Troubleshooting Common Combination Weigher Problems

Introduction: Why fast troubleshooting matters for a combination weigher

The combination weigher (also known as a multihead weigher) is the heart of many modern packaging lines. When it runs smoothly, you get fast throughput, high accuracy, and minimal giveaway. When problems occur, downtime and product loss quickly impact margins. This guide helps packaging engineers and operators quickly diagnose and fix frequent issues, minimize downtime, and improve long-term performance.

Understand the fundamentals of your combination weigher

Before troubleshooting, it helps to know basic components and their roles: the feeding system (vibratory trays and inlets), weighing hoppers (individual weigh cells), combination calculation logic (software), discharge chutes, and the control panel/HMI. Many problems arise from a mismatch between product properties and machine settings, mechanical wear, or sensor/electrical faults.

Common problem: Inaccurate average weight

Symptoms and immediate checks

Symptom: Packs are underweight or overweight relative to target. Immediate checks: verify target net weight, confirm calibration date, check recent product changeovers, and inspect weigh hoppers for residue or damage.

Causes and step-by-step fixes

1) Calibration drift: Re-calibrate load cells following the manufacturer's procedure. Perform a two-point or full-scale calibration if available. 2) Hopper residue or sticking: Clean hoppers and feed tracks thoroughly; sticky products (e.g., powders, oils) often need special coatings or vibrating adjustments. 3) Mechanical wear: Examine load cell mounts and hopper seals for looseness. Replace damaged parts. 4) Incorrect combination parameters: Re-run the combination algorithm and check that minimum/maximum limits are set correctly for the product batch.

Common problem: Inconsistent fills or high giveaway

Symptoms and immediate checks

Symptom: Pack-to-pack variation is high. First check product flow consistency at the infeed and the level in feeder pans.

Causes and corrective actions

1) Uneven feed distribution: Adjust vibratory feeder amplitude and angle to obtain even distribution across all feeding lanes. 2) Product segregation: For mixed-size products (e.g., mixed nuts), consider using pre-weighing distribution devices or slower feed rates. 3) Incorrect combination strategy: Use combination weigher software to test alternative combinations—sometimes fewer heads with better matched weights reduce variance. 4) Environmental factors: Temperature and humidity can affect powders; control environment or adjust settings accordingly.

Common problem: Hopper blockages or product bridging

Symptoms and diagnostics

Symptom: Hoppers clog intermittently, causing missed discharges or jams. Check product characteristics (particle size, moisture, shape) and observe during operation.

Solutions and prevention

1) Modify feed geometry: Add agitators or change the feeder pan texture/coating. 2) Air-knife or pulsation: Use air jets to prevent bridging for lightweight or flaky products. 3) Material compatibility: Consider anti-stick coatings or stainless-steel finishes for oily products. 4) Pre-hopper conditioning: For powders, use de-aeration or vibration in the bulk hopper to ensure consistent flow to the vibratory feeders.

Common problem: Mechanical noise or unusual vibration

What to inspect

Unusual noise often indicates loose hardware, misaligned components, or failing bearings. Power off the machine and perform a visual and tactile inspection.

Fixes

1) Tighten all mounting bolts and check spring isolators. 2) Inspect vibrating motors and replace worn bearings. 3) Confirm vibrator frequency and amplitude settings match the product and line speed. 4) Replace worn cams or linkages in the discharge area.

Common problem: Electrical or control errors (HMI alarms)

Initial troubleshooting

When alarms appear on the HMI, consult the alarm codes in the operator manual. Common categories include load-cell errors, encoder faults, communication loss, or I/O module failures.

Stepwise resolution

1) Soft reset: Save current settings, then perform a controlled restart of the weigher and PLC. 2) Check connectors and cables for loose or corroded contacts. 3) Inspect power supply voltages—unstable voltage can cause intermittent errors. 4) Update firmware only if recommended by the manufacturer; improper updates can create new issues. 5) For persistent communication errors, check Ethernet/SERIAL integrity and any network switches.

Common problem: Slow cycle speed or lost throughput

Causes to evaluate

Throughput loss can stem from conservative settings, product issues, or mechanical limits. Verify if the machine is mechanically capable of the target speed and whether product characteristics prevent higher speed.

Optimization tips

1) Re-tune the combination algorithm—allowing a slightly larger tolerance might increase speed while still controlling giveaway. 2) Increase feeder vibratory intensity in small increments while monitoring accuracy. 3) Consider using more heads or a larger model for higher targets. 4) Remove bottlenecks downstream (e.g., bagging or sealing units).

Routine maintenance to minimize recurring problems

Daily, weekly, and monthly checks

Daily: Clean hoppers and feeders; remove product build-up. Weekly: Inspect load cell mounts, check sealing and hoppers for wear, test emergency stops. Monthly: Verify load-cell calibration with certified test weights; inspect bearings and vibratory motors. Keep a maintenance log to show trends and support E-E-A-T documentation.

When to recalibrate and how often

Recalibrate whenever you change significant product types, after mechanical repairs, or if you notice drift. As a best practice, perform a full calibration at least quarterly on high-use lines and log calibration results. For regulated industries (food, pharma), follow specific documentation and traceability protocols.

Comparison: Typical specification ranges for combination weigher vs linear weigher

The table below summarizes typical real-world ranges to help you decide if a combination weigher suits your product and line speed needs.

Documenting failures: helpful data to collect before contacting support

When you contact technical support—either Kenwei or another supplier—prepare these details: product type and specs (size, moisture), recent changeovers, HMI alarm codes, photos/videos of the issue, last calibration date, and the maintenance log. This speeds diagnosis and remote support efficiency.

Why choose Kenwei for combination weigher service and upgrades

Kenwei is a powerful manufacturer of multi-head weighers committed to high-speed, high-precision solutions. Based in Guangdong, Kenwei offers one-stop automated weighing and packaging systems, including metal detectors, linear weighers, and check weighers. Our capabilities cover design, manufacturing, installation, commissioning, training, and rapid after-sales service. For persistent or complex issues, our global service team provides on-site troubleshooting, spare parts, and software upgrades tailored to your process.

Practical troubleshooting checklist (quick reference)

- Verify target weight and calibration status.
- Check hopper cleanliness and product flow.
- Inspect mechanical fasteners and load cell mounts.
- Review HMI alarm codes and system logs.
- Tune feeder vibration and combination strategies.
- Keep maintenance and calibration records.
- Contact certified service if root cause is electrical or load-cell related.

Conclusion: Reduce downtime with structured troubleshooting

A structured troubleshooting approach saves time and reduces product loss. Start with basic checks—cleaning, calibration, and feeder adjustments—then move to deeper mechanical and electrical diagnostics. Preventive maintenance and operator training are key to long-term performance. If you need certified service, Kenwei can support system optimization, spare parts, and tailored maintenance programs to keep your combination weigher running at peak efficiency.

FAQ

Q: How often should I clean my combination weigher?

A: Daily cleaning is recommended for sticky or dusty products; otherwise clean at least once per production shift and perform deep clean during scheduled maintenance.

Q: My machine shows a load-cell error—can I keep running?

A: No. Load-cell errors compromise accuracy. Stop the line, check connectors, and recalibrate. If the issue persists, call certified service.

Q: Can I run different products on the same combination weigher?

A: Yes—combination weighers are designed for flexibility. However, you may need to change feeder settings, hoppers, or coatings and perform a new calibration after each product changeover.

Q: What reduces giveaway while maintaining speed?

A: Optimize combination algorithms, fine-tune feeder settings, and ensure consistent feed. Sometimes increasing the number of heads or using tighter control limits can help, but always balance accuracy against throughput needs.

Q: When should I consider upgrading my weigher?

A: Consider upgrading if your product mix changes dramatically, required throughput exceeds current capacity, or frequent maintenance and parts replacement increase total cost of ownership. Kenwei can provide assessments and upgrade paths.

Contact and support

For technical assistance, spare parts, or upgrade options, visit https://www.kenweigroup.com/ or contact Kenwei's service team. Provide calibration logs, photos/videos, and alarm codes to accelerate support.