Rolling Over 

On average, Plus Mark rolled 2.2 extra inches of gift wrap on each cardboard core due to accuracy limitations.  With production topping 70 million rolls per year, the company was losing more than 150 million inches of wrap annually - enough paper to wrap from Los Angeles to New York City.  Additionally, measuring the wrap once each hour required operators to spread a sample roll on the plant floor and compare against tape markers.  Not only was this system inefficient and inaccurate, but it also resulted in more lost gift wrap.

For shorter rolls, operators selected lengths with a proportional infinite variable (PIV) gearbox.  For longer lengths, a counter was used in conjunction with a clutch and brake.  The system permitted selection of lengths only within one-inch increments, and accuracy varied with clutch and brake wear as well as temperature changes. Because rolls could not be under specified lengths, the company ended up giving away inches of extra gift wrap with each unit sold.  The high cost of excess product -- coupled with excessive downtime and maintenance expenses -- pushed Plus Mark to explore manufacturing alternatives, according to Tom Dubois, industrial engineer with Plus Mark.  

“We were at a point where we had to retrofit or buy new machines,” Dubois explains.  “Our competitors had purchased new equipment, and we needed to upgrade to stay in an industry leadership position and reduce costs.”  

Chattanooga, Tenn.-based integrator Jim Jones, president of Automation Insights, designed and implemented the successful retrofit at Plus Mark at 10 percent of the cost of a new machine. The solution provides upgraded machine controls for smoother operation, faster production, and lower maintenance.  The system measures each roll and supplies operators with a digital readout.  Roll lengths can be selected within 0.1-inch increments for higher accuracy and less waste.  Overall, cut-to-length accuracy has improved by 70 percent, according to Dubois.    

Automatic Controls

Jones and his team retrofitted more than 50 machines at Plus Mark with compact GE Fanuc Series 90-30 programmable logic controllers (PLCs). The GE Fanuc Model 313 CPU resides in the backplane of the unit, saving space and leaving room for an additional I/O module. The PLC runs at a 0.6ms/K scan rate with 1024 register memory words and 12K bytes user logic memory.  “We didn't have a lot of extra room on the machines, and we had to keep controls accessible and out of the operators' way,” Jones says.  “Operators need to get in the machines and check the web for accuracy.  With the Series 90-30 PLC, we have all the power that we need in a small module.”

For fast and accurate motion, the GE Fanuc control system closes all control loops -- position, velocity, and torque -- within the controller.  All drive parameters are stored in the controller in a standard motor database.  By reducing the number of mechanical drive-train components, the servo system increases machine reliability and provides greater accuracy.  Controlled accelerations and decelerations decrease jarring for less wear on other machine components -- which results in longer life and lower maintenance.    

"Rolls cut and drop 20 to 30 times per minute," Dubois says. "With the old system, the machines experienced a sharp jolt with every completed roll.  Now, the motion is smoother and quieter, and our equipment will last several more years."  

The GE Fanuc servo provides motion accuracy within 1.0 mm/second.  The all-digital system supplies the greatest resistance to environmental changes, reduces setup time, and delivers significant throughput advantages.  The low-maintenance servo also has no component “drift,” contains no commutator brushes, and require no tuning.  A serial encoder built into the motor provides precise motion control feedback.    

Automatic Spooler Verlin White operates a retrofitted machine and has seen an increase in product quality with the servo system.  “The machine operates faster, and we're able to produce tighter rolls,” he explains.  “Additionally, the paper pulls out smoothly from the feed end.”  

Easy Operation

In addition to easier operation, the plant is enjoying less maintenance and greater uptime.  The old system required twice weekly tightening of the chain and annual replacement or rebuild of the PIV, according to Danny Garber, Plus Mark master mechanic.    

“The servo system eases maintenance with cleaner, simpler operation,” Garber says.  “Overall, we've cut maintenance costs in half and increased uptime by approximately 40 percent.”    

With less time spent on maintenance, the team has more time to explore other improvements - which are now possible since the servo system retrofit.  For example, with the load reduced on the main drive, Plus Mark was able to install a new gear for even faster production.  “The new gear buys us another 50 percent gain in speed,” Dubois says.  “We're now running faster than we would be with a new machine - and wrapping up our competition for 1/10th the cost.”   

Visit our web site to learn how GE Fanuc Motion Solutions can help you or e-mail Jeff Christensen.