How to choose a form-fill-seal machine

Short answer: first decide whether your product and pack suit a vertical (VFFS) or a horizontal (HFFS) machine. Then choose the filler that suits your product. List the bag styles and films you need to run now and in the next few years. Size the machine for a tested speed on your own product, not a brochure maximum. Finally, check seal quality, gas flushing, hygiene and changeover. The purchase price matters, but downtime, film waste and changeovers decide what the machine really costs to run.

This guide works through those decisions in order, and ends with the questions to put to every maker before you buy.

What does a form-fill-seal machine do?

A form-fill-seal machine makes a pack from a flat roll of film, fills it and seals it in one continuous cycle. On a vertical machine, the film is pulled over a forming shoulder and wrapped around a hollow tube. A vertical jaw seals the long back seam. A horizontal jaw makes the bottom seal, product drops through the tube, and the same jaw then seals the top of that bag and the bottom of the next one before cutting it free. The machine can also blow air or an inert gas such as nitrogen into the bag as it is sealed. Hang holes for retail racks can be punched at the same time.

The machine sits at the centre of the packaging station. Upstream, a filler portions the product. Downstream, packs usually pass a checkweigher and a metal detector before case packing. So the choice is really about a small system, not a single machine.

Vertical or horizontal: which do you need?

Vertical form-fill-seal (VFFS) machines fill product downwards through the forming tube, so gravity does the work. They are widely used for snacks, frozen food, confectionery, cereals, powders and other products that flow. Typical formats are pillow bags, gusseted bags, block-bottom bags and some stand-up (Doy) bags. A vertical machine usually fits into a smaller floor area, which matters when it sits under a weigher on a mezzanine.

Horizontal form-fill-seal (HFFS) machines carry the film horizontally through a series of stations. The film is folded, the sides and bottom are sealed, the pouch is cut and opened, and the product goes in through the open top before the top seal is made. Because every pouch passes through separate stations, horizontal machines are well suited to stand-up and shaped pouches and to closures such as zippers, caps and tear-off openings. They can handle liquids, powders, granules and solid pieces, but they generally take up more floor space than a vertical machine.

A useful rule of thumb:

• Loose product going into a pillow or gusseted bag: start with VFFS.
• Premium stand-up pouches with zippers or caps, liquids in pouches, or products that must be placed rather than dropped: look at HFFS as well.

Some pack styles, such as simple stand-up pouches, can be made on either type. In that case, compare floor space, changeover time and the speed each maker will guarantee on your product.

How do you match the filler to your product?

The filler decides how accurately each pack is filled and often limits how fast the line can run. Match it to the product:

• Solid pieces such as chips, nuts, frozen vegetables and sweets: a multihead weigher. It weighs many small hoppers at once and releases the combination closest to the target weight. Sticky products such as fresh meat or grated cheese may need belt or screw feeders instead of vibration.
• Powders and dry mixes such as flour and sugar: usually an auger filler, which doses by turning a screw. How evenly the powder is supplied to the auger matters as much as the filler itself.
• Free-flowing granules: a vibratory (linear) weigh filler or a multihead weigher, depending on the speed and accuracy you need.
• Liquids, sauces and pastes: a flow filler or a positive-displacement pump filler, on a horizontal machine or on a vertical machine set up for liquids.

Also ask how the filler hands over to the bagger. Timing between the weigher discharge and the jaw closing affects both speed and the risk of product being caught in the seal.

Which bag styles and films will you run?

List every pack you expect to run: the bag style, the width and length range, the fill weight range and the film. Then ask each maker which change parts that list needs. Forming shoulders, tubes and sealing jaws are usually specific to a bag width or style, and each extra set adds cost and changeover time.

Film matters as much as format. Laminated films, mono-material recyclable films and paper-based films seal differently. They need different temperatures, pressures and dwell times, and some have a narrower window in which a good seal forms. Makers now market machines designed to seal recyclable mono-materials and paper-based films at rated speed. If you plan to move to recyclable packaging, run trials on those films before you buy.

How fast does it need to run?

Work out the output you need at the end of the line, in packs per minute. Then add margin for stoppages and changeovers. Next, choose the motion type:

• Intermittent motion: the film stops for each seal. This approach is reliable and suits a wide range of products and medium outputs.
• Continuous motion: the jaws travel with the moving film, so the machine can run faster for long periods.

Treat every speed figure as specific to one product. One maker quotes up to 300 bags per minute for its fastest vertical series, but it also states that actual output depends on product type, bag format, film and line configuration. A fragile product, a long bag or a slow-sealing film will all bring that number down. Ask for a tested speed on your product, your film and your bag size, and ask how the test was run.

What makes a good seal?

A seal has to be strong, leak-tight where needed, and free of trapped product. Good seals come from the right time, temperature and pressure on clean film. Machines that control jaw force precisely, for example with servo-driven jaws, can keep seal quality steady across films and speeds. Ask how the machine keeps product out of the seal area, how it detects a bad seal and what happens to a bad pack. For gas-flushed or vacuum packs, ask how seal integrity is checked on the line and in the lab.

Does your product need nitrogen flushing?

If your product contains fats that go rancid, such as fried snacks and nuts, or is fragile, ask about gas flushing. Nitrogen flushing replaces the air in the pack with nitrogen during sealing. Nitrogen is a comparatively inert gas, so displacing oxygen slows oxidation. The gas also cushions the product and stops the pack collapsing. Modified atmosphere packs for meat, cheese and fresh produce use other gas mixtures, often on different machines. Ask the maker how residual oxygen is measured, and where the nitrogen will come from. Many plants use an on-site nitrogen generator.

Flushing is not a substitute for food safety controls. Low-oxygen packs still depend on temperature control and hygiene.

What should you check for hygiene and cleaning?

Look at how the machine is cleaned, and how often. A dry snack plant and a frozen food or fresh cheese plant need very different levels of hygienic design. Check the materials in the product zone. Look for gaps and horizontal ledges where product can collect, and for whether parts can be removed without tools. Ask whether the machine is rated for washdown. EHEDG publishes guidelines on hygienic design and methods for assessing whether equipment can be cleaned. They are a good reference when you compare what different makers claim.

What drives the cost?

Prices vary widely, so compare quotes on the same scope. The main cost drivers are:

• Motion type: continuous-motion machines are generally more complex than intermittent ones.
• The filler: a multihead weigher, auger or liquid filler is often a large share of the system cost.
• Formats: each extra bag width or style needs change parts and adds changeover time.
• Options: gas flushing, zippers, hole punching, printers and coders, and integrated checkweighing or metal detection.
• Hygiene: washdown construction and hygienic design cost more than a standard frame.
• Support: installation, training, spare parts and service contracts.

Running costs matter as much as the price. Makers themselves point to film waste at changeover and unplanned downtime as significant variable costs, along with spare parts, planned maintenance and operator training. A cheaper machine that wastes film on every changeover can cost more over its life.

What should you ask makers before you buy?

Send every maker the same brief: your product, fill weights, bag styles and sizes, films, target output and hygiene level. Then ask:

1. What speed will you guarantee on my product and film, and can I see a trial?
2. Which change parts does my format list need, and how long does a changeover take?
3. How do you control seal quality, and how are bad seals detected and rejected?
4. Which filler do you recommend, and who is responsible for the interface between filler and bagger?
5. What does the machine need from the plant: power, compressed air, nitrogen and floor space?
6. What spare parts should I hold, where is your nearest service engineer, and what training is included?

Compare the answers side by side, then see form-fill-seal machines by maker on this site, where every model specification links to the maker's own document.