Collaboration yields static control to speed bagmaking task

Staff -- Converting Magazine, 1/1/2001

Whether converting bread bags or diaper bags, high quality at top production speed is the norm. The need for speed has led bagmaking machine manufacturers to engineer ways of increasing web-handling speeds and automating bag handling at the end of the bagmaking process. In particular, reducing manual labor in handling finished bags continues to be a driving force.

The Hudson-Sharp Machine Co., Green Bay, Wis., manufactures plastic bagmaking machinery worldwide. The company has operations in Green Bay; Aalst, Belgium; Araraquara, Brazil; and Melbourne, Australia and sales teams with representation in 19 countries.

Hudson-Sharp has engineered the 275WHS automatic servo wicketing bag machine that punches up speed with a three servo-axis design. Two servos drive separate sets of draw rolls that control web tension. The third servo drives seal-head motion. Machine operation provides real-time seal dwell that is not cam-driven, allowing for reportedly more accurate, "on-the-fly" control of seal-dwell time. Via a patented cycle configuration, the system can seal various film gauges at speeds up to 400 cycles/min, depending on options chosen.

A new wicketed automation stack processor (WASP) from Hudson-Sharp is said to eliminate virtually all tedious handiwork on finished bags. The WASP uses a robotic-transfer system to grasp a stack of bags, lift and then place the stack onto a backer board and a wicket wire. A front board sandwich sheet is then placed on top of the stack before the holding washers are added to secure the package. Automating this process reportedly saves converters labor expense by reducing the pack-off bottleneck to inspection only. In addition, bagmaking customers save on costs related to repetitive motion injuries.

Need to be 'static-free'

Efficient use of the automated WASP system happens only if stacks delivered from the bagmaker are consistently the same size and shape. Static electricity is a common problem in bagmaking because the plastic web is highly susceptible to static charge. Static slows production and affects the integrity of the stacks, says Danford Anderson, Hudson-Sharp, engineering supervisor. Common problems include curled bag corners, larger or puffy stacks, and airborne contamination.

"Static electricity stays on the bags, and the problem trickles down to the end user," Anderson explains. "For example, bakeries that bag bread using automated loaders may have problems if the bag doesn't open because of static electricity-the bread falls on the floor."

Hudson-Sharp discovered that most converters reduce the speed of their bagmaking systems to avoid quality problems rather than try to fix the static-control problem. The problem can be compounded when converters apply an oxi-dry powder, a commonly used substance to keep bags from sticking together. The powder may accumulate on the bag machine's static-control bars, reducing their effectiveness.

The problem of static electricity in bagmaking and other converting applications has been studied extensively by Ion Systems Industrial, Windsor Locks, Conn. Its Virtual AC( Static Neutralizer is said to effectively eliminate static on bags. Recently, the company conducted a study of static-neutralizing equipment with a flexible-packaging converter. The study compared the performance of a conventional static-control system with three dual static bars and a two-bar Virtual AC 8001 system on a bag machine with an automatic wicketer.

Large numbers of finished bags processed by each system were tested for residual static charge. On average, the three conventional dual static bars left twice the residual charge on the bags compared to the bags neutralized with two Virtual AC bars.

Long-distance neutralizing

The key to the Virtual AC's effectiveness lies in the system's ability to neutralize static charges from a long range as well as throughout the bagmaking process. The neutralizing bars are also less affected by dirt or dust, which can shut down traditional static bars. The high performance level can be maintained with the help of an intelligent display module that provides real-time diagnostics.

The display gives the operator a clear understanding of bar performance and confidence in the static-control process. Featuring lighted indicators, the display module offers immediate feedback indicating the efficiency level of the neutralizing bar and when the bar must be cleaned. A "neutralizing OK" indicator assures the operator that the system is working properly. A malfunction light appears if there is a power-supply or bar failure.

After seeing the effectiveness of the Virtual AC, Hudson-Sharp took a proactive approach to the static-control problem. The company now offers Virtual AC bars on all its bagmaking machinery. "One of our largest customers has already commented about the improved static control they've achieved with the Virtual AC bars," says Paul Staab, North American sales manager. "They specifically like the control module that assures them of the static-neutralization process."

Together, Hudson-Sharp and Ion Systems Industrial are helping converters run their bagmaking systems at optimal speeds, reduce downtime caused by unanticipated static problems, and increase productivity.