Flexible Packaging Line Output: Calculating Capacity
Most people buying a flexible packaging line ask for price first and capacity second. That order is backwards. A line quoted on price alone can be built from five machines that each run fast and produce nothing useful at the end, because the slowest machine sets the output of everything upstream of it. The full range of flexible packaging equipment XIAOPAI works with is quoted the other way around, stage by stage, because that is the only way the number survives contact with production. Here is how output is actually calculated on a complete production line, using figures from the machine specifications rather than from a brochure headline.
CAPACITY IS SET BY THE SLOWEST STAGE
A complete flexible packaging line runs in a fixed order: blown film extrusion, flexographic printing, lamination, slitting and rewinding, then tube cutting or bag making. Material moves from left to right at a single speed. Every stage downstream of a constraint inherits that constraint's throughput. The blow film machine is usually where the constraint sits, because it is the only stage that creates the film. On the IBC three-layer line XIAOPAI sources for this kind of project, maximum extrusion output is 200-300 kg/h with a haul-off speed of 100-120 m/min on a 1600mm film width and a φ1800mm winding diameter. On the higher-output SG-3L1400 configuration the maximum extrusion figure is 320-400 kg/h. Whichever machine you buy, every other number on the line has to be sized against that figure rather than alongside it.THREE NUMBERS PER MACHINE, NOT ONE
Each machine publishes several speed figures, and they are not interchangeable. Taking them one at a time avoids the most common arithmetic error in a line quotation. Extrusion output is measured in kilograms of film per hour. That is the number that determines how much finished material the line can originate. The ABC-1800 IBC line runs 200-300 kg/h; the SG-3L1400 three-layer configuration runs 320-400 kg/h. A supplier who quotes you a line without stating which of these the price assumes has not answered the question you asked. Machine speed is measured in metres per minute and belongs to the transport mechanism, not to the product. The Master Series CI flexo printing machine at 1000mm print width publishes a mechanical speed of 400 m/min across six printing units, with a print repeat from 370mm to 1000mm. That figure describes the carriage. It does not tell you how much substrate reaches the rewind at any given gsm. Effective working speed is the one that matters commercially, and it is always lower than mechanical speed. Changeovers, registration checks, splice stops, reel changes and cleaning take time that never appears in a specification sheet. Any honest capacity figure has an uptime assumption attached to it. If a quotation arrives without one, assume it was not measured.
THE LAMINATING AND SLITTING CEILING
Downstream stages rarely become the constraint if they are matched properly, but they set the ceiling for how wide and how fast the line can run. The XPM-1100J roll-to-roll laminating machine with a coating unit works at 80-100 m/min. The XPM-1080RN automatic film laminating machine with hot knife runs at 105 m/min on the main position, with the disc cutter section at 80-100 m/min and the hot knife position at 70-80 m/min. Note that the hot knife is the slowest figure on the machine: when a hot knife is fitted, that number governs. For slitting, the horizontal 1300 type publishes a mechanical speed of 200 m/min and a slitting speed of 150 m/min, with a 45cm, 60cm, 65cm or 90cm effective slitting width and a 35-600 gsm weight range. The heavier duty CLFQ-W1100 automatic high-speed rewinding and slitting machine is a different class again: 400 m/min mechanical, 350 m/min rewinding and 350 m/min cutting, on a gsm range of 35-600. Matching a 350 m/min slitter behind a 200 m/min film line buys nothing.CONVERTING FILM OUTPUT INTO FINISHED UNITS
Buyers usually need bags or pouches per shift, not kilograms per hour. The conversion is arithmetic, but the inputs must come from the film specification rather than from the machine catalogue. Start from the extrusion figure. Take the blow film output, subtract the trim loss implied by your finished bag width against the film width, and you have the net film available. That film then carries the print repeat, so the number of print repeats per linear metre sets how many bags each linear metre can yield once you account for the registration waste. Apply the effective running speed of the constraint stage and the result is finished units per hour. Two things distort this calculation badly. First, gsm: a 35 gsm film carries far more bag volume per kilogram than a 90 gsm film, so the same kg/h figure yields a very different unit count. Second, the slitting stage, if the finished bag width does not divide cleanly into the slitting width, produces slit waste that never shows up in the extrusion number. The industry view on how these lines are specified and run is worth reading alongside the datasheets. Flexible Packaging Association documents how converters measure output in practice, and its industry resources page covers the production side in more depth.
