Parameter selection on the touch panel, connected via the standard Ethernet interface of the LMC058 Motion Controller.

Variety is the spice of life! The trend toward diversification in soft drinks, juices, and bottled water, as well as in the beer sector, has led to significant growth in product variety. This has similarly increased the variety of returnable bottles being used, with understandable logistical consequences. When crates containing returnable empties are received, for example, a rising number of them contain mixes of different bottle types.

The problem of how to most economically handle the checking and sorting of empties has led to innovative, robot-supported solutions. Kassel-based Recop Electronic GmbH, founded in 1994, is well-known in this field. Recop, with approximately 70 employees, installs customized solutions worldwide for automated checking and sorting of empties. These sorting robots, which are used both for pure sorting as well as production and filling operations, can check a variety of parameters depending upon their assigned task. The possibilities are numerous, ranging from the identification of individual bottles and detection of ultraviolet or embossed labels to check the mouths of bottles, or even identify case logos and case geometries.

Recop’s customers include Badische Staatsbrauerei Rothaus AG, the second-largest brewery in the state of Baden-Württemberg. Rothaus, which is famous in southern Germany for its highly popular ‘Tannenzäpfle’ beer, currently offers five different beer products in 0.3 and 0.5-litre bottles. To sort the returned 0.3-litre bottles and separate out non-matching bottles, the brewery installed a sorting system made by Recop with a capacity of approximately 500 crates per hour. This performance level is based upon a 50 percent mix of non-matching bottles among the empties.

Bottle Identification in the Crate – No Lifting Necessary!

These flexible and expandable sorting systems always have at their core one or more sorting robots and one or more sorting tables. Multiple hinged chain conveyors running in parallel beneath a portal robot feed in the crates of unsorted empties. Before they reach the portal robot, the crates pass through an identification station equipped with the appropriate sensor technology based upon the parameters that need to be checked. The sensors identify the complete contents of each crate and report this data to the controller.

In order to ensure sufficient empties for the sorting process, the system moves four crates at a time into the portal robot’s work envelope and arranges them into a group. The sorting robot has already identified the contents of each of the four crates. It then moves over the individual crates in position, and uses the gripper head built by Recop to pull out either individual bottles or all the bottles at once with a single targeted lifting operation. Loaded with the bottles, the gripper head travels across the sorting table and sets them down on a staging grid.

The sorting robot keeps placing bottles on the sorting table until it has enough of each of the individual types there to completely fill each of the crates. The portal’s controller specifies which bottles from each crate will be placed in which positions.

– The sorting takes place based upon a patented strategy developed by Recop, explains Uwe Pröger, Technical Director of Production and CAD Construction. Sorting is generally done using dedicated lines, with one hinged chain conveyor feeding crates with matching bottles, and the other feeding crates with non-matching bottles. Once the crates are completely filled, they leave the portal’s work envelope on their respective roller conveyors. Matching bottles are fed back into the process and non-matching bottles are moved into a storage area.

Each sorting system consists of standard components that are individually adapted to each customer’s performance requirements and available space, also taking into account the complexity of their sorting arrangements. The sorting systems can also be used for multiple functions: in an alternative operating mode, for example, the portal can place filled bottles into empty crates.

The system installed at Rothaus is a pure sorting system with one portal robot and two roller conveyors. The robot kinematics with servomotors, servo drives, motion controllers, and various other components for the automation solution come from the Schneider Electric product portfolio. The robot’s drive controller is supplemented by a PLC, which also connects to the company network to pass on production data.

Customized Portal Kinematics Instead of Off-the-shelf Equipment

The load requirements in the Rothaus system are impressive, and demand a corresponding level of performance in the drive technology. The portion of the portal that moves in the X-axis – the head of the robot, the linear axes, and the drives – in itself weighs 350 kg (770 lbs.). During operation, this portion is accelerated on the path between the conveyor and the sorting table at 7 m/s2 up to a speed of 3 to 4 m/s. Pröger uses a comparison to emphasize just how fast this is: “To maintain comfort for passengers, elevators generally accelerate at less than 1.8 m/s2.”

The robot cell with overhead portal is supplied with empties from two parallel roller conveyors.

The portal kinematics come from the Schneider Electric Linear Motion product line, a modular system with basic elements and complete solutions for a variety of one-, two-, and three-dimensional motion tasks. The portal axes with belt or spindle drives, the linear table drives, and the cantilever axes can be customized in terms of length and stroke for individual applications. Different axis diameters and lengths allow the system to be adapted to each load situation. Drive solutions from the Schneider Electric portfolio also accommodate various configurations, from point-to-point positioning operations to actual motion control/robotics solutions, to meet the widest possible range of requirements.

The system’s portal is based upon a MAXR42 double-axis system. Given the load requirements, Rothaus selected the strongest type available (PAS44). Because of the high acceleration, it appeared that compliance with the long service life requirements might be difficult using the standard design of the PAS 44 axes.

– Here Schneider Electric responded with a customized solution for Recop, explains Pröger.

– The profiles for the X-axis were modified accordingly with stronger belts and different drive wheels in order to optimize the transmission ratio. This gave us a good solution, and one that currently has no off-the-shelf alternative.

Servo Technology for Precisely-defined Acceleration Profiles

The demanding requirements at Rothaus meant that automation using servo drive technology was the only option. For distributing the acceleration load, each of the portal’s X-axes were equipped with servo motors in fully synchronous operation to prevent torsion. One servomotor is sufficient for the Y-axis (positioning above the conveyor), since the entire travel time in the X-axis is available for the Y-axis movement. Pneumatic actuators generate the vertical stroke of the Recop gripper head.

Another aspect of server technology is the ability to drive the head with defined acceleration and braking profiles. The forces acting on the drive mechanism are limited by the design of the profiles. The transverse acceleration affecting the empties suspended from the packaging head can also be limited. The positioning precision and/or repetition precision of the servo solution is also superior compared to other approaches.

The three BMH series servomotors are synchronized with their Lexium LXM32 servo drives by a Modicon LMC058 motion controller. The two X-axes are driven synchronously via the CANmotion bus from Schneider Electric. The control panel is connected using the controller’s standard Ethernet TCP/IP interface.

Robot Programming with Software Libraries

The software libraries provided by Schneider Electric were a useful resource when programming the entire solution. Application Function Blocks significantly simplified the transformation of the motion data into the portal kinematics. Recop also received support from a Schneider Electric software engineer.

Uwe Pröger is very happy with the result:

– Following an optimization phase, the equipment is now fully capable of handling the - very considerable - accelerations that occur in the process. Pröger also values his automation partner’s focus on providing complete solutions:

– We can obtain all of the components for the portal robot solution, from kinematic elements to drives and controllers, and above all, software, from a single source. 

Christian Hoepner

Schneider Electric,

christian.hoepner@schneider-electric.com