01 · MARK
Mark north and south.
Test every block on its own, away from the others. Mark both broad faces: N red, S blue.
Printable Halbach array · 10 magnets
Ten magnets.
One focused field.
Turn each magnet a quarter turn from the one before it, and the field gathers on one face. This 3D-printed holder locks ten 12.7 × 12.7 × 3.2 mm blocks into that pattern.
Halbach holderReal CAD · drag to rotate
Exploded · hardware not shown
63.85 × 29.05 × 15.45Envelope · mm
10 magnetsFive N–S pairs
2 printed partsBody + lid
3.5× fieldBase vs lid side, 5 mm out
01 · How it works
Twist the row, move the field.
Each magnet’s field loops out of its north face and back into its south face. Rotate every magnet 90° from its neighbor, and those loops pile up underneath and cancel on top.
Five magnets, side view2D sketch
Above the row
Below the row
—
Field 3 mm from the blocks, relative to the stronger side. Idealized square magnets in 2D; the real holder is modeled in 3D below.
- Every magnet makes loops.Field leaves the north face, curves around and returns to the south face.
- Twisting shifts the loops.Turning each magnet a quarter turn slides its loops along the row, so neighbors overlap.
- One side adds, one cancels.Below, neighboring fields point the same way and add up. Above, they oppose and mostly cancel.
02 · The real array
Stronger on the base side.
A 3D calculation of these exact blocks and spacing. Slide to compare both faces at the same distance.
Field strength · slice through the middle of the row3D model
3.51×
Base side ÷ lid side
Base side
Lid side
Average (RMS) field along the row, as a fraction of the magnets’ remanence Br. It compares this array’s two faces, not this array with one magnet.
This is field strength, not holding force. Pull force and load capacity are untested.
Use the closed base as the work face. Its 0.8 mm wall covers the magnets; the flat pairs sit 3.95 mm up so their centers line up with the upright pairs.
03 · Find the poles
Mark every north face.
These blocks are magnetized through their thickness, so the two broad faces are the poles. A compass’s north tip points at a magnet’s south face.
One magnet, edge-on3D model slice
Test each block on its own.
- Hold a compass close to one broad face.
- Red tip points at the face? It’s S. Mark it blue.
- Red tip points away? It’s N. Mark it red.
Compass probe|B| / Br = —x = 12 mm · z = 8 mm
An ideal compass: it ignores Earth’s field. One uniformly magnetized block, field normalized to Br. Magpylib reference.
04 · Build
Mark. Pair. Load. Close.
Print and check the fit coupon first. Work on a non-metal surface, wear eye protection and keep a wood or plastic guide handy.
02 · PAIR
Make five pairs.
Stack two blocks, N face against S face. They should snap together; if they push apart, recheck your marks. Each 6.4 mm pair acts as one thicker magnet.
03 · LOAD
Follow the arrows.
From the notch, point north ↑ → ↓ ← ↑. Pairs 1, 3 and 5 lie flat; 2 and 4 stand up. Neighbors push and twist, so guide one pair at a time. Thin slow-cure epoxy can help hold them.
04 · CLOSE
Fit the lid.
Match the lid pin to the notch, fingers facing in. Fit four M3 nuts, 1 mm washers and M3 × 16 mm screws. Tighten evenly; nothing should poke out of the base.
Strong magnets pinch and chip. Restrain each pair until the lid is on, keep fingers out of closing gaps, and stop if you can’t hold a pair securely. Keep magnets away from children and implanted medical devices. This is an untested prototype: no overhead or safety-critical loads.
05 · Make it
Print the kit.
Print the fit coupon first.
Its three pockets test 0.20 / 0.35 / 0.50 mm total clearance, smallest at the notch. The holder uses 0.35 mm (0.175 mm per side). Blocks should slide in freely; test a two-block pair too.
MATERIALPETG; PLA for a fit check
LAYER / NOZZLE0.20 mm / 0.40 mm
WALLS / INFILL5 walls / 50%
TOP / BOTTOMAt least 4 layers each
BODYWork face flat on the bed
LIDBroad face down, fingers up
SUPPORTSOff; check nut-pocket bridges
SCALE100%, millimeters
Files are already placed at Z = 0 in these orientations. Support the nut-pocket roofs only if your slicer shows they need it.
Hardware
Four M3 × 16 mm screws, four M3 nuts and four 1 mm washers, ideally nylon or brass. Nominal nuts: 5.5 mm across flats × 2.4 mm thick. Modeled pockets: 5.7 × 2.6 mm; holes: 3.4 mm. Screw length excludes the head; don’t countersink. Seat the nuts before loading magnets and check engagement with your hardware.
If the coupon is too tight or too loose
Measure the coated blocks and test the 6.4 mm pairs too. Change clearance in cad/design.py and rebuild. Don’t scale the STL: that also changes the screw holes and lid fit.
Model assumptions and checks
The field model uses uniform blocks, Br = 1 T, the real pair spacing and 401 samples along the row at y = 0. It leaves out steel, plating and glue gaps, temperature and demagnetization. CAD checks cover valid solids, watertight meshes, bed placement and nominal magnet fit. Physical fit, strength and durability are untested.
Fit couponThree clearances · print this first
DownloadHalbach bodyFive pockets · thin work face
DownloadRetaining lidThree fingers · alignment pin
DownloadFull kit · STL + STEP + source
STL downloads work offline from this page. Keep the ZIP beside it for the STEP files and source. Magnets in the 3D preview are illustrative; you only print the body and lid.