June 19 2014
More efficient packaging thanks to spatial object recognition
Gerhard Schubert GmbH is introducing a new milestone in the field of image recognition. The 3D scanner is making spatial vision a reality. This innovation increases the performance capabilities of the TLM packaging lines both in the pick-and-place process and quality control. Customers profit from fewer rejects, greater production capacity and better quality control. Depending on the product, the new technology can even lower raw material costs considerably.
The 3D scanner is positioned over a conveyor belt and determines the three-dimensional data of the products to be handled from that position.
Monitoring with even greater precision: Quality control
The height profile is opening up new control parameters for quality control. The TLM Vision System can determine the volume and, if the product density is consistent, the weight of each product using the information from the 3D scanner. A setpoint/actual value comparison can also be made for the stack height or stack length in the case of upright placement in boxes. This is possible because the new height or length is also logged and taken into account after each placement occurs. A TLM line with the new scanner can detect 3D defects. This enables, for example, a brown sandwich cookie with brown cream, but no top part, to be easily identified and rejected.
New possibilities for pick-and-place
Another attractive area of application for this innovation is the prioritizing of product pickup. The TLM Vision System can determine where overlapping products are located, for example. The first robots of a picker line prefer to pick up the products on top. This enables products which are partially overlapping to be processed as well. This results in increased efficiency of the pick-and-place process with fewer rejects and thus higher productivity.
Information on the volume and weight serves as the basis for a high-caliber grouping process. The robots are able to complete the individual product formation in such a way that its weight lies within a defined range. This type of weight optimization can save the customer up to 3% in raw materials, depending on the application, which is currently over-producing to fulfill the legal regulations.
Always a clear view: Tolerance to belt soiling
When the 3D scanner is used, the Vision System can tolerate belt soiling as long as it's below a certain height threshold. Products in low-contrast environments are also detected better than before. Thus tricky conditions like this no longer represent an obstacle to image recognition. Availability, efficiency, quality and productivity rise as a result.
Field testing passed with flying colors
The first TLM picker line with a 3D scanner has already begun operation at the factory of a confectioner in Belgium which produces baked goods. The 1,200 mm-long 3D scanner features seven line cameras and six light projectors at a distance of 100 mm. This enables a height resolution of 0.5 mm within a height measuring range of 60 mm. With this application, the crucial element was ensuring product recognition despite the crumbs and, especially, the chocolate residue on the conveyor belt.
Method of functioning and technology of the 3D scanner
Since 1996, Schubert has been using line sensors for the Vision System. The first unit was a transmitted light scanner. This was followed by the reflected light scanner and color reflected light scanner. These scanner types will also be used in the future. They operate reliably in continuous operation and are easy to commission. As with all TLM system components, they are easily added to the company's modular machine concept.
The 3D scanner also has all of these features. Development is based on the stereoscopic approach, i.e. the scanner captures two views of each product from different angles. The calculated height profile includes the height of each point in space captured in both views. The conveyor belt represents zero height here. Therefore, the Schubert 3D scanner is a stereo 3D scanner.
Multiple color line sensors are arranged next to one another at a set distance, making the scanner modular in nature. The field of view of each color line sensor extends to the optical axis of the two neighboring sensors on the left and right sides. Every physical point of the products, as well as those of the conveyor belt, which is imaged by two neighboring sensors immediately contributes to the creation of the scene's height profile.The Vision System then reconstructs the 3D images from the height profile.
Light projectors located between the sensors project slightly overlapping bands of light onto the fields of view of the two neighboring sensors. The light pattern is the result of an ingenious principle which enables unambiguous assignment of the image points in the stereo views. To locate the projection angle of the light pattern in the areas of overlap, the 3D scanner uses two different colors in an alternating fashion (e.g. red and blue).
The 3D scanner also features white-light illumination for capturing color images. The color images are reconstructed from the stereo captures without distortion or parallax. Both the color light bands and the white illumination can be switched on and off in an alternating fashion to prevent undesired reciprocal effects.
