At their Halstead, Kansas manufacturing facility, Legg Manufacturing, a part of the Continental Conveyor Belt Group, began a project to manufacture 8' wide belting. Calender drives, featuring NORD's MAXXDRIVE large industrial gearing, proved to be the solution.
Legg Manufacturing
In the 1930's, Legg Company began making rubberized patches for agricultural binder canvasses that led into the manufacturing of industrial belts. From those humble beginnings in Halstead, Kansas, the company has become a well-known supplier of industrial and agricultural belting serving the market with a innovative and diverse product line.
Focus on the Project
Legg decided to expand their production capabilities with the addition of a new calender drive unit. And it was to be of massive size. Legg's process is to layer rubber onto fabric in order to manufacture 6' wide conveyor belts but the concept behind the new application was to produce 8’ wide belts, substantially improving manufacturing efficiencies. The scale of this concept would require large industrial gear drives to produce the desired product.
Project Challenge
Focus on the Customer
On the manufacturing floor, NORD has been a part of Legg operations for decades. It all began in 1996 wen Legg faced several difficult challenges with rewinder drives . “We had a very simple mandrel, with plain shafts with plain ends,” San Nikkel, R & D and Engineer Manager explained. “If a chuck failed, the entire shaft and roll could fall to the floor. It was a dangerous situation that had to be resolved. I examined several different chain drive options, and rejected them all. I knew that chain maintenance would be a problem. I wanted the bearing journals to be on the mandrel, and did not want to have to dismantle the bearings to take the roll off. NORD supplied all the reduction in one gearbox, without any kind of chain drive involved, it really simplified my maintenance challenges.”
“I wanted to avoid long drive shafts, so we needed to be able to stack four drives in a unique way. The fact that this had never been done before did not deter NORD engineering in the least. In fact, the NORD application engineering group regarded it as an exciting challenge, and went to work” explained Larry Gooch, the engineering consultant for Legg. NORD engineering configured standard MAXXDRIVE boxes into a decidedly non-standard configuration. This unique installation required custom engineering of standard drive units. Since the drives needed to be stacked 3-high, with the fourth off to the side, the gear case mounting required sufficient support to accommodate the bending moments. Additionally, thermal loads were such that a central lubrication system that feeds from a remote reservoir was devised.
Engineering Challenges - The multiple drives and the stacked configuration presented some significant engineering challenges. Larry continues, “In a single-drive calender system, power automatically distributes itself to where it is needed in each roll. Here, we had to calculate maximum load requirements for each roller, and make sure the drive could deliver, with power to spare. Also, we worked closely with NORD on custom bracing for the 3-high stacked configuration. Significant overturning moments were going to occur, especially on the bottom box. The cast iron construction takes compression loads quite well, but we wanted to make sure that attachment flanges were not over-stressed.”
Precise Control - The Legg calender is designed so that each roller is individually driven by a NORD drive allowing for more precise process control. Additionally, the use of NORD drives is not limited to the calender on this line. The same size drives that power the calender are also used upstream on both the warm-up and finishing mills that then feed rubber to the calender. Downstream, additional NORD drives power multiple rewind stands.
