1.Why does striping produce burrs?
Shearing Mechanism: When the cutting tool presses into the material, it first plastically deforms, then microcracks begin to form at the cutting edge. These microcracks in the upper and lower cutting tools propagate and converge, ultimately separating the materials.
Fraction Formation: During this process, the propagation paths of the microcracks cannot perfectly align, resulting in a small area of uncut metal remaining along the thickness of the strip edge. This is known as burr. Furthermore, as the cutting tool becomes dull, its action shifts from "cutting" to "extrusion and tearing," resulting in even larger burrs.
2.What are the common forms of burrs?
Whiskers: Small, thread-like protrusions of zinc metal. These are generally less harmful and can be easily removed or fall off during subsequent handling.
Flanges: The edge is compressed and raised to one or both sides, forming a slight curl. This type of burr is more persistent and more harmful.
3.What are the common grades of burrs?
Excellent: The edge is smooth, with only slight, barely noticeable burrs, and no noticeable scratching sensation when touched.
Acceptable: Visible burrs are present, but they are low-profile, non-sharp, and do not affect subsequent use or safety.
Unacceptable: The burrs are large, sharp, and have a noticeable beading pattern, which can easily scratch the operator and can be pressed into adjacent coils during subsequent coiling, damaging the zinc coating surface.
4.What are the potential hazards of burrs?
Safety Risks: Extremely sharp, easily scratching the operator's hands and arms.
Surface Quality Damage: During rewinding, hard burrs can intrude into or scratch the adjacent inner galvanized surface, causing scratches or indentations, affecting the product's appearance and corrosion resistance.
Coating Issues: If spray coating is required after slitting, burrs can cause uneven coating coverage at the edges, making them susceptible to rust.
Processing Difficulties: During subsequent stamping, bending, and other processes, burrs can accelerate mold wear or cause product cracking.
5.How to control and reduce burrs?
Sharp Cutting Tools (The Most Critical Factor):
Use dedicated, high-quality circular shears.
Establish a strict cycle for cutting and sharpening the cutters to ensure they remain sharp.
Precise Knife Gap Adjustment:
The gap between the upper and lower cutters must be precisely set based on the thickness and hardness of the galvanized coil. Too little gap accelerates cutter wear, while too much gap can cause material tearing and produce large burrs.
Appropriate Knife Overlap:
The overlap between the upper and lower cutters must be precisely controlled to ensure a clean cut.
Good Equipment Condition:
The slitting machine must be rigid and stable to avoid vibration during the cutting process.
Optimized Material Properties:
The base material and ductility of the zinc coating of the galvanized coil itself also affect burrs. Excessively soft material or a thick, sticky zinc coating can exacerbate burrs.