The rapid introduction of Industry 4.0 (i4.0) technologies is transforming manufacturing across a range of industries, including packaging printing. New data-driven smart systems offer advances in manufacturing speed and agility for increased productivity and less downtime and waste.
Many companies are exploring and integrating i4.0 technologies to make the Factory of the Future a reality today. This includes Barry-Wehmiller’s PCMC, a supplier of equipment for flexographic printing, bag and tissue converting, packaging, and nonwovens technology. Using advanced intelligence and machine-learning capabilities in the drives and controls platform from Bosch Rexroth, PCMC recently introduced an i4.0 smart technology solution called SteadyPrint that solves the longstanding problem of “bounce” in flexographic printing.
Printing is centuries old, with “modern” printing concepts invented by Gutenberg in the 15th century. Since then, printing has been as much an art as a science, even with the advent of today’s high-speed flexographic printing systems. Although these systems incorporate advanced automation that enables printing complex jobs at speeds up to 2,000-ft per minute, certain aspects of printing operations often depend on an operator’s artful manipulation — even “tweaking” — to print a perfect image. Waste associated with the issue of “bounce” is most often seen at the start of print runs with challenging graphics. These challenging graphics often have a hard leading edge on a printing plate that meets the opposing impression roll, causing an impact that affects print registration. This issue leads to poor print quality, with uneven ink distribution, or colors that are out of registration. Press operators typically tweak various settings on the press manually until they minimize out the bounce effect, at times being unable to eliminate these adverse effects on the print quality.
“Every flexographic printer struggles with certain bounce jobs,” said Rodney Pennings, PCMC Sales Director. “In printing, the overall goal is to get the presses quickly up and running at full speed, keeping the amount of set-up time and wasted material as low as possible. Bounce leads to wasted time and materials, and companies must depend on experienced press operators to fine-tune print settings and still get the press running at the highest possible machine speed with quality output.”
According to Pennings, PCMC incorporated the latest i4.0 technology in its new SteadyPrint feature as a solution to reduce print set-up time, increase quality, and reduce print waste, even with less-experienced machine operators. PCMC tapped into Bosch Rexroth for the resources and capabilities needed to develop SteadyPrint, including:
• Intelligent motion control technology that can “learn” and respond with torque offsets
• Support for high-speed Sercos communications architecture for real-time motion control advantages
• The Open Core Interface tool that enables access to additional motion control functionality and analysis using third-party programming languages
PCMC also worked CMA Flodyne/Hydradyne of De Pere, WI to develop the SteadyPrint functionality for the company’s Fusion and ELSMax flexographic printing presses. SteadyPrint is based on a disturbance-canceling algorithm that uses the intelligence in the servo drives to “learn” the electronic signature of each print job and rapidly cancel out the disturbance that generates bounce. When customers were given the opportunity to test the feature by bringing sample jobs into PCMC, they were able to improve press speeds between 200% and 400% and reduce waste by up to 35%.
“We had multiple customers come in to do bounce trials and, while every customer’s print job is different, all of them doubled or tripled their speed, or went to full speed much faster than ever before,” Pennings said. “One customer had a complex job that could only run at 300-ft per minute on their press due to bounce. They ran the same job on our Fusion press with SteadyPrint at 1,500-ft per minute with no operator adjustment.”
Each Fusion press system consists of a large central impression cylinder, eight to 10-ft in diameter, surrounded by eight or ten printing “decks” with two cylinders, one containing the image and the other applying the ink.
The Fusion press, like other PCMC presses, was already using IndraDrive M servo drives and IndraDyn T frameless torque motors to control the cylinders and the IndraMotion MLC motion logic automation platform for overall machine control.
To develop SteadyPrint, Rexroth motion control engineer Brian Schmidt said they used capabilities inherent in the Rexroth IndraDrive servo drives to gather new data about the motion on each axis.
“Our IndraDrive servo drive registers bounce as a torque disturbance. The drive will counteract the disturbance and smooth out the motion, but while the disturbance is happening, print quality is adversely affected.” Schmidt said that by capturing data on the torque feedback, velocity feedback, and position feedback of the drives, the torque feedback had a signature that repeated once per rotation of the roll.
“We developed a concept to record this pattern,” Schmidt said. “We then apply a compensation algorithm, to offset the effects of the torque disturbance, significantly reducing position errors.”
According to Schmidt, each print job takes just a few rotations of the cylinders for the drives to “learn” the necessary torque offset to apply; the SteadyPrint feature then engages the drive-based algorithm and eliminates the need for manual mechanical adjustments to smooth out print quality and eliminate bounce. This also eliminates the wasted material from mechanical adjustment and enables full-speed printing almost from the outset of each print run.
PCMC is adding refinements to the Fusion press mechanical design to minimize deflection, including an improved mandrel support arrangement that increases deck stability. The company is also using the IndraDrive drive-based torque offset algorithm to implement its SteadyPrint capability across the full line of Fusion press systems as well as the company’s ELSMax presses.
According to Pennings, the SteadyPrint feature confirms a core advantage of Bosch Rexroth’s approach to automation and motion control: Using distributed, drive-integrated intelligence to solve motion control challenges is often the smartest and most effective approach, rather than depending on a PLC to handle all the processing.
“There is no way we could do this if the intelligence wasn’t in the drive,” he said. “Given the speed and dynamics of how these print jobs run — 1,000 to 2,000-ft per minute, with repeats as low as 12-in. long — it wouldn’t be possible to have the controller handle the compensation. It has to be in the drive.”
The high-speed Sercos Ethernet-based communications bus as the backbone for its motion control platform has also enabled PCMC to advance its connected machine concept.
“With Sercos, we have an expanded view of all the data that the drive captures,” Pennings said. “That lets us have a deeper look into the drive and allows us to implement system dashboards and predictive maintenance capabilities where we can connect remotely through the cloud to support customers in real-time to manage their systems.”
According to Schmidt, the Open Core Interface enhances PCMC’s flexibility to provide connected machine functionality to its customers. The Open Core Interface is a machine control programming interface to create high-level, language-based applications. PCMC used Open Core Interface to extract data from the drives, such as torque, position, and velocity data, and then made it available for analysis using third-party programming languages and data analytics packages, rather than going through traditional PLC methods of exchanging data.
The Flexographic Technical Association (FTA) recently awarded its FTA Technical Innovation Award, Heavy Metal Category, to PCMC for the SteadyPrint system. Pennings credited the close working partnership his people developed through multiple innovation sessions and system refinements for the success and recognition that SteadyPrint has accomplished.