded NdFeB — the default choice — survives molding temperatures (180–300°C) without degradation, net-shape pressed to ±0.1mm
- ✓Sintered NdFeB — requires Ni-Cu-Ni or epoxy coating before molding; molding temp must stay below 180°C — use PA or PPO, not PPS at full temp
- ✓Ferrite — temperature-tolerant and cost-efficient; size is the constraint (ferrite is 3× the volume for equivalent flux)
Design for Overmolding
Get the most from insert molding with these guidelines:
- ✓Uniform wall — 1.5–3.0mm polymer wall for optimal fill and shrinkage control
- ✓Magnet retention — mold polymer over magnet shoulders or through-holes for mechanical interlock, not just adhesion
- ✓Mold flow direction — design gate location so polymer flows along (not across) the magnet — prevents displacement during injection
- ✓Sink marks — avoid thick polymer sections over the magnet; use ribs to maintain stiffness with uniform wall
Frequently Asked Questions
Can sintered NdFeB be overmolded?
Yes, with a coating (Ni-Cu-Ni or epoxy) to protect against corrosion during molding and in service. The molding temperature must stay below the magnet's grade limit — for PPS molding at 180°C, use SH-grade or higher NdFeB or switch to SmCo. We verify compatibility during DFM review.
How does overmolding compare to coating for corrosion protection?
Overmolding is superior: 1–3mm of polymer vs 15–25µm of coating. An overmolded magnet survives salt spray, steam sterilization, and chemical exposure that would eventually penetrate any coating. For anything wet or corrosive, overmolding is worth the tooling investment.
What's the tooling cost and lead time?
Tooling runs $3,000–$15,000 depending on size and complexity, with 4–6 weeks to first articles. For volumes above 50,000/year, tooling amortization typically pays back within the first year via eliminated coating and assembly operations.
Do you offer food-grade and medical-grade overmolding?
Yes — PPS is FDA-compliant for food contact, and PEEK meets USP Class VI for medical devices. Our facilities can produce cleanroom-packed overmolded magnets for medical and pharmaceutical applications. Ask for our compliance documentation package.
Overmolding Process Controls
Bond & Seal Integrity
Adhesion and wetting verified per tool qualification; seal tested to your IP or pressure spec for submersible and fluid-contact parts.
Thermal Management
Mold temperature profiles selected to protect magnet properties; post-mold magnetic verification confirms no degradation from the molding cycle.
Material Compatibility
Engineering polymers (PPS, PBT, PA, TPU) matched to your media and temperature; magnet substrate and coating selected for the overmold system.
Have an Assembly Drawing or BOM?
Send it to our team — we'll review the design and quote it as a validated, ready-to-install assembly.