Why Film Refuses the Rigid Route

The product page answers the obvious question — why not just feed film into a rigid line? — with two mechanical facts. Film wraps around crusher rotors, and film floats instead of sinking. Each of those breaks a stage that a rigid-plastic line takes for granted: feeding, because baled film tears into unfeedable tangles instead of flowing; size reduction, because a rotor that grabs film builds a wrap instead of a cut; and dewatering, because the separation principle of the whole route assumes material that behaves predictably in water.

The line is therefore published as built for low bulk density, and its material fit reads across almost the whole flexible world: LDPE film, agricultural film, shopping bags, woven bags, jumbo bags and mixed flexible packaging. The contamination list is just as specific — soil, sand, organic residue, paper labels and printing ink on film surfaces — and the published output definition follows from it: squeezed film with surface water removed, ready for thermal drying or densifying.

That output definition is worth pausing on, because it already tells you how the line ends. A rigid line ends with flakes spun dry in a centrifugal chamber. A film line ends with film squeezed between screw surfaces. Everything upstream is arranged to make that final squeezing step work.

Sized by Wet Throughput, Not the Dry Figure

The most commonly misread line on the published specification is the capacity column. The film product page carries the same WL reference table as the rigid line, but with an explicit caveat: film lines are usually sized by wet throughput, which is lower than the dry figure for the same model. Low bulk density is the reason — the same model moves fewer kilograms of film per hour than kilograms of rigid scrap, because the conveying and washing stages run on volume before they run on weight.

Read the typical-feed column top to bottom and the film progression is visible: small film and bag volumes, then woven bags and shopping film, then agricultural and stretch film, then large film recovery plants. What the table deliberately does not publish is a film-specific wet capacity per model. The published position is that film throughput depends strongly on bulk density and contamination, and the wet capacity for film is confirmed in a material trial, project by project.

That restraint is useful when comparing quotes. A supplier who quotes film capacity by converting a rigid-plastic figure is guessing; the published route is to run your bales through a trial and size from the measured wet figure. The same logic applies to the water column — 3-5 t/h on WL-500 rising to 12-20 t/h on WL-5000 — which is circulation demand in a closed-loop design, not pure consumption.

Six Stages Built Around Anti-Wrapping

The published process sequence has six stages, and the page frames the whole chain with one sentence: anti-wrapping handling at the front end is what separates a working film line from a blocked one. Read the stages in that light:

• Bale opening. Bales are loosened without tearing the film into unfeedable tangles. This is where wrapping prevention starts — a bale opener that shreds the bale creates the tangles the rest of the line then has to survive.
• Anti-wrapping feed. Controlled conveying prevents film from wrapping on shafts. Every rotating surface downstream is a potential wrap point; the feed stage is configured so film arrives as manageable pieces, not ribbons.
• Wet size reduction. Cutting in water keeps the film moving and starts soil removal. The water bath does double duty: it stops the cut pieces from clumping and carries loose soil away the moment it is released.
• Intensive washing. Friction washing lifts soil and organic residue from the film surface. The FW series runs at 500-800 rpm with water demand of 2-12 m³/h across models, and larger or heavily contaminated lines use two or three washers in series — the published route for agricultural film with high soil content is a heavier pre-wash and soil-removal stage.
• Squeezing. Mechanical squeezing removes the bulk of the water. This is the stage a rigid line replaces with centrifugal spinning — more on that below.
• Thermal drying. Residual moisture is driven off before densifying or granulation, holding the series outlet moisture at 2% or lower.

Two details in that sequence are easy to underestimate. First, cutting happens in water — dry cutting film produces light, static-prone fluff that flies and clings; wet cutting keeps the pieces in the flow. Second, paper labels and printing ink are on the published contamination list for this line, and label adhesive survives rinsing the same way it does on rigid flake; our post on label removal before washing covers why that residue is attacked mechanically rather than chemically.

Squeezing, Not Spinning

The published dewatering guide states the split in one sentence: vertical machines spin flakes dry by centrifugal force; horizontal machines squeeze film and bags by screw pressure. The choice is set by material form, not by capacity alone, because film and rigid flakes behave differently inside a dewatering chamber — and the published FAQ adds the practical warning that one machine handling both drops in efficiency.

Note how the two structures are even rated differently: vertical machines are published by dewatering rate — 95% or higher on rigid flakes — while horizontal machines are published by outlet moisture, which rises with throughput on the same model. That asymmetry is honest engineering: a spinning chamber can report how much water it removed from free-draining flakes; a screw press squeezing film reports what actually comes out the end.

The film product page connects this to the final number: the published outlet moisture for the series is 2% or lower after thermal drying, and the figure before drying depends on the squeezing stage. The dryer is sized on the outlet moisture of the dewatering machine — which is why the published guidance notes that less water carried into the dryer means lower energy cost and higher drying stability. If the squeezed film continues to downstream sorting rather than granulation, moisture matters there too: the published selection notes for the WX horizontal air separator put the sticking threshold at roughly 10% moisture, above which particles clump and separation quality drops. For how the same VD/HD trade-off plays out on rigid material, see our posts on vertical versus horizontal dewatering and on fixing dewatering before blaming the dryer.

What to Send With the Enquiry

The film line page closes with three inputs: send your film type, bulk density and soil level. Those three decide the configuration, and each maps to a published adjustment:

• Film type — LDPE film, agricultural film, shopping bags, woven bags, jumbo bags or mixed flexible packaging. The typical-feed column of the WL table shows how far the film family spans, and the feed and cutting stages are configured around the form your film arrives in.
• Bulk density — the variable that separates wet throughput from the dry figure. It is the reason the wet capacity for your film is confirmed in a material trial instead of read off a catalogue column.
• Soil level — agricultural film with high soil content runs with a heavier pre-wash and soil-removal stage, and the configuration depends on the soil load in your material.

Send those three and the published framework does the rest: the WL-500 to WL-5000 reference range brackets the line size, a material trial converts your bulk density into a wet throughput figure, and the squeezing stage is matched to the moisture your dryer — or your downstream sorting — needs. Our earlier post, Film Washing Line: From Waste Film to Clean Flake, covers the end-to-end route for readers new to the material.

Frequently Asked Questions