Household waste does not arrive at the plant loose, it arrives in bags. Until those bags are opened, no sorting machine can do anything useful: the screen sieves whole bags, the optical sorter sees black plastic, and the robot recognises nothing. A bag opener machine solves exactly this, tearing the bag and releasing its contents.
The detail that matters is that a bag opener opens but does not shred. The glass bottle, the aluminium can, the cardboard box and the film all have to leave the bag whole and recognisable, otherwise every euro invested in optical or robotic sorting downstream is wasted. See the full range of waste sorting equipment and how the machines connect.
Key Advantages of a Bag Breaker
• Opens without destroying, the rotating knife tears the sack but does not cut the material inside, so the fractions stay whole for the sorting downstream.
• Spring-loaded counter-knife, when an oversized object enters, the spring gives way and the knife gap opens, so the machine rides over the obstruction instead of jamming and stopping the line.
• Removes the hardest manual work, opening bags by hand is the most unpleasant task in a sorting plant and the one most exposed to cuts and puncture injuries.
• Works on any bag type, plastic, paper or woven polypropylene, including large bulk bags, by adjusting the gap between the knives.
• Raises line efficiency, evenly released material enters the screen and the separators better, so every machine downstream works at the capacity it was bought for.
• Adjustable to the flow, the gap between the moving and the fixed knife is set according to the dominant bag type and the moisture of the material.
Technical Specifications, Bag Opener Machine
| Parameter | 1.2 m width | 1.6 m width | 1.8 m width |
|---|---|---|---|
| Working width (mm) | 1200 | 1600 | 1800 |
| Indicative throughput (t/h) | 10–25 | 25–45 | 45–60 |
| Working principle | Rotating knife against fixed knife | Rotating knife against fixed knife | Rotating knife against fixed knife |
| Overload protection | Spring-loaded counter-knife | Spring-loaded counter-knife | Spring-loaded counter-knife |
| Bag types | Plastic, paper, woven PP | Plastic, paper, woven PP | Plastic, paper, woven PP, bulk bags |
| Drive | Electric motor with gearbox | Electric motor with gearbox | Electric motor with gearbox |
Throughput figures are indicative and depend heavily on waste density and bag size. The final configuration, including motor power and knife geometry, is set after a trial on your material.
Applications for Waste Bag Opening
• Household waste sorting plants, opening bags from kerbside collection, immediately after the feeder.
• Separate collection, opening bags of separately collected recyclables, where the material has to come out as clean as possible.
• Organic waste and composting, releasing food waste from bags before biological treatment, with subsequent plastic removal.
• Bagged industrial waste, opening large sacks of production offcuts and packaging materials.
• Transfer stations, preparing waste for compaction or onward transport.
How It Works
A movable knife mounted on a rotor turns against a fixed counter-knife. A calculated working gap is left between the two, wide enough to tear the bag material but not so narrow that the knives collide. The bag enters, is caught and torn, and the contents fall freely onto the next conveyor. The counter-knife is not rigid but supported on a spring. When an object harder or larger than the spring force appears in the flow, the counter-knife retracts, the gap widens, the object passes, and the spring then returns the knife to position. This is the mechanism that keeps the machine running on real waste, where bricks and metal parts also turn up.
Selection Guide
Width is chosen from plant throughput and bag size. For a small sorting plant, up to roughly 100 tonnes per day, the 1.2 metre version is enough. For medium volumes the 1.6 metre width is used. The 1.8 metre version is for high flows and for cases where industrial-size bags appear frequently. A practical rule: the bag opener should have throughput at least equal to the feeder upstream, otherwise it becomes the bottleneck of the line.
Frequently Asked Questions
Does the bag opener shred the waste inside?
No, and that is the whole point. The knife gap is calculated to tear the bag material, not to cut the contents. Bottles, cans and cardboard come out whole. If you need size reduction, that is the job of a shredder, a completely different machine placed at another point in the flow.
What happens if a metal part or a brick enters?
The counter-knife is spring-mounted. When the force from the object exceeds the spring pressure, the counter-knife retracts and the knife gap widens, so the object passes without jamming the rotor. Once through, the spring returns the counter-knife to the working position. This is the protection that avoids repeated stoppages.
Does it work on woven sacks and bulk bags?
Yes. Woven polypropylene sacks tear as readily as plastic ones once the knife gap is set. For large bulk bags the 1.8 metre version is recommended, as it has the necessary passage space.
Why not open bags by hand, is that not cheaper?
On paper it looks cheaper, in practice it is not. Manual opening caps the line throughput at what a few people can do, exposes operators to cuts, punctures and contact with contaminated waste, and produces an uneven flow that upsets the machines downstream. At any industrial volume, a machine pays the difference back.
Is the equipment supplied new?
Yes. We supply new units only, made to order for your application, with complete technical documentation.
What maintenance does it need?
Periodic checking and adjustment of the knife gap, inspection of the sharpness of the moving knife and counter-knife, checking the protection spring and lubricating the rotor bearings. The knives are wear parts and are replaced according to running hours.
Why URSTAG?
URSTAG is a premium brand of recycling equipment, with over 15 years of experience. You don't just get a machine, you get a solution engineered by specialists, built from top-tier components and backed by a team that supports you from design through commissioning.
• European engineering, every machine and every complete line is designed by our engineering teams in Europe, with a focus on reliability, safety and energy efficiency.
• Premium components, we build on motors and automation from industry leaders: Siemens, Schneider Electric, ABB, WEG, SEW-Eurodrive, NORD Drivesystems and Bonfiglioli.
• Over 15 years of experience, we know how materials and machines behave in real-world operation, and we configure each solution for your flow and volume.
• New equipment, configured for you, we supply new units, made to order for your application, with complete technical documentation.
• Delivery, installation and training included, we handle transport, commissioning and operator training, with support throughout the equipment's life.
As a premium brand, URSTAG relies on European engineering, top-tier components and experience. You choose a partner that supports your production long term, with equipment built to run reliably in demanding industrial environments.
