Slitting Line & Cut to Length Line

**Slitting Process:**

1. **Coil loading** --- The incoming coil is lifted by overhead crane or coil car onto the uncoiler mandrel and centered
2. **Decoiling** --- The uncoiler pays out strip through the entry pinch roll and edge guide unit
3. **Edge guiding** --- Photoelectric or laser sensors align the strip laterally before the slitter to maintain consistent slit widths
4. **Slitting** --- Paired circular blades on upper and lower arbors cut the strip into multiple narrower webs simultaneously
5. **Tension control** --- A tension stand (driven pit roller or bridle) maintains consistent tension across all slit strands to prevent camber and interweaving
6. **Recoiling** --- Individual slit strips are rewound onto the recoiler mandrel, separated by separator discs, producing narrow coils ready for shipment or downstream processing

**Cut-to-Length Process:**

1. **Coil loading** --- Incoming coil placed on the uncoiler mandrel
2. **Decoiling** --- Strip fed through pinch rolls into the leveler
3. **Leveling** --- Multi-roll leveler (typically 9--21 rolls) removes coil set and delivers dead-flat sheet
4. **Length measuring** --- Encoder wheel or laser gauge measures the strip length to the programmed dimension
5. **Shear cutting** --- A flying shear or stop-cut shear cuts the leveled sheet to the exact programmed length
6. **Stacking** --- Cut sheets are conveyed to the stacking table, aligned, and stacked for bundling and shipment

Quality control on slitting and CTL lines focuses on dimensional accuracy, edge condition, and material surface integrity:

• **Strip width accuracy** --- Measured with digital calipers or laser gauges; tolerance ranges from ±0.1 mm (precision strip) to ±0.5 mm (construction grade), verified across all simultaneous strands
• **Edge burr height measurement** --- Burr gauges or microscopy confirm burr height stays below the specified limit (typically \<0.03 mm for thin precision strip, \<0.1 mm for heavy gauge); excessive burr indicates blade wear or incorrect clearance
• **Coil telescoping check** --- Inspect recoiled strips for lateral shift (telescoping) which indicates uneven tension or separator disc misalignment; maximum telescoping should not exceed 3 mm
• **Material surface scratch inspection** --- Visual or automated surface inspection for roller marks, guide scratches, or tension blemishes, especially critical for pre-painted and stainless coils
• **Blade alignment verification** --- Confirm upper and lower blade arbor parallelism within 0.02 mm/m and individual blade vertical/horizontal alignment before each production run
• **Tension mark detection** --- Check slit strip surfaces for bridle or tension roller impressions, which indicate excessive grip pressure or contaminated rollers
• **Recoil tightness and edge alignment** --- Verify recoiled strip coils are wound tightly without loose wraps, and that coil edges are aligned (no stagger) for safe handling and downstream decoiling
• **CTL length accuracy** --- Shear-cut sheet length measured against the programmed dimension; tolerance typically ±0.5 mm for sheets up to 3,000 mm; diagonal squareness checked with a tape measure

Slitting lines and CTL lines are among the heaviest and most complex machines in a steel processing facility, and their shipment demands careful planning. The main slitter unit --- comprising the arbors, gearbox, and drive motor --- can weigh 8--15 tons on its own and must be secured to a flat-rack container or a 40HQ with reinforced flooring and verified weight distribution. The uncoiler and recoiler mandrels are wrapped with anti-rust VCI paper and plastic film, with bearing surfaces coated in preservative grease. All hydraulic systems are drained to shipping levels to prevent leakage, and hydraulic ports are sealed with blanking plates.

The circular slitting blades are the most shipment-sensitive component. A typical blade set comprises 50--100+ individual discs of D2 tool steel or tungsten carbide, each precision-ground to ±0.005 mm flatness. Every blade is placed in an individual protective sleeve, then packed in custom wooden crates with foam dividers that prevent blade-to-blade contact during transit. Blade crates are marked \"FRAGILE --- PRECISION TOOLING\" and stowed last for priority unloading. All electrical cabinets are moisture-sealed with barrier bags and desiccant, and the PLC program is backed up to a USB drive shipped separately in the document pouch.

Unionindus delivers full-scope after-sales support for slitting lines and CTL lines, from installation commissioning through long-term maintenance:

• **Blade sharpening and replacement schedule** --- Recommended sharpening intervals based on material grade and tonnage processed (e.g., every 80--120 tons for D2 blades on mild steel, every 40--60 tons on high-strength steel); sharpening service available at our tooling center or on-site
• **Blade overlap and clearance adjustment** --- On-site training and reference charts for setting vertical overlap (typically 1--3 mm) and horizontal clearance (10% of material thickness for mild steel, 12--15% for high-strength grades) to control burr height
• **Tension control calibration** --- Load-cell verification and PID parameter tuning for the tension stand to prevent strip camber, interweaving, and telescoping on the recoiler
• **Edge-guide alignment** --- Photoelectric sensor calibration and mechanical guide roller alignment to maintain strip tracking within ±0.5 mm across the full coil length
• **Recoiler tension adjustment** --- Mandrel expansion system check and drum alignment verification to ensure tight, telescoping-free recoiling of narrow strips
• **Strip width measurement and adjustment** --- Setup of the first-slit measurement system and separator disc positioning; procedure for verifying and correcting width drift during a production run
• **CTL length accuracy calibration** --- Encoder zero-reference check, shear blade gap setting for different thicknesses, and flying shear timing adjustment to maintain ±0.5 mm length tolerance
• **Emergency stop and safety system testing** --- Full verification of E-stop circuits, light curtain function, guard interlocks, and overload protection before handover; annual re-test protocol provided