Bring traceability to molded parts production
Yamaha Robotics FA Section reports that robots from its competitively priced SCARA portfolio have enabled a customer making injection-molded products to implement traceability, as well as raising output and improving quality.
Injection molded parts tend to be produced in large volumes yet, at the same time, quality expectations are high. Even small cosmetic defects can be easily visible, while perfection in terms of form and dimensions is often critical in parts for applications like automotive components, electronic connectors, medical syringes, and surgical tools.
Contractors that specialise in this field can offer advantages such as cutting-edge design knowhow and process capabilities to OEMs that may have only limited in-house expertise and manufacturing capacity. With the potential for fast turnaround and economies of scale, they also need to ensure top-notch quality control and customer support. Yamaha has helped to raise the game in both respects with a solution bringing together the low-cost YK-XE SCARA, RCXiVY2+ vision system, and YRG electric gripper.
Quality control challenge
With an array of automated injection molding machines operated continuously, producing molded items at an extremely fast rate, shift workers were fully occupied palletising items as they were removed from the machines by high-speed take-out robots.
The established process flow involves these robots removing the freshly produced items from their molding cavities at the end of each cycle and placing them on a constantly moving conveyor. The conveyor transports the items towards the palletising station, dropping them into a collection box at the end of the belt. From this box, an operator picks the items one at a time to inspect visually and place in the pallet, discarding any that are seen to be defective.
The production team noticed that items could easily become damaged by impacts and rubbing when dropped in the box. Moreover, the box effectively randomized production, preventing the team from tracing any defective molding back to its cavity of origin. In addition, operators had little time to inspect each item, giving the possibility for defective units to be passed as OK and packed for shipping to the customer. They saw the opportunity to strengthen quality control in the factory while also addressing staffing challenges.
“Picking, inspecting, and palletizing the molded products, at a high rate, for the duration of a shift, is repetitive work that demands a high level of concentration. It’s not a popular job and this company was having difficulty finding people to work in those conditions,” comments Tatsuo Katakura, Sales General Manager at Yamaha Robotics FA Section. “A SCARA robot is the perfect starting point for a solution to quality control and automation challenges like this and our YK-XE range offers the opportunity to lower the cost of ownership by saving quality control overheads.”
Improving efficiency
Working with the customer to implement a solution, Yamaha engineers chose the YK400XE-4 from the low-cost, high-performance SCARA portfolio to take care of palletising the molded parts. Its 4kg payload capacity is ample for handling the small items and the arm structure, specially optimized for low vibration at high speeds, allows an extremely fast cycle time of less than 0.4 seconds; fast enough to keep pace with the work rate of multiple molding machines and take-out robots operating upstream.
With its arm length of 400mm, the YK400XE-4 has the perfect reach to pick items from the 300mm-wide conveyor and place them directly in the pallets that are 300mm deep and 400mm wide, as figure 2 also shows. Alternatively, the team could have chosen a SCARA from the YK-TW omnidirectional range.
By transferring the molded pieces directly from the conveyor to the pallet, the engineering team achieved two important goals. Firstly, items are protected against damage as they are no longer dropped into the collection box. Moreover, the SCARA can automatically associate the position of each item as it is placed in the pallet with its originating cavity ID. Recording this information can help the company strengthen quality control and drive improvement initiatives, as well as provide traceability information for customers if required.
Easy to integrate vision
To track items as they move along the conveyor, and thus calculate the position for the SCARA to pick each one from the correct location, the team turned to Yamaha’s RCXiVY2+ vision system. This system is conceived to integrate easily with the SCARA and is controlled from within the RCX robot controller. “Unlike conventional approaches that often require specialized computer vision expertise, the project team in this case was able to integrate the camera and accomplish the complete system setup independently within a short timeframe,” observes Tatsuro Katakura.
Yamaha has created special vision instructions that simplify programming for robot engineers. Directly integrating vision in the RCX controller saves coordinate conversion, which is often needed when mapping third-party vision data and robot point data, and it’s easy to calculate position whether the camera is in a fixed position or mounted on the robot. The robot program also controls the camera optics and lighting system.
“The RCXiVY2+ system has powerful features built in, including conveyor tracking for accurate high-speed pickup, random part-position searching, on-the-fly adjustment for orientation, and OK/NG judgement,” adds Katakura. “There is also a special blob detection function, which is up to 10 times faster than conventional edge detection, to quickly position the robot when picking up irregular shaped items.”
To complete the project, the team chose a YRG series gripper from the large selection of off-the-shelf accessories available directly from Yamaha. Like the RCXiVY2+ for robot vision, these electric grippers are controlled from the main RCX340 multi-axis controller and designed to be easy to use, requiring no data exchange with the host system. Leveraging full electric control of the gripper, the team was able to quickly configure and optimize parameters including speed, positioning, and gripping force, with sensor-free detection in the event of mis-gripping or dropping.
By accomplishing this project, introducing a robot to palletise injection-molded components has improved quality control, increased efficiency, and enabled the business to introduce traceability, which had been impossible to achieve before. The project team was able to highlight the advantages of the new system within the company, seeking the green light to expand the solution to other lines in the future.
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