Test and measurement

We don’t release a Polymagnet until we’ve measured it. Every unit that leaves our facility has a validated force curve, confirmed maxel placement, and documented field data. Measurement is embedded in our design process from the first prototype through volume production.

This page describes the tools, methods, and standards we use to characterize Polymagnets and verify that they meet customer specifications.

Force vs. distance measurement

The force vs. distance curve is the primary performance metric for any Polymagnet. It describes how much force the magnet produces at every separation distance from its mating surface.

We measure force curves using precision load cells mounted on a motorized linear stage. The stage pulls the Polymagnet away from its mating surface at controlled speed. Our load cell records force at each distance increment. Resolution is sub-millinewton in force and sub-micrometer in distance.

The measured curve shows peak force, decay rate, engagement distance, and any inflection points. We compare it against the predicted curve from our design software. If the two diverge beyond the specified tolerance, we modify the maxel code and reprint.

Most Polymagnet functions can be specified through their force curve alone. Latch engagement, alignment centering, shear resistance, spring rate, and torque transfer all appear as measurable features on the curve. A single test captures the complete mechanical behavior.

Shear force testing

Shear force, the lateral resistance parallel to the magnet face, is measured on a separate fixture. We hold the Polymagnet against a ferrous plate and apply a controlled lateral load until the magnet displaces. The fixture records force at initial displacement, peak resistance, and failure.

We test shear on thin metal targets using calibrated steel shims of known thickness. The same Polymagnet is tested across a range of thicknesses to generate a shear vs. thickness curve. This data is critical for consumer electronics, automotive trim, and medical devices where the target metal is thin. We publish shear data for every Max-Attach product in our catalog, and customers can request equivalent data for custom Polymagnets.

Torque displacement testing

Magnetic torque couplings require a rotational test. Our fixture mounts the coupling on a precision rotary stage and applies angular displacement while a calibrated transducer measures torque. The output is a torque vs. displacement curve.

We characterize onset slope, peak torque, and slip torque. Our SBIR contract for torque transfer improvement used this method to validate that specific maxel codes produced steeper onset curves than conventional magnetic couplings. The test data was the primary evidence that our codes outperformed single-dipole couplings by more than 600% in certain configurations.

Surface field mapping

Every Polymagnet has a unique magnetic field at its surface. We map this field using Hall probe arrays scanned across the magnet face. The probe records field strength and polarity at each position, producing a two-dimensional field map.

Surface field maps verify two things. First, that the MagPrinter placed every maxel at the correct position with the correct polarity and saturation. A missing or weak maxel shows up as a deviation from the expected field. Second, field maps are our quality control tool in production. We compare each unit’s map against the reference for that code. Units outside tolerance are rejected or re-magnetized.

We’ve also developed visual field mapping tools for customer demonstrations. These display the magnetic field in a color-coded image that makes the maxel arrangement visible. Engineers evaluating Polymagnet technology for the first time find these useful because the difference from a conventional magnet is visible in the first image.

Environmental testing

Polymagnets must perform across the temperature, humidity, and vibration conditions of their target application. We conduct environmental testing in-house.

Temperature testing covers the operating range of the magnetic material. Neodymium is the most common Polymagnet material, but it loses strength as temperature rises. The rate of loss varies by grade, and some grades are more temperature-stable than others. We measure force curves at elevated temperatures so the customer knows the exact derating for their operating range. Applications above 150 degrees C move to samarium cobalt, which holds its field strength up to 300 degrees C.

Vibration testing uses standard shake-table equipment. We mount Polymagnet assemblies on the table and subject them to sinusoidal and random vibration profiles. Automotive, aerospace, and defense applications have specific standards (e.g. MIL-STD-810). We test to those standards when required by the customer. Our vibration data has confirmed that Polymagnet force profiles remain stable after extended vibration exposure, which is expected given the absence of mechanical parts. Conventional magnetic closures sometimes loosen under vibration due to reduced friction. Polymagnets that are coded for direct shear force resist this degradation.

Salt spray and humidity testing are conducted for Polymagnets that will be used in marine, outdoor, or high-humidity environments. Neodymium magnets corrode without protection, so Polymagnets for these applications receive coatings (nickel, epoxy, or Parylene) before we conduct the exposure tests.

Finite element analysis

Before printing a prototype, our engineers model the magnetic field and force behavior using finite element analysis (FEA). The model accepts the maxel code as input and predicts the three-dimensional field structure, the force vs. distance curve, and the interaction with the specified mating surface.

FEA catches design issues before we use any material. A code that seems reasonable on paper might produce an unexpected force feature, like a secondary peak or a dead zone. Our model will reveal that. We’ve saved significant prototyping time by iterating in software before moving to the MagPrinter. This is especially valuable for complex magnetization projects where the geometry is non-standard and the expected behavior has no analog in our existing catalog.

Our FEA tools are calibrated against measured data from thousands of Polymagnet configurations. Model-to-measurement correlation is high across the full range of materials, maxel sizes, and code densities we use. We update the calibration data set with every new configuration we print and measure.

Production quality control

Volume production of Polymagnets requires consistent quality across every unit. Our QC process has three checkpoints:

• Pre-print inspection. Verification of magnet blank dimensions, material grade, and surface condition before magnetization
• Post-print field map. Automated surface field scan of every unit against the reference map for that code. Units outside tolerance are flagged.
• Sample force testing. Force curve measurement on a statistical sample from each lot to confirm the population meets its force specification

We maintain traceability for every production lot. Each lot is linked to the specific MagPrinter, magnetizing coil, and software revision that produced it. If a performance issue surfaces in the field, we can trace the unit to its production lot and pull the associated QC data.

Data delivery

Customers receive documented performance data with every order. Standard documentation includes the force vs. distance curve, the surface field map, and the material certification for the magnetic blank. Custom orders include additional data: shear curves, torque displacement measurements, or temperature derating curves.

All measurement data is provided in digital format. We archive a copy of every data set. If a customer reorders the same Polymagnet months or years later, the original data is available for comparison to the new lot. This archive has proven useful for customers who return to a product design after an extended period. The original measured performance is on file, and any deviation in new production can be detected against the baseline.