Valmet IQ Targets Corrugated Board Warp at Sheets Unlimited

Valmet announced on August 12, 2026 that it will supply a Valmet IQ Quality Control System for the Sheets Unlimited corrugator in Washington, United States. The project targets moisture imbalance, a major cause of corrugated-board warp. Delivery is planned for the fourth quarter of 2026, followed by commissioning in January 2027.

The order addresses board warp by measuring and controlling the moisture and temperature conditions that create it.

What Valmet will deliver

Valmet’s official trade press release identifies four main components: Valmet IQ Warp Measurement, Valmet IQ Moisturizer, Valmet IQ Multipoint Moisture, and microwave moisture measurement. These elements will be integrated with automatic closed-loop controls and an interface to the corrugator’s existing heating equipment.

The order was recorded in Valmet’s second-quarter 2026 orders received. Valmet did not disclose its value. The schedule is important because the claimed production benefits remain prospective. Sheets Unlimited has selected and evaluated the system, but the site will not have operating results until after installation, tuning, and sustained production testing in 2027.

Why moisture imbalance creates a converting problem

Corrugated board combines liners and fluted medium through heat, moisture, pressure, and adhesive. If the two sides leave the process with different moisture or thermal conditions, they can shrink differently as the sheet stabilizes. The result may be cross-direction warp, machine-direction warp, edge lift, twist, or a shape that changes after stacking.

Warp is not only a visual defect. It can reduce feeder stability, printing registration, die-cutting consistency, folding accuracy, stacking quality, and throughput in downstream equipment. Operators may slow the line or sort sheets after production, but those actions manage the consequence rather than the process condition that created it.

Sheets Unlimited buys roll stock from multiple mills. Different grades, moisture histories, and fibre characteristics can change how paper responds to heat and adhesive. A fixed setpoint that works for one roll may perform poorly after a material change. This variability is the control problem behind the investment.

Small moisture differences can become large handling problems after the board cools and reaches converting equipment.

How the closed loop should work

The measurement system observes paper temperature, moisture balance, total moisture, and board warp at defined process locations. The control layer then coordinates existing heating elements and the automatic moisturizing system. Valmet describes its corrugator platform as combining online moisture, temperature, and warp measurements with closed-loop control.

This architecture is more useful than a single end-of-line warp alarm. Earlier moisture and temperature measurements can show which material or process change is developing. Final warp measurement confirms the resulting sheet shape. The controller can then adjust heat or added moisture within approved limits rather than asking an operator to infer the cause from finished board.

However, a measurement does not become a good control variable automatically. Sensor placement, scan coverage, calibration, response time, sheet grade, machine speed, and measurement confidence all influence the loop. The controls must distinguish real material changes from noise, sheet gaps, grade transitions, threading conditions, and temporary process disturbances.

For plants maintaining DCS and process-control systems, the project illustrates a familiar principle: close the loop around the variable that causes the defect, but preserve enough raw data for diagnosis. Operators should be able to see measured profiles, controller targets, actuator outputs, grade information, alarms, and any period when a measurement is invalid.

Commissioning must prove more than flat board

January 2027 commissioning should begin with instrument and actuator checks. Moisture, temperature, and warp measurements need calibration or verification against approved references. The heating interface and moisturizer outputs should be tested across their safe operating ranges. Direction, scaling, saturation, manual modes, interlocks, and failure responses must be confirmed before closed-loop operation.

Control tuning should use representative products and roll-stock variation. A loop tuned on one grade at one speed may overcorrect another. Engineers should record baseline performance before enabling automatic control, then compare warp distribution, waste, speed restrictions, adhesive quality, and downstream converting interruptions under matched production conditions.

Acceptance criteria should be defined numerically. Useful measures include sheets outside the warp limit, trim or scrap, feeder stoppages, average production speed, moisture-profile variation, operator interventions, and customer or internal converting claims. These metrics should be reviewed by grade and supplier, not only as one plant-wide average.

A safe degraded mode is also necessary. If a moisture scanner, warp sensor, communications path, or moisturizer fails, the system must identify invalid data and move to a controlled manual or bounded fallback condition. It should not continue changing heat or moisture based on stale measurement values. Alarm priorities and operator instructions need to be validated during commissioning.

Commissioning should test grade changes, sensor faults, actuator limits, and downstream converting results.

Maintenance and data requirements

Online quality control adds instruments and actuators that require their own maintenance plan. Scanner cleanliness, calibration drift, microwave measurement condition, moisturizer nozzles, valves, filters, heating interfaces, and mechanical alignment can all influence performance. A slowly degrading measurement may produce plausible values while moving the process away from its target.

Historical data should preserve raw measurements and controller actions. When warp returns, engineers need to compare roll source, grade, speed, steam or heating conditions, adhesive process, moisture profile, actuator output, and maintenance events. Without that context, the plant can confuse a material problem with a sensor or control problem.

The measurement and controller hardware should also be covered by spare-parts planning. Relevant PLC and PAC system components, network interfaces, sensors, and output devices must be documented with firmware, configuration backups, calibration records, and replacement procedures.

Engineering view

The Sheets Unlimited order is a useful example of automation moving quality decisions upstream. Instead of detecting warped sheets after value has been added, the project aims to measure the process variables that cause warp and adjust them during production. That is a stronger control strategy than inspection alone.

The result should still be judged after the January 2027 startup. Valmet’s press release describes the intended functions and expected benefits, not verified site performance. The best evidence will be stable converting throughput, fewer interventions, lower waste, and repeatable quality across changing roll stock. If those metrics improve without hiding sensor or actuator problems, the QCS will have solved an engineering problem rather than only adding another dashboard.