Electric Actuators Improve Productivity of Modular Bagging System
System automatically compensates for variations in bag dimensions, eliminating manual setups
By Design News Staff -- Design News, November 1, 2009
Thiele Technologies, a leader in packaging technology and equipment, faced a problem of how to compensate for inconsistent bag dimensions on its popular modular bag filling and sealing system. Serving customers in the diverse bulk-materials processing industries, the bagging system is designed to measure, fill and seal bags containing anything from pet food to salt, sugar, soil, seed, fertilizer or animal feed. A switch from higher-cost bags with consistent dimensions to lower-cost, irregular-sized bags by their customer base resulted in inconsistent bag positioning causing improper filling, sealing and rejection of packaged products. Repeatability is critical to a filling and sealing operation, so to solve the problem, a bag top reference system was designed to compensate for the varying lengths.
The bag top reference system features rodless electromechanical actuators. It employs four customized Tolomatic rodless electric screw actuators that precisely position the bags before they are inserted into the filling/sealing line. Two vertical actuators (operated by servomotors) adjust the vertical position of the bags. As the bags are loaded into the staging trays, the vertical actuators catch and lower the bag tops to a precise reference point determined by video cameras controlled by the system's PLC. At the same time, two horizontal actuators (modified with two carriers and screws with right- and left-hand dual thread technology) center the bags in their trays. The horizontal actuators are joined by a coupler and operated by a servomotor connected to a compact 180-degree Tolomatic belt drive actuator. The bags, once vertically aligned, are picked up by a pneumatic arm and inserted into the filling/sealing line.
While many of the other actuators in the bagging system are pneumatic, improving repeatability was a key objective. Electric actuators were employed for the bag top reference system for their speed and accuracy (positioning tolerance of the bag tops is only 0.031 inches). The rodless actuator solution also saved much needed machinery space making it possible to install it in the existing machinery without a significant modification to the design of the bag trays. In addition to compensating for varying bag dimensions, the new automated bag top reference mechanism now allows an operator to change the size of the bag being run with a simple touch of a button instead of manually adjusting the bag trays.
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