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The small but powerful semiconductors in our smartphones and other devices can take several weeks and hundreds of steps to manufacture. During production, cleaning solvents play a crucial role in maintaining a high level of purity in these small and delicate microelectronics.
DuPont’s small-batch production facility in Hayward, California, makes semiconductor cleaning solvents in dozens of varieties. Unfortunately, the batch control systems used in the plant started showing their age in recent years.
The systems no longer were supported. They also were creating production issues, such as pop-up alerts that frustrated operators and alarms that were difficult to manage. More importantly, a customer audit found the systems lacked recipe-based automation that could help improve quality control in the production process.
The plant faced a choice: replace the legacy batch control systems or stay with the status quo and lose thousands of dollars in monthly business. The plant moved forward with the upgrade. In doing so, it not only improved quality control but also helped raise plant throughput to create new monthly sales.
Need for an upgrade
Most of the legacy control systems at the Hayward plant were manually operated. Only the bulk addition of material from a storage tank to a blend tank was automated. Operators manually added all other materials using a drum-pumping station and solids-conveying station. Operators also set the timing for the materials to blend and circulate through filters and took product samples. Once the desired product was achieved, operators manually sent it to the filling systems in the packaging area. Here, workers dispensed product into packages that ranged from 1- and 5-gallon containers to 200-gallon totes.
These manual processes introduced the potential for errors. For example, an operator might intend to mix a material for 15 minutes but end up mixing for 18 minutes because of the need to carry out another task. Instances like these created the potential for slight product variations.
The legacy systems also at times disrupted production. “The HMI was configured in a way that it generated a pop-up alert every time we opened or closed a valve,” shares Nancy Givens, an automation and process control engineering consultant for DuPont. “If the operator wanted to open three valves, they’d get three pop-ups. This was frustrating for operators. And it created opportunities for errors. Cluttered interfaces could result in operators opening or closing the wrong valves.”
Alarms were another issue. The legacy systems used a mix of hard-coded and user-editable alarm setpoints. The hard-coded alarms were difficult to manage, with operators often struggling to locate specific code. The alarms also didn’t use modern alarming best practices, such as the ability to assign priorities.
These issues — combined with the customer’s demand for greater quality control — necessitated a control system upgrade.
Phase One: Controls Upgrade
Givens worked with system integrator TechKnowsion and Rockwell Automation, a DuPont global alliance supplier, to plan and execute the controls upgrade. The team carried out the upgrade using a two-phased approach.
In the first phase, they replaced the batch system’s programmable logic controller (PLC) and HMI with a PlantPAx distributed control system (DCS). This involved reverse engineering the legacy PLC’s code to determine the requirements for new control code. “We didn’t want to just duplicate or convert the code,” explains Givens. “We went back to the functional requirements of the system to significantly clean up and improve the code. We then incorporated that code into our PlantPAx-based process objects library, which we have customized over the years to our specific needs within DuPont.”
The control system’s new HMI used modern visualization practices to give operators a better viewing experience. “The legacy HMI used multiple colors that could create cluttered screens,” Givens notes. “The new grayscale HMI highlights items in red to alert operators of critical issues. I’ve done spot checks on the floor since we implemented the new HMI, and our operators always know where to pay attention. They never miss a thing.”
Phase Two: Batch Automation
In phase two the Rockwell Automation global solutions team worked directly with DuPont to configure and install FactoryTalk Batch software to achieve full recipe control and sequential automation.
Givens and her team wanted to follow the ISA S88 standard that lays out the framework for implementing batch systems. This required Rockwell Automation first to build a physical model of the production equipment and then create a procedural model of the automated manufacturing phases. These phases serve as building blocks for use whenever needed in different recipes.
“Phase management features within batch software allowed us to explicitly follow the S88 standard,” Givens says. “This saved significant time. The team only had to configure a phase, such as mixing or addition, once. We could then reuse it multiple times. It’s much more efficient than creating new code for each recipe.”
The team also utilized the batch software for manual processes, such as sampling and recipe reviews. The software provides manual phases that integrate with automated phases to give users a seamless operating experience between the two. “We widely use this feature across DuPont,” Givens says. “We find it easier and smoother to implement than writing manual-process code in the controller.”
Finally, the team worked with Rockwell Automation to install the software for tracking materials in the plant’s storage tanks. The software replaced a paper-based logging system that required manual inventory tracking.
The software also incorporates automatic tank switching. “Previously, if a tank ran out of material during an addition phase, operators had to track how much material was added and calculate the remaining amount needed from the tank,” Givens explains. “Now, the software automatically calculates the remaining amount of material needed, switches tanks, and adds the required amount of material until it reaches the setpoint.”
Quality control and throughput
The new automated system was implemented in one week, all during scheduled downtime. The upgrade took the plant from obsolete to fully supported platforms. In addition, the new HMI resolved the pop-up and alarm-management issues that had frustrated workers.
The Rockwell Automation library of process objects cut design, configuration and deployment time. In fact, Givens estimates the library helped trim programming configuration time by 40%. Even today, with the new system up and running, the library continues to provide efficiency savings.
“The library is helpful for maintenance and troubleshooting,” says Givens. “If we want to go in and change a description, we don’t have to go into an engineering workstation or programming software. We can do it right in the HMI using the faceplates. Or, if a valve won’t open, an operator can open a faceplate and then open an interlock icon to see what’s wrong. In the past, workers may have had to configure a screen to see the valve interlocks or sift through paper documents to troubleshoot the issue. Now, the answer is just a couple clicks away.”
Meanwhile, the batch software took the plant from very limited automation to full batch automation, including automated cleaning processes. This helped the plant achieve the level of quality control that DuPont’s customer wanted. After modifying the software to improve coordination between the different production units, the plant also saw a significant boost in throughput.