May 2021 Volume 3

AUTOMATION

Robotic Billet Loading Systems By Joe Stambaugh

Elevator feeders and vibratory bowls are two of the most popular methods used to reliably load and feed induction heating systems. Regarding these systems there are often complaints about noise, dust and various feeding issues. Over the past ten years, robots with vision systems have evolved to the point that it is now possible to utilize them to reliably feed an induction heating system. Considerations When Selecting a System When considering a robotic billet bin pick system for an application a good procedure is to first consider the billet shape and its dimensions. A cylindrical shaped billet presents the easiest shape for a vision system to identify using 3-D vision software. Then consider the diameter and overall length of the billet to be picked, keeping the billet diameter and length within a known range of pickable billet diameters and lengths. Typically the overall length should be 1.5 times the diameter of the billet. In addition, the billet should be no smaller in diameter than 1 inch. If the billet is outside of the range, testing must take place to ensure that billet picking is possible. In the case of larger diameter billets, a feeder shaker loader can be utilized to level out the billets to form a single layer making it easier for the robot to pull out the heavier larger diameter billets. Integrating the Robotic System Some companies, such as Ajax TOCCO, prefer to design their robotic billet picking systems to be fully integrated with fast-moving infeed chain conveyors, which feed the billets into the pinch roll drives or linear actuator pushers. In these cases it is possible to utilize a two-bin system where a second bin provides a full bin of billets for the robot to pick fromwhen the first bin is empty. At that point, the robot switches over to the second bin of billets, and the first bin is removed and replaced with a new full bin of billets. In a typical Ajax TOCCO installation, a rail mounted FANUC iRVision® system is placed above the dual bin arrangement on one side of the machine. After the robot empties one bin it automatically switches bins and the rail mounted 3D camera simply moves to the second bin via the linear rail unit. Optionally the 3D camera can be mounted to the robot’s arm. By utilizing a Safety PLC in conjunction with dual check safety speed and position check software the travel of the robot can be restricted. By restricting the robot to Cartesian space the robot now can be restrained to the area where it needs to work to accomplish its tasks. Dual Check Safety Speed and Position Check Software enhances protection as it limits robot travel. Limiting the robot’s travel consumes the minimum amount of the customer’s floor

space. Safe zones can be both enabled and disabled via the Safety PLC. Utilizing these safe zones along with the proper guarding, an operator can now safely replace a tub of billets or stop the system and enter and exit the workspace.

IR rail mounted vision system in operation. The goal in positioning the robot within the cell is to develop a placement of all components that will minimize floor space and further require the fewest and shortest movements by the robot, so that it can achieve the fastest possible cycle time. Cycle times as fast as 6 seconds can be achieved, with the average cycle time closer to 10 to 12 seconds. The robot is commonly equipped with an electromagnet end effector of the proper size and configuration to best pick the billet diameter and length range. In the event that the billets are made from a non-magnetic material then grippers must be used. This sometimes results in a reduced range of billet diameters that the unit is able to pick. It is assumed that in most cases the robot magnet or gripper will come into contact with the side of the bin.This generally happens when a customer introduces a bin that has been damaged and the sides are dented or bent. Additional impact spring loaded slides are then added to the tooling with integral limit switches. When impact occurs the springs allow the tooling to retract to the point that the limit switch is closed and sends a signal to the Safety PLC which signals the robot to retract and select another billet. It is best for a customer to supply straight wall bins for these applications, or at least corrugated style totes that are uniform and with limited dents. A straight wall tote also makes it easier for the totes to be able

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FIA MAGAZINE | MAY 2021