· KAIPU Engineering · glossary · 2 min read
Burr — Industry Glossary Entry
Definition of burr in industrial cutting: the unwanted projection of material on the cut edge, how it is measured, what causes it, and how to minimise it on slitter, shear and granulator blades.
Burr (also: flash, feather, whisker) is the unwanted projection of substrate material that forms on the cut edge during an industrial cutting operation. It is the single most common quality complaint on a slitting, shearing or blanking line, and it is the metric most-often specified on a knife drawing.
Measurement: Burr height is measured as the maximum projection of the burr above the cut surface, typically in micrometres (µm) for thin strip and sheet, or in millimetres (mm) for plate. Common methods: optical microscope with calibrated reticle, contact profilometer, or 10× loupe with a calibrated reference.
Typical targets:
- Paper, film, foil slitting: ≤ 25 µm (food packaging), ≤ 50 µm (industrial)
- Stainless strip slitting: ≤ 25 µm (precision), ≤ 50 µm (general)
- Plate shearing (carbon steel, ≤ 6 mm): ≤ 0.10 mm
- Plate shearing (stainless, ≤ 4 mm): ≤ 0.10 mm
Causes: The burr grows when the cut is not clean. The common causes, in order of frequency:
- Worn knife edge. As the hone radius grows, the cut transitions from shearing to tearing.
- Excessive hone. A hone > 15 µm on a thin knife pushes material rather than cutting it.
- Insufficient hone. A razor edge on stainless gall and forms built-up edge.
- Insufficient clearance angle. A 12° clearance on a 0.5 mm sheet will drag.
- Excessive clearance angle. A 30° clearance on a 0.1 mm strip will not support the cut.
- Blade gap (shear). Gap < 5 % of thickness causes work-hardening and burr. Gap > 12 % causes rollover.
- Material variability. A change in incoming substrate hardness or surface finish will change burr.
Fixes:
- Re-grind or replace the knife.
- Adjust hone to the substrate-appropriate radius (5–10 µm for paper, 10–15 µm for tissue, 0.05–0.10 mm for plate).
- Adjust clearance to the substrate-appropriate angle (18–22° for paper and film, 25–30° for tissue, 12–18° for hard plastics and metals).
- Adjust shear blade gap to 5–12 % of thickness.
- Audit incoming substrate for hardness and finish drift.
See also: The KAIPU 5-Factor Blade Selection Framework, Maintenance: how to extend slitter life, Hone (micro-hone).