20047 - Vision inspection of packing at a robotic workstation

We upgraded a robotic station for automatic unloading and packing of engines by adding a Cognex vision system. The station now handles new types of collective boxes and checks by itself that every package has been correctly prepared and filled. The project also included an insert pressing module, a universal set-down area for NOK parts and changes to the robot and PLC programs.

Intended use of the machine

The upgrade eliminates packing errors: the wrong box or insert, a reversed insert, an occupied or empty slot. The Stäubli robot places parts only in a box that has passed all inspections, and the vision system continuously sends it the numbers of free slots.

Description of operation

Each new collective box goes through two inspection stages. First, at the pressing station, a cylinder presses the insert down and inductive sensors check its height, which identifies the packaging type. Then, at the loading station, the Cognex camera performs:

• box type inspection, recognised by colour (green, blue, grey);
• insert type inspection, recognised by shape (black polystyrene, white foam, black-and-white plastic);
• insert orientation inspection, with a separate algorithm for each type;
• slot occupancy inspection: information on free slots is sent to the PLC and on to the robot.

Once full, the box is released to the collection area. A non-conforming box is also sent to the operator and is not loaded. In non-standard situations (an occupied slot, an empty slot after packing is finished, incorrect pressing) the HMI panel displays a message. The operator can repeat the operation, have the robot add the missing part or release the box.

Machine design

VISION INSPECTION MODULE

The module consists of a Cognex camera with illuminators, mounted on a main frame with a reinforcing frame above the loading station.

INSERT PRESSING MODULE

The module consists of a pressing plate with a cylinder and pressure regulator, and four inductive sensors. The sensors check the insert height and identify the type of transport box.

UNIVERSAL NOK SET-DOWN AREA

The set-down area accommodates parts of all references handled by the station. At changeover, the system reminds the operator to empty the area so that parts from different production runs are not mixed.

SOFTWARE

We modified the PLC program and the Stäubli robot program, and added a camera operation page and new operator messages to the HMI panel. For each engine reference, one to three permitted packaging types can be assigned together with the corresponding pressing sensors. Teknomatik has specialists trained in programming Stäubli robots.

Safety level

The station has retained its complete safety system: emergency stops, interlocked safety locks, cell fencing and warning pictograms. A missing part is added with the robot speed limited to 5% of its maximum, so that the operator can follow the movement in real time.

Benefits for the customer/user

• automatic inspection of box type, insert and insert orientation before packing;
• inspection of empty and occupied slots, so complete packages are shipped to the customer;
• handling of three types of collective boxes, selected in the reference settings;
• quick removal of NOK parts to the universal set-down area;
• upgrade of an existing station instead of buying a new one.