Coded, correlated and multipole magnets: 25 answers

Question 1

What is a coded magnet?

Accepted Answer

A coded magnet is a permanent magnet whose face carries a designed pattern of many small north and south regions, instead of one north face and one south face. The pattern is the code. Two magnets printed with matching codes interact strongly with each other, and the pattern decides how the pair behaves as it approaches, touches or turns.

That matters to an engineer because a conventional magnet's behavior is set almost entirely by its size, shape and grade. A coded magnet's behavior is also set by its pattern. The same blank can be patterned to hold harder at contact, pull itself into alignment, push away until it passes a set point and then latch, or click between rotational positions.

The category traces to Correlated Magnetics Research (CMR) of Huntsville, Alabama, which sells coded magnets under the Polymagnet name. CMR's history page says its co-founder borrowed patterns, or codes, from signal processing theory to arrange magnetic fields. CMR describes Polymagnets as programmable magnets, and its catalog sorts them by behavior: attach, align, latch, spring and torque.

You will also see the terms programmable magnet, correlated magnet and smart magnet used for the same idea. Multipole magnet is a broader term that also covers simple alternating-pole rings.

Question 2

How do correlated magnets differ from conventional magnets?

Accepted Answer

A conventional magnet has one north pole and one south pole. Its field loops a long way out from the magnet, its strength at any distance is fixed by size, shape and grade, and two of them have no preferred rotational position when they meet.

A correlated magnet carries a pattern of many poles on the working face. CMR, which uses the phrase correlated magnetic systems in its press material, explains the effect with two principles on its FAQ: flux leaves one pole and seeks the opposite pole, and it takes the lowest-energy path to get there. Packing many small opposite poles side by side gives the flux short paths, so the field is concentrated close to the surface instead of leaking into the air.

Three practical differences follow. Holding force at contact goes up, because less flux is wasted. Reach goes down, because the field falls off faster with distance; CMR recommends keeping the gap to a Polymagnet or its steel target under 2 mm, depending on geometry and pattern. And the pattern can add behavior: a pair can align, latch, spring or detent rather than simply attract.

The trade-offs are real. Correlated pairs are made as matched pairs, and some behaviors, such as latch and spring, only work when the two parts are mechanically constrained and centered.

Question 3

Who manufactures programmable magnets?

Accepted Answer

The company that created the category is Correlated Magnetics Research (CMR) in Huntsville, Alabama, which sells programmable magnets under the Polymagnet name. It offers four things: an online catalog of pre-engineered magnet pairs, custom magnet design and production sourcing, Polyvision design software, and magnetizers for lab and production use (listed on its site as Polydesk, Polylab and Polymag 6.2). Its site says Polymagnets are made in any quantity from prototype to production volume.

Some distributors carry Polymagnet parts. CMR's own blog lists Amazing Magnets, Industrial Magnetics and Mechanisms Market as sellers of the Polymagnet Demo Kit.

If you need multipole magnetization rather than software-defined patterns, more suppliers exist. Our own check of 23 magnet makers' websites, published on the WholeMagnetics multi-pole page, found six that state multi-pole manufacturing: CMR, Storch Magnetics, Goudsmit Magnetics, Adams Magnetic Products, Dexter Magnetic Technologies and SuperMagnetMan. CMR was the only one in that check that programs a pole pattern in software; the others magnetize fixed patterns such as alternating-pole rings for sensors and encoders.

When you compare quotes, ask whether the supplier needs a dedicated magnetizing fixture for your pattern. That decides tooling cost and how fast you can change the design.

Question 4

What is a Polymagnet?

Accepted Answer

Polymagnet is the trade name Correlated Magnetics Research (CMR) uses for its programmable magnets. A Polymagnet starts as an ordinary rare-earth magnet. CMR then magnetizes a pattern of many north and south regions across its face, and that pattern sets how the magnet behaves.

CMR's home page describes them as programmable magnets that combine many magnetic fields. Its About page explains the manufacturing difference: rather than the simple north-south arrangement of off-the-shelf magnets, the pattern is designed in software and programmed into the magnet in minutes, not weeks.

The catalog groups Polymagnets by behavior. Attach magnets are tuned for holding force on steel. Align magnets center or rotate into position. Latch pairs repel until pushed past a set point, then attract. Spring pairs rest at a set distance apart. Torque parts give rotational detents and twist-to-release.

You can buy catalog pairs online, order custom designs, or license the tools: Polyvision pattern design software and CMR's magnetizers. CMR states it holds more than 100 issued US patents with more pending, and that those patents cover behaviors whether they are produced with Polymagnets, conventionally magnetized magnets or assemblies of discrete magnets.

Question 5

What is a maxel?

Accepted Answer

A maxel is a magnetic pixel: one of the small magnetized regions printed across the face of a coded magnet. Just as an image is built from pixels, a coded magnet's pattern is built from maxels, each magnetized north or south.

The term comes from the programmable-magnet work of Correlated Magnetics Research (CMR). Its Polyvision design software page says the tool lets users create custom Polymagnets by controlling magnetic patterns at the maxel level, with a real-time visual display of the pattern as it is designed.

Why the unit matters: the size, spacing and arrangement of maxels set how far the field reaches and what the pair does. Small, tightly packed opposite regions keep flux loops short, which concentrates holding force near the surface. Arranging regions in rings, stripes or asymmetric codes produces alignment, rotational detents, latching or spring behavior.

Maxels are written with a magnetizer that applies a focused magnetic pulse at each location. A Popular Mechanics article reposted on CMR's blog describes the earlier MagPrinter doing exactly this, encoding multiple poles across a magnet's surface with a focused electromagnetic field. To see the result on a finished part, lay magnetic viewing film over it.

Question 6

What is the difference between a multipole magnet, a Halbach array and a coded magnet?

Accepted Answer

All three shape a magnetic field on purpose, but they do it differently and suit different jobs.

A multipole magnet usually means a single magnet magnetized with several alternating north and south poles, such as a ring with six or twelve poles. These are standard in motors, encoders and Hall-effect sensors. The pattern is regular and comes from a magnetizing fixture built for it.

A Halbach array is an assembly of separate magnets, each oriented at a rotating angle, so flux is concentrated on one side of the array and largely cancelled on the other. It is a way to arrange discrete parts, used where a strong one-sided field is wanted.

A coded magnet, sold by Correlated Magnetics Research as the Polymagnet, carries a designed and often irregular pattern of many small regions on one piece. The pattern is chosen for a behavior between two mating parts: alignment, latching, a contactless spring, rotational detents. CMR designs the pattern in software and prints it with a programmable magnetizer, so no dedicated fixture is needed per design.

One note for anyone designing around these: CMR states on its FAQ that its patents typically cover behaviors regardless of whether they are achieved with Polymagnets, conventionally magnetized magnets or assemblies of discrete magnets. Check freedom to operate before building a look-alike from separate magnets.

Question 7

How does a multipole magnet's pull force compare with a conventional magnet of the same size?

Accepted Answer

At contact, and on the right target, a patterned magnet can hold much harder than a conventional magnet of the same size and grade. Away from contact it usually holds less, because its field reaches a shorter distance.

The reason is flux leakage. A conventional magnet sends much of its flux on long loops through the air, and that flux does no work holding steel. A multipole or coded pattern gives the flux short paths into the target, so more of the magnet's energy goes into the joint.

Correlated Magnetics Research publishes several figures for its Polymagnets. Its applications page says up to 5 times stronger than conventional magnets. Its home page says up to 4 times the strength of conventional magnets on standard sheet metal, which is what attach Polymagnets are tuned for. Its attach design note claims up to 8 times more shear strength. Treat these as vendor maxima from CMR's in-house testing, measured with magnets held parallel and aligned.

Size still matters. CMR notes that magnet energy scales with volume, that very small magnets have little energy unless practically touching their target, and that it has engineered magnets down to 4 mm in diameter. It recommends a gap under 2 mm. Test your own geometry, target thickness and coating before committing to a number.

Question 8

How do you get precise, repeatable alignment with magnets?

Accepted Answer

Ordinary magnets are poor at alignment. Two disc magnets attract wherever they meet, have no preferred rotational position, and can settle off-center. Designers usually add pins, bosses or pockets to fix that.

A patterned magnet pair can do the locating itself. Correlated Magnetics Research's Align Polymagnets are made as matched pairs whose patterns only reach their lowest-energy state in one position, so the parts pull themselves into place. CMR's design note describes three kinds: centering, rotational and lateral alignment. Centering pairs come in versions with different precision and different tolerance for starting off-center. Rotational pairs prefer one or several angles; the catalog includes detents at 90, 120 and 180 degrees, and CMR says almost any angle and number of positions is possible as a custom design.

CMR claims Align Polymagnets perform the same way every time without recalibration or maintenance, and its applications page proposes them for tripods, cameras, scopes, laser pointers and optics, where repeatable positioning would otherwise need a feedback loop or active control.

Practical points: alignment force is strongest at close range, so bring parts near before relying on the magnets to finish the job, and add a mechanical stop where loads could knock the joint out of position. Catalog parts include center-alignment pairs with #6 countersinks and 2- and 3-position rotational alignment pairs.

Question 9

Magnetic latch vs mechanical latch: which should I use?

Accepted Answer

A mechanical latch holds by geometry: a hook, pawl or detent physically blocks movement. It can resist high loads and impacts and gives a positive lock, but it has moving parts that wear, can jam with dirt, and needs a gap or opening for the catch.

A plain magnetic catch has no moving parts but grabs from a distance and can feel abrupt. A latch made from patterned magnets changes that. Correlated Magnetics Research's Latch Polymagnets repel each other until they are pushed to a defined distance, then attract and close. That gives a door or lid that stays open on its own and snaps shut once pushed past the transition point. CMR's applications page proposes these for cabinets and says different latch designs give different repel and attach strengths to set the feel.

There is also evidence from aerospace. CMR's blog reposts a NASA Armstrong article on a magnetic release mechanism that released a small glider from a remotely piloted aircraft five times in a row. NASA said the design potentially has fewer parts, needs less maintenance and is more reliable than conventional mechanical mechanisms, and avoids the safety process that pyrotechnic releases carry.

Choose mechanical when the joint must survive shock loads or must be lockable. Choose magnetic for sealed, wipe-clean or low-wear closures. Note that latch pairs must be constrained and centered to work properly.

Question 10

What is a magnetic spring and how does it work?

Accepted Answer

A magnetic spring is a pair of magnets that resists being pushed together and resists being pulled apart, so the two parts come to rest at a set distance with no contact.

Two conventional magnets cannot do this: facing one way they attract all the way to contact, facing the other way they repel. Correlated Magnetics Research makes Spring Polymagnets by patterning the faces so that attraction dominates at longer range and repulsion dominates at short range. The pair settles where the two balance. CMR's design note says the pair rests at an equilibrium distance, repels when pushed and pulls back when separated.

Two conditions apply. Spring pairs do not align themselves, so they must be constrained and centered, typically with a guide rod or slide; CMR's catalog includes a brass constraining rod. And physics rules out free levitation: Earnshaw's theorem means static magnets cannot hold a stable hover on their own, which CMR's FAQ also points out.

Uses include contactless suspension and soft-close travel. CMR notes spring pairs also damp vibration between the two parts and can be tuned as a vibration isolator. Its home page mentions linear magnetic springs for tablet designs, where the goal is a feel that is neither too weak nor too sticky. The catalog spring part is a 1 inch ring pair rated short-range repel.

Question 11

How do you make a rotational detent with magnets?

Accepted Answer

A detent is the click you feel as a knob, dial or hinge passes set positions. Mechanically it is usually a spring-loaded ball or leaf riding over notches, which wears, can loosen, and changes feel over time.

Patterned magnets can produce the same click with no contact. Two faces printed with matching repeating patterns pull toward the positions where the patterns line up and resist the positions in between. Correlated Magnetics Research's catalog has detent Polymagnet pairs with 12 positions at 30 degree spacing in a 1 inch D-shape, offered with M4 or #6 countersinks, a 4-position 90 degree pair, and a drawer detent pair for linear motion. Its align design note says custom pairs can have almost any angle and number of positions.

Detents can also be combined with sensing. In a 2015 press release on its site, CMR described a dimmer built with AKM Semiconductor in which a single round magnet carried an outer ring pattern read by a rotational Hall-effect sensor and inner rings that gave a tuned detent feel at set positions.

Because there is no rubbing contact, the feel should not drift with wear, and the mechanism can sit behind a sealed wall. Expect lower holding torque than a stiff mechanical detent of the same size, and check torque against your knob inertia.

Question 12

How do twist-to-release magnets work?

Accepted Answer

A strong magnet is easy to attach and hard to pull straight off. That is the core problem with magnetic mounts: the force that keeps a phone or cover secure also makes it a struggle to remove.

Twist-to-release pairs solve it with the pattern. When the two faces are aligned, their patterns attract fully. Rotate one part a few degrees and the patterns slide out of correlation, so attraction drops sharply and the part lifts off with little effort. Correlated Magnetics Research's catalog lists twist-release Polymagnet pairs, including a 20 degree version with a detent, an M4 countersink and a 1 inch D-shape, and twist-release pairs sized for mobile devices and small tablets.

CMR has published real uses. A 2016 press release on its site describes the OnYou running armband for iPhone 6 and 6s, where CMR says conventional magnets were either too big or too weak to give both a secure hold and an easy twist-off. CMR's applications page proposes the same action for storm shutters, released by twisting a magnet in each corner.

When designing one in, give the user a clear grip and a rotation stop, and remember the joint resists straight pull far better than torque, by design.

Question 13

Can strong magnets be used near a compass, credit card or sensitive electronics?

Accepted Answer

Strong conventional magnets are a problem inside thin devices. Their fields extend well beyond the magnet, so they can disturb a compass or magnetometer, interfere with nearby sensors, and wipe the magnetic stripe on a card that rests against the product.

Patterned magnets reduce that reach. Correlated Magnetics Research says the same process that concentrates a Polymagnet's force near its surface also minimizes stray fields where they are not wanted, and that its magnets are designed not to interfere with sensitive electronics or damage credit cards. Its attach design note adds that, unlike conventional magnets, the reach of a Polymagnet's field can be set to suit the design rather than growing with strength.

CMR also covers other tools for this in its advanced webinar: taming fields near compasses and cards, and using shunts (steel pieces that carry flux) to raise strength and cut interference. A NASA Armstrong report reposted on CMR's blog makes a related point, that printed magnetic poles keep loops tight and reduce electromagnetic interference concerns.

Short reach is a design input, not a guarantee. Measure the field at the sensor location with a gaussmeter in your actual layout, including any steel nearby, before signing off.

Question 14

Why do magnets slide down vertical surfaces, and how do you increase shear holding force?

Accepted Answer

A magnet on a wall is loaded in shear, not in pull. What stops it sliding is mostly friction, which equals the magnetic pull multiplied by the friction coefficient between the two surfaces. Because that coefficient is well below one on smooth painted or plated steel, a magnet rated for a heavy pull load can slide under a much lighter hanging load.

There are three standard fixes: raise the pull force, raise friction with a rubber or textured face, or add a mechanical ledge. Patterned magnets add a fourth. Correlated Magnetics Research says its attach Polymagnets show up to 8 times more shear strength than standard magnets, a vendor figure from its own testing. Its applications page builds on that for retail fixtures that can be reconfigured quickly and for organization systems that hold heavy items on walls.

Published products show the idea. CMR's Hooked on Paint line paired Polymagnets with magnetic paint for hanging frames on walls, and a later post on CMR's blog describes Gator Magnetics garage organization products built with Polymagnets.

Test on your real surface. Paint, powder coat and thin sheet steel all reduce holding force, and shear rating depends heavily on the finish.

Question 15

How are coded or programmable magnets made?

Accepted Answer

Coded magnets start as ordinary magnets. Correlated Magnetics Research says its Polymagnets begin as rare-earth magnets, usually sintered neodymium. The difference is the magnetizing step.

A conventional magnet is magnetized in one pulse, all in one direction. A multipole part made the traditional way needs a magnetizing fixture, a tooled coil shaped for that one pattern. A Popular Mechanics article reposted on CMR's blog put the traditional cost of made-to-order magnet patterns at $1,000 to $100,000 per pattern; treat that as a historical figure from the article, not a current quote.

CMR's approach replaces the fixture with a programmable magnetizer. Its About page says patterns are designed in software and programmed into a magnet in minutes rather than weeks. The magnetizer writes the pattern region by region (each region is a maxel), so a design change is a file change, not new tooling.

CMR sells this equipment as well as parts. Its site lists magnetizers named Polydesk, Polylab and Polymag 6.2, its FAQ describes units for lab use and full production, and Polyvision software is used to design the patterns. Production can also be sourced through CMR's custom services.

Question 16

What software is used to design magnet pole patterns?

Accepted Answer

General magnetics simulation is usually done with finite element tools, which model fields and forces for any geometry. Those tools can simulate a patterned magnet, but you have to draw each pole region yourself, and they do not drive a magnetizer.

For programmable magnets, Correlated Magnetics Research sells Polyvision, called PMCAD on its FAQ. Its product page says Polyvision lets users create custom Polymagnets by controlling magnetic patterns at the maxel level, the individual magnetized spots, with an interface that shows the pattern in real time. CMR positions it for engineering, product development and research, for building multi-pole configurations aimed at specific behaviors.

The practical value is the link to production. CMR's webinar on the subject describes Polyvision together with its prototyping equipment as a path from concept to physical prototype with fast revisions. A pattern designed in software can be printed by CMR's magnetizers, which CMR sells for lab and production use, or ordered as custom parts.

If you are new to the behaviors, CMR's catalog and its Demo Kit are a cheaper first step than software. Handling a latch or spring pair shows the force curve faster than a simulation does.

Question 17

How much do coded magnets cost, and how fast can you prototype one?

Accepted Answer

Catalog parts are inexpensive. On 4 October 2026 Correlated Magnetics Research's online catalog listed the named behavior pairs we checked at about $20 to $48 per pair; for example, a sliding latch pair at $19.80, a 12-position detent pair at $37.00 and a large-tablet portrait/landscape pair at $48.00. The Polymagnet Demo Kit, with attach, align, latch, spring and complex demonstrators, was listed at $149.00. Prices change, so check the catalog.

Custom parts are priced by complexity. CMR's FAQ says pricing depends on the complexity of the behavior and on combinations of functions, and that for most applications the lifetime cost is less than traditional fixturing.

Lead time is where programmable magnetization differs most. A conventional multipole design needs a dedicated magnetizing fixture before the first part exists. CMR says a Polymagnet can be prototyped in minutes and changed on the fly in production without fixture cost or lead time. Its About page says a changed pattern can produce new prototypes in days, and its custom solutions page offers rapid prototyping in minutes or hours rather than months.

CMR's custom offering also includes design services, testing and verification, training and production sourcing. If you expect many design turns, ask whether buying Polyvision software or a lab magnetizer is cheaper than repeated custom orders.

Question 18

What temperatures can coded magnets handle?

Accepted Answer

A coded magnet has the temperature limits of the material it is printed on. The pattern does not make the material tougher or weaker.

Most catalog Polymagnets are sintered neodymium (NdFeB). Correlated Magnetics Research's neodymium note says NIB magnets generally operate from -138 C to 80 C (-215 F to 176 F). Its FAQ adds that heat is one of two ways to demagnetize them, at roughly 130 F to 200 F over about 45 minutes depending on grade; the other is a strong reverse field, on the order of five times the strength of an NdFeB magnet. Higher-coercivity grades extend the limit.

For wider ranges, CMR points to samarium cobalt (SmCo). It publishes typical properties for its sintered SmCo grades, and a NASA project shows how far that goes: CMR says it worked with NASA from 2020 to 2022 on 0.6 inch thick SmCo Polymagnets for a magnetic coupler, which kept their force and function above 140 C and below -180 C in testing.

Design with margin. Check the grade's demagnetization curve at your maximum temperature and at the working gap, because a magnet in an open circuit loses strength at a lower temperature than one clamped to steel.

Question 19

What materials and coatings are coded magnets made from?

Accepted Answer

Correlated Magnetics Research prints its patterns on three material families, according to its FAQ: sintered neodymium (NdFeB), sintered samarium cobalt (SmCo), and flexible NdFeB, which CMR says is significantly stronger than a ferrite refrigerator magnet. It publishes typical property data for each.

Sintered NdFeB is the strongest and the default. CMR's neodymium note explains that sintered magnets are anisotropic, meaning they have a preferred magnetization direction; bonded magnets are roughly half as strong but can be moulded in almost any shape and have no preferred direction. Its Demo Kit magnets are 1 inch diameter by 0.125 inch thick, grade N40.

On coatings, CMR says all catalog magnets use nickel-copper-nickel (NiCuNi), that other coatings including PTFE are available for high-volume work, and that SmCo is normally uncoated. Uncoated sintered NdFeB corrodes, so coating choice matters for outdoor, wet or medical environments.

For compliance, CMR's FAQ states that typical neodymium magnets it supplies with the standard NiCuNi coating are RoHS and RoHS II compliant and contain no REACH substances of very high concern. It makes no statement for other coatings and evaluates them case by case.

Question 20

How should coded magnets be mounted, and how big can the gap be?

Accepted Answer

Mounting and gap matter more for patterned magnets than for conventional ones, because the field is concentrated close to the surface.

On gap, Correlated Magnetics Research recommends under 2 mm between a Polymagnet and its mating magnet or steel target, and says the right figure depends on geometry, pattern and application. Every layer counts toward that gap: plastic housing walls, paint, adhesive, coatings and labels. Design the enclosure so the magnets sit as close to the mating face as possible.

On fixing, CMR's FAQ ranks a screw through a countersink as the best method, followed by bonding the magnet to steel. It does not recommend bonding high-force Polymagnets directly to plastic, because the joint can fail before the magnet does. That is why many catalog pairs come with M4 or #6 countersunk holes.

Constraint matters too. Latch and spring pairs only work when the two parts are held centered, usually by a guide, rod or hinge. CMR's catalog includes a brass constraining rod and a zinc-coated steel plate for testing. And CMR notes its force data comes from magnets held parallel and aligned; a part that can tilt during engagement will see lower force.

Question 21

How can you see the pole pattern on a magnet?

Accepted Answer

Use magnetic viewing film. It is a thin sheet containing tiny magnetic particles or flakes that turn to face the field beneath them. Laid over a magnet, it shows where poles are and where the field changes direction, as a pattern of light and dark or colored lines.

For coded magnets it is the quickest inspection tool there is. You can confirm a part has the right pattern, check that a mating pair is matched and oriented correctly, and spot a part that was magnetized wrong or partly demagnetized. A plain disc shows one uniform area; a patterned magnet shows rings, stripes or a grid of regions.

Correlated Magnetics Research sells high-resolution color viewing film in its catalog in two sizes, 100 mm by 75 mm and 200 mm by 300 mm, and includes a piece of green viewing film in its Polymagnet Demo Kit.

Film shows where poles are, not how strong the field is. For strength, use a gaussmeter or a pull-force test rig. Keep film away from strong magnets when stored, and do not slide magnets across it, which can scratch it.

Question 22

Why do magnet pull force ratings overstate real-world holding force?

Accepted Answer

Most published pull figures are measured in ideal conditions that a product rarely reproduces.

Correlated Magnetics Research's FAQ names the two common test setups. Case 1 is the maximum pull between a magnet and an effectively infinitely thick piece of steel. Case 2 is a magnet sandwiched between two infinitely thick steel pieces, pulled against a third. CMR says data from these idealized setups can overstate the force achievable in product design by 2 times or more.

Real joints lose force in several ways. The steel is thin, so it saturates. There is a gap from paint, plating, plastic or dirt. The load is in shear, not straight pull. And the magnet tilts as it engages or releases. CMR notes that its own published data comes from in-house force testing with magnets held parallel and aligned, compared against conventional magnets of the same size and grade, and that unconstrained testing may give lower numbers.

Use catalog numbers only to compare options. Then build a test with your real target material and thickness, the real gap, and the real load direction, and design around the lowest result you measure, with a safety factor.

Question 23

Can coded magnets levitate or make frictionless bearings?

Accepted Answer

Not by themselves. Earnshaw's theorem shows that no arrangement of static permanent magnets can hold an object in stable levitation. Push two repelling magnets together and, unless something stops them, they slide sideways or flip over.

Correlated Magnetics Research addresses this directly on its FAQ. With a light mechanical constraint that stops lateral movement, a repelling pair will appear to hover; CMR calls this its spring function. It says two axes must be constrained for many of its functions, including the spring, to work. Magnetic bearing systems are possible, CMR says, as long as part of the system is held apart mechanically.

Patterned magnets also do not create frictionless motion or free energy. The mechanical constraint still has friction, and CMR states it will not accept custom design requests for levitation, frictionless-motion or free-energy projects.

What coded magnets can usefully do here is provide a contactless spring: a pair that rests a set distance apart and returns there when pushed or pulled. CMR's spring design note adds that the pair damps vibration between the two parts, which can be tuned for a specific mass and frequency range.

Question 24

Who invented coded magnets?

Accepted Answer

Coded, or correlated, magnets were developed by Correlated Magnetics Research (CMR), founded in 2008 and based in Huntsville, Alabama. The company sells the technology as Polymagnets.

CMR's history page credits co-founder and Chief Scientist Larry Fullerton. It says he set out to build a self-assembling toy to interest his grandchildren in math and science, and drew on his background in wireless communications, arranging magnets in patterns, or codes, borrowed from signal processing theory. Encoding magnets with those complex fields became the basis of the company.

The patent record grew quickly. A December 2014 CMR press release reported 121 issued patents and 58 applications on file in the US, Europe and Asia. CMR's FAQ today says it has more than 100 issued US patents with many more pending, covering the processes and equipment used to make Polymagnets as well as magnet behaviors.

Recognition followed. A Popular Mechanics article reposted on CMR's blog says the MagPrinter technology won a 2010 Popular Mechanics Breakthrough Award, and CMR reports demonstrating the technology to President Obama at Capital Factory in Austin in May 2013.

Question 25

Do coded magnets lose strength or wear out over time?

Accepted Answer

Not under normal conditions. The pattern is part of the magnetization, and a patterned magnet keeps it as long as the material keeps its magnetism.

Correlated Magnetics Research's FAQ says an NdFeB magnet naturally loses its magnetism at about 1 percent every 100 years, and that Polymagnets behave exactly the same way. Two things can demagnetize one: sustained heat (CMR cites roughly 130 F to 200 F over about 45 minutes, depending on grade) or a very strong reverse magnetic field, on the order of five times the strength of an NdFeB magnet.

Mechanically, a magnetic joint has no rubbing parts to wear. CMR says its Align Polymagnets perform consistently every time without recalibration or maintenance, and that is the main argument for magnetic latches and detents over spring-and-ball mechanisms.

The realistic failure modes are elsewhere. Uncoated or damaged NdFeB corrodes, so coating damage in a wet environment is the bigger risk. Sintered magnets are brittle and can chip if parts slam together. Adhesive joints can creep. Design out impact, protect the coating, and choose a higher-coercivity grade or SmCo if the part runs hot.

Coded and multipole magnets, answered