Inspection system sorts out defective concrete products

Examining paving blocks and slabs as well as sorting out defective specimens on the dry side are found amongst the activities that still have to be painstakingly carried out manually in many concrete production facilities. This procedure is susceptible to error and no longer up to date. The BT Master SC Inspection System made by ibea from the German port of Hamburg can provide the remedy.

Examining and sorting out fresh concrete products on the dry side demands a high degree of concentration and physical energy expenditure from the production staff concerned. Undesired differences in colour, blowholes and fine cracks on the surface of a concrete product, as well as geometric deviations from the specified shape all, have to be detected with the naked eye. The heavy blocks or slabs still have to be removed from the production board in some places with muscle power and the space then once again closed with a fault-free product. On top of this, the employee only has little time for this examining and exchanging work – all in all, a strenuous activity that still has to be carried out for many hours each day.

The BT Master SC Inspection System made by ibea, a company from Hamburg, can provide the remedy in a concrete production facility. The BT Master SC is a modification of the BT Masters, an inspection system for concrete blocks and heavy clay ceramics successfully employed in some of the most modern factories in Europe. This digital solution scans the surfaces and geometry of concrete products on a production board and discovers all deviations from the specified production output (blowholes, broken corners, protrusions, depressions, impurities, cracks, deviations in colour and texture, etc.). Defective products are subsequently exchanged for flawless ones using a robot arm. This, at last, turns the examination and exchange process in manufacturing concrete products into a reliable production procedure. Employees previously responsible for this job can engage in more profitable tasks.

Unproblematic integration into existing systems

The BT Master SC Inspection System consists of three units operating together – a scanning unit, an evaluation unit and a sorting unit. The scanning unit determines the characteristics of a product’s surfaces and geometry with the aid of a camera. The evaluation unit compares these actual values with the target values for the product. The sorting unit then takes products, whose surface quality and/or geometry deviate from specified target values, from the production board and fills the spaces thus created with fault-free products.

Producers can define their own quality specifications for surfaces and geometry before beginning production and configure the inspection system accordingly. For example, criteria for examining and sorting high-class garden and landscaping products can be defined in a different way than those for examining and sorting ordinary grey goods.

The scanning unit is installed on the dry side of a circulation system just before the palletising process as an inline solution above the existing conveyor belt. It spans the belt transversely to its direction of movement, like a portal. It is possible to install it without any elaborate modification work in a current system.

Finding defects with the 2D camera module and 3D measurement module

The scanning unit is equipped with a 2D camera module and 3D measurement module. When a production board bearing concrete products travels under the scanning unit on the conveyor belt, the 2D camera module generates a colour image from above, on which the surfaces of the concrete blocks or slabs on the board are recognisable. This image records all deviations in colour or black/white on the products’ surfaces. It discovers both products exhibiting differences in colour in small areas (dappled products) as well as those deviating in their overall colour from the rest of the production. These deviations in colour or black/white in turn permit conclusions to be drawn concerning deviations in colour and texture, impurities, material contamination and much more. The utilisation of modern colour cameras makes it possible to recognise spalling or fissures even in embossed surfaces.

The 3D measurement module – consisting of a high-performance laser and a high-resolution camera – simultaneously generates an image using laser cutting. The laser is located in the scanning unit above the travelling conveyor belt. It projects its beam from above onto the entire width of the conveyor belt transversely to its direction of travel. The production boards with their products then run beneath this “laser curtain”. The contours of each individual paving block or slab stand out in the laser light. The high-resolution 3D camera, fixed somewhat behind the laser above on the scanning unit portal in the direction of the conveyor belt’s travel, captures this process as an image. The width and height of a paving block, for example, can be determined precisely over its entire length in this way. The 3D measurement module can record products’ widths, heights, angles and lengths with an accuracy of 0.1 mm or 0.5o. It recognises unevenness or irregularities in products reliably. Its clever software can correct and compensate for distortions in perspective from camera images caused by inaccuracies in travel or position of individual concrete products on a production board.

One hundred percent fault-free concrete products

The scanning unit transfers the recorded data to the evaluation unit after this scanning process. The evaluation unit’s computer is housed in a PC cabinet protected against dust and thus able to cope admirably with the rough conditions in a concrete production facility.

The evaluation unit compares the current values, which the 2D camera module and 3D measurement module have recorded, with the target values laid down by the producer before beginning the production process. The evaluation unit compares, for example, colour images representing the target state of concrete product surfaces with actual images from the 2D camera module. Should the actual values of a paving block or slab be found outside of the range of possible target values laid down before commencing production, the sorting unit’s 5-axis robot receives an instruction via a programmable logic controller (PLC) to remove the relevant concrete product from the production board and replace it with a fault-free product.

The robot has been equipped with a vacuum grab and the standard version can move concrete products with individual weights up to 50 kg (greater loads are also feasible). Its vacuum matrix with chambers that can be combined or controlled individually makes it possible – without set-up times – to grab the most varied block formats or, for example, two blocks located beside each other. The robot can also remove sample blocks selected according to predetermined criteria and make them available for ongoing quality assurance whilst the production line is running.

The production board can continue on its journey with wholly flawless concrete products after completing this examination and exchange process.

Ibea is a company that previously built and commissioned systems principally for the heavy clay industry. It has now constructed a reference system for a German manufacturer of concrete blocks. The system functions unproblematically and has increased production efficiency by 40%, according to information from ibea.