Bei Ihrem Schnitt ist etwas schiefgelaufen. Die Kanten sind abgesplittert, die Oberfläche ist grau, die Dicke variiert über den Schnitt hinweg, oder der Draht ist mitten im Schnitt gerissen und Sie haben jetzt einen $50 SmCo-Rohling mit einer Rille darin. Bevor Sie etwas verändern, lesen Sie diese Anleitung zur Fehlerbehebung beim Schneiden von Magneten – denn die häufigste Korrektur, die wir bei Bedienern sehen, ist die Anpassung des falschen Parameters.
Wir haben jeden Schnittfehler katalogisiert, auf den wir bei Tausenden von NdFeB, Ferritund SmCo Schnittaufträgen auf unserer Endlos-Diamant-Seilsägen. gestoßen sind. Die Probleme lassen sich in fünf Kategorien einteilen: Kantendefekte, Oberflächenfehler, Maßfehler, Drahtprobleme und Nachschnittfehler. Jedes davon hat eine spezifische Ursache – und normalerweise eine spezifische Lösung. Diese Aufschlüsselung zur Fehlerbehebung beim Schneiden von Magneten deckt sie alle ab.
Kantensplitterung – Der häufigste Defekt beim Schneiden von Magneten
Null Duktilität ist das Kernproblem. Gesinterte Magnete verhalten sich unter Belastung wie Keramik – wie in der Bruchmechanikforschung zum Schneiden von NdFeB mit Diamantdraht beschrieben, geht das Material von duktilem Mikroschneiden zu sprödem Bruch über, wenn die Schnittkraft zunimmt. Kantensplitterung ist das, was spröder Bruch im Makromaßstab aussieht.
Warum tritt die Splitterung nur auf einer Seite auf?
Wenn die Eintrittsseite des Schnitts sauber ist, die Austrittsseite aber abgesplittert ist, ist die Ursache mechanisch. Wenn sich der Draht dem unteren Rand des Werkstücks nähert, wird die verbleibende Materialbrücke dünner, bis sie die Schnittlast nicht mehr tragen kann. Anstatt geschnitten zu werden, bricht sie – und erzeugt einen Splitter.
Fix: Reduzieren Sie die Vorschubgeschwindigkeit für die letzten 2–3 mm des Schnitts. Auf unseren Maschinen programmieren wir ein zweistufiges Profil: normale Vorschubgeschwindigkeit für den Großteil, dann eine 50%-Reduzierung für die Austrittszone. Diese einzelne Anpassung eliminiert die Splitterung auf der Austrittsseite in 80% der Fälle.
Wenn die Reduzierung der Vorschubgeschwindigkeit nicht hilft, fügen Sie eine Opfer-Trägerplatte hinzu, die mit Wachs oder Klebstoff auf der Austrittsseite des Werkstücks befestigt ist. Das Trägermaterial stützt den letzten Millimeter des Schnitts und verhindert so den Bruch. Graphit oder Aluminium funktionieren beide.
Warum tritt die Splitterung auf beiden Seiten auf?
Bilaterale Splitterung deutet auf eine übermäßige Schnittkraft über den gesamten Schnitt hin – nicht nur am Austritt. Der Diamantdraht übt mehr seitliche Kraft aus, als das Material aufnehmen kann, ohne an den Kanten zu brechen.
Fix (in order of impact):
- Reduce feed rate by 20–30%. Feed rate is the dominant factor controlling cutting force per grit.
- Check wire tension. Tension above 130 N on Ferrit or above 120 N on SmCo is too high for most cross-sections. Reduce in 10 N increments.
- Inspect the wire. Worn wire with missing or flattened diamond grits requires more force to cut, which increases chipping. Replace the wire.
Why Do Chips Appear Random Rather Than at Edges?
Random chipping — fragments missing from the flat face rather than the edge — almost always indicates internal material defects. Voids, inclusions, or micro-cracks from the sintering process create weak points that fail under cutting stress.
This isn’t a cutting problem. It’s a material quality problem. If random chipping is persistent across multiple blanks from the same batch, discuss with your magnet supplier. In our experience, about 5% of sintered NdFeB blanks from smaller suppliers have internal defect levels high enough to cause random chipping regardless of cutting parameters.
Surface Defects — What’s Wrong with My Cut Surface?
Why Is the Cut Surface Grey or Discolored?
On NdFeB: this is oxidation. The Nd-rich grain boundary phase reacted with moisture — either from water-based coolant, humidity in the shop air, or water contamination in your oil coolant system.
Fix: Switch to auf Öl basierendes Kühlmittel if you’re using water. If already using oil, check for water contamination: condensation in the tank (common in humid environments), residual water from a previous ferrite cutting run, or a coolant line leak. Drain, flush, and refill with fresh oil.
Also check time-to-protection. If cut parts sit exposed to shop air for more than 30 minutes before oil-coating or packaging, oxidation starts. Speed up your post-cut handling.
On ferrite or SmCo: grey discoloration is unusual and likely not oxidation. It’s more commonly cutting residue or coolant staining. Clean with isopropyl alcohol. If it doesn’t clean off, the discoloration may be subsurface damage from excessive cutting force — reduce feed rate.
Why Does Surface Roughness Suddenly Increase?
You were getting Ra 0.4 μm last week, now the same parameters produce Ra 1.0+ μm. Three likely causes:
Wire wear. Diamond grits flatten and detach over the wire’s service life. As the cutting surface degrades, the removal mechanism shifts from clean micro-cutting to blunt ploughing — which tears the surface rather than cutting it. Track cumulative cutting meters and correlate with Ra measurements to establish your wire replacement threshold. On NdFeB, we typically see noticeable roughness increase after 40–50 hours of continuous cutting with 0.35 mm galvanisch beschichtetem Diamantdraht.
Coolant contamination. Swarf particles accumulating in the coolant get recirculated through the cutting zone, scratching the cut surface. Check coolant clarity. If it’s noticeably darker than fresh fluid, change it. Check filter condition — a clogged filter means unfiltered coolant is bypassing directly to the cutting zone.
Guide wheel groove wear. Worn grooves allow the wire to oscillate laterally during cutting, creating periodic waviness superimposed on the surface roughness. The telltale sign: regular ridge patterns at 0.5–2 mm intervals on the cut face. Inspect the grooves under magnification. If the V-groove profile is rounded or widened, replace the guide wheel or re-machine the groove.
Why Are There Periodic Lines on the Cut Surface?
Regular, parallel lines or ridges spaced evenly across the cut face — this is waviness, not roughness. The cause is almost always lateral wire vibration.
Root cause checklist:
Wire lateral vibration comes from three sources: guide wheel groove wear (most common), insufficient wire tension (wire sags and oscillates), or external vibration transmitted through the machine base. Check in that order.
We had one case where waviness appeared intermittently — some cuts were clean, others had pronounced ridges. Turned out the building’s HVAC system cycled on and off, and when the compressor ran, it transmitted vibration through the concrete floor into the machine. Added vibration isolation pads under the machine feet. Problem solved.
Dimensional Errors — Why Are My Slices Wrong?
Why Do Slices Get Progressively Thinner or Thicker?
If the first few slices from a block are on-spec but later slices drift, the cause is cumulative wire deflection or workpiece shifting.
Wire deflection: As the wire wears during a multi-cut run, it loses diamond coating thickness. The effective cutting diameter decreases slightly, which changes the kerf width. Each successive slice may be marginally thicker (because less material is being removed). The fix is straightforward: replace the wire at a consistent interval rather than running it until visible degradation.
Workpiece shifting: If the workpiece isn’t properly fixtured, the cutting force gradually pushes it. Each cut shifts the workpiece a few microns further, creating a progressive thickness drift. Re-clamp or re-bond the workpiece between cuts if drift exceeds your tolerance.
Why Is One Slice Thicker on One Side Than the Other?
Tapered slices — thicker at the top, thinner at the bottom, or vice versa — indicate wire deflection during the cut. The wire bows under cutting force, and the amount of bow varies with depth.
Fix: Reduce feed rate. Wire bow is directly proportional to cutting force, and feed rate is the primary feed force driver. If reducing feed rate doesn’t fully eliminate the taper, increase wire tension in 10 N increments — higher tension reduces bow amplitude. But don’t exceed the recommended maximum for your material (150 N for NdFeB, 130 N for ferrite, 120 N for SmCo).
Also check the workpiece cross-section size. Larger cross-sections create more wire bow because the unsupported wire span is longer. For blocks above 40 mm, consider reducing feed rate to 1.0 mm/min regardless of material type.
Wire Problems — Breakage, Wear, and Tracking
Why Does the Wire Keep Breaking?
Wire breakage during magnet cutting has four common causes, in order of frequency:
1. Wire past its service life. The most common cause. Diamond coating wears down, the steel core is exposed, and the core can’t handle the cutting load alone. As MDPI research on diamond wire sawing of NdFeB confirms, wire condition is a primary factor in surface quality degradation. Track cumulative cutting hours and replace proactively. For NdFeB, we recommend replacing at 40–50 hours. For SmCo, replace earlier at 30–40 hours (the cost of a wire loop is negligible versus a ruined SmCo blank).
2. Sharp workpiece corners. When the wire contacts a sharp 90° corner on the workpiece, the stress concentration at the contact point can exceed the wire’s tensile strength. Pre-chamfer workpiece edges with a hand stone before cutting, or rotate the workpiece so the wire enters a flat face rather than a corner.
3. Excessive tension. Running tension above 150 N on 0.35 mm wire approaches the yield point of the steel core. If you’ve been incrementally increasing tension to compensate for other issues (wire bow, surface quality), you may have gone too far. Reset to baseline (100 N) and address the root cause instead.
4. Coolant starvation. If coolant isn’t reaching the cutting zone — clogged nozzle, empty tank, pump failure — the wire runs dry. Without lubrication, friction and heat spike, and the wire fails. This one is obvious in hindsight but easy to miss during operation. Check coolant flow before every cutting run.
Why Does the Wire Jump Off the Guide Wheels?
Wire tracking problems — the wire slipping out of the guide wheel grooves — cause immediate cutting failure and potential wire breakage.
Fix: Inspect guide wheel grooves. Worn or debris-filled grooves can’t hold the wire in position. Clean the grooves with compressed air and a fine brush. If the groove profile is visibly worn (rounded edges, widened channel), replace the guide wheel. Also check wire tension — too-low tension allows the wire to wander, especially during direction changes in contour cutting applications.
Auf unserem SG20-R machines, guide wheel grooves typically last 200–300 hours of cutting before needing replacement. Track hours and inspect regularly.
Post-Cut Failures — Magnet Cutting Troubleshooting After the Saw
Why Do Parts Crack Hours After Cutting?
Delayed cracking — parts that look perfect after cutting but crack in storage — is the most frustrating problem in magnet cutting because it’s invisible until it’s too late.
Two root causes:
Residual stress from fixturing. If mechanical clamping applied excessive force during cutting, the part retains internal stress. Once the clamping force is released, the stress redistributes over time, eventually exceeding the fracture strength at an internal flaw. This is especially common with Ferrit, which has the lowest fracture toughness of all common magnet materials.
Fix: Reduce clamping force. Switch from mechanical clamping to adhesive mounting for thin parts (under 5 mm). Allow 24 hours of stress relaxation before final inspection — if parts are going to crack from residual stress, it usually happens within the first 12 hours.
Residual stress from sintering. Some blanks come out of the sintering furnace with internal stress from uneven cooling. The cutting process releases these stresses asymmetrically, and the redistribution causes cracking hours or days later. This is a material issue, not a cutting issue — but it’s worth knowing so you don’t waste time adjusting cutting parameters.
Indicator: If delayed cracking occurs across multiple blanks from the same sintering batch but not from other batches, the sintering process is the root cause. Discuss with your magnet supplier.
Why Does the Coating Peel After Plating?
NdFeB parts were cut, chamfered, cleaned, and plated — but the NiCuNi coating blisters or peels during thermal cycling or adhesion testing.
Root causes (in order of likelihood):
- Inadequate surface cleaning. Oil-based cutting coolant trapped in surface micropores wasn’t fully removed during ultrasonic degreasing. Residual oil creates a weak boundary layer under the plating. Fix: extend ultrasonic cleaning time, increase bath temperature to 55–60 °C, and add a second degreasing cycle.
- Surface oxidation before plating. If cleaned parts sat too long before entering the plating bath, the surface re-oxidized. The oxide layer prevents proper adhesion of the nickel strike layer. Fix: minimize time between final cleaning and plating — ideally under 10 minutes.
- Subsurface damage from cutting. Aggressive cutting parameters can create a damaged layer 10–30 μm deep with micro-cracks and loosened grains. The plating adheres to this damaged layer, and when the layer degrades under stress, the plating goes with it. Fix: reduce feed rate to stay in the gentle cutting regime, or add a light grinding pass to remove the damaged layer before plating.
Magnet Cutting Troubleshooting Quick Reference
| Symptom | Most Likely Cause | First Fix to Try |
|---|---|---|
| Exit-side chipping | Wire exit fracture | Reduce feed rate for last 2–3 mm |
| Both-side chipping | Excessive cutting force | Reduce feed rate 20–30% |
| Grey surface (NdFeB) | Water/moisture contact | Switch to oil coolant; check for contamination |
| Increasing Ra over time | Wire wear or dirty coolant | Replace wire; change coolant |
| Periodic ridges on surface | Guide wheel groove wear | Inspect/replace guide wheels |
| Progressive thickness drift | Wire wear or workpiece shift | Replace wire; re-fixture |
| Tapered slices | Wire bow under load | Reduce feed rate; increase tension slightly |
| Drahtbruch | Past service life | Track hours; replace proactively |
| Delayed cracking | Clamping stress or sintering stress | Reduce clamp force; switch to adhesive mount |
| Coating peel | Insufficient cleaning or surface damage | Extend ultrasonic cleaning; reduce feed rate |
This table covers about 90% of the magnet cutting troubleshooting issues we encounter. For the other 10%, the cause is usually something environmental or machine-specific — and that’s where a free test cut with documented parameters can help isolate the variable.
Magnet Cutting Troubleshooting: Parameters vs. Machine Condition
One pattern we see repeatedly: an operator encounters a cutting problem and immediately starts adjusting feed rate, tension, and wire speed — often making multiple changes at once. After half a day of trial-and-error, the problem is still there because it was a machine condition issue, not a parameter issue.
Check the machine first if:
The problem appeared suddenly on a material and geometry you’ve been cutting successfully. Parameters don’t suddenly stop working on the same material. Something changed mechanically — guide wheel wear, coolant flow blockage, loose workpiece, or vibration from an external source.
Adjust parameters if:
You’re cutting a new material or geometry for the first time and haven’t established baseline settings. Start with the recommended ranges from our material guides (NdFeB, Ferrit, SmCo) and adjust one variable at a time. Never change more than one parameter between test cuts — otherwise you can’t isolate which change caused the improvement or made things worse.
