PC control redefines intralogistics distribution center efficiency
How to move 67,000 garment shuttles, boost efficiency and communicate through EtherCAT
Distribution centers need to make every cubic foot count. Material handling equipment need to be cost-effective and use warehouse space efficiently. Since most conveyors sit close to the ground, they take up significant space. SDI launched the JOEY Pouch Sorter system to raise unit sortation to the ceiling and promote efficient product transport.
“The system relies on automatic switches and gravity accumulation to move pouches or garment hangers effectively,” says Jim Suggs, CTO at SDI. “The first system we commissioned in 2016 used 5,000 pouches to sort about 3,000 units per hour, which is relatively small. The second system used 67,000 shuttles to buffer and sort 7,000 units per hour.”
Founded in 1970, California-based SDI provides turnkey material handling systems complete with controls and software for fast-paced distribution centers.
Its technologies include distribution center management solution (DCMS) software, tilt-tray, garment-on-hanger, bomb-bay (or split tray) sortation equipment and the pouch sorter.
SDI is expert at third-party conveyors, high-speed merges and other systems. “We integrate numerous intralogistics solutions. We pick the best provider for the application and combine the best technologies with our top-tier unit sortation equipment,” Suggs says.
The pouch sorter offered the potential to reduce equipment size and expense. However, coordinating thousands of pouches in a single system required a powerful, reliable control and networking platform, explains Kyle Upwood, senior controls engineer. “The pouch sorter is demanding from a controls response point of view.”
SDI recognized the limitations in its legacy automation platform used on its unit sorter and conveying solutions.
“For our auto-induct onto the unit sorters, for example, we do the motion control on the metering itself and automatically induct the products onto tilt-tray sorters,” Suggs says. “We also use high-speed merges, which require high-speed motion control.”
Engineers at SDI’s Florida-based controls division were challenged to find controllers and a fieldbus for such rapid response times. At the time, their previous vendor’s control software could not run on an OS above Windows 7, soon to be obsolete, and the software required outdated flowchart-style programming. The machine controllers offered extremely limited memory and depended on OPC DA to communicate with other devices, which was superseded by OPC UA long ago.
Besides performance, SDI engineers focused on flexibility, scalability and cost. The team looked at value at time of purchase and overall for the product lifecycle.
“The technology most automation and controls vendors offered was simply not advanced enough,” explained Mike McCanney, SDI controls director. “These options were also significantly lacking in terms of both memory and storage. With any application, we always deliver our entire DCMS controls solution, even if it’s not entirely used, to enable easier upgrades or customizations to meet client demands in the future. Therefore, the controller needs enough memory capacity to store that sizable project.”
The new controls platform needed to convert and repurpose existing code from SDI’s broad portfolio with ease and help improve the company’s build process when commissioning machines.
“As we started converting code, traditional PLC platforms don’t support some of our fairly simple programming constructs,” McCanney said. “We wanted to preserve what we call ‘the build,’ which is our method for automatically mapping I/O terminals and points. This software uses site-specific drawings and a library of preconfigured code for unit sorters, carton sorters, regular conveyors and other technologies to write the complete code project within hours. The commissioning engineer visits the site, loads the code and hits ‘go.’”
What got our attention was the real-time communication speed of EtherCAT, Suggs said. The EtherCAT industrial Ethernet system enables a range of topologies — including line, tree and star — and can incorporate up to 65,535 nodes per network segment. That’s useful in widely distributed material handling applications.
EtherCAT benefits helped SDI solve performance issues with its legacy fieldbus to enhance sorting applications, said Mark Olton, area sales engineer, Beckhoff. “EtherCAT allowed SDI to incorporate third-party devices and networks, such as EtherNet/IP, AS-Interface and PROFIBUS. The system openness inherent in EtherCAT proved helpful, especially since most distribution center customers are unable to simply rip and replace their entire network infrastructure.”
SDI engineers also explored PC control technology from Beckhoff. After several successful in-house tests on SDI conveying systems, they specified the Beckhoff C6920 control Cabinet Industrial PC (IPC) due to the power required by large and complex architectures.
“The C6920 is a powerful PC, and it works well in the pouch sorter because of the high-performance demands and large number of scanners,” Upwood said.
For less demanding conveying and sortation systems, SDI scaled down to the Beckhoff CX5130 embedded PC. “While the C6920 remains important in many situations, we standardized on the CX5130 as our main machine controller. It comfortably provides the necessary performance level for most applications and offers an optimal price point for us,” Suggs explains.
The same code can run on either controller without requiring changes beyond the runtime license.
The universal engineering environment and runtime software allowed SDI to increase its capabilities while preserving existing code. Unlike the previous platform, TwinCAT offers programming in all IEC 61131-3 languages with object-oriented extensions as well as computer science languages through its integration into Microsoft Visual Studio.
“Using more modern programming methods has changed how we create code,” McCanney said. SDI also improved on its build process using TwinCAT Automation Interface, which enables the automatic creation and manipulation of TwinCAT eXtended automation engineering (XAE) configurations.
The Automation Interface functionality is possible using all COM-capable and dynamic script programming languages, such as .NET, Windows PowerShell or IronPython. The TwinCAT Automation Device Specification (ADS) interface offered additional benefits for commissioning and communication in distributed, multi-controller architectures.
“TwinCAT treats individual software modules, such as the PLC, independently as a server or client, and ADS exchanges messages between these objects within the system and over the TCP/IP connections,” Olton explains.
As a device- and fieldbus-independent interface, ADS eliminated the requirement for outdated OPC DA in all new SDI applications. “With EtherCAT and ADS as a backbone for cross-controller communication, we can implement a more distributed controls environment with smaller controllers spread across fulfillment centers,” McCanney says.
The pouch sorter allows SDI to optimize the existing footprint in distribution centers while increasing throughput considerably. By transitioning its controls platform to Beckhoff, SDI sees performance gains in all solutions.
For the pouch sorter this has enabled installation of larger and more complex applications, according to Suggs. “A recent application for a large clothing manufacturer boasts 67,000 shuttles with numerous switches and 70 scanners where the shuttle makes logic decisions in real-time,” he says. “This system uses garment hangers, rather than pouches, on the 67,000 shuttles. It tracks the items, typically suits, through various buffers to a matrix sortation system. This automatically produces the stack sequence – a small, medium and large suit, in that exact order – before delivering it to the packing station.”
The upgraded controls platform results include increased messaging to the database, according to Upwood. “We increased the single point machine rate by 58% to now over 10,000 units per hour. This was achieved while also increasing the barcode cameras that are required to run at this new max rate by 40%. I/O points increased by 51%, and high-speed track switching devices increased by 182%,” he says.
Less than two years after choosing Beckhoff, SDI migrated nearly all existing code to the new platform and enhanced its design and build processes. “There was a lot of concern when we first began shifting control platforms about how easy it would be to convert our libraries of code. Beckhoff made it much easier than we anticipated,” McCanney says.
Some SDI code is deprecated or for discontinued equipment, but the progress the company has made in programming is significant. “With the last major pieces that we had to finish, including the high-speed merge and the auto induct, we are likely 85% complete as of today,” Suggs adds. “In addition, TwinCAT Automation Interface greatly improved our capability to create software that adapts well on every new application.”
By implementing Beckhoff IPCs, SDI exceeded its memory and processing power requirements, but it also reduced cost compared to comparable offerings from other vendors. “To get that amount of memory from one particular competitor would have cost $20,000,” McCanney says. “With Beckhoff, it just feels like we’ve roared into the 21st century. I didn’t realize how much our previous controls platform was holding us back. For a company of our size to deliver large-scale automated systems to major retailers and apparel manufacturers, we benefitted greatly by implementing Beckhoff as our standard platform.” With increased controller and networking capabilities, SDI can continue designing and implementing more innovative pouch sorters and other material handling innovations to further optimize floor space usage in today’s distribution centers.