Automation – potentials, classification of human-robot interaction and assembly system design
Why is the use of robots for automation often considered when designing assembly systems? What are the different operating modes of human-robot interaction for automation? And how is a mounting system designed? We answer the questions below:
Potential of automation
The potential of automation basically lies in maintaining competitiveness and reducing physical and mental stress on people. Competitiveness can be maintained by maintaining a consistent level of quality, improving quality through high precision, reducing throughput times and increasing output. Physical and mental stress can be reduced by an ergonomic workplace design and appropriate challenging work content for people.
Classification of different operating modes of humans and robots
Industrial robots and cobots, among others, can be used to automate assembly systems. An industrial robot is a programmable machine that handles, assembles or processes workpieces. The main components are the manipulator (robot arm), effector (gripper or tool) and the controller. The term cobot also refers to an industrial robot that works together with people and is therefore not enclosed by protective devices. In the area of human-robot interaction, there is a classification into three operating modes:
- Human-robot coexistence: side by side, separate workspaces, sequential work execution
- Human-robot cooperation: cooperation, intervention zones, parallel work execution
- Human-robot collaboration: collaboration, shared workspaces, parallel work execution, tactile interaction
The more cobots and workers have in common (workspace, execution of activities, tactile interaction), the lower the performance speed of the robot may be, for example. In addition, more sensors are needed to monitor specific robot data (pressure, force, position, etc.) and to detect people.
Design of assembly systems
When designing an assembly system, the assembly process should be divided into product-side assembly units and process-related assembly functions. VDI 2860 defines five assembly functions for this: joining, handling, checking, adjusting and auxiliary operations. When designing the individual assembly functions, different forms of interaction between humans and robots can now be designed based on the different operating modes of industrial robots and cobots. This raises the question of which features of an assembly activity speak in favor of low-effort automation and make the use of robots appear sensible in principle. This question will be addressed in the next section.
Characteristics for the basic suitability of a robot application
Which features indicate the basic suitability of using a robot for assembly automation? Here, the assembly object, the assembly process and the provision can be distinguished.
Assembly object
With regard to the assembly object, it makes sense to keep the number of manageable components as low as possible. The object should be dimensionally stable and insensitive to visible or functional damage and should not weigh more than five kilograms and be between one and 500 millimeters in size. It should also provide a way to grip, align, and position. Small deviations in component tolerances and consistently high component quality with a small number of defective components also speak in favor of assembly using robots.
Assembly process
From the point of view of the assembly process, a sufficient cycle time is particularly important. Cycle times that are too short result in the robot arm moving at too high a speed and thus in higher risks due to higher speeds. Simple, linear (joining) movements without rotation or path movements as well as continuous guidance of the movement path speak for low-effort automation. In addition, the movement space for joining and positioning should be collision-free and easily accessible. A small number of variants is just as helpful as the lowest possible joining force or torque. Constructively provided joining aids and the lowest possible precision requirements can simplify automation. Controls or special operations can in most cases be carried out by measuring devices using sensors, but the absence of such activities facilitates the use of robots.
Deployment
The place of staging should be fully accessible and the staging should take place in the magazine, where the location and position of the components is clearly defined. The individual objects should be prevented from getting caught, jamming or sticking when they are separated. In addition, the provision should be integrated into the entire logistics concept and additional processes should be avoided.
Detailed planning
If the result of the rough estimate is positive, the system should be planned in more detail. After defining the process, the (non-)separating protective devices, the component weight and geometry, the gripping technology and gripper changing systems, the parts supply and removal, cycle time, work and axis areas, safety-related functions as well as the type, manufacturer and operating mode can be defined. As part of the safety investigation, a risk assessment should be carried out for the entire system, consisting of the robot, tool, components and workplace environment, and appropriate protective measures should be derived.
Conclusion
Using the features shown, it is possible to quickly assess whether the use of robots with little effort is fundamentally possible and sensible. After this first, rough assessment, a detailed check and detailed planning should always be carried out, in particular a risk assessment and a closer look at the overall system. A conclusive answer to the question of the usefulness of using robots can therefore only be given within the framework of detailed planning after thorough planning and evaluation of the entire assembly system.
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