Packaging supplier solves its ice cream headaches
As one of the world’s leading suppliers of ice cream novelty packaging and filling machinery, Norse Dairy Systems, was watching its profit melt away through mechanical downtime and wasted materials on its production lines. It turned to Martin Control Systems for a solution that boosted production by more than 27%.
Norse Dairy Systems (NDS in Columbus, OH), a division of Interbake Foods, is considered to be the top manufacturer of sugar cones in the world. Four years ago, NDS management sought to improve the production of paper cone sleeves, which are used to hold the wafer cone. The machines that roll back the rim on the sleeves suffered from as much as 13% downtime and tens of thousands of dollars in wasted scrap paper.
The original rolled rim machine was chain-driven with glue applications, blunter, mandrel blow-off and vacuum, and rimming functions timed with cams. The cams, which are disks or cylinders varying in shape, travel in a rotary motion pushing against an actuator to achieve a linear motion. To adjust the timing for these functions, operators had to stop production and use hand tools to advance or retard the cam timing, then restart the machine to test the changes.
NDS contacted Martin Control Systems Inc. (MartinCSI) of Dublin, OH, in search of a solution. After conducting a system analysis, MartinCSI suggested re-engineering the drive system to incorporate a programmable logic controller (PLC). This solution would allow operators to make adjustments electronically on-the-fly. The system would be controlled by a Rockwell Automation Allen-Bradley CompactLogix PLC and use an Allen-Bradley PanelView Plus 1500 as the touch-screen human machine interface (HMI).
|Paper cone sleeves hold the wafer cone. The machines that roll back the rim on the sleeves suffered from as much as 13% downtime and tens of thousands of dollars in wasted scrap paper, says Norse Dairy Systems.|
An Allen-Bradley PowerFlex 70 drive would be used for main drive speed control. An EMP Model 200 single motor registration system would be reused to control paper registration into the cutting knives. As part of the project, all chains also were replaced with timing belts for better control and timing accuracy.
For real-time monitoring of the machine’s timing, a resolver was mounted on the main drive shaft and connected to an Advanced Micro Controls resolver input module mounted in the CompactLogix rack. MartinCSI replaced the mechanical cams with an electronic timing schedule based on resolver position.
The new control system provides runtime details about machine performance such as sleeve count, production speed (cones per minute), percentage of the maximum speed the machine is running, roll diameter (inches), and gate plug location. The main drive motor status and the rimming motor status are also displayed on the touch screen.
Quick-start resolver calibration
For quick startup after maintenance operations, MartinCSI implemented a resolver calibration function that uses a button on the HMI to retime the resolver to the machine’s zero position. Using the touch screen, operators can also change main motor speed, which is controlled by the PowerFlex 70. The knives, which are driven through the timing belts in a 1:1 relationship, run at the same speed as the rest of the machine, as do the resolver counts. When the machine speed is changed, it is no longer necessary to re-time the functions to the resolver, as built-in compensation is provided for higher drive speeds.
Brake tension on the paper unroll is now adjusted electronically in real time while running, using an I-P transducer and an pneumatic disk brake. An ultrasonic sensor is used to monitor the diminishing diameter of the paper roll; as the diameter and weight of the roll decrease, brake tension is slowly reduced to maintain steady paper tension. The operator can establish diameter and tension ratios through the touch screen, and make adjustments while the machine is running.
Maintenance features, such as the ability to jog the machine forward using an operator plug for safety, were included in the new control system. The program monitors the location of the operator plug and, when connected into the operator’s station, the machine has full capabilities. When the operator plug is removed and inserted into the remote pushbutton station, the emergency stop and jog forward are the only available functions, and all jog functions from the operator’s station are locked out.
To improve overall quality, a servo-controlled paper positioning function replaced a manual screw and wheel system. An edge sensor now tracks the edge of the paper in relation to the rollers and signals for an adjustment of the paper roll to keep it centered in the knives. In 2006, after the re-engineering, rebuild, installation and training, total downtime of the rim roll machine was only 5.15%. See accompanying charts for other results.
Minimizing scrap paper waste
As the project progressed, the internal quality team at NDS determined that the scrap paper levels of the rim roll machine were becoming the leading drain on profits. Rolls were scrapped with up to three inches of paper thickness remaining, producing total profit losses of more than $40,000 a year. Operators cited the difficulty and amount of downtime necessary to rethread the paper through the machine.
MartinCSI developed two solutions to address this issue, focusing on the paper left on a roll at the end of its run, and a practice known as manually “holding blanks” during mandrel cleaning. To ensure all paper was used, a sensor was installed to monitor the presence of paper coming off the roll and into the machine. When the sensor detects the absence of paper, the machine is stopped and -an alarm notifies the operator that the paper roll needs to be changed. This simple sensor eliminated the end of roll scrap, saving the company 100% of the dollars that were previously lost.
|In 2004, the total scrap for the rolled rim work center was 15.63%. By 2006, the total scrap from the work center was only 8.16%, NDS says.|
Scrap due to manually held blanks occurs when glue on the mandrel, which sometimes “squeezes out” from the paper cones during production, is cleaned. MartinCSI developed a control function to slow the machine when necessary to scrape the mandrel of glue. MartinCSI personnel also observed that paper tended to get jammed coming into the mandrel without operator knowledge, so they added a function within the logic to use the cone counter to alert the operators of a jam.
In 2004, the total scrap for the rolled rim work center was 15.63%. By 2006, the total scrap from the work center was only 8.16%, says Norse Dairy Systems.
Overall, the project enabled NDS to generate an significant rise in production, due to decreased downtime and a drop in labor costs (one operator can now run twice as many machines). In 2007, NDS management raised production standards for the rim roll machines, and statistics show that they continue to exceed expectations.
|End of roll||$40,026.44||$0.00||$40,026.44|
|Manually held blanks||$35,512.00||$7,380.69||$28,131.31|
|Year||Scrap %||Change from before install|
|Year||Downtime||% change from before install|
|Year||% of standard met||Difference from previous year|
For more detail on the scrap reduction project and solution, view this story online under Automation Integrator Guide supplement, at www.controleng.com/archives for mid-December 2008.
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