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Concentric and eccentric rotors: what each maker claims

Inside the head of an eddy current separator, the magnet rotor sits either centred in the shell (concentric) or offset toward the point where material leaves the belt (eccentric). The makers disagree on which suits fine material, so this page sets out what each layout does, what each maker claims, and how to test the choice on your own material.

By [author name, role and employer] · Technical review by [reviewer name, role and employer] · Updated

  • Aluminum and non-ferrous
  • Ferrous
  • Fiber
  • Glass
  • Film
  • Other and residue

1What each layout does

Both layouts work the same way at heart. A rotor of alternating magnets spins fast inside a non-metallic shell at the head of the belt, and conductive non-ferrous metal is thrown forward over a splitter. (Source: Eriez, RevX-E manual RM-99, 2015.) How an eddy current separator works covers the rest.

The two layouts differ in where the rotor's field reaches the material.

Concentric and eccentric rotor layouts, cross-sections Two cross-sections of a separator head, each with a belt carrying a single layer of mixed material over a non-metallic shell. Left, concentric: the magnet rotor is centred in the shell, and the field is the same all round the head; a steel piece that got past the magnet is held on the belt under the head. Right, eccentric: a smaller magnet assembly sits offset toward the point where material leaves the belt, and the field acts over a short arc there; a steel piece drops off the belt once it leaves the field and lands among the non-metals. A dashed outline shows the assembly moved to another position. In both, aluminum is thrown forward over the splitter and non-metals drop short of it. Concentric N S N S N S N S N S N S 1 2 4 6 Eccentric N S N S N S N S N S 1 3 5 7 A Concentric and eccentric rotor layouts, cross-sections Two cross-sections of a separator head, each with a belt carrying a single layer of mixed material over a non-metallic shell. Left, concentric: the magnet rotor is centred in the shell, and the field is the same all round the head; a steel piece that got past the magnet is held on the belt under the head. Right, eccentric: a smaller magnet assembly sits offset toward the point where material leaves the belt, and the field acts over a short arc there; a steel piece drops off the belt once it leaves the field and lands among the non-metals. A dashed outline shows the assembly moved to another position. In both, aluminum is thrown forward over the splitter and non-metals drop short of it. Concentric N S N S N S N S 1 2 4 6 Eccentric N S N S N S 1 3 5 7 A
  1. 1Shell. Non-metallic, so the field passes through. Turns with the belt.
  2. 2Concentric rotor. Magnets of alternating polarity, centred in the shell.
  3. 3Eccentric magnet assembly. Offset toward the point where material leaves the belt.
  4. 4Concentric field. The same all round the head, so it acts wherever the belt wraps the head.
  5. 5Eccentric field. Acts over a short arc at the drop-off point: about 30 degrees, in Bunge's account.
  6. 6Steel on a concentric rotor. Held on the belt under the head, where it heats.
  7. 7Steel on an eccentric rotor. Leaves the field, drops off the belt and often lands with the non-metals.
  8. AField position. On several eccentric machines the assembly can be moved, shown dashed, to shift where the field acts.
Figure 1. Concentric and eccentric rotor layouts, cross-sections of the separator head. Schematic, not to scale; pole counts, offsets and field angles vary by model. Sources: Bunting, Eddy current separators, undated, and 5 key eddy current separator operating parameters, 2020; IFE, The new NANOS eddy current separator, 2024; Bunge, 2019; Eriez RM-99, 2015.

Concentric

In a concentric rotor the magnets are centred in the shell, so the field is the same all round the head (Source: Bunting, Eddy current separators, undated). IFE says this gives a wider working zone, in which the push acts on each piece for longer (Source: IFE, The new NANOS eddy current separator, 2024).

Eccentric

In an eccentric rotor the magnet assembly is offset toward the discharge, so the field is concentrated at the point where pieces leave the belt (Source: Bunting, Eddy current separators, undated). On Eriez's RevX-E, for example, the rotor sits offset near the upper side of the shell (Source: Eriez, RevX-E manual RM-99, 2015). Bunge puts the zone where an eccentric field acts at about 30 degrees of arc (Source: Bunge, 2019).

On several eccentric machines the field position can be moved:

  • Eriez's RevX-E manual describes indexing the rotor forward or back.
  • STEINERT says the position of its pole system can be adjusted to suit the feed.
  • The manual from Industrial Magnetics (IMI) has the installer set the rotor's "magnetic hot spot", usually at the highest point of the shell or toward the discharge end.
  • IMRO says the pole drum in its eccentric RCSX D can be turned through 0 to 20 degrees while it runs.

Sources: Eriez RM-99, 2015; STEINERT, Eddy current separators, undated; STEINERT, EddyC FINES, undated; Industrial Magnetics, eddy current separator service manual 900505, undated; IMRO, Non-ferrous separators, eccentric, undated.

STEINERT says it originated the eccentric pole system (Source: STEINERT, Eddy current separators, undated). Bunge writes that most makers took up the eccentric layout once the patent on it expired (Source: Bunge, 2019).

2Piece size and rotor layout

Several makers tie the choice to piece size. IFE puts the dividing line at about 20 mm (Source: IFE, The new NANOS eddy current separator, 2024):

  • centric rotors for pieces above roughly 20 mm, where the strength of the push matters more than the exact release point
  • eccentric rotors for pieces below roughly 20 mm, such as electronic scrap and incinerator slag, where a precise release point matters

IFE gives the line as approximate. Its 2026 brochure says its eccentric machines suit sizes up to 25 mm. (Source: IFE, Eddy current separators brochure, 2026.)

Bunting draws its line at about 10 mm. It describes concentric rotors as giving a balanced, even throw for coarser metal above about 10 mm in a steady feed. It calls eccentric rotors better for small, light or poorly conducting pieces, especially under 10 mm. (Source: Bunting, Eddy current separators, undated.)

One maker's models, by rotor layout (Bunting's own figures; not a ranking)
ModelLayoutSmallest piece statedSome streams Bunting pairs it with
ECOConcentric20 mm in the model table; the FAQ on the same page says above 25 mmUnsorted household refuse, 0 to 300 mm
HICConcentric10 mmGlass cullet, 0 to 50 mm; incinerator ash, 0 to 40 mm
HIEEccentric3 mmElectronic scrap (WEEE), 0 to 30 mm
HIFEEccentric1 mmElectronic scrap (WEEE), 0 to 30 mm

Source: Bunting, Eddy current separators (model table, application table and FAQ), undated. Read 2026-10-06.

Bunting ties eccentric rotors to small pieces. Its own application table still pairs the concentric HIC with streams that start at 0 mm, among them glass cullet (0 to 50 mm) and incinerator ash (0 to 40 mm). Ask any maker which model it would put on your stream, and why.

Rotor layout alone does not set the lower limit either. SGM says it builds concentric rotors, and it lists a concentric model, the BVIS, down to 0.2 mm. (Sources: SGM, Eddy current separators, undated; SGM, BVIS model, undated.)

So compare limits model by model. The size table on the eddy current reference lists what makers state, and Sizing an eddy current separator covers the other questions that set the model.

3What makers say about fine material

On fine material, the makers disagree. The table puts each claim beside the maker that publishes it.

What makers say about rotor layout and fine material (each claim is the named maker's own; not a ranking)
MakerLayouts it showsWhat it says
BuntingBothEccentric for small, light or poorly conducting pieces, especially under 10 mm. Concentric for coarser metal above about 10 mm, in a steady feed.
COGELMEBothOffers both layouts for aluminum from 1 to 400 mm. No claim about which layout suits fines was found on the page read.
DingsBothMarkets its eccentric 9900 for fractional-size non-ferrous metal in recycling. Its comparison article says the 9900 suits the same applications as its concentric 9100; the difference it names is that the eccentric releases stray steel. Its concentric 9500 is for shredded material.
IFEBothEccentric below roughly 20 mm, where a precise release point matters. Centric above, where the strength of the push matters more.
IMROEccentric (RCSX D)Argues for eccentric rotors in general, not for fines in particular. It says a concentric field acts on the material too early.
SGMConcentricConcentric suits fine and ultra-fine material: pieces stay in the field longer and separate gradually, where an eccentric rotor ejects them at once.
STEINERTEccentricArgues for its eccentric pole system in general: the field is concentrated where pieces leave the belt, so stray steel does not stick and belt and shell wear stay low (section 4). Not an argument about fines in particular.

Sources: Bunting, Eddy current separators, undated; COGELME, Eddy current separator, undated; Dings, Eddy current separator, undated; Dings, Eccentric vs. concentric eddy current separators for recycling, undated; IFE, The new NANOS eddy current separator, 2024; IMRO, Non-ferrous separators, eccentric, undated; SGM, Eddy current separators, undated; STEINERT, Eddy current separators, undated. All read 2026-10-06.

Who publishes this. Recyclers Guide is published by [LLC name], an affiliate of Remcon Equipment, Inc. Remcon designs and builds conveyors and eddy current separator systems around rotors or complete separators made by others, builds overhead magnet units, magnetic head pulleys and trommels, resells screens and feeders, and integrates equipment discussed on this site.

Two makers tie eccentric rotors to smaller pieces: Bunting, and IFE with its approximate 20 mm line. Dings markets its eccentric 9900 for fractional sizes, but says its concentric 9100 suits the same applications; its case for the eccentric layout is stray steel. STEINERT and IMRO argue for eccentric rotors on other grounds. One maker, SGM, argues that concentric suits fines. Because they disagree, section 6 covers how to test the choice on your own material.

Very fine metal raises more than the choice of layout. Recovering fine non-ferrous metal covers the rest.

4Steel that gets past the magnet

No magnet catches every piece of steel, so some reaches the separator (Sources: Bunge, 2019; Industrial Magnetics, eddy current separator service manual 900505, undated). The two layouts handle it differently.

On a concentric rotor

Bunting says steel is held by the field and stays on the belt at the bottom of the rotor, where it heats. When the belt stops, it can burn through the belt into the shell, and in time damage the rotor. (Source: Bunting, 5 key eddy current separator operating parameters, 2020.)

Bunting also notes that magnetic material can be hard to clear from the belt on a concentric rotor (Source: Bunting, Eddy current versus electrostatic separation, 2020). Bunge adds that a concentric rotor's wide field zone makes the belt more prone to damage (Source: Bunge, 2019).

IMRO, which shows an eccentric machine, says some concentric machines use a ceramic-lined shell to protect against steel, and that the lining widens the gap between the magnets and the material (Source: IMRO, Non-ferrous separators, eccentric, undated).

On an eccentric rotor

Bunting says the belt carries steel out of the field and it drops off, often into the non-metal fraction. (Sources: Bunting, Eddy current versus electrostatic separation, 2020, and 5 key eddy current separator operating parameters, 2020.)

Dings and STEINERT make the case on wear. Dings says steel that slipped past the magnet is then less likely to cling to the shell and damage the belt. STEINERT says its eccentric pole system keeps leftover steel from sticking to the head pulley, which keeps belt and shell wear low. (Sources: Dings, Eccentric vs. concentric eddy current separators for recycling, undated; STEINERT, Eddy current separators, undated.)

Steel has to come out before the separator

Neither layout replaces the magnet. Eriez designs its eccentric separator to run with a minimum of ferrous metal in the feed, with magnets upstream where needed. Bunting advises taking ferrous metal out first with overhead, pulley or drum magnets. (Sources: Eriez RM-99, 2015; Bunting, 5 key eddy current separator operating parameters, 2020.)

This guide follows the separator makers' manuals: magnets go ahead of the separator, and the separator is not relied on to remove steel.

Removing ferrous metal before the separator covers the magnets, and eddy current against magnetic separation covers the order they go in.

5Who sells each layout

Four makers show both layouts on the pages read for this guide.

Makers that show both layouts (on the pages read for this guide, October 6, 2026)
MakerConcentricEccentric
BuntingHIC and ECOHIE and HIFE
COGELMEOffered; no model names on the page readOffered; no model names on the page read
Dings9100 and 95009900
IFEINPINPx NANOS, STRATOS and VIOS

Sources: Bunting, Eddy current separators, undated; COGELME, Eddy current separator, undated; Dings, Eddy current separator, undated; IFE, Eddy current separator, undated. All read 2026-10-06.

IFE also says a centric INP machine can be converted to its eccentric NANOS by swapping the rotor. (Sources: IFE, Eddy current separator, undated; IFE, The new NANOS eddy current separator, 2024.)

Other makers show one layout on the pages read. STEINERT builds its separators around its eccentric pole system, and Eriez's RevX-E and UHF machines are eccentric. IMRO shows an eccentric model, the RCSX D. SGM says it uses concentric rotors. (Sources: STEINERT, Eddy current separators, undated; Eriez, Eddy current separators, undated; IMRO, Non-ferrous separators, eccentric, undated; SGM, Eddy current separators, undated.)

If a maker sells both layouts, ask it to run your sample on each (section 6). Eddy current makers are listed in the directory.

What the publisher's affiliate builds

Remcon Equipment, the publisher's affiliate, designs and builds eddy current separator systems around rotors or complete separators made by others, and supplies separators with both layouts. Its own page says when it uses each. That is the publisher's affiliate's practice, not a finding of this guide: how the publisher's affiliate uses each layout.

[First-hand note: what the affiliate's shop sees on fine material with each layout, disclosed as the affiliate's experience. To come from the affiliate's shop]

6Testing with your own material

Makers disagree, and the figures each one publishes are its own claims. So test the choice on your own material. Bunting advises a test because waste is not uniform in shape or size. (Source: Bunting, Maximising non-ferrous metal separation, 2019.)

Several makers offer trials. STEINERT runs four test centres, in Germany, Australia, Brazil and the USA, where buyers can trial their own material at industrial scale. Bunting lists laboratory-scale trials among its options. Goudsmit's recycling test centre is set up with eddy current separators fed by vibratory feeders. (Sources: STEINERT, Test centres, undated; Bunting, Eddy current separators, undated; Goudsmit, Magnets for the recycling industry, undated.)

Making the results comparable

  • Send the size range the separator will see. Screen the sample first if your line will. STEINERT asks that the largest piece in its fines machine's feed be no more than three times the smallest. (Source: STEINERT, EddyC FINES, undated.) Screening ahead of separation covers size fractions.
  • Run the same sample on both layouts if the maker sells both, at the same belt speed and feed rate.
  • Ask which splitter setting each result was taken at, and for both recovery and purity at that setting. Bunge notes that coarse pieces separate better with a low splitter and small pieces with a high one, and that the right setting is found by test. (Source: Bunge, 2019.) Setting the splitter covers the trade-off.
  • On an eccentric machine, ask where the field position was set, and whether it can be moved while the machine runs (section 1).
  • Tell the maker how ferrous metal is removed upstream, and how many magnets do it.

The RFQ checklist lists the rest of what a maker needs before it quotes.

7Questions

Do makers agree on which rotor layout suits fine material?

No. Bunting ties eccentric rotors to pieces under about 10 mm, and IFE suggests eccentric rotors below roughly 20 mm. Dings markets its eccentric 9900 for fractional-size pieces, but says its concentric 9100 suits the same applications. STEINERT and IMRO argue for eccentric rotors in general, not for fines in particular. SGM argues the other way: it says its concentric rotors keep pieces in the field longer, which suits fine and ultra-fine material. Test with your own material. Sources: Bunting, Eddy current separators, undated; Dings, Eddy current separator, undated; Dings, Eccentric vs. concentric eddy current separators for recycling, undated; IFE, The new NANOS eddy current separator, 2024; STEINERT, Eddy current separators, undated; IMRO, Non-ferrous separators, eccentric, undated; SGM, Eddy current separators, undated.

Where does IFE draw the line between centric and eccentric rotors?

At roughly 20 mm, which IFE gives as an approximate guide. It suggests centric rotors for coarser pieces, where the strength of the push matters more than the release point, and eccentric rotors for smaller pieces, where a precise release point matters. Its 2026 brochure says its eccentric machines suit sizes up to 25 mm. Sources: IFE, The new NANOS eddy current separator, 2024; IFE, Eddy current separators brochure, 2026.

Does an eccentric rotor deal with steel that gets past the magnet?

Its makers say stray steel moves out of the field and drops off the belt, so it is less likely to cling to the shell and damage the belt. Bunting advises taking ferrous metal out first, and Eriez designs its eccentric separator to run with a minimum of ferrous metal in the feed. This guide follows the separator makers' manuals: magnets go ahead of the separator, and the separator is not relied on to remove steel. Sources: Bunting, 5 key eddy current separator operating parameters, 2020; Dings, Eccentric vs. concentric eddy current separators for recycling, undated; STEINERT, Eddy current separators, undated; Eriez, RevX-E manual RM-99, 2015.

Which makers sell both layouts?

On the pages read for this guide, Bunting, Dings, IFE and COGELME show both concentric and eccentric machines. IFE also says its centric machine can be converted to its eccentric NANOS by swapping the rotor. Sources: Bunting, Eddy current separators, undated; Dings, Eddy current separator, undated; IFE, Eddy current separator, undated; COGELME, Eddy current separator, undated.

Read the eddy current reference Find manufacturers

8Sources

Manufacturers' figures and arguments are their own published claims; this site has not tested the equipment. Remcon Equipment, Inc. is the publisher's affiliate.

  1. Eriez Magnetics. RevX-E eddy current separator installation, operation and maintenance manual, RM-99. April 2015. https://www.eriez.com/Documents/Literature/IOMs/Metals-Recycling/RM-99-Eriez-RevXE-Eddy-Current-Separator-IOM.pdf. Read 2026-10-06.
  2. Bunting. Eddy current separators (product page, with model table, application table and FAQ). Undated. https://buntingmagnetics.com/product/magnetic-separation/eddy-current-separators. Read 2026-10-06.
  3. IFE Aufbereitungstechnik. The new NANOS eddy current separator (news). 2024. https://www.ife-bulk.com/en/company/news/the-new-nanos-eddy-current-separator. Read 2026-10-06.
  4. Eriez Magnetics. Eddy current separators (product page). Undated. https://www.eriez.com/Products/Metals-Recycling/Nonferrous-Recovery/Eddy-Current-Separators. Read 2026-10-06.
  5. R. Bunge, UMTEC, OST Eastern Switzerland University of Applied Sciences. Recovery of metals from waste incinerator bottom ash (technical monograph). June 2019. https://www.ost.ch/fileadmin/dateiliste/3_forschung_dienstleistung/institute/umtec/fachartikel/2019/19-03_recovery_of_metals_from_waste_incinerator_bottom_ash.pdf. Read 2026-10-06.
  6. STEINERT. EddyC FINES (product page). Undated. https://steinertglobal.com/us/sorting-systems/magnetic-separation/eddy-current-separators/steinert-eddyc-fines/. Read 2026-10-06.
  7. Industrial Magnetics, Inc. (IMI). Eddy current separator service manual, endless belt, 900505. Undated. https://assets.magnetics.com/assets/files/manuals/900505_ECS_Service_Manual_Endless_Belt.pdf. Read 2026-10-06. Industrial Magnetics supplies eddy current separators and magnets to Remcon Equipment, the publisher's affiliate.
  8. IMRO Maschinenbau. Non-ferrous separators, eccentric (product page). Undated. https://www.imro-maschinenbau.de/en/products/separation-technology/non-ferrous-separators-eccentric/. Read 2026-10-06.
  9. STEINERT. Eddy current separators (product page). Undated. https://steinertglobal.com/us/sorting-systems/magnetic-separation/eddy-current-separators/. Read 2026-10-06.
  10. Bunting. 5 key eddy current separator operating parameters (blog). November 10, 2020. https://buntingmagnetics.com/blog/5-key-eddy-current-separator-operating-parameters. Read 2026-10-06.
  11. IFE Aufbereitungstechnik. Eddy current separators (brochure). March 2026. https://www.ife-bulk.com/fileadmin/user_upload/ife-bulk/Produkte/Wirbelstromscheider/IFE-eddy-current-separators_web.pdf. Read 2026-10-06.
  12. SGM Magnetics. Eddy current separators (product page). Undated. https://www.sgmmagnetics.com/en/products/eddy-current-separators/. Read 2026-10-06.
  13. SGM Magnetics. BVIS model (product page). Undated. https://www.sgmmagnetics.com/en/products/bvis-model/. Read 2026-10-06.
  14. Dings Magnetic Group. Eddy current separator (product page). Undated. https://dingsmagnets.com/products/eddy-current-separator/. Read 2026-10-06. Dings has supplied magnets to Remcon Equipment, the publisher's affiliate.
  15. COGELME. Eddy current separator (product page). Undated. https://www.cogelme.eu/en-eddy-current-separator/. Read 2026-10-06.
  16. Bunting. Eddy current versus electrostatic separation (blog). July 20, 2020. https://buntingmagnetics.com/blog/eddy-current-versus-electrostatic-separation. Read 2026-10-06.
  17. Dings Magnetic Group. Eccentric vs. concentric eddy current separators for recycling. Undated. https://dingsmagnets.com/eccentric-vs-concentric-eddy-current-separator-use-in-recycling/. Read 2026-10-06. Dings has supplied magnets to Remcon Equipment, the publisher's affiliate.
  18. IFE Aufbereitungstechnik. Eddy current separator (product page). Undated. https://www.ife-bulk.com/en/machines/eddy-current-separator. Read 2026-10-06.
  19. Remcon Equipment, Inc. (the publisher's affiliate). Eddy current aluminum separators. https://www.remconequipment.com/eddy-current-aluminum-separators. Read 2026-10-06.
  20. Bunting. Maximising non-ferrous metal separation (blog). December 3, 2019. https://buntingmagnetics.com/blog/maximising-non-ferrous-metal-separation. Read 2026-10-06.
  21. STEINERT. Test centres. Undated. https://steinertglobal.com/services/test-centres/. Read 2026-10-06.
  22. Goudsmit Magnetics. Magnets for the recycling industry. Undated. https://www.goudsmitmagnetics.com/en-us/magnets-for-the-recycling-industry. Read 2026-10-06.

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