Automating a handcrafted process

Although often perceived as a threat to traditional industries, in reality automation can empower artisans to have greater control over their skilled processes and can help to ensure consistent product quality. When Denby Pottery, a producer of handcrafted tableware, looked at refurbishing its process control systems it out to find a reliable and well-connected solution which would allow it to efficiently monitor, control and improve its clay production line. 

Clay is a raw material that can vary greatly from one batch to another. It therefore requires plant operators to have a good understanding of the clay’s physicochemical properties to accurately control the process parameters and obtain a consistent and high-quality output.

Commenting on the application requirements, Steven Sands, technical engineering project manager at Denby Pottery, said: “One of the key considerations is the dry weight of the material and its application in recipe calculations. Also, high accuracy and precision in controlling the concentration of solids in liquids are essential requirements in this process, so we have used some form of automation for a long time now.”

To remain competitive and maintain the quality of the clay consistency, Denby Pottery decided to update its obsolete ISN York management system. Sands explained further: “The control system was prone to regular failure and running on an outdated platform that had no compatibility with current control elements. In addition, several replacement parts for the system needed to be custom made, as they were no longer available off the shelf. Therefore, the system was proving increasingly costly and time-consuming to maintain.”

This was affecting plant productivity, jeopardising the manufacturing processes that lie beyond the clay production lines. Steve Hazell, engineering manager at Denby Pottery, takes up the story: “Some time ago we experienced a major breakdown of the control system. Before solving the issues, the plant experienced an outage of four days.”

In addition to addressing issues with the previous control system, Denby Pottery wanted to embrace the principles of modern smart manufacturing to gain greater control over its production materials, processes and machines. In particular, it wanted to measure clay quality attributes ‘on the fly’ to fine-tune the manufacturing process in real-time and improve the quality consistency of the clay.

The solution to address all these challenges was provided by Mitsubishi Electric and its technical distribution partner, BPX. The initial installation of a fibre optic network opened a wide range of opportunities for Denby Pottery to monitor and control their manufacturing materials, processes, machines and full production lines. Improved machine communications enabled greater control over the clay manufacturing processes, easy interaction between the processes and identification of any equipment malfunction.

The machines on the production lines were equipped with Mitsubishi Electric MELSEC NET H Remote I/O Nodes connected to a Qn series dual redundant PLC system – linked, in turn, to three Mitsubishi Electric GOT2000 series HMIs, which were installed to monitor different areas of the factory and report to a central Mitsubishi Electric Manufacturing Execution System (MES) interface within the engineering department.

By using the MES interface module and the Virtual Network Computing (VNC) Viewer functionalities of the GOT2000 HMIs, the operators are now able to remotely control and monitor the production line and obtain data on the Overall Equipment Effectiveness (OEE). 

Another useful VNC server function allows the plant operators to view and operate the GOT screens remotely and securely from any connected mobile device or PC.

The resulting decentralised control system simplifies maintenance and operation of the plant with the facility to securely programme from remote locations by the HMIs interfaced to the Qn series controllers.

While the replacement of the legacy control system addressed the reliability issues of the plant, a dual redundant PLC system was selected to increase the system robustness by providing a highly reliable solution. The standby system – with its own CPU, fully synchronised to the controlling CPU during operation – can mirror the controlling CPU and instigate a seamless bypass in the event of failure of the main CPU. This minimises any risk of plant downtime.

Tyler Hatton, automation manager at Denby Pottery, said: "The versatility of the system has allowed us to expand into OEE machine monitoring on various pieces of equipment and machinery. This is helping us highlight problems and improve efficiency throughout the factory."

Since installation of the new system the previously encountered maintenance issues have ceased. Sands explains: “The system is now completely reliable, even during a power cut. In the case of a machine failure, the visual features of the HMIs alert plant operators and enable them to quickly detect the cause and solve it. This, coupled with Mitsubishi Electric’s round-the-clock support and responsiveness, made it possible to slash downtime as well as quickly identify, investigate and plan any maintenance tasks.”

The solutions have provided Denby Pottery with its wished for ‘Smart Factory’ monitoring capabilities and has correspondingly increased flexibility of the production line. Additional benefits include improved accuracy of the calculations on clay properties and increased quality of the clay and its consistency. More impressively, the clay manufacturing time halved, increasing time-efficiency and productivity.

Hazell concludes: “Thanks to the flexible control system we have now and due to the positive experience with our suppliers, we are now looking to expand the network and will be implementing additional functionality such as barcode readers for product serialisation and traceability in the future.”