Multihead Weighers: How They Improve Accuracy and Reduce Giveaway

Quick Answer

A multihead weigher splits product into many small portions, then picks the combination of portions that lands closest to your target weight. That combination approach cuts giveaway, lifts packing speed and keeps every pack within legal weight rules. Choose your multihead weigher by product type, head count, speed and washdown needs, and pair it with a checkweigher for full control of pack weight.

What Is a Multihead Weigher?

A multihead weigher, also called a combination weigher, sits above a packing machine and drops accurate portions into each pack. Instead of weighing one big scoop and hoping it is right, it weighs many small amounts at once and selects the best mix. That is why it fills snacks, nuts, produce, confectionery and many meat products faster and more accurately than a single-scale filler.

Volumetric fillers stop just under the target weight and rely on luck, which makes them slow and prone to giveaway. Combination weighing removes that guesswork. It sees the actual weight in every hopper and decides what to release.

How a Multihead Weigher Works

Infeed and Hoppers

Product reaches the weigher on an infeed conveyor. Vibratory infeeds are the most common, although sticky products may need belt conveyors or water sprays. The product then spreads across a ring of heads. Each head holds a feed hopper and a weigh hopper, and the weigh hopper holds a known portion. Radial designs are the near-universal choice, and linear designs suit some free-flowing products.

Combination Selection

A computer reads the weight in every weigh hopper and calculates which hoppers, released together, come closest to the target. More hoppers create more possible combinations, and more combinations give a better chance of the perfect pack weight. In one published example, a machine with 12 chambers offers 4,096 possible combinations, and one with 18 chambers offers about a quarter of a million.

Discharge and Refill

The selected hoppers open and drop their contents into the packing machine below. Machines with multiple discharges can pick a second combination from the remaining hoppers while the first pack seals. The emptied hoppers refill and the cycle repeats within a fraction of a second.

Why Giveaway Matters

Giveaway is the extra product you put in every pack above the declared weight. A few grams per pack sounds small, but across thousands of packs per shift it becomes real money. Combination weighing shaves that overfill by hitting the target more closely each time.

Accuracy also keeps you on the right side of the law. Under the Weights and Measures (Packaged Goods) Regulations 2006, packers must follow three rules. The average content must not fall below the nominal quantity, only a small share of packs may fall short by more than the tolerable negative error, and no pack may fall short by twice that error. Packers must also use suitable equipment and keep records of their checks. Trading Standards enforce these rules, and the regulations cover packs from 5 g up to 25 kg.

Which Products Suit a Multihead Weigher?

These machines handle a wide range of food. Common uses include fruit and vegetables, nuts, seeds, snacks, confectionery, cereals, rice and grains. Wet and sticky products such as chicken pieces and fragile bakery items can work well too, provided the machine has the right surfaces and handling.

Choosing a Multihead Weigher

Head Count and Speed

More heads deliver more combinations and faster packing, but they also cost more and take up more space. One manufacturer quotes about 120 packs per minute on a 14-head machine, and real output depends on product and pack size. Choose a head count that matches your packing machine speed instead of buying the biggest model.

Configuration

Single-product, single-outlet machines favour throughput. Multi-product machines can fill several components into one tray, and multi-product, single-outlet setups suit blends such as mixed nuts. Decide how you will pack before you choose, because the configuration is hard to change later.

Hygiene and Washdown

Check the contact surfaces, the hopper seals and the access for cleaning. Sticky products cling to flat surfaces, which is why dimpled or embossed metal helps. Deep-fried foods build up oil at high temperature and need more frequent washdowns. In freezing rooms, washdown water can freeze, so some processors run machines dry until product arrives.

Multihead Weigher or Checkweigher?

They do different jobs and work best together. The weigher fills the pack accurately, and a checkweigher then confirms the finished pack meets its declared weight and rejects any that do not. Our guide to checkweighers explains how they work and where to place one on your line.

Where the Weigher Sits on the Packing Line

The weigher sits at the top of a vertical packing machine or above a tray sealer, so product drops straight into the pack. Product usually arrives from a feed conveyor or bucket elevator, which keeps the weigher supplied at a steady rate. A starved weigher cannot pick good combinations, so match the infeed rate to the packing speed.

After the packing machine, a metal detector or X-ray system and a checkweigher complete the line. Plan the layout early, because the weigher stands on a frame above the packer and needs headroom and safe access for cleaning.

Setting Up and Calibrating

Good results depend on set-up as much as hardware. Operators enter the target weight and tolerance, choose how the machine uses its heads for each combination, and run it with real product. Dense product behaves differently from light, bulky product, and sticky pieces can cling to hoppers and distort readings, so test with your own range before you settle on settings.

Calibrate load cells on a schedule, and check them again whenever you change product or finish a deep clean. Keep weight records, because they feed your quality system and support the checks that Trading Standards expect from packers. Train operators to spot drift early, such as a rise in average pack weight or an increase in rejects, and to flag it before it becomes costly.

Buying a Used Multihead Weigher

A used machine can deliver excellent value, but the details matter. Ask for the calibration history and run the machine with your own product. Inspect the load cells, hopper doors, seals and contact surfaces for wear. Test the controls and confirm the software recipes save and recall correctly.

Check the stainless steel for pitting and cracked welds, and confirm the washdown rating suits your environment. Make sure parts and technical support remain available for the model. Finally, check that the discharge layout matches the packing machine beneath it.

How Machinery Masters Can Help

Machinery Masters is a UK-based marketplace for new and used industrial equipment, with verified sellers and financing available for qualified buyers. Browse the Packaging Equipment collection for filling machines, form-fill-seal machines, sealing equipment and more, and explore Inspection and Quality Control for checkweighers and detection systems.

Tell us what you need through Start Buying and machine matches land in your inbox within minutes. If you want to spread the cost, see our financing options. Upgrading your packing line? Create an advert for the old machine and generate your listing in minutes.

Frequently Asked Questions

How does a multihead weigher reduce giveaway?

It weighs many small portions at once and selects the combination closest to the target weight. That lets every pack land near the declared weight instead of overfilling to stay safe.

What is the difference between a multihead and a combination weigher?

The terms describe the same type of machine. Both use several weigh heads and a computer that selects the best combination of portions.

Can these machines handle sticky products?

Yes, with the right design. Dimpled or embossed contact surfaces, belt infeeds and water sprays help sticky product flow, and frequent cleaning keeps the machine reliable.

How many heads do I need?

Choose the head count that matches your packing machine speed and pack size. More heads give more combinations and higher accuracy, but you only need as many as your line can use.

Is it worth buying a used multihead weigher?

Often, yes. Check calibration records, load cells, seals and contact surfaces, and test with your own product before you commit.

Sources and Further Reading

• Packaged goods: weights and measures regulations (GOV.UK)
• Computerized combination weighers eliminate product give-away (Food Processing)