Small non-contact drive coupling
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FAIZEAL — Small Non-Contact Magnetic Coupling
Miniature Pancake Disc-Type Halbach Permanent Magnet Coupling for Hermetic, Vacuum, Medical, Laboratory, and Semiconductor Applications
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This small magnetic coupling was custom-engineered by FAIZEAL for an American customer requiring a hermetic, leak-free, non-contact torque transmission solution in a compact footprint. The design integrates a dual-rotor 6-pole Halbach permanent magnet array inside a square housing, with an internal stainless steel containment sleeve isolating the drive and driven sides — eliminating any mechanical seal, dynamic O-ring, or shaft penetration between the input and output environments.
The product belongs to the pancake disc-type magnetic coupling family, where magnetic flux crosses axially (parallel to the rotation axis) rather than radially. This axial-flux topology enables a very short axial length while delivering high torque density in a small envelope. The 6-pole configuration (3 pole pairs) provides smooth torque transmission with low cogging and low torque ripple, which is critical for laboratory, medical, and semiconductor precision applications.
The custom design for the American client targets three core requirements simultaneously: (1) absolute hermetic sealing between wet/dirty/contaminated process media and the external drive environment, (2) small form factor for integration into compact benchtop and rack-mount equipment, and (3) precision torque transmission with no backlash, no wear, and no particulate generation over a long service life.
This product description is intended for original equipment manufacturers (OEMs), system integrators, design engineers, technical procurement specialists, and laboratory equipment manufacturers in North America, Europe, and Asia who require a reliable, hermetic, non-contact torque transmission solution for sensitive process environments.
The magnetic coupling operates on the principle of permanent magnet torque transmission across a non-magnetic containment barrier, without any mechanical contact between the input (driver) and output (driven) sides.
Magnet Array Design — The coupling uses a 6-pole Halbach permanent magnet array, where each pole pair consists of two arc segments oriented at specific magnetization angles. Unlike a conventional radial-flux array that produces equal magnetic fields on both sides of the rotor, the Halbach array concentrates magnetic flux on the coupling air gap side while canceling flux on the back side. This self-shielding effect delivers three engineering benefits: (1) 30-50% higher air-gap flux density than conventional radial magnetization at the same magnet volume, (2) much thinner and lighter back-iron, and (3) nearly sinusoidal air-gap flux distribution, which directly reduces cogging torque and torque ripple.
Axial Flux Topology — Because the magnet array is oriented with its pole axis parallel to the rotation axis, magnetic flux crosses axially across the short gap between the driver rotor (input side) and the driven rotor (output side). This is fundamentally different from cylindrical radial-flux couplings, where flux crosses radially across a tubular air gap. The axial-flux topology produces a flat, pancake-shaped coupling geometry that is ideal when the available axial length is short but radial space is more abundant.
Containment Sleeve Function — Between the driver rotor and driven rotor sits a thin-walled, non-magnetic containment sleeve (also called isolating can or barrier can). The sleeve mechanically separates the two rotors while allowing magnetic flux to pass through unimpeded. This sleeve is the hermetic barrier: process media (chemicals, biological fluids, vacuum, sterile solutions, ultra-pure solvents) remain on one side of the sleeve, while the drive motor, encoder, and bearings remain completely isolated on the other side. There is no rotating seal, no dynamic O-ring, no shaft seal — therefore no leak path exists.
Torque Transmission Mechanism — When the driver rotor rotates, the rotating magnetic field exerts a synchronizing torque on the driven rotor through the containment sleeve. The driven rotor follows the driver at exactly the same rotational speed (synchronous coupling, no slip in normal operation). The maximum transmittable torque is determined by the magnetic field strength, the air gap geometry, and the rotor area. If the driven load torque exceeds this maximum, the coupling slips — protecting the drive motor from overload damage without mechanical failure. This inherent overload protection is a major safety advantage over rigid mechanical couplings.
The axial magnetic attraction force between the driver and driven rotors is given by:
F_a = (B_g² × A_eff) / (2μ₀)
where F_a is the axial attraction force (N), B_g is the air-gap flux density (T), A_eff is the effective rotor area (m²), and μ₀ = 4π × 10⁻⁷ H/m is the permeability of free space. For a typical 6-pole Halbach array with N52 NdFeB, B_g reaches 0.4-0.6 T, producing manageable axial force while maintaining high torque capacity.
The maximum transmittable torque is given by:
T_max = (B_g² × π × r_m² × n_p) / (2μ₀) × k_stack × k_Halbach
where T_max is the peak torque (N·m), r_m is the mean rotor radius (m), n_p is the number of pole pairs, k_stack is the stacking factor for multi-disc designs (typically 0.85-0.95), and k_Halbach is the Halbach gain factor (1.5-2.0 depending on segmentation).
The transmitted torque at any rotor angular displacement follows a sinusoidal relationship:
T(θ) = T_max × sin(n_p × θ)
where θ is the load angle (mechanical degrees between driver and driven rotors). At zero load, θ = 0 and torque is zero. As load increases, θ increases until T reaches T_max at θ = 90°/n_p. Beyond this critical angle, the coupling slips. For stable operation, the design load angle should remain below 30°/n_p.
When the magnetic field rotates relative to the conductive containment sleeve, eddy currents are induced in the sleeve wall:
P_e = k_e × (π × f × B_g)² × t² × V / ρ
where f is the magnetic field alternating frequency (Hz), t is the sleeve wall thickness (m), V is the sleeve volume (m³), ρ is the sleeve electrical resistivity (Ω·m), and k_e is a geometry constant. For a typical 316L stainless steel sleeve rotating at 3000 RPM, eddy current loss must be carefully managed to prevent sleeve overheating.
The containment sleeve material selection balances three competing factors: (1) magnetic transparency (must not block flux), (2) corrosion resistance to the process media, and (3) electrical resistivity (higher resistivity reduces eddy current loss). FAIZEAL offers sleeve materials including 316L stainless steel (general chemical), Hastelloy C-276 (aggressive acids), titanium Grade 2 (chlorides), PEEK polymer (zero eddy current, lower temperature), and aluminum oxide ceramic (extreme corrosion).
The coupling service life is dominated by three factors: magnet demagnetization (theoretically infinite for sintered NdFeB at operating temperatures below 80°C), bearing wear (L10 = 20,000-50,000 h depending on load and speed), and containment sleeve integrity (no mechanical wear because there is no contact). For properly specified applications, FAIZEAL magnetic couplings routinely deliver MTBF > 50,000 hours and service life exceeding 10 years.
Based on the provided product images, this custom magnetic coupling comprises the following physical components:
The square housing visible in the product photo is the outer protective enclosure that isolates the entire magnetic coupling assembly from the external environment. The housing material is selected based on the customer's process environment. Common options include glass-fiber reinforced polyamide (PA66-GF) for general laboratory use, polypropylene (PP) for chemical resistance, PVDF for aggressive chemicals, 304 stainless steel for medical applications, and aluminum alloy for lightweight industrial use. The housing provides mechanical protection, mounting features (typically 4 corner mounting holes or side flanges), and in some designs integral bearing housings for the driver and driven shafts.
The driver rotor visible through the housing window is a 6-pole Halbach permanent magnet array. The Halbach arrangement concentrates flux on the air-gap side (toward the driven rotor) while minimizing back-iron flux. Each pole pair consists of two arc-shaped NdFeB segments oriented at optimized magnetization angles. The rotor is mounted on the input shaft, which is mechanically connected to the customer's drive motor through a coupling, gear, or direct mount. The rotor back plate (back-iron) is typically low-carbon steel (1010 or DT4 electrical iron) or can be eliminated entirely to reduce weight and inertia.
The driven rotor (visible in the third detail photo showing two 6-pole rotor patterns) mirrors the driver rotor design and is mounted on the output shaft that drives the customer's load (pump impeller, stirrer, valve actuator, fan, encoder). Both rotors are geometrically identical and magnetically matched to produce balanced magnetic attraction along the rotation axis.
The cylindrical component shown in the second image (image#2) is the containment sleeve assembly. This sleeve is the hermetic barrier separating the process media from the drive environment. The sleeve shown has three 120°-spaced internal hex socket head cap screws on its end face for flange mounting to the housing or process vessel wall. Standard sleeve materials include:
• 316L stainless steel — general chemical resistance, FDA-compliant for food contact
• Hastelloy C-276 / C-22 — aggressive acids, chlorides, sea water
• Titanium Grade 2 — light weight, chloride resistance
• Duplex 2205 stainless steel — high strength, chloride resistance
• PEEK polymer — zero eddy current loss, limited temperature range
• Aluminum oxide (Al₂O₃) ceramic — extreme chemical resistance, brittle
Standard sleeve wall thickness is 0.5-1.5 mm, optimized to minimize eddy current loss (which scales with the square of thickness) while maintaining sufficient mechanical strength to withstand pressure differential. Standard pressure rating is 10-50 bar depending on diameter and material; high-pressure designs up to 100 bar are available.
The smaller cylindrical component shown in image#2 is the inner rotor or driven shaft assembly. This component slides inside the containment sleeve and is mounted on the output shaft. The inner rotor surface is precision machined to maintain a uniform air gap (typically 0.5-1.5 mm) between the rotor and the sleeve inner wall, ensuring consistent magnetic flux density and torque capacity throughout the rotation cycle.
The driver and driven shafts are supported by high-precision ball bearings or sleeve bearings depending on the application. The bearing housings are integrated into the square housing. Because the driven shaft is fully enclosed by the housing and sleeve, there is no rotating seal, no dynamic O-ring, and no shaft penetration to the process side — eliminating the primary leak path of conventional pump and mixer designs.
The non-contact magnetic torque transmission eliminates any mechanical seal between the drive and the process environment. There is no rotating seal, no dynamic O-ring, no packing gland, no mechanical seal face — and therefore no leak path. This is the only torque transmission technology that can claim truly hermetic (zero leak) separation, which is critical for:
• Toxic, hazardous, or carcinogenic chemicals
• Sterile pharmaceutical and biotechnology processes
• Ultra-high vacuum (UHV) systems
• Semiconductor wet etch and CMP processes
• Food and beverage sanitary processes
• Cryogenic fluids (LN₂, LHe)
• Radioactive or biologically active media
With no mechanical contact between driver and driven sides, there is no wear, no friction, no lubrication requirement, and no consumable parts to replace. Conventional mechanical seals typically require replacement every 6-18 months in chemical service. FAIZEAL magnetic couplings routinely operate for 10+ years without maintenance intervention, dramatically reducing total cost of ownership.
If the driven load torque exceeds the magnetic coupling's maximum transmittable torque, the driven rotor slips relative to the driver. This slipping protects the drive motor, gearbox, and downstream equipment from overload damage — without any mechanical failure. When the overload condition clears, the coupling automatically re-engages synchronously. This is a critical safety feature compared to rigid couplings, which would transmit the overload torque directly to the drive train and potentially damage expensive components.
The non-contact magnetic transmission tolerates significant angular misalignment (typically ±0.5°), parallel misalignment (typically ±0.5 mm), and axial movement (typically ±1-2 mm) between driver and driven shafts. This eliminates the precision alignment requirement of rigid couplings and the vibration sensitivity of gear or chain drives — simplifying installation, reducing commissioning time, and improving reliability in field-deployed equipment.
Because there is no friction between driver and driven sides, the coupling generates zero wear particles, zero dust, and zero contamination. This is essential for cleanroom applications (ISO Class 3-5), pharmaceutical aseptic processing, semiconductor fabrication, and analytical instrument environments where even microscopic particulates can compromise product quality or measurement accuracy.
While the initial purchase price of a magnetic coupling is typically 2-5× higher than a comparable mechanical seal pump, the total cost of ownership over a 10-year service life is dramatically lower because:
• Zero maintenance labor cost (vs. annual seal service for mechanical seal pumps)
• Zero spare parts cost (no seal faces, O-rings, bearings to replace)
• Zero unplanned downtime from seal failure
• Zero product loss from seal leakage
• Zero environmental contamination cost
• Zero workplace safety incident cost
For critical-service applications, FAIZEAL magnetic couplings deliver payback periods of 6-18 months versus mechanical seal alternatives.
The custom 6-pole Halbach pancake magnetic coupling is designed for the following application categories, with particular fit for North American laboratory, medical, semiconductor, and chemical processing OEMs:
• Peristaltic pump drive heads (leak-free alternative to sealed pump heads)
• Centrifuge drive systems
• Stirred reactor magnetic drive couplings (100 mL to 50 L scale)
• Rotary evaporator drives
• HPLC pump drive modules
• Mass spectrometer sample introduction
• Vacuum chamber sample manipulators
• Blood pump drive couplings (extracorporeal circulation)
• Dialysis machine couplings
• IV infusion pump drive couplings
• Sterile fluid handling equipment
• Pharmaceutical mixing and filling equipment
• Diagnostic analyzer stirring drives
• Surgical irrigation pump drives
• Chemical mechanical planarization (CMP) slurry delivery pumps
• Wet etch bath recirculation pumps
• Ultra-pure chemical (UPC) distribution pumps
• Photoresist delivery pumps
• Spin coater drive couplings
• Wafer cleaning tool drive couplings
• Specialty chemical batch reactor drives (pilot plant scale)
• Pharmaceutical intermediate synthesis reactors
• Agitated crystallizer drives
• Corrosive chemical transfer pumps
• Acid and base metering pumps
• Photographic chemical processing
• Turbo molecular pump backup bearings
• Ion pump drive couplings
• Cryopump drive couplings
• Load lock chamber rotary drives
• Vacuum valve actuators
• Space simulation chamber drives
• Sanitary centrifugal pump drives
• Aseptic filling machine drives
• Sterile mixing equipment drives
• Dairy processing pump drives
• Brewery yeast propagation stirring
• Radioactive liquid transfer pump drives
• Hot cell manipulator drives
• Radioisotope production reactor stirring
• Spent fuel pool circulation pumps
• Decontamination equipment drives
• Downhole chemical injection pump drives
• Subsea umbilical pump drives
• Hydraulic actuation pump drives
• Wireline tool drive couplings
• Coiled tubing tool drives
FAIZEAL provides full custom engineering support for North American OEMs, with engineering communication in English, on-time delivery to U.S. destinations, and complete documentation packages including 2D drawings, 3D STEP files, FEA magnetic simulation reports, material certificates, and PPAP-style qualification reports when required.
• Rotor diameter: Ø15-100 mm typical (custom up to Ø300 mm available)
• Housing size: scaled to rotor diameter with 20-50 mm radial clearance
• Axial length: 15-80 mm depending on pole count and torque requirement
• Maximum torque: 0.1-50 N·m typical for this size range
• Through magnet grade selection, pole count optimization, and multi-disc stacking
• Magnet grade: NdFeB N35-N52, N42SH/N40UH/N38EH temperature grades
• Sleeve material: 316L, Hastelloy C-276/C-22, Titanium Gr2, Duplex 2205, PEEK, ceramic
• Housing material: PA66-GF, PP, PVDF, 304SS, 316LSS, aluminum 6061
• Surface treatment: Ni-Cu-Ni plating, epoxy coating, PTFE coating, passivation
• Mounting flange: 3-hole, 4-hole, custom bolt patterns
• Shaft interface: round bore, keyed bore, splined, threaded, D-bore
• Electrical feedthrough: optional Hermetic feedthrough for encoder/sensor signals
• Pneumatic/hydraulic ports: optional integration for process connections
• Speed: up to 5000 RPM continuous, higher on request
• Pressure rating: 10-100 bar depending on sleeve diameter and material
• Temperature: -60°C to +350°C with appropriate grade selection
• Torque overload protection: adjustable slip torque setting
• FDA-compliant materials for food contact
• USP Class VI biocompatibility for medical applications
• ASME BPE for bioprocessing equipment
• SEMI standards for semiconductor equipment
• ATEX/IECEx for explosion-proof environments
• RoHS, REACH compliance
• ISO 9001 quality management
• Material traceability with mill certificates
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Application keywords: laboratory instrument, analytical instrument, medical device, blood pump, dialysis, IV infusion, pharmaceutical mixing, semiconductor wet process, CMP slurry, wet etch, ultra-pure chemical, chemical reactor, crystallizer, vacuum chamber, cryogenic pump, sanitary pump, dairy processing, radioactive transfer, downhole tool, subsea pump.
FAIZEAL — Custom Permanent Magnet Magnetic Couplings, Pancake Disc-Type Halbach Couplings, Hermetic Seal-Less Couplings for Laboratory, Medical, Semiconductor, Chemical, and Vacuum Applications. Ningbo, China. Established 2017. ISO 9001 certified. FDA, USP Class VI, ASME BPE, SEMI, ATEX compliant materials. Global shipping with North American logistics support. Engineering communication in English. Custom prototypes in 2-4 weeks, production in 4-8 weeks.
