The Doypack is the most commonly used preformed stand-up pouch: flat bottom, wide sealing edge, and a rounded slope that showcases the product beautifully. This page is about the machine that fills and seals these pouches—the packaging machine for preformed bags — and about the choices you make in the process.
How It Works in Four Steps
- Carry handle and transport. A gripping system retrieves the bags one by one from a storage rack and places them on a clamp-plate conveyor. The storage rack typically holds 200 to 500 bags.
- Open and shape. Suction cups pull the bag open while a stream of air keeps the bag walls apart. Sensors check to make sure the bag is actually there and open.
- Fill. The dosing device is attached to your product; see the table below.
- Seal. Sealing is done in two steps: first below the filling point, then the main seam—possibly with a degassing valve, zipper, or spout in the seal seam.
Dosage Guidelines by Product
| Dosing Type | Suitable for | Accuracy |
|---|---|---|
| Multihead Weigher | beans, granules, loose products | ±0.5 g |
| Screw Feeder | powder, instant coffee | ±1% |
| Piston Filler | liquids, pastes, viscous liquids | ±1% |
The choice of dosing equipment depends on your product, not the other way around: first determine the product and the dosing weight, then specify the machine.
Sizes, Weights, and Speed
Sizes range from 100 x 150 mm to 400 x 500 mm, with bag capacities from 50 g to 5 kg. The speed ranges from 30 to 60 bags per minute, depending on the dose, product behavior, and whether a degassing pause is required. Within a single bag family, changing formats is simply a matter of adjusting the grip width and selecting the program—it doesn’t take hours of work.
When the VFFS approach makes more sense
At rates above 80 bags per minute, or when the cost of the bags is negligible compared to the cost of the material, a vertical form, fill, and seal machine The better method: unroll from the roll, which results in lower foil consumption per piece. The full analysis can be found in preformed bags or VFFS.
Frequently Asked Questions
Q: Can a single machine handle all my doypack sizes?
Usually within a range of approximately 100 to 400 mm in bag width. Extreme exceptions—such as mini-sachets alongside 5-kg bags—require a second grip or a second line. Submit your size list to the supplier before finalizing the specifications.
Q: What about a degassing valve for coffee?
The valve is inserted into the seal during the sealing process, provided the machine is equipped for this purpose. For coffee, this is standard: it allows CO2 to escape and keeps oxygen out. See the guide on Packaging coffee on a VFFS machine for a comprehensive comparison of routes.
Q: What is a realistic goal for the first year?
Expect a ramp-up period during which seal parameters and dosage adjustments will be fine-tuned. After that period, the line should reach its rated speed; plan for maintenance and spare parts starting on day one, according to the preventive maintenance schedule.
Related pages
packaging machine for preformed bags | Doypack | block-bottom bag | preformed bags or VFFS
Request a technical proposal Please specify the product, bag size, and desired output.
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