Streamlining assembly systems using PC-based control
Itron is a world-leading technology and services company dedicated to the resourceful use of energy and water. The company’s Waseca manufacturing facility designs and produces gas and water metering devices, also known as encoder receiver transmitter (ERT) modules, and has engineering teams in-house that focus on product R&D, assembly, and production. Currently, the Waseca facility manufactures Itron’s 100G series gas ERTs and 100W series water ERTs.
During the final few months of 2015, the facility significantly had to increase the capacity of water ERT module production. In addition, the production of gas ERTs has steadily increased each year. With rapidly increasing demands for higher production, the Itron facility is in a constant state of change. Assembly cells and lines are continually added and retrofitted to ensure the factory can keep up with ERT market demand.
Previously, Itron assembly cells were weighed down by a control platform that required five separate pieces of hardware for the automation and human-machine interface (HMI) systems. "This was an ongoing problem for years," said Adam Moyer, principal controls engineer at Itron. "We conducted extensive research to find a viable replacement for the traditional programmable logic controller (PLC) for control and separate PC for HMI. Even though production levels are under constant change, a change in the control system platform can be a challenging endeavor with elements of uncertainty and risk for engineers. However, simply adding new machines of the same design was not a permanent solution."
Factory to field production history
To maintain its product quality, Itron emphasizes comprehensive traceability from the beginning of the assembly process, to the supply chain, to the end of the line when a device is purchased and installed (see Figure 1). Traceability ensures the best measures to answer quickly any quality question from the field because Itron easily can pinpoint the full history of every component in every ERT it manufactures. The unique serial number of every Itron ERT is saved to a Microsoft SQL server, and every production step and quality test for each ERT is recorded in the database.
For every component that goes into Itron products, a wide range of parameters are logged, such as the lot code, manufactured on date, the component manufacturer, the date each component was used, and all settings and configurations on the machine that manufactured each ERT. Another large source of production data, Itron performs a series of detailed tests on all products, which can include visual inspection, radio-frequency testing, programming tests on ERT microprocessors, and more. This has helped establish quality assurance with a history of every product down to the smallest component and section of code.
"This is precisely the reason we ultimately went with PC- and EtherCAT-based control technology for automation and quality assurance," Moyer said. "It helped us establish connectivity between the automation system and remote databases while managing the incredible volumes of data to implement complete traceability."
This line of thinking began when Itron first encountered PC-based control technology in January 2014. At that time, a European-built dispensing machine purchased for potting ERT devices arrived at the Waseca facility. The advanced machinery was equipped with a PC-based control system. "This was an eye-opener for us because our previous experience was with stand-alone PLCs and white-box PCs that served as our link to the SQL database," said Moyer. With PC-based control, Itron could streamline its system architecture with one multitasking controller that integrates both the PLC and PC functionality into one powerful device. "We ended up manufacturing our own assembly systems designed in-house at Itron repeatedly over the last 2 years, and it has worked very well," Moyer said.
Major manufacturing steps at the Itron facility include soldering, assembly, and potting processes to seal the ERT products (including curing after potting material is dispensed) as well as final testing before moving products into the supply chain (see Figure 2). After the final automated test, visual verification is handled by Itron production experts. Each of these steps, which is either fully automated or semi-automated, is controlled by the PC-based control system and EtherCAT. Some of the soldering and assembly steps use 4-axis articulated robots networked via EtherCAT-these are also automated by embedded PCs and automation software.
Shape-shifting, PC-based control
After evaluating a series of PC-based controller formats (including cabinet and pole/arm mounted versions), Itron selected DIN-rail-mounted embedded PCs (see Figure 3). This midrange controller features a 2-core Intel Atom processor (1.75 GHz) so it can capably handle many machine functions, such as PLC, motion control, and HMI on one device. At Itron, one embedded PC runs PLC automation software for all control tasks in addition to HMI software used on the same assembly cell. "Having the HMI software run on the main automation controller primarily is responsible for Itron decreasing cabinet space requirements and streamlining assembly cell integration," Moyer said.
These benefits extended beyond the initial cost savings on the hardware. Itron generated even more savings because the company no longer has to write and manage revisions for code in two separate systems or create complex mechanisms just so hardware from different manufacturers can communicate. For every system the Itron team in Waseca has built since January 2014, it has reduced its previous standard configuration of five pieces of hardware (PLC, two PCs, and two HMIs) to two (one embedded PC and one HMI display). The savings are exponential whenever the company adds another PC-based system.
At Itron, some assembly cells interface with the SQL database to send data to view production status from the floor. The PC-based controllers send a variety of data and parameters to the database. Production managers and operations managers across the globe can view the status of any line through their mobile device or laptop. The connectivity from the controller to the database is central to capitalizing on the data. Itron monitors everything from complete track-and-trace of manufactured products down to the component and exact time of each manufacturing step, to yield data, to real‑time data for product quality.
In addition to high performance and compact controller footprint, Itron selected the embedded PC because it uses the Microsoft Windows 7 operating system onboard and the video output to connect easily to its touchscreens. Another important factor was that the embedded PC installs easily on DIN rail in Itron’s electrical panels and directly connects to the EtherCAT input/output (I/O) terminal system. The two network ports on the embedded PC also are used by Itron-one connects to a network for the plant’s machinery, and the other interfaces with the Itron corporate intranet as the interface with internal and external databases.
Also on the networking front, Itron has switched all plant communication protocols at the Waseca facility to the EtherCAT industrial Ethernet system (see Figure 4). As a result, EtherCAT is used as the network for vision systems, solenoid banks, and even highly articulated robots. EtherCAT has become the complete system bus at Itron’s Waseca location, increasing the speed of data transmission, pulse rates, and overall cycle times. It delivers high flexibility in terms of wiring topologies, and there are widely available EtherCAT devices for industrial needs from multiple vendors. Saving considerable start-up time, automation software automatically identifies EtherCAT devices connected to the system, regardless of vendor.
In addition to handling assembly cell control and database connectivity, Itron also uses automation software for safety programming and runtime. Another key development for Itron assembly processes is programmable safety integrated into the standard automation system using integrated safety I/O technology. In the past, Itron implemented stand-alone safety controllers in its machine designs. The safety I/O technology is highly beneficial because it is integrated into the standard controller and is managed with the same automation software. "After switching to the new safety I/O technology, we no longer have to handshake between the controller and the safety system. This saves a considerable amount of cabinet space while further reducing costs and programming efforts," said Moyer. Specifically, Itron uses the programmable safety technology to integrate light curtains and safety for robotics and other motion functions, pneumatics, and more (see Figure 5).
Automated cost savings
Itron also has established better data acquisition and storage along with more reliable connection to SQL databases and other enterprise-level services. The company always has accessed roughly the same amount of data but can now do it 15% to 20% faster in terms of overall process cycle time.
The time spent developing software and the machine’s integration also has been drastically reduced. In the previous control system design with five pieces of control hardware, it took Itron as much as five times longer for programming compared to today when writing code for one multitasking piece of equipment. "We are literally savings weeks of engineering time-software, electrical, and mechanical-for every new system we bring online," Moyer said. When Itron duplicates these efforts on machines 10 or more times, the savings increase exponentially every time.
Measurable improvements to plant floor space and the assembly cell footprint also continue as a result of PC-based control hardware and software integration. Cabinet space usage is reduced by 25%, which generates significant equipment savings on each assembly cell. System reliability and throughput have also improved using PC-based control and EtherCAT. With control functions and HMI integrated into one system, downtime has been reduced by at least 5%. "This is significant for an already high-performing facility because we have much faster start-up through automation software and EtherCAT connectivity as well as far fewer potential points of failure due to control hardware reductions," said Moyer.
Overall, Itron already has tallied impressive results using PC-based control, and today PC-based control and EtherCAT automate approximately 35% of its factory (see Figure 6). With PC-based assembly technology, Itron can capably respond to each inevitable increase in product demand.
Shane Novacek is marketing communications manager at Beckhoff Automation LLC, based in Savage, Minn. Spending his entire professional career as a business-to-business communicator focused on high-tech industries, he has written extensively about automation, controls, and industrial devices for 14 years.
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