M-DB1 Double Belt Bagging Machine

What does the second belt add?

In a belt machine, filling time is set by two phases: coarse flow, in which most of the bag is filled quickly, and fine flow, which slows down as the target approaches. With one belt, both phases run over the same belt, which turns either fast or slow. Speeding up the belt to shorten the coarse phase lengthens the braking distance in the fine phase.

The M-DB1 has two belts. During coarse filling both belts run together and raise the total flow into the weigh hopper. As the target weight approaches, one belt can be stopped and the other slowed so that the last part is completed with a fine stream. This shortens the coarse phase and frees control of the last grams from the speed of a single belt. That is where the “finer dosing” in our short description comes from.

Finding the right step in the range

• Moving from the M-SB1 to the M-DB1: the single-belt model stays at 250–400 bags per hour. Two belts come in when a shift has to produce more than 3,000 bags, or when you want bag tolerance to sit near the lower end of the range more often.
• Compared with the M-DF1: the two machines share the same output, hopper volume and weight (400–750 bags per hour, 3000 litres, 2,300 kg). The only distinction is the product: the double-gate M-DF1 for grain and granular fertiliser, the double-belt M-DB1 for pellets, coal and pumice.
• Compared with the M-DB2-2L: the M-DB1 has a single filling spout; every bag passes through the same point. On the two-station M-DB2-2L filling is shared between two spouts, leaving each operator more time per bag. If bag placing is the bottleneck, choose the two-station line; if it is not, the M-DB1 is the simpler solution.

Planning the line at high pace

600 bags an hour means one bag every 6 seconds (3,600 / 600 = 6). At a single spout, the empty bag must be put on, the bag holder closed, filling completed and the full bag released onto the conveyor within that time. That is why, on M-DB1 installations, the bag placing point, sewing machine and conveyor are sized together to run at the same speed.

On the product side, continuous feeding matters too. For example, if pellets are taken at roughly 0.6–0.7 kg per litre, the 3000-litre hopper holds about 2 tonnes of pellets; at 15 tonnes an hour that is a buffer of around 8 minutes. The flow rate of the elevator or conveyor filling the hopper must not fall below the machine’s hourly consumption; otherwise the hopper slowly empties and the machine starts to wait.

Infrastructure and installation

The machine weighs about 2,300 kg; with a full hopper, the load on the support structure rises to several tonnes. The platform or floor it stands on must therefore be planned for that load. If the machine is mounted on a steel platform, remember to leave safe access around it for servicing the belts and weigh hopper. The electrical connection is 400 VAC, 50–60 Hz, three-phase, with ±5–10% mains deviation accepted. Compressed air at 8–10 bar drives the pneumatics, with a 300-litre compressor listed as the reference. In high-pace operation, where both belts and the bag holder move frequently, it is especially important that the compressor is rated for continuous duty.

With dusty products such as coal and pumice, adding a dust extraction connection to the spout makes both the operator’s surroundings and cleaning around the belts and weigh hopper easier.

Looking after two belts

Maintenance on a two-belt machine resembles that of the single-belt model, but the two belts must be kept in similar condition. If one belt is slacker or has product built up on its surface, the amounts the two belts carry during coarse filling become unbalanced and the fine phase gets longer. Weekly checks of tension and tracking, the state of the scrapers and cleaning of the weigh hopper keep that balance. When abrasive pumice is handled, the belt surfaces should be inspected more often. Scheduling maintenance so that both belts are checked on the same day makes any difference between them easier to notice and avoids separate stoppages.