Paper packaging demand keeps climbing as e-commerce, food and beverage, and pharmaceutical production expand, which makes a corrugated carton production line one of the most reliable industrial projects in terms of guaranteed local offtake. Yet most investors contact Chinese suppliers asking for a quotation on "a carton line" without specifying speed, web width or the number of plies — and receive offers that are impossible to compare. This guide shows how to define the line in numbers before you send the first message.
A corrugated project is two plants, not one
Treating the project as a single unit is a fundamental mistake. In practice it is two technically and financially separate sections, and they can be purchased in two phases if cash flow is tight.
Part one: the corrugated board line
- Mill roll stands, one for every paper ply required.
- The single facer, which forms the flute between two heated rolls and defines the flute profile.
- The bridge, which absorbs the difference between fluting speed and main line speed.
- The glue unit and double facer hot-plate section that complete bonding and drying.
- Slitter scorer, cut-off unit and automatic stacker.
Part two: the converting line
- Flexo printer slotter die-cutter.
- Folder gluer or stitcher, depending on box design.
- Bundling and strapping unit before warehousing.
Sizing output: from m/min to boxes per day
The speed printed in a Chinese catalogue is always a maximum mechanical speed. Real operating speed runs 30% to 45% lower because of order changeovers, roll splices and steam temperature stabilisation. The practical formula:
Daily output (m²) = actual speed (m/min) × web width (m) × real running minutes.
Worked example: a line rated at 150 m/min with a 1.6 m web width, running at a realistic 90 m/min for 480 net minutes per shift, yields 90 × 1.6 × 480 = 69,120 m² per day. If one box consumes 1.2 m² of board, that is roughly 57,600 boxes per day before trim waste, which normally runs between 5% and 12% depending on how well orders are combined across the web width.
| Line class | Rated speed (m/min) | Web width | Best suited to |
|---|---|---|---|
| Economy | 60 – 80 | 1.4 m | Small, varied orders and local markets |
| Mid-range | 120 – 150 | 1.6 m | Regional packaging plants with repeat orders |
| High output | 200 – 250 | 1.8 – 2.5 m | Large volumes and supply to major manufacturers |
Three plies or five?
This is not a marketing preference; it follows from the weight of the packed product and stacking height in the warehouse. Three-ply board with a B or C flute covers most retail products up to roughly 15 kg, while five-ply (BC or EB) is necessary for heavy goods, export shipments and tall stacking. The difference goes straight into paper consumption and cost per box, so fix the required edge crush or box compression value (ECT or BCT) in your specification before choosing the construction.
Specifications to lock into the contract
- Usable web width, not the overall machine width.
- Available flute profiles, spare corrugating rolls, their material and surface treatment.
- Required steam pressure and the matching boiler capacity — a separate cost item many buyers overlook.
- Guaranteed waste rate and a trial run on the buyer's own paper during pre-shipment inspection.
- Scoring accuracy and colour registration tolerance on the printer, stated in millimetres.
The golden rule: never buy more speed than your market can absorb. A slow line that runs steadily earns more than a fast line idling for orders and spare parts.
Common mistakes in this sector
- Leaving the steam and compressed air systems out of the budget, though they can be a significant share of project cost.
- Calculating capacity at maximum speed without deducting changeover time between orders.
- Starting up without a stable supply contract for kraft and testliner paper.
- Ignoring the ceiling height the bridge requires — usually higher than factory owners expect.
A corrugated line is a rewarding project when its specification is built on your real market numbers rather than the supplier's catalogue. Define expected monthly demand in square metres, translate it into speed, web width and ply count, and only then request quotations so the comparison is fair. Contact our team to review your requirement and prepare a precise technical specification you can negotiate with several Chinese manufacturers at once.