Multihead Weighers: How They Work and Why You Need One

In this article, you'll learn:

• How multihead weighers achieve ±0.5g accuracy at high speed
• When a combination weigher makes sense vs. simpler alternatives
• Key specs to evaluate before purchasing
• Common mistakes buyers make with weighing equipment
• How weighing systems integrate into your packaging line

The Problem Nobody Talks About

A factory in Malaysia called us last year. They'd bought a mid-range VFFS machine, paired it with a cheap volumetric filler, and were hemorrhaging money on overfill. Their product was mixed nuts. Target weight 200g. Average actual fill: 212g. That's 6% overfill on every single bag.

At 10,000 bags/day, 365 days/year, that's roughly $180,000 in "free" product given away annually. All because of a $15,000 weighing system they decided to skip.

This is more common than you'd think.

How Multihead Weighers Actually Work

A multihead weigher is a bowl feeder that dumps product into multiple weighing hoppers simultaneously. Each head holds a small portion. The system adds up combinations of these portions until it finds the mix that matches your target weight exactly.

Here's the sequence:

1. Distribution — Product flows from an elevated hopper into a central disperser
2. Feeding — The disperser rotates, feeding product into individual weighing cups
3. Rough feed — Each cup takes a first portion (60-70% of target weight)
4. Fine feed — A second pass adds small amounts for precision
5. Combination calculation — The control system tests combinations of all cups
6. Discharge — The best combination dumps into your packaging machine

The key insight: by combining many small portions, you can hit ±0.5g accuracy even with irregularly-shaped products like whole nuts or dried fruit.

Why this matters: A single large hopper might be off by ±10g. Ten small hoppers combined gives you access to hundreds of weight combinations. Statistics does the work.

When You Actually Need a Multihead Weigher

Not everyone needs one. Here's how to know:

You need a multihead weigher if:

• Fill weight accuracy is critical (±1g or better)
• Your product has irregular shape or size variation
• Production speed exceeds 40 bags/minute
• You're packaging high-value products where overfill costs add up
• Regulatory compliance requires weight verification

A volumetric filler is fine if:

• ±2-3% accuracy is acceptable
• Your product flows consistently (granules, powders)
• Speed is under 30 bags/minute
• Product cost is low relative to labor

The ROI threshold is roughly $0.50/g in product savings. If you're overfilling by 5g on a $20/kg product, a weigher pays for itself in months.

Browse our combination weighers and multihead weighing systems to see what's available for your line.

Understanding the Numbers: 10-Head vs 16-Head vs 32-Head

The number of heads determines two things: accuracy and speed.

More heads = more combinations = better accuracy. But there's diminishing returns. A 10-head weigher can achieve ±0.5g. Going to 20 heads improves that only marginally while adding cost and complexity.

For most snack and nut packaging (50g-500g), a 16-head multihead weighing system hits the sweet spot of accuracy and price.

The Combination Principle: Why It Works

This is where most buyers get confused. A 10-head weigher doesn't weigh 10 portions and pick the closest one. It weighs every possible combination of portions and selects the combination closest to target.

For 10 heads, that's 2^10 = 1,024 potential combinations. The system tests all of them in milliseconds and picks the winner.

This is why irregular products work better than you'd expect. A 30g piece of cashew and a 5g broken piece can combine perfectly because the system sees the total, not individual portions.

Common Mistakes Buyers Make

Mistake 1: Buying based on head count instead of accuracy specs
A 32-head weigher isn't automatically "better" than a 14-head. Check the published accuracy spec and test it with your actual product. Different heads achieve different accuracy levels depending on bucket design and control system.

Mistake 2: Ignoring product characteristics
Multihead weighers work best with free-flowing, reasonably uniform products. Sticky products, wet products, or products with extreme size variation require special configurations. Always request a product trial before committing.

Mistake 3: Underestimating hopper requirements
A 16-head weigher needs a consistent product supply. If your upstream equipment delivers in bursts, you'll get feeding errors and accuracy drops. Budget for a buffer hopper and proper feeding system.

Mistake 4: Not planning for integration
The weigher and the packaging machine need to communicate. Timing must be synchronized so the discharge happens when the bag is in position. Poor integration causes product spillage and downtime.

Integration With Your Packaging Line

A weigher doesn't work alone. It's part of a system.

Upstream:

• Buffer hopper to smooth out supply variations
• Feeding conveyor to maintain consistent product level
• Metal detector if required for food safety

Downstream:

• Packaging machine (VFFS or premade pouch)
• Checkweigher to verify final weight (catches any weigher drift)
• Reject mechanism to divert underweight packages

The checkweigher is often overlooked but matters. If you're shipping 100,000 bags/month and even 1% are underweight, that's 1,000 potential compliance issues. A checkweigher catches these before they leave your facility.

Keypack Intelligent's 16-head multihead weighing systems are configured for plug-and-play integration with VFFS equipment, including pre-installed timing controls and reject signal outputs.

Maintenance: What Actually Matters

Multihead weighers need regular attention. Here's what to prioritize:

Daily:

• Clean weighing hoppers (product buildup affects accuracy)
• Check for product jamming in distribution bowl
• Verify discharge gates open fully

Weekly:

• Calibrate against known weights
• Check bucket wear (weighing surfaces degrade over time)
• Inspect feeder belts and timing

Quarterly:

• Full calibration by qualified technician
• Replace worn weighing sensors
• Update firmware if updates are available

Most accuracy problems we see in the field aren't equipment failures—they're maintenance gaps. A weigher that's not calibrated weekly will drift 2-3g over a month.

Frequently Asked Questions

Q: What's the difference between a combination weigher and a linear weigher?
A: Combination weighers use multiple heads and test weight combinations for maximum accuracy. Linear weighers use a single vibrating trough and are more gentle on fragile products but less accurate. For most snack and nut applications, combination weighers are the standard.

Q: How do I know if my product is suitable for a multihead weigher?
A: Free-flowing, reasonably uniform products work best. Request a product trial with your actual samples. Keypack Intelligent offers free sampling tests at our facility before you commit to equipment.

Q: What's realistic accuracy for a 16-head weigher?
A: ±0.5g to ±1g for most products in the 100g-1kg range. Accuracy varies with product characteristics—uniform products like almonds perform better than mixed nuts with high size variation.

Q: Can a multihead weigher handle multiple products?
A: Yes, with recipe storage. Modern systems can store settings for 50+ products and switch configurations automatically. Changeover typically takes 5-15 minutes depending on product similarity.

Conclusion

Multihead weighers solve a real problem: getting consistent fill weights at production speed without overfilling product into the customer's pocket.

The math is usually straightforward. If you're overfilling by even 3-5% on a product worth more than $10/kg, a weighing system pays back in months. The key is matching the weigher configuration to your actual product and production requirements—not just buying the most heads or the lowest price.

Keypack Intelligent's weighing systems come configured for your specific product and integrate with your existing packaging line. We include commissioning, operator training, and ongoing support.

👉 Talk to an Application Engineer About Your Weighing Requirements

Want to see weighing equipment in action?
Browse our fully automatic weighing and filling lines or request a product trial with your samples.

References

• OIML International Recommendation R107 (Non-automatic Weighing Instruments)
• PMMI Packaging Machinery Census 2024