Technology comparison
Eddy current against magnetic separation: which goes first, and why
A magnet and an eddy current separator are not alternatives. On an aluminum line they work in sequence: the magnet takes out iron and steel first, so the separator can throw aluminum and other non-ferrous metal clear of everything else.
- Aluminum and non-ferrous
- Ferrous
- Fiber
- Glass
- Film
- Other and residue
1What each machine does
The two machines act on different metals, with opposite forces.
A magnet attracts iron and steel and pulls them out of the stream (Source: Bunge, 2019). An eddy current separator pushes conductive non-ferrous metal away. Its spinning rotor sets up currents in each conductive piece, and those currents push the piece off the belt and forward over a splitter. (Source: IFE, 2026.) How an eddy current separator works shows the rotor in section.
Neither machine does the other's job. Non-ferrous metal passes the magnet and goes on with the stream: ReMA's Zorba grade, for example, is shredded non-ferrous metal that has passed one or more magnets (Source: ReMA, July 2026). Steel, in turn, is attracted to the separator's rotor instead of being thrown, and steel held in the rotor's field heats up (Source: Bunting, 2020).
Non-ferrous metals do not all respond to the rotor equally. Bunge ranks aluminum and magnesium as the easiest to separate, and lead and chromium-nickel stainless steel as the hardest. (Source: Bunge, 2019.) The materials table gives the figures behind that order.
| Criterion | Magnetic separation | Eddy current separation |
|---|---|---|
| Force on its target | Attraction, toward the magnet | Repulsion, away from the rotor and over a splitter |
| Main targets | Iron and steel | Aluminum and magnesium respond most; copper, zinc, brass and lead less |
| What happens to the other machine's target | Non-ferrous metal passes on with the stream | Steel is attracted, not thrown, and heats in the field |
| Stainless steel | Not a dependable catch: ReMA's stainless-rich grade, Zurik, is material that has passed magnets | Weak response: a conductivity-to-density ratio of about 0.18, against about 13.7 for aluminum |
| Needs from the feed | A burden shallow enough for the field to reach, because magnetic pull falls off steeply with distance | One layer, with the steel already removed |
| Place in an aluminum line | Ahead of the eddy current separator | After the magnets |
Sources: Bunge, 2019 (attraction, reach, response by metal); IFE, Eddy current separators brochure, 2026 (repulsion); Bunting, 5 key eddy current separator operating parameters, 2020 (steel at the rotor); ReMA, July 2026, pp. 11 and 17 (Zorba, Zurik); Goudsmit, What determines the separation efficiency of eddy current systems, undated (ratios); Industrial Magnetics, manual 900505, undated (one layer, magnets upstream); Bunting, Eddy current separators, undated (place in the line). 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.
2Why the magnet goes first
Three separate reasons put the magnet ahead of the separator: steel can damage the separator, it can disturb the separation, and buyers' grades require it out.
Damage to the separator
Steel held in the rotor's field heats up. Two separator makers' manuals say the hot steel can damage the belt and the shell, and Industrial Magnetics (IMI) says the heat can weaken the rotor magnets for good. (Sources: IMI, manual 900505, undated; Eriez, RevX-E manual RM-99, 2015.)
Stops are a particular risk. In an emergency stop the belt halts while the rotor coasts on, so a pinned steel piece can reach red heat and melt into the belt. (Source: Bunge, 2019.) What steel does at the separator covers the damage in full.
Effect on the separation
A magnetic piece disturbs the rotor's field. Conductive pieces near it are not pushed away as they should be. (Source: Bunge, 2019.)
What buyers' grades require
ReMA's grades for used beverage cans, including Taldon, Taldack and Talcred, require magnetically separated material, and Taldon and Talcred exclude steel. Zorba, the shredded non-ferrous grade, must have passed one or more magnets, and so must Zurik. (Source: ReMA, July 2026, pp. 8, 11 and 17.) Aluminum scrap grades and what buyers accept covers each grade.
The order the makers describe
Makers of both machines describe the same order. Bunting says an eddy current separator often follows a drum magnet or another machine that removes ferrous metal. STEINERT places its separators after crushing, sizing and magnetic separation. (Sources: Bunting, Eddy current separators, undated; STEINERT, Eddy current separators, undated.)
Designing an aluminum recovery line puts every machine in order, from freeing the metal to refining the product.
3Running more than one magnet
No magnet removes all ferrous metal. IMI's manual asks for at least one magnet ahead of the separator (a drum, a magnetic head pulley or a cross-belt magnet, alone or together) and says that more than one lowers the risk of damage. (Source: IMI, manual 900505, undated.) Bunge adds that some magnetic pieces get through even aggressive magnets upstream (Source: Bunge, 2019).
Dings describes when to pair the two. A magnetic head pulley suits a shallow burden. On a deeper burden, an overhead cross-belt magnet goes first and lifts steel out of the upper part of the burden; the head pulley then catches steel lying on the belt. (Source: Dings, Magnetic head pulley applications, undated.) Bunting's summary of recycling plants also places head pulleys as a second clean-up at discharge points (Source: Bunting, 2026).
Remcon Equipment, the publisher's affiliate, compares a magnetic head pulley with an overhead magnet on its magnetic head pulley page.
Some separator makers offer a magnet as part of the machine. Goudsmit offers an infeed module carrying a drum magnet or a magnetic head pulley, to strip remaining ferrous metal before the rotor. Bunting offers a chassis with a drum, pulley or overband magnet ahead of the separator, and Magnapower lists a drum magnet among its separator accessories. (Sources: Goudsmit, EddyXpert eddy current separators, undated; Bunting, Eddy current separators, undated; Magnapower, Eddy current separators, undated.)
Choosing each magnet and placing it are covered in magnet types and placing the magnet.
[Worked example: the magnets ahead of the separator on the affiliate's own builds, once its publication is approved]
4Steel that reaches the separator
Some steel gets past every magnet, so separator makers say what their machines do with it. They do not all say the same thing. The table puts each statement beside the maker that publishes it.
| Maker | What the maker says |
|---|---|
| Industrial Magnetics (IMI) | Steel trapped in the rotor's field superheats and can permanently weaken the rotor magnets. IMI does not cover this "ferrous burnout" under warranty, and asks for at least one magnet ahead of its separator. |
| Eriez | Its eccentric separator is designed to run with a minimum of ferrous metal in the feed, with magnets upstream where needed. For belt or shell damage, its manual says to eliminate ferrous metal from the feed and check the upstream magnet. |
| Bunting | On a concentric rotor, steel stays on the belt under the rotor and heats; when the belt stops it can burn through the belt onto the shell. An eccentric rotor lets steel drop off, often into the non-metal stream. Bunting advises taking ferrous metal out first with overhead, pulley or drum magnets. |
| Magnapower | Steel held by the rotor heats up fast and wears the belt, then the rotor. Magnapower strongly advises removing ferrous metal before the separator. |
| STEINERT | Its eccentric pole system keeps residual ferrous metal from sticking to the separator's head, which it says keeps belt and shell wear low. |
| Dings | In its eccentric design, steel that slipped past the upstream magnet drops off the belt once it leaves the rotor's field, so it is less likely to cling to the shell and damage it or the belt. |
| Green Machine | Its separator can also separate ferrous metal, by pulling it out under the head into a receiving hopper. |
Sources: IMI, manual 900505, undated; Eriez, RevX-E manual RM-99, 2015; Bunting, 5 key eddy current separator operating parameters, 2020; Magnapower, Eddy current separators (FAQ), undated; STEINERT, Eddy current separators, undated; Dings, Eccentric vs. concentric eddy current separators for recycling, undated; Green Machine, Eddy current separators, undated. All read 2026-10-06.
Bunting, Dings and STEINERT tie the shedding of stray steel to the eccentric rotor layout. What each maker claims for each layout is set out in concentric and eccentric rotors.
Steel has to come out before the separator
Neither manual cited here relies on the rotor to clear steel. IMI asks for at least one magnet upstream, and Eriez designs its eccentric separator for a minimum of ferrous metal in the feed. (Sources: IMI, manual 900505, undated; Eriez, RevX-E manual RM-99, 2015.)
This guide follows the separator makers' manuals: magnets go ahead of the separator, and the separator is not relied on to remove steel.
5Where stainless steel goes
Stainless steel is the metal neither machine handles well.
Common stainless grades barely respond to the separator's rotor. Their ratio of conductivity to density is about 0.18, against about 13.7 for aluminum. (Source: Goudsmit, separation efficiency, undated.) Bunge notes that chromium steels are lost to the residue, while some weakly magnetic chromium-nickel grades end up in the non-ferrous product (Source: Bunge, 2019).
The magnet does not settle it either. ReMA defines Zurik, a shredded grade that is mostly stainless steel, as material produced by sensor sorting, such as induction or X-ray, that has passed magnets. (Source: ReMA, July 2026, p. 17.)
So plants that want the stainless add another machine after the separator:
- Bunting's summary of recycling plants puts stainless steel separators after the eddy current separator (Source: Bunting, 2026).
- One documented auto shredder ran magnetic separation, then a trommel, then non-ferrous recovery, then an inductive sorter for stainless steel (Source: Argonne National Laboratory, 2011).
- In bottom ash, induction sorting detects all metals, stainless included, in pieces over about 4 mm, with recovery and grade that can exceed 90%, if the material is spread in a thin layer (Source: Šyc et al., 2020).
Some separators offer a third cut instead: IFE lists an optional three-product splitter for stainless on its VIOS and ENOS models (Source: IFE, 2026). Sensor-based sorting for metals explains induction and X-ray sorting, and eddy current against sensor-based sorting compares the two.
6What to tell each maker
Each maker needs to know what the other machine does.
- Tell the separator maker how ferrous metal is removed upstream: which magnets, and how many. Ask how its warranty treats damage from steel. (Source: IMI, manual 900505, undated; the manual excludes ferrous burnout from warranty.)
- Tell the magnet maker your belt width and speed, the depth of material, and the size and shape of the steel. What to tell the manufacturer lists the inputs magnet makers size on.
- If stainless steel must come out, say so, and say where: it calls for another machine after the separator, such as a sensor sorter (section 5).
The RFQ checklist sets out every item for each machine. Eddy current and magnet makers are listed in the directory.
7Questions
Which goes first, the magnet or the eddy current separator?
The magnet. Separator makers' manuals call for magnets ahead of the separator, because steel held in the rotor's field heats up and can damage the belt, the shell and the rotor magnets. The buyers' grades for cans and for Zorba also require material that has been through a magnet. Sources: IMI, manual 900505, undated; Eriez, RevX-E manual RM-99, 2015; ReMA, July 2026.
Can an eddy current separator take steel out on its own?
Makers differ. Green Machine says its separator can pull ferrous metal out under the head into a hopper. Bunting, Magnapower, Eriez and IMI ask for ferrous metal to be removed before the separator. This guide follows the separator makers' manuals: magnets go ahead of the separator, and the separator is not relied on to remove steel. Sources: Green Machine, Eddy current separators, undated; Bunting, 2020; Magnapower, Eddy current separators, undated; Eriez, RevX-E manual RM-99, 2015; IMI, manual 900505, undated.
Does steel in the feed lower aluminum recovery?
It can. Bunge reports that a magnetic piece disturbs the separator's field, so conductive pieces near it are not pushed away as they should be. Source: Bunge, 2019.
8Sources
Every source below was read on 2026-10-06. Manufacturers' statements are their own claims about their own machines; the publisher has not tested the equipment.
- 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.
- 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.
- Recycled Materials Association (ReMA). ReMA's ISRI Specifications. July 2026 (pp. 8, 11 and 17). https://www.isrispecs.org/wp-content/uploads/2026/09/2026-July-ReMA_ISRI_Specifications.pdf. Read 2026-10-06.
- 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.
- Goudsmit Magnetics. What determines the separation efficiency of eddy current systems (knowledge base). Undated. https://www.goudsmitmagnetics.com/en-us/knowledge-base-efficiency-of-eddy-current-separators. Read 2026-10-06.
- 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.
- Bunting. Eddy current separators (product page). Undated. https://buntingmagnetics.com/product/magnetic-separation/eddy-current-separators. Read 2026-10-06.
- 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.
- STEINERT. Eddy current separators (product page). Undated. https://steinertglobal.com/us/sorting-systems/magnetic-separation/eddy-current-separators/. Read 2026-10-06.
- Dings Magnetic Group. Magnetic head pulley applications. Undated. https://dingsmagnets.com/magnetic-head-pulleys-uses-and-applications/. Read 2026-10-06. Dings has supplied magnets to Remcon Equipment, the publisher's affiliate.
- Bunting. Which magnetic separators do recycling plants use to maximize metal recovery? (blog). June 11, 2026. https://buntingmagnetics.com/blog/which-magnetic-separators-do-recycling-plants-use-to-maximize-metal-recovery. Read 2026-10-06.
- Remcon Equipment, Inc. (the publisher's affiliate). Magnetic head pulley. https://www.remconequipment.com/magnetic-head-pulley. Read 2026-10-06.
- Goudsmit Magnetics. EddyXpert eddy current separators (product page). Undated. https://www.goudsmitmagnetics.com/en-us/products/belt-conveyor-magnetic-separators/eddyxpert-eddy-current-separators. Read 2026-10-06.
- Magnapower. Eddy current separators (product page and FAQ). Undated. https://magnapower.com/separators/eddy-current-separators/. Read 2026-10-06.
- 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.
- Green Machine. Eddy current separators (product page). Undated. https://www.greenmachine.com/equipment/eddy-current-separators. Read 2026-10-06.
- C. Duranceau and J. Spangenberger, Argonne National Laboratory. All Auto Shredding: evaluation of automotive shredder residue generated by shredding only vehicles, ANL/ES-C0201801. July 11, 2011. https://publications.anl.gov/anlpubs/2011/09/70931.pdf. Read 2026-10-06.
- Šyc, M., et al. Metal recovery from incineration bottom ash: state-of-the-art and recent developments. Journal of Hazardous Materials 393, 2020 (peer-reviewed; postprint). https://cris.unibo.it/bitstream/11585/762085/5/S%cc%8cyc2020_postprint.pdf. Read 2026-10-06.
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