Slitting Line Running Cost — Knife Change Time, Setup and Shift Output

Knife change on a slitting line is a configuration job rather than a swap: knives, spacers and rubber sleeves are set up for each strip thickness, and that set-up holds slit width to ±0.2 mm and burr to 4% of thickness. The set takes up to 15 strips at 2 mm, 10 at 4 mm, 6 at 6 mm and 4 at 8 mm.

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What Is Slitting Line Running Cost

Running cost on a slitting line machine comes from three places: the tooling that wears, the time the line stands while the knife set is rebuilt for a new thickness, and the coil lost when the set-up is wrong. A knife change on this line is a configuration job rather than a swap: knives, spacers and rubber sleeves are set up for each strip thickness, and that set-up is what holds slit width to ±0.2 mm and burr to 4% of thickness.

What the four tooling items each do

Slitting knives make the cut. Spacers set the distance between cuts and therefore the finished strip width. Rubber sleeves sit between the elements on the arbor. Separator discs keep the slit strips apart after the cut so they do not interleave before the recoiler. The four work as one set: wear on the knives or spacers, or a wrong build of the set, shows up as out-of-tolerance width, heavy burr and camber at the same time.

Where the running cost goes

The knife set wears with cutting volume and has to be rebuilt for every change of thickness; from 15 strips at 2 mm to 4 strips at 8 mm it is a different stack, not a different setting. The largest cost, though, is usually rejected coil: a coil of up to 32 tonnes that fails on width, burr, camber or telescoping cannot be used by the next line, so set-up discipline matters more than the price of the tooling.

Strip slit on this line can go straight on to our tube mill and welded pipe production lines.

Slitting Line Running Cost — Method and Measured Values

These are the figures from the line specification that the knife set and its running cost depend on:

• Coil: hot-rolled steel coil 1–12 mm thick and 800–2000 mm wide, up to 32 tonnes.
• Strips per set: up to 15 at 2 mm, 10 at 4 mm, 6 at 6 mm and 4 at 8 mm; minimum strip width 80 mm.
• Scrap edge: 5–15 mm, wound off by the scrap winder.
• Limits the set has to hold: slit width ±0.2 mm and burr no more than 4% of thickness; camber and telescoping are held by tension and looper control.
• Line speed: 30/100 m/min.
• Tooling: slitting knives, spacer bushings, rubber sleeves and separator discs.

Steel slitting line machine

The SL-12×2000 steel slitting line takes hot-rolled coil 1–12 mm thick, 800–2000 mm wide and up to 32 tonnes, through a double-head uncoiler, the slitter and a 32-tonne recoiler, at a line speed of 30/100 m/min. The full specification is on our steel coil slitting machine page.

Sources and Standards Referenced in Our Records

Our slitting lines are CE marked under the EC Machinery Directive 2006/42/EC. The strip counts, minimum strip width, tolerances, scrap width and line speed on this page are taken from the technical specification of our SL-12×2000 coil slitting line.

Step-by-Step Procedure

1. Build the knife set for the coil thickness: slitting knives, spacer bushings, rubber sleeves and separator discs, up to 15 strips at 2 mm down to 4 strips at 8 mm.
2. Load the coil from the coil saddle onto the double-head uncoiler with the loading car.
3. Feed the strip through the pinch rolls and the 2+5-roll pre-leveller.
4. Trim the head end on the hydraulic shear and run the strip over the roller table and side guide into the slitter.
5. Slit the strip and wind the trimmed edges onto the scrap winder.
6. Pass the strips through the looper, the separating unit and the tension unit.
7. Recoil the strips on the recoiler with separator and take the coils off with the unloading car.

Worked Example — What Is On File and What Is Not

On file: the knife set is built for each thickness, up to 15 strips at 2 mm, 10 at 4 mm, 6 at 6 mm and 4 at 8 mm, with a minimum strip width of 80 mm. Slitting knives, spacer bushings, rubber sleeves and separator discs are supplied with the line as a set and can be resupplied.

Not given as fixed figures: knife life in tonnes slit, knife change time, tooling cost per tonne and shift output. All four depend on the steel grade, the thickness mix and how often the set is rebuilt, so we work them out with you against your coil programme. Distributors can also see our wholesale coil slitting machines page.