For film waste, the short answer is: choose an agglomerator when you need dense, extrudable feed from LDPE, HDPE, or PP film, and choose a granulator when you are cutting rigid plastics — or when film is only a small share of a mixed stream. The two machines are often quoted against each other, but they do different jobs: a granulator cuts, an agglomerator densifies. Picking the wrong one shows up immediately as a wrapped rotor or an extruder that starves on fluffy regrind.
This comparison walks through how each machine behaves on film, the six factors that decide between them, and the washing-line scenario where a plant genuinely needs both. The figures come from machines we build and test-run at Energycle.
The Quick Answer
| Granulator | Agglomeratore | |
|---|---|---|
| Principio di funzionamento | Cold cutting with rotary knives against a screen | Friction heating + water quench in a batch tank |
| Produzione | Flakes / regrind, size set by screen | Dense irregular granules (agglomerate) |
| Output bulk density (film feed) | ~30–60 kg/m³ — still fluffy | ~250–400 kg/m³ — free-flowing |
| Best feedstock | Rigid parts, pipe, sheet, bottles | Film, bags, raffia, non-wovens |
| Film behaviour | Tends to wrap the rotor and blind the screen | Designed for it |
| Energy (film feed) | ~0.05–0.08 kWh/kg | ~0.2–0.25 kWh/kg |
| Downstream fit | Regrind for molding or washing lines | Stable feed for extruders and pelletizers |
Regola pratica: if the material bends and flutters, densify it in an agglomerator. If it shatters or holds its shape, cut it in a granulator.
How a Granulator Works — and Where Film Jams It
A granulator is a rotary cutting machine. A bladed rotor spins against fixed bed knives, and everything stays in the chamber until it fits through a screen — typically 8–12 mm for recycling work. On rigid plastics it is the standard answer: fast, predictable, and cheap to run per kilogram. Our guide to granulatori industriali covers rotor styles and screen selection in detail.
Film is where granulators struggle. Thin film does not fracture against the knives the way rigid plastic does — it stretches, folds, and wraps around the rotor shaft, forcing shutdowns to cut it free. Even when a film-specific rotor avoids wrapping, the output is the real problem: granulated film is still feather-light. You have spent energy cutting it, and it still bridges in hoppers, floats out of feed throats, and fills a truck with air.
How an Agglomerator Works
An agglomerator skips cutting-to-size entirely. High-speed knives at the bottom of a steel tank heat film by friction until it shrinks into semi-plasticized crumbs; a shot of water then quenches the batch into dense, pourable granules. No screen, no external heaters — the main motor supplies all the process heat. The full cycle-by-cycle breakdown is in our guide to what an agglomerator is and how it works, and model specs are on the agglomeratore di film plastico pagina.
Head-to-Head: Six Factors That Decide
1. Output density
This is the deciding factor for most film processors. Agglomerate at 250–400 kg/m³ feeds an extruder steadily and cuts freight and storage volume by a factor of five to ten. Granulated film at 30–60 kg/m³ solves nothing downstream — the material is smaller but just as unmanageable.
2. Feed tolerance
Granulators want consistent, rigid feed and punish stringy contamination. Agglomerators accept film, bag, and raffia scrap in loose batches, including material a granulator would wrap. Neither machine tolerates sand or metal well — both eat blades.
3. Energy per kilogram
Cutting is cheaper than heating: a granulator draws roughly 0.05–0.08 kWh/kg on film against 0.2–0.25 kWh/kg for agglomeration. But the comparison is honest only if granulated output were actually usable — for film, the extra kilowatt-hours buy the density that makes everything after the machine cheaper.
4. Blades and maintenance
Both machines live and die by knife condition. A granulator adds a screen to inspect and unblock; an agglomerator adds water-dosing hardware. Expect comparable sharpening schedules on clean feed — and budget tool-steel blades (D2/SKD-11 grade) either way.
5. Capital cost
Size for size, the two machines sit in a similar price band, so purchase price rarely decides. The real cost difference appears downstream: fluffy regrind needs bigger silos, force feeders, and more handling labor than dense agglomerate.
6. Downstream fit
Granulator regrind suits injection molders blending rigid flake back into virgin material, and washing lines that need small wet flake. Agglomerate suits extrusion and pelletizing — which is where nearly all recovered film ends up. For the wider machine map, see our guida di selezione trinciatore vs. granulatore vs. pellettizzatore.
When to Choose a Granulator for Film Waste
- Film is a minor share of a mixed stream that is mostly rigid plastic, and one machine must handle everything.
- You are wet-granulating inside a washing line, where flake — not density — is the requirement.
- Your downstream process is compounding or molding that specifies flake feed, not granules.
When to Choose an Agglomerator
- Your stream is predominantly PE film, PP raffia, woven bags, or non-wovens.
- An extruder or pelletizer downstream starves, surges, or bridges on loose film feed.
- You ship or store scrap and are paying to move air — densification pays back in freight alone.
- You want a sellable intermediate product without investing in a full pelletizing line.
Quando hai bisogno di entrambi
Post-consumer film lines routinely run both machines. Dirty agricultural or post-consumer film is wet-cut by a granulator inside the washing section — small flake washes and rinses far better than whole film. After drying, an agglomerator densifies the clean flake so the pelletizing extruder receives a uniform, meterable feed. In that layout the machines are stages, not rivals: the granulator serves the washing step, the agglomerator serves the extruder. Our linea di shredding e densificazione di film PP/PE shows the complete sequence, and our comparison of the film agglomerator vs. film compactor vs. screw press densifier covers the other densification options for that slot.
Domande frequenti
Can a granulator handle plastic film at all?
Yes, with film-specific rotors and careful feeding — many washing lines wet-granulate film daily. What a granulator cannot do is densify: granulated film stays at roughly 30–60 kg/m³ and still handles poorly.
Is agglomerate better than regrind for extrusion?
For film-based feedstock, yes. Agglomerate flows and doses like a granular solid, so the extruder feed section runs full and steady. Fluffy film regrind bridges in hoppers and often needs a force feeder to move at all.
Which machine is cheaper to run?
Per kilogram through the machine, the granulator — cutting takes less energy than friction heating. Per kilogram of usable extruder feed, the agglomerator usually wins once storage, freight, and feeding problems are priced in.
Do I still need a shredder ahead of either machine?
For oversized input such as jumbo bags, rolls, or baled film, yes — a single-shaft shredder ahead of the line keeps feed size consistent and protects the knives of whichever machine comes next.
La conclusione
Granulators cut; agglomerators densify. For film waste the question is almost always density, which is why the agglomerator is the default answer — reserve the granulator for rigid streams and for the wet-cutting stage inside washing lines. If your stream mixes both, plan the line around stages rather than forcing one machine to do two jobs.
Send us your material mix, current bale or bulk density, and target throughput, and our engineers will lay out the right machine — or the right sequence. Request a configuration and quote.
