Coded multipole magnets for mechanical design
A programmed pole pattern can do the work of a spring, a latch, a detent, or a shaft through a wall. Nothing slides, nothing fatigues, nothing draws power. It holds strongly on contact and lets go on a motion you design.
The core idea
A conventional magnet has one north and one south. A coded magnet carries dozens of small magnetic regions on a single face, each with its own polarity, printed in a deliberate pattern. The pattern is the design. Change it and the two faces behave differently when they meet: they can spring apart, snap together, click into set positions, or refuse to hold until you twist them.
That lets you take a part whose job is force, holding, or positioning and do it with a field instead of a mechanism. No pivot to seize, no coil to take a set, no contact surface to wear. The behavior is fixed in the magnet when it is made.
These are called coded, programmable, or multipole magnets. They are made by Correlated Magnetics Research and sold under the name Polymagnet. This page is about using them to retire a mechanical part. For the physics and the full catalog, go to the maker.
Replace a part
Each one trades a mechanical part for a magnetic one. Each has an honest limit worth knowing before you commit.
in place of a coil spring
Two patterned faces set to repel push back harder the closer they get. You tune the force-versus-gap curve with the pattern, so the push can rise gently or steeply as the gap closes. Because nothing bends, there is no metal fatigue and no sag over millions of cycles.
It makes a clean non-contact return force or a soft stop, with no coil to break or corrode.
in place of a mechanical catch
Two faces designed to attract in one alignment hold firmly the instant they touch. Move them the way the pattern dislikes, a slide, a peel, or a twist, and the matching poles fall out of register and the hold collapses. The release is built into the geometry, not into a spring-loaded part.
You get a catch with no lever, no keeper, and no moving piece to jam.
in place of a ball-and-spring detent
A rotational pattern gives a face preferred angles. Turn it and it settles into a click-stop, then into the next one. The number of stops and how hard each one holds are set by the pattern, so a dial can have four crisp positions or twelve. There is no ball, no spring, and no ramp to wear flat.
The feel stays the same on the first turn and the hundred-thousandth.
in place of a shaft and seal
Put a patterned rotor on each side of a thin non-magnetic barrier and torque passes across with no physical link. Drive one, the other follows. Nothing penetrates the wall, so there is no dynamic seal to leak, wear, or let contamination through. Useful when one side is sealed, sterile, or submerged.
Why it wins, and the one catch
The work is done by a field, not by parts rubbing or flexing. Nothing fatigues, so the hundred-thousandth cycle feels like the first.
These are permanent magnets. The behavior is set when the magnet is made and holds with nothing plugged in.
Because the force can cross a gap or a thin wall, you can enclose both halves. Good for wet, sterile, or sealed assemblies.
Own the limit
Arranging many poles on one face pulls the field in tight. Neighboring opposite poles cancel each other at a distance, so a coded magnet is strong where the faces nearly touch and falls off much faster than a plain magnet of the same size as the gap opens. That is the honest cost. If your part needs to act across a wide air gap, this is the wrong tool. If it works close in, the short reach is exactly why the hold, the click, and the release stay crisp.
FAQ
For a return force or a soft stop over a short travel, yes. Two repelling coded faces give a force that rises as the gap closes, and you shape that curve with the pattern. It is not a replacement for a long-stroke compression spring. It shines where the motion is small and you want no fatigue and no contact.
A fridge magnet has one broad pole, so its field reaches out. A coded magnet packs many small alternating poles onto one face. Their fields cancel a short way off, which collapses the reach but makes the near-contact behavior sharp and tunable. The weak reach is the direct price of the fine control.
The release is in the motion. The faces hold hard in their matched alignment. Slide, peel, or twist them the way the pattern is designed to dislike, and the poles stop matching, so the holding force drops to almost nothing. The part releases because you moved it the right way, not because a catch let go.
There is no mechanical set or fatigue, so the behavior does not drift from use the way a worn spring or detent does. Like any permanent magnet, output does vary with temperature within the material's limits, so account for your operating range when you spec the material.
They are made by Correlated Magnetics Research and sold as Polymagnet. The pattern is custom work, so the way to get the right force, hold, or detent for your part is to bring the mechanism you want to replace to the maker. Start at polymagnet.com.
Spec the part
If a spring, latch, detent, or through-wall coupling in your design is a maintenance item or a wear point, a coded magnet may retire it. The pattern is engineered to your force, hold, and release. Take it to the people who invented the technology.
Go to PolymagnetCoded multipole magnets are invented and manufactured by Polymagnet, from Correlated Magnetics Research. This site is a guide to using them in mechanical design.