Workplace Optimization Using a Collaborative Robot

Abstract

The study describes increasing the productivity of the production process using robotization. The application of robots in the manufacturing process and logistics requires a very thorough analysis and knowledge of manufacturing processes. The theoretical part describes the knowledge gained from the scientific literature concerning the robotization and technical standards of the Czech Republic. In the practical part there is an analysis of the current situation – i.e. defining a selected production line and selected workplaces on these lines, especially in terms of activities. The activities performed at these sites and their duration are crucial for determining the suitability of the site for implementing the robot. In the next chapter, the workplaces are evaluated in terms of activities that can be transferred from the operator to the robot to determine which percentage replacement of the operator is feasible. Thus, the selection of suitable activities (processes) for automation will be made at the workplace. The technical solution of the implementation is also proposed for the selected workplace. To achieve a successful application of the collaborative robot into the production process, it was necessary to change the location of the workplace, including electrical and air distribution, investment in a new conveyor and laser gauges. The new layout was based on saving space and saving human influence in the production process. The whole study shows a systematic approach to the introduction of the above-described issue.

1 Introduction

Due to the ever-increasing pressure to improve productivity and production quality, there is a growing interest in the use of automatic production equipment. Another reason is, for example, increasing the competitiveness of companies and keeping them on the financial market. Automation leads to changes in production, technology, and overall logistics processes, not only in engineering but also in other sectors. Manipulators and robots are increasingly gaining ground in various industries in the automation of both whole processes and individual process operations. Improvement of efficiency, quality and labor productivity cannot be ensured without modernization, reconstruction and automation of production facilities.

This publication analyzes the current process in the workplace. The assignment of the project was to apply a collaborative robot to a workplace involved 2 workers. The aim was economic savings. The main requirement was an economic return within a maximum of two years. For a successful application, it was necessary to change the production layout of the workplace.

2 Literature Review

Without perfect knowledge of production operations, it is not possible to interfere with production processes [1].

The process is a general term for the gradual flow of events, states, activities or work. In the real world, there are several types of processes, so the term process is used in practice in different meanings [1, 2].

The production process is essentially the sum of all processes in the transformation of materials and raw materials with the participation of labor and means of production into a product. The production process has two interconnected components - technological and working processes [3, 6]. One possible way of analyzing a manufacturing process performed by a worker is described in Porter’s reference. He uses the Basic MOST methodology to obtain concrete real data with those further worked to rationalize the process [4, 10, 14].

In his book, Porter defines the application of the robot to the manufacturing process as a step that eliminates the human aspect and the possibility of creating manufacturing errors.

The official definition of a robot, invented by the International Organization for Standardization of Robot Definitions, is according to ISO 8373 as follows [4, 5, 7]: by standard, an industrial robot is an automatically controlled, reprogrammable multipurpose manipulator, programmable in three or more axes, which can be either fixed or mobile, for use in industrial automation [5, 8]. Industrial robots and manipulators are manipulation mechanisms that can be divided and described by function, design, application possibilities, degree of autonomy, control level, etc.

In addition to the basic classification and classification according to the concept, we can further specify the different types of industrial robots and manipulators according to the individual characteristics, which further the whole group branches into subgroups from the simplest single-purpose feed manipulators to cognitive robots, equipped with the ability of perception and a certain “rational thinking” [4, 5, 8].

Programmable manipulators - are controlled by a programming device.

Design, drive, and function are independent of the machine being operated [6].

Handling abilities - grasping and moving objects, various assembly operations, adjusting objects, handling auxiliary objects such as tools [8].

3 Research Methodology

If we want to regulate, evaluate and measure processes, we must measure their performance. An important thing to measure performance is to first determine the measurement points. Both outputs and process inputs must then be measured. The determination of the measuring points depends on the required surveyed indicators and methods of analysis. The number of measurement points must correspond to the possibility of variability during the process. When measuring only inputs and outputs, it would never be possible to identify the causes of deviations from requirements that may arise at any point in the process. Automation, among other things, allows ensuring greater safety, health, comfort and well-being of people at work because it deprives workers hard, health, and life-threatening or fatigue work [10, 15].

The process is effective if its output reaches planned and required parameters, both qualitative and quantitative. On the other hand, the process is effective if all the required and planned parameters achieve the added value that the internal or external customer appreciates. Considering the Pareto principle on process efficiency, it can be said that a process is optimally effective if 80% of the result is obtained at 20% of the input effort [2, 15].

According to [15], the process can be evaluated in two ways:

• 1. Evaluation of processes in terms of performance (efficiency, process efficiency).

• 2. Evaluation of processes in terms of variability (process variability due to internal and external influences).

Electromagnetic compatibility (EMC) is another thing that needs to be addressed in terms of safety during implementation. The design and construction of the robot must avoid dangerous movements or situations due to the expected effects of electromagnetic disturbance (EMI), radio frequency disturbance (RFI) and electrostatic discharge (ESD) [7].

When a robot is implemented on site, EMC measurements must be made, and safe values must be achieved. In addition, when implementing a robot on a line that is somehow connected to the robot by software, for example, an EMC measurement for the entire system (robot + line) must be performed. Implementing a robot is, therefore, a very complex legislative issue and it is important to realize which applications robot will be used with, what tools it will work with, etc. It is therefore advisable to carry out a thorough analysis of the workplace where the robot will work and all processes, operations, and activities that robots will perform [7, 12].

Since the aim of the work is to design a suitable robot for implementation in the workplace, it is necessary to obtain the necessary information about the safety requirements that are imposed on it and that are set by certain regulations. Although the robot is constructed and its maximum potential will only be used to work side by side with people in direct contact, it was necessary to find an appropriate regulation that sets out the rules allowing it. Regulations mean directives, laws, decrees, standards, etc.

The collaboration between humans and robots has been described by the authors of EN ISO 10218-1 and EN ISO 10218-2 standards. Already in these standards the requirements of operational cooperation (4 basic principles) of humans and robots are defined [7, 12].

• Principle 1 - Safety monitored stop - see article 5.10.2 in EN ISO 10218-1 and article 5.11.5.2 in EN ISO 10218-2.

• Principle 2 - Manual guidance - see article 5.10.3 in EN ISO 10218-1 and article 5.11.5.3 in EN ISO 10218-2.

• Principle 3 - Speed and position monitoring - see article 5.10.4 in EN ISO 10218-1 and article 5.11.5.4 in EN ISO 10218-2 [11].

3.1 Measurement

Based on production observations, analysis of production videos and acquired files from the company, it was possible to describe all activities performed on the lines. A table has been created for each selected workplace, listing all activities performed by two operators. Each activity is assigned a duration. The duration of each activity in the tables was obtained by the arithmetic mean of several values of the duration of the activity, which were obtained from the analysis of video recordings.

MOST is a sensitive method. This feature is very effective in evaluating alternative methods of performing operations with respect to time and cost. The MOST analysis is, therefore, more economical and less demanding compared to other methods. For example, the following general motion sequence model illustrates:

$$ {\text{A}}_{6} {\text{B}}_{6} {\text{G}}_{3} {\text{A}}_{10} {\text{B}}_{0} {\text{P}}_{3} {\text{A}}_{0} \ldots \ldots \ldots \ldots 280\;{\text{TMU}} $$

(1)

Movement of a heavy (10 kg) object from the pallet lying on the ground to the workbench with bending (B6) and walking (A6, A10). High index values indicate that this work is ineffective and ergonomically unacceptable (especially during frequent repetitions) and therefore a rationalization of the workplace is required. The movement of the object will be more effective with less fatigue after installing the roller conveyor to the workbench:

$$ {\text{A}}_{3} {\text{B}}_{0} {\text{G}}_{3} {\text{M}}_{6} {\text{X}}_{0} {\text{I}}_{0} {\text{A}}_{0} \ldots \ldots \ldots ..120\;{\text{TMU}} $$

(2)

The fact that MOST is a sensitive method greatly increases its value as a means of measuring labor productivity.

In what situations can the MOST method be used? As manual work usually involves rotating some cycles from one to the next, the MOST method can produce, with its statistically determined times, total times comparable to much more detailed methods for most manual operations. Therefore, the MOST method is suitable for any manual work that involves changing from one cycle to the next regardless of the length of the cycle. Basic MOST should not be used in situations where there is a short cycle (usually within 10 s) and is repeated periodically for a period [3, 13, 15].

3.2 Description of Analyzed Workplace

Two operators work in the workplace because of the handling of a heavy object. The start of the operation is the turning of the air conditioning unit which weighs 20 kg. Then the worker presses a button that is connected to the information system. It transmits information about the position of the unit on the production line. the signal is transferred to a printer that prints four nameplates. These labels are removed by the operator number 2 and glued to the cardboard box. After sticking the labels, the scanner reads the production label, which sends a finished status signal. This finished unit leaves for other workplaces.

Figure 1 shows the original state of the workplace with two workers.

Fig. 1.

Layout before.

The main task of the successful project was to install a robot to replace both workers. At the same time, the line clock is not disturbed. When installing the robot, it is necessary to think over how the robot recognizes the position where to stick the nameplate. The internal rule of the company is the return of the rationalization measure within a maximum of 2 years.

3.3 Time Measurement

Among the most used methods of time measurement in companies are chronometric. In practice, the application of these methods often fails to observe basic statistical principles and the time standard is determined based on one measurement.

Operation analysis consists of a series of sequential models describing the movement of objects operating. The total time of the complete MOST analysis is given by summing the times calculated from each sequence. The resulting operating time can be left in TMUs or converted to hours, minutes, and seconds. It’s worth emphasizing that this time reflects pure work content at 100% performance. The final form of the time standard will include time allowances that include PRD: personal time (P = Personal), rest and exhaustion (R = rest) and unavoidable time loss (D = Delays). Therefore, if the normal time TMU = 1 h and the expected time addition of PRD is 15%, then the final time standard will be 1.15 h [1, 16].

In general, the aim is to replace the process of gluing production and packaging labels to packaged units. See Fig. 1. During monitoring and analysis of the process, problems were recorded that prevented the robot from being impelled. This procedure must always be followed when applying a new type of device.

Table 2 describes the problem. All these problems must be solved before the application of the robot.

Table 1. Summary D5 line.

Table 2. Mapping problem for the application of robotization.

3.4 Mapping of Production Workplace

Another procedure was to create a model in a graphics program. The created model of the workplace serves as a point of reference when changing the layout. Moving individual parts of the production line changes the complete layout. It is always necessary to check how much space there is in the given part of the line for moving boxes and shelves. During the move, it was very difficult to deal with the electrical wiring. Eventually, they had to be completely changed.

In the case of the final design, we work with the created part of the layout and try to place it in the layout of the entire hall. This analysis was performed in VisTable 2019, which can identify material flows.

Figure 2 shows a model of the workplace before the application of robotization. The original layout of the workplace was 15 m². This made it very difficult to load the material and move around the workplace. Workers at this workplace were forced to walk for material up to 3.5 m from their workplace. Creating the model was a clear impetus to the application of the robot, which would replace the workers.

Fig. 2.

Model of the old workplace.

When selecting the robot, mainly parameters such as the size of the serviced space by the robot and the load-carrying capacity of the robot needed for blade handling were considered. The speed and accuracy of today’s robots are so high that when selecting a robot for a workstation where ±1 mm accuracy is required, all types of robots considered meet the requirements. The glued manufacture labels which have specific codes are then automatically read by another machine. If the deflection is > 1 mm, the production code is not read, and the production line is stopped.

3.5 Selection of a Suitable Robot Type

When solving the robotics design of the workplace for gluing production labels, the requirements of the contracting company were followed. For robotized workplaces, it is important to know the component used in the workplace. The goal is to make the robot to be able to grasp the labels from the printer and stick them to the exact ones on the wrapped unit. These locations are checked with a laser reading the exact position according to the checkpoint. It was difficult to establish this checkpoint because the workplace produces different types and shapes of products. Catching the labels has been solved by using suction cups that attach the label to the non-sticky portion and place the sticky portion on the box. These suction cups were manufactured internally using 3D printing. Figure 3 shows the final solution for the robot.

Fig. 3.

Final robot application.

The robot was selected based on cooperation with the supplier company. The type of robot was chosen to suit the length of its arm and also to keep the operation costs low. The frame construction had to be designed to maintain the weight of the robot.

4 Results

The whole study is based on the topic of the dissertation. Specifically, the methodology of the procedure for the successful application of robotic equipment was used. First, the original workplace was mapped. The layout of the workplace was drawn into a simulation program and the current state was modeled. The assembly process of the workers was very accurately mapped by the MOST methodology, which taught the default value, which symbolized the target speed of the robot speed.

In parallel to the time analysis, there was an analysis of the robot selection, where the main factors were speed efficiency and, of course, cost. The main condition for changing the process and the investments required for this is to guarantee a payback period of 2 years. It is a question of a lifetime whether the robot will not be broken in the process and will not disrupt the production process.

The requirement for workplace robotization was also based on the knowledge that workers indirectly adhere to the production cycle. In the early hours, there was a situation where the workers worked very quickly and then waited for the previous workplace. In the afternoon, these workers did not manage to suffer due to fatigue and exhaustion. The result of this finding confirmed also by the MOST analysis was that workers do not work with even power. The applied robot does the same job as it describes the workflow for employees. However internal data is forbidden to publish.

5 Conclusion

In every project, there is always the most important part of the process analysis. The number of analyses performed depends on the complexity of the process, but nowhere is exactly given how many analyzes are needed. Based on a practical study, the methodology for the implantation of a robotic solution could be described as follows:

Analysis of layout ► Time analysis of the current process ► Application of 5S methodology ► Analysis of performed tasks ► Time analysis of the new process ► Selection of a suitable robot type ► Economy calculation ► New layout design ► Robot application ► Creating standards TPM

The company’s goal was to replace 2 workers by the robot. The price of the two workers was 900,000 CZK/year. The robot cost 1.5 million CZK. Costs of layout reconstruction and robot installation 200,000 CZK. Operating costs 200 000 CZK/year. Acceleration of production and a 16% reduction in scrap yields a profit of 130,000 CZK/year. The profit from saving space is 10 000 CZK/year. The return of the robot is, therefore:

$$ \textbf{16}*900000/12\, + \,200000\, + \,\textbf{16}*2000000/12 - \textbf{16}*130000/12 - \textbf{16}*10000/12 = {\mathbf{Robot}}\;{\mathbf{cost}} $$

(3)

This was accomplished. The total investment will be a return within 16 months. At the same time, the layout of the workplace was saved from 15 m² to 9 m². In the time analysis, 5 s were saved. This accelerated production and at the same time automated it. Figure 4 shows a comparison of the original and the new time analysis and compare the timing of the robot and the two workers.

Fig. 4.

Picture of process analysis.