Scara robots change the profitability of automation

Automation continues to transform many industries and increase their productivity by improving production rates and quality. However, many companies value human skills such as dexterity and vision for tasks such as inspection, especially when objects are difficult to handle - such as molded plastic parts or textiles - and defects are easy to see or feel.

This can present companies with a major dilemma. Full automation may be technically feasible, albeit excessively expensive. If the production volume or unit price of items produced is low, the projected return on investment for automation may be unacceptably low. Small Scara robots designed for light picking and packing tasks are available at affordable prices. They can be used cost-effectively in addition to human inspectors to increase productivity and quality. With a little imagination, the sequence of process steps can be adapted to achieve optimal results.

Increase in throughput and quality

Recently, Yamaha helped a customer that manufactures injection molded parts for industrial applications overcome a quality control issue that had been hindering productivity. The solution was to use a Yamaha YK-XE Series Scara robot with the RCXiVY2+ vision system and a YRG Series electric gripper to assist workers in inspecting the molded parts. With the help of the robot, the inspectors were able to detect casting defects and determine their causes precisely so that they could be rectified quickly. In addition to improving quality, the inclusion of the robot in the process also helped to increase production output.

The quality control problem arose from the fact that a single employee was responsible for inspecting and packaging the items produced by an injection molding machine with multiple mold cavities. At the end of each injection molding cycle, a removal robot takes all the parts from the machine and places them on a conveyor belt. The conveyor belt drops all the molded parts into a container from which the operator removes, inspects and palletizes them one by one. In this situation, it is impossible for the inspector to trace recurring defects back to the cavity in the injection molding machine that caused them. As a result, a large number of faulty units could be produced before the cause was identified, leading to a waste of resources and also increasing the possibility of faulty units leaving the factory.

To improve quality control, the particular cavity from which a faulty part originates would have to be identified. This is beyond the capabilities of a single operator who is under pressure to pick and pack items at a speed compatible with production output. Another approach could be to inspect each molded part as it is ejected from its cavity before it is placed on the conveyor belt with the other parts. This would likely require multiple inspectors, which would increase the overall cost of manufacturing.

Thanks to the speed of the robot, the parts could be palletized in the correct order and made available for inspection. © Yamaha

Yamaha's YK-XE Scara robot provided a solution that allowed items to be palletized at high speed and removed directly from the conveyor belt. This allowed them to remain in the same order in which they came out of their cavities. In this way, each item that was inspected and found to be faulty was assigned directly to the cavity that caused it, enabling the cause to be rectified quickly. The integrated RCXiVY2+ vision system can simultaneously track the position and orientation of up to 100 parts on the conveyor belt so that the robot picks up and palletizes each moulded part quickly and accurately.

The YK-XE Scara series includes robots for payloads up to 10 kg and offers arm lengths between 400 mm and 710 mm. These robots help factories adopt robotic technology at an affordable cost. They offer valuable features such as ample cabling and pneumatic hoses to control the end effectors. These can be routed through axes and end caps, increasing convenience and protecting against breakage and disconnection. The acceleration of the robot arm is automatically adapted to the weight of the payload to ensure maximum speed and avoid vibrations, enabling high accuracy. Other series in Yamaha's Scara family include the omnidirectional YK-TW series, which enables large pallet formats.

Use of an image processing system

Another case involved a company that manufactured electronic displays used in automotive instrumentation. The display device consists of an assembled circuit board, a pointer mechanism, a screen-printed dial and electrical connectors. The team wanted to increase production output by using Scara robots to quickly pick and palletize the assembled units coming off the production line. The pallets are then transported to the next processing stage.

It was clear to the team that a vision system would be required to ensure that the components were correctly aligned for error-free palletizing, and the RCXiVY2+ robotic vision system was chosen. Camera management and image processing are integrated into the RCX340 controller, which also runs the robot application. The camera can be attached to the robot or mounted on its own bracket. Yamaha's system has special image processing commands that simplify programming. The team was able to get the system up and running in a short time.

The low cost of small Scara robots for light production and packaging tasks enables more flexible approaches to the introduction of automation in industry. Speed, accuracy and reliability are known strengths of robots. They can also provide information that helps to improve process control and maintain production flow. As small Scara robots enable flexible automation at low cost, they can also be used to advantage for smaller quantities or low-cost requirements.

Machine vision is a critical resource in many handling and packaging applications. Moving vision control with robotics-specific vision commands to the robot area can speed and simplify integration and improve system performance.