Efficient automation of several work steps

de Man develops bag filling plant with de- / palletizing for Sitraplas: Filling, weighing, knocking over, rolling, palletizing and on the other hand depalletizing and emptying - at Sitraplas, it was important to manage many processes as efficiently as possible in one system. de Man Automation + Service GmbH & Co. KG from Borgholzhausen has solved this task perfectly. For some time now, valve bags with plastic compounds have been traded by a Comau robot. Since then, the performance has been doubled.

SITRAPLAS GmbH from Bünde has been producing high-quality technical plastic compounds job-related since 2005. The spectrum ranges from the coloring of engineering plastics to the development of customized compounds according to customer requirements for a wide variety of applications. Both the batch sizes (25 kg up to several tons), the design of the box valve sacks (neutral / company logo) and the bag sizes used (20/25 kg, 140/200 mm height) vary, which makes different packing patterns necessary. So far, these bags have been filled and palletized manually. This not only put a considerable strain on the spine of the employees, but also prevented an increase in the production volume of an average of four tons per shift. "Our goal was to find an ergonomically optimized solution for automatic bagging and palletizing, which enables an increase in packaging performance," says Managing Director Tim Hencken. The use of a robot turned out to be the ideal solution, since it could be used for depalletizing and decanting the raw material delivered in parallel to palletizing without conversion. Sitraplas commissioned de Man Automation + Service GmbH & Co. KG from Borgholzhausen for the implementation. The general contractor was the only provider to present a solution for connecting the valve bags used to the existing system and was also recommended to the company by business partners.

Perfectly filled
de Man's planning was based on the packaging scales already in operation, including the loading platform and bulk container. The sacks to be filled are now provided in a magazine. This holds two empty sack stacks with a total of 100 sacks to avoid interruptions in the palletizing process. If the stack is processed at the removal position, this is recognized by a sensor and the stack is immediately pushed from the reserve position with a slide. The operator can then insert a new stack in the reserve position through an opening in the protective fence. The bag-placer now removes an empty bag from the removal position using a vacuum suction device and puts it on the bagging tube. Here the sack is recognized by a sensor, clamped and the granulate is filled. A holding plate pushes the sack forward in an upright position when the amount is small, so that it can be filled more easily and the granulate is better distributed. The sack is then weighed, released and knocked over by a push-off unit. The sack valve closes due to the granulate. To ensure that the sacks lie straight on the conveyor belt, they are brought into the correct position by an aligner when they fall over.

Optimally used
The belt conveyor now transports the filled sacks from the filling station to the buffer location, where they are made available for pick-up by the robot. The contents of the sacks are evenly distributed by a roller during transport in order to simplify the pick-up by the robot and to ensure an even palletizing image. Due to the different filling levels of the bags, the height of the roller can be adjusted manually. The robot - a Comau Smart NJ110 with six axes is used - now takes the bags from the buffer location and stacks them on pallets (CP1, CP3 and CP6) according to the previously defined pattern. The gripper sucks the sack from above with a suction cup. If there is no sack ready for palletizing or the palletizing is not activated, the robot depalletizes sacks with raw goods and fills them into a container. In this way, the capacity of the system is optimally used and a second work step is efficiently automated, which previously represented a considerable amount of work and a health burden for the employees. For depalletizing, the robot opens the sacks with the raw goods at a sack slit, empties the contents into a receptacle and disposes of the empty sacks in a garbage container. Here, three different types of bags had to be taken into account when handling, which differed in height, width and length.

Generate packing schemes yourself
Special convenience with de Man systems: The customer can create new palletizing schemes themselves in the packing scheme generator specially developed by de Man and does not have to request a service call. This enables Sitraplas management to react flexibly and quickly to shipping requirements when assembling the packages. Of course, safety was also taken into account: the entire system is surrounded by a protective fence. Access is via protective doors, the approval of which must be requested. The safety interlock with guard locking only allows the protective doors to be opened when the dangerous movements within the system have stopped safely. An emergency release enables trapped people to leave the cell. How often with such complex projects, technical problems arose during the commissioning phase at the customer, but all of them were resolved. At the same time, subsequent customer requests were also implemented. After the delayed final acceptance, the system now runs as requested. The robot application even doubled the packaging performance. "Thanks to the installation of an automatic material supply system, which is carried out independently of this project, a continuous material supply can be generated and the packaging performance can even be increased up to three times", Managing Director Tim Hencken is pleased about the significantly increased productivity.

Copyright Pictures: Michael Adamski, https://adamski-fotografie.de