Data gathering from disparate PLCs

29 October 2019

Find out how a medical appliance manufacturer cost-effectively solved a data gathering headache in a factory full of multiple branded devices.

A move into new premises and upgrades to network architecture and server, resulted in Welland Medical’s existing data capture system no longer functioning. The company, which specialises in the design, development and manufacture of stoma care appliances and accessories, sought quotes to obtain a replacement/upgrade of this its data capture system proved to be prohibitively expensive. 

So, the company set out to find a data capture system for its factory production machines to monitor and record production key performance indicators (KPIs) and synchronise this to a database that could be queried to produce live data and historical operational and management reporting. 

Welland Medical’s installed factory production machines have a variety of brands of PLCs at their heart, all of which reside on an automation Ethernet network along with various human machine interface (HMI) and other devices. It can be a challenge to gather meaningful production data from multiple brand devices.

A faceless HMI solution
Lamonde Automation was able to offer a solution with the Weintek cMT Server, a faceless HMI. The cost of the unit was a small, one-off hardware cost, plus installation and configuration by Lamonde, but there are no ongoing costs as no licence is required.

Compared to a traditional approach to this kind of problem, which would require multiple OPC server licences to communicate with the installed PLCs and devices, the cMT Server offers a cost-effective solution, costing just a small percentage of the price for a single OPC server.

The specific unit recommended and installed by Lamond Automation was the Weintek cMT-SVR-100 which provides all the interface and datalogging capability that would be reasonably expected of an HMI, but without taking up precious panel real-estate or providing an unnecessary additional touch screen. 

While primarily the cMT is acting as a data-concentrator/communication gateway, but the HMI application has been developed to make it a useful shop-floor diagnostic tool accessible by Android/IOS devices using Wi-Fi, as well as via a PC running the Weintek cMT Viewer app.     

Using bit-triggered data sampling, each PLC presents a snapshot of the production data: product code, an ASCII string, and four 32bit registers providing current, real-time parts per hour, batch count and a downtime reason code, and a spare register for future use.

Captured data is written to an SD card installed in the cMT-SVR-100 in real-time on a rolling 31-day FiFo (first in first out) cycle and periodically synchronised to a MySQL Database residing on the Welland Medical server. 

Providing resilience
Resilience is provided by the 31 days of storage on the SD card so, should there be a temporary issue with the server, the data will be available to resync once the server issue is resolved. 

Further integrity is provided by the front-end, developed by a third-party. By synchronising the captured database with a second database, a further layer of data integrity is provided so any erroneous writes or table dropping calamity (it happens!) affects only a mirror of the real machine data.
All the data is displayed on monitors at the end of the production line and in the staff canteen, providing highly visible business-rich information, far more than Welland Medical had on its old system.

Commenting on the project, James Jeffery, senior projects engineer at Welland Medical, said: “We were looking for a method to move data from various production lines into our MySQL server. This would feed a front-end program and provide live OEE type data on large screens on the shop floor, but our machines have many different brands of PLCs fitted.

“We found the solution offered by Lamond Automation easy to use and can extract data from the majority of makes of PLCs for a very small cost. Lamond wrote the program for this and provided training on site for our engineers. A front end was programmed by an external SQL server expert. The few problems we did suffer were very quickly resolved.”

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