Foundry cores insertion
producing hollow cast iron parts requires insertion of cores into moulds before casting. Both cores and moulds are made of compacted sand with very close tolerances (±0.1mm) and so they have to be assembled with great care. Cores have to be inserted in accurate housings of the mould to prevent cast iron from filling up all the inner mould volume: after solidification cores are destroyed with moulds and the generated solids present hollows in place of them. Cores can weight up to 80-100kg each and, in these cases, up to three or four operators are involved for manual handling. This way of working causes large inaccuracy during insertion, damages on core housings, sand traces within the metal matrix of products and incomplete saturation of casting plant capacity: all that means wasted production, delay on shipments, costs rising and great physical efforts for operators.
in our robotic cell for automatic core insertion an anthropomorphic robot, equipped with special devices, performs all the required operations. The arm payload of up 200kg is not afraid of hard works and a rapid tool change let the proper tool always available. Cores are identified and localized by a powerful vision system which guides the robot to picking locations with extreme accuracy. Moulds move on trolleys, position and tilt angle of which are localized by 2 cameras and 3 mechanical probes within ±0.05mm. According to these measurements, the insertion path is optimized to avoid scratches and damages on core housings: each time the movement is adjusted as to be absolutely perpendicular to mould surface. The operator is only responsible for random cores loading on the inlet conveyor belt: with the aid of a pneumatic lifter and with no accuracy requirements this becomes a very simple task. Production change takes almost a couple of minutes: simply replace gripper tools. In case of new articles, the system software guides operator through the correct training procedure.
a long list of benefits can be summarized as follow: -accuracy and care are granted in core insertion:
– no damages on core housings and no sand absorbed in final products;
– no stress or fatigue for operators means health benefits;
– high production rate (8 sec. for a 100kg core) saturates casting plant capacity: this means costs saving;
– constant and reliable working: shipments are scheduled for sure;
– no production wastes due to human factors (lack of concentration, fatigue, …);
– manpower is only assigned to random core loading, with the aid of a lifter: reduced manpower involves costs saving;
– few steps required to teach new articles.
working cycle starts with the loading step, the only task assigned to the operator: with the aid of a pneumatic lifter, cores are directly picked up from the pallet and laid down on the inlet conveyor belt in random order. One at a time, cores are moved under the main high resolution camera and localized with great accuracy: their coordinates are now available for robot trajectories generation. Great care is also taken during core picking: air pressure to robot pneumatic grippers is electronically calibrated as to provide enough holding force and to preserve core in its entirety. In the meanwhile a new mould is carried in by a trolley: its location is detected by a vision system with 2 cameras, while its tilt angle with respect to the vertical is measured by a 3 probes system. Core insertion trajectory into the mould can be calculated case-by-case as to be absolutely perpendicular to mould surface: housings and mould shapes are preserved. If production changes, it takes just a minute to setup the robot. Moreover the robot is equipped with a rapid tool change to let it automatically handle different types of cores. When the system has to be trained to handle new articles, a simple procedure guides the operator through few steps to the goal.