Machine Controls Go All In

 
Diehl says the reduced amount of scrap or waste product resulting from improved quality control, as well as lower energy consumption (a huge issue for certain customers because a new control system often can be justified by the energy savings alone)and increased production rates (from tighter controls that often allow machines to run faster and produce cost savings due to reduced labor and staffing requirements) are the factors that determine whether they can, in poker parlance "go all in" with new automation for a customer.
 
Diehl points out that sometimes you make upgrade decisions after you improve your customers' operating data collection. That was the case with SpaceKraft (www.spacekraft.com), a Salem, Ore.-based business unit of Weyerhaeuser, that makes recyclable bulk containers,essentially corrugated boxes designed to ship bulk liquids.
 
The manufacturing process starts with kraft paper that is corrugated and glued around a square or rectangular mandrel several layers thick by a machine called a winder. Following winding, the "endclosure" adds end pieces to the top and bottom.
 
In discussing SpaceKraft's manufacturing issues with Concept's people, it was clear that Concept gathered a lot of information that helped with automation decisions from process control data generated by Rockwell Automation's PlantMetrics software.
 
SpaceKraft production manager Glen Lawson initially planned to undertake a different capital project, but when Concept installed PlantMetrics in the plant and ran an Overall Equipment Effectiveness (OEE) analysis, the results suggested that the SpaceKraft plant had different bottlenecks than what the manager had initially thought. The original project was put on hold and Concept Systems was tasked to pursue projects relating to improving "endclosure" machine performance.
 
"The endclosure process was determined to be the bottleneck in the entire plant," says Lawson. "The bayonets that hold the box in position were too slow and a rate-limiting sequential motion function appeared to be a candidate for coordinated, simultaneous motion control to improve cycle time"
 
Concept also found opportunities to shorten machine downtime on both the winder and endclosure machines by adding a graphical human machine interface and installing PlantMetrics quality analysis software, which allowed the plant operators to analyze production data pinpointing areas of process inefficiency. "The results from removing the bottleneck have shown an improved increase/output by a measurable 31%," says Lawson.
 
All in the Family Cancelled
Upgrade justification also could result from knowing when it's time to say good-bye to reliable, but increasingly limited home-grown, family-style proprietary controls. Miller Weldmaster (www.weldmaster.com), based in Navarre, Ohio, has focused on rotary heat sealing equipment for more than 30 years, gaining an international reputation in the thermoplastics industry.
 
Its Multi-Sealer is a web process machine that performs five basic functions on thermoplastic roll material (See Figure 2). The machine unrolls the raw thermoplastic fabric, folds and welds the hems along both edges of the fabric, and accumulates material to allow for constant tensions and speeds throughout the line. Grommets are inserted into the hem at programmable intervals along the length of the fabric and, finally, the machine cuts a finished piece to a precise, user-specified length.

Figure 2: Time For Open Architecture

Miller Weldmaster's justification for its thermoplastic web processing machine control upgrade resulted from knowing it was time to say goodbye to its home-grown, family-style proprietary controls and connectivity.

"Miller Weldmaster's standard machines are typically used to fabricate tarpaulins, building products, flexible ducting, billboards, and garments," says Brain Henry, Miller Weldmaster's director of engineering. "This type of machine was equipped with a proprietary hard-wired control system that required the operator to make frequent mechanical adjustments to set cut lengths and grommet placement. These mechanical setups were repeated at the beginning of every product run."
 
To maintain its market status, the company realized it needed to find a more efficient, accurate process. "The objective was a control system that would increase manufacturing capacity through a reduction in setup time, provide higher dimensional accuracy and repeatability in the finished product, reduce operator burden and the chance for operator error, offer remote diagnostics capability, and maintain a simple control architecture using locally available, off-the-shelf components," says Henry.
 
Miller Weldmaster realized customers could benefit greatly from an automatic setup where grommet locations and product dimensions could be stored as recipes for each part. "If the operator merely calls up the part number for each product on the operator interface screen, setup time could be virtually eliminated," recalls Henry
 
Dimensional accuracy needed improvement from +/- 0.375 in. and the availability of remote diagnostics via modems or the web should be possible. The company realized the potential benefit for increased service performance and reduced travel costs by allowing Miller Weldmaster service engineers to troubleshoot and maintain the installed machine remotely.