ERGONOMIC CASE STUDY OF AN ASSEMBLY LINE AND SOLUTION IMPLEMENTATION IN ECCO FINISHING / CARLISLE FLUID TECHNOLOGIES (CFT)

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Bachelor Degree Project

ERGONOMIC CASE STUDY OF AN ASSEMBLY LINE AND

SOLUTION IMPLEMENTATION IN ECCO FINISHING / CARLISLE FLUID TECHNOLOGIES (CFT)

Bachelor degree project in Product Design Engineering

Level G2E 30 ECTS Spring term Year 2020 Erika Salguero Norling Daniel Kaufmann Dávila Supervisor: Ari Kolbeinsson

Assistant supervisor: Francisco García Rivera Company supervisor: Walter Låstberg

Examiner: Anna Brolin

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Assurance of own work

This project report has on June 3 been submitted by Erika Salguero Norling and Daniel Kaufmann Dávila to University of Skövde as a part in obtaining credits on basic level G2E within Product Design Engineering.

I/we hereby confirm that for all the material included in this report which is not our own, I/we have reported a source and that I/we have not – for obtaining credits – included any material that I/we have earlier obtained credits within my/our academic studies.

Erika Salguero Norling Daniel Kaufmann Dávila

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Abstract

The main objective of the project is to identify, study, and understand potential improvements of the Sealing Applicators production line of Ecco Finishing/Carlisle Fluid Technologies Company. The ergonomic cases in the plant, established as working postures, will be analysed using manual methods and virtual simulation tools. The analyses will be based on the measurements and depth of the data that is compiled during the visits to the plant. The software used to perform the ergonomic simulations, Siemens Jack 9.0, also has its limitations for each working posture of the production line, as some data for building the postures is missing due to limitations of the measurement taking process. The final result of the project is set of data that includes a solution implementation of the working postures analysed, also developed with simulations in Siemens Jack 9.0, of the production line, that could improve daily working life of the workers in the plant as well as management of the company. The project results reveal a need to add as well as alter elements of the workstation to make sure that the posture the user performs when working adheres to ergonomic principles.

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1. Introduction

The project will be developed in conjunction with Ecco Finishing AB/Carlisle Fluid Technologies at the company’s main production facility in Skara, Sweden. Ecco Finishing AB has manufactured application tools for liquid paint, wax, glue, and sealing materials since 1931. The company is a privately held and in a very specialized sector of the market that holds a profitable position both in Sweden and worldwide. At the same time, it is a small company with an employee base of only 26 people. Since 2019, it is also part of the Carlisle Fluid Technologies Group. Due to higher demand on their sealing applicator line expansions are planned in the future and the company is looking for solutions and improvement in the ergonomics aspect of the assembly line.

As a result of the specialized nature of their products, the production methods at the plant are completely manual. Because of this, there is the possibility for improvements in efficiency and worker health by creating an ergonomic case study of the Ecco Finishing/Carlisle Fluid Technologies sealing applicators production line.

The plant space for this production line is much reduced, and the company is looking to improve efficiency as a production increase is expected due to the demand of the product and potential expansions of the production line. The main objective of the project is to find areas of improvement in the production process at the plant; study and understand them, and suggest changes that could be implemented to increase productivity and ergonomic comfort to the workers. One important aspect of the project is the study of the workers themselves and how their postures affect the efficiency and productivity of the assembly line, a posture is defined as “the way in which someone usually holds their shoulders, neck and back, or a particular position in which someone stands, sits, etc.” (“posture”, n.d.). The main stakeholders of the project are the directors of operations and the employees at the Skara plant. The overall strategy and approach will be to first read up on the topic; how human ergonomics function and what problems we would be able to find during our visits to the production facility in Skara initially observing and making notes of the current situation in the plant. After this process, measurements of the working station and the workers will be taken. From the visit to the plant, working postures will be selected for further analysis and based on the theory; ergonomic improvements will be applied to them to make the less harmful for the worker.

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1.1 Problem description

The project consists of an analysis of the potential postures that the worker could perform during the assembly line. The production process completely manual, and usually, the workers assume postures that could cause injury if performed repeatedly or for long periods. All the tasks performed are mechanical, following established steps, and require concentration and fine motor skills so that they can be performed successfully. The assembly process does not involve building the complete applicator from start to finish. The process involves building each one of the components separately as many times as the order requires and after each first assembly is finished they are then combined to create a final product. Because of this, the worker assumes different positions on each different step of the process for a determined period that could cause health problems in the short or long term. The following pictures show the workspaces that comprise the study (see Figures 1.1-1.4).

The initial hypothesis for the analysis, made after reading various sources such as Delleman, Haslegrave, and Chaffin (2004). “Working Postures and Movements” and Elbert, Kroemer, and Hoffman (2018). Ergonomics: “How to Design for Ease and Efficiency” is that problems will be found specifically in the neck and back of the workers, due to them having to bend the neck at unnatural angles for extended periods to be able to focus on the fine details of building the assembly. Another aspect that needs special attention is if any worker that has been with the company for a long time has experienced any injuries, and what have they done to prevent further incidents and to not make the injury itself worse.

Figure 1.3. Testing area Figure 1.3. Electronics working area Figure 1.4. Sealing applicator production area

Figure 1.1. Main working space Figure 1.2. Testing area

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1.2 Strategy and approach of the project

The strategy and approach will be to first read up on the topic; how human ergonomics function and what problems we would be able to find during our visits to the production facility in Skara. After the research is conducted a questionnaire and a list of the tasks to be performed during the visit will be made with the prime objective being to successfully observe and note on the current situation at the plant. The tasks consist of initially observing the entire production process of one of the sealant applicators from start to finish. As the demonstration is going on notes and pictures will be taken regarding the tasks the worker performed and asked questions on their physical well-being as well as how tiring his work would tend to be. The working areas also need to be measured so that all of the problematic tasks can be analysed using specialised software. During the entire process, the most problematic postures will be hypothesized based on the research done previously and will be the main focus of the next steps of the project. The methodology for the project will be analysed and explained in the background section of this report.

The analysis for each task will be conducted using both manual and virtual methods, to create a point of comparison between the two techniques. The virtual analysis will be performed using Digital Human Modelling, specifically, an ergonomics analysis software: Siemens Jack 9.0; developed by Siemens (www.plm.automation.siemens.com); due to its simplicity and completeness in terms of analysis tools. The software uses virtual manikins to replicate and analyse loads and the potential problems that incorrect postures might create on the human body.

Manual calculations will also be used to determine the potential risks to the workers conducting the tasks and to do an initial analysis and hypothesis working with the simulations on Jack 9.0. The initial posture simulations and risk assessment will be made using the measurements of the worker that performs each posture at the plant.

The solutions will be made based on anthropometric measurements done with a confidence ellipse; according to Walter, Gafni and Birch (2008), a confidence ellipse is a statistical method that allows for the analysis of the correlation of two sets of linear data using an ellipse on a Cartesian plane. An example of a basic confidence ellipse is shown in Figure 1.5. The method allows any future worker at the plant can use these result to their advantage, setting healthier postures and being more comfortable at their job.

Figure 1.5. Confidence ellipse. Walter, Gafni and Birch (2008)

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5 The work needed for the analysis will be based upon previous successful studies, as the methodology has already been proven to be useful and therefore the probability that results of this study will be successful will be more effective. The study made by St-Vincent, Lortie and Chicoine (2001) titled Participatory Ergonomics Training in the Manufacturing Sector and Ergonomic Analysis Tools is a useful starting point as it follows a very logical sequence. The sequence analysed by the study (see Figure 1.6) begins with research and planning on how the study will be implemented as well as how to effectively collaborate with the subjects of the study themselves. The analysis of the work routines to find problems and hazardous conditions is also performed in collaboration with the workers. This study relies on existing research to identify and understand the problem, creating an effective basis for the solutions. The collaboration with the target audience of the study will also help adapt the methodology to best fit the environment and the results to the users.

Figure 1.6 Workflow for the study conducted by Vincent, Lortie and Chicoine (2001).

Another methodology (see Figure 1.7) in which to base for the project’s methodology is the study conducted by Shinde and Jadhav (2012) titled Ergonomic analysis of an assembly workstation to identify time consuming and fatigue causing factors using application of motion study. The study follows a similar process to the one conducted by St-Vincent, Lortie and Chicoine (2001) however this one only documents the postures using video. The method is understandable as recording a video is the main objective of the study. The study or workstations specifically makes this source useful as this study is working on making changes and improvements to the workstations. The documentation process shown by Shinde and Jadhav (2012) works, however, since the focus of the project is the simulations the video aspect itself is not so important and can, therefore, be minimized.

Figure 1.7. Workflow for Shinde and Jadhav (2012) study.

It is also important to analyse the methodology of a study that worked with computer-aided ergonomics, as this is the main objective of the current study. The study conducted by Gonen, Oral, and Yosunlukaya (2016) Computer‐Aided Ergonomic Analysis for Assembly Unit of an Agricultural Device is a similar study to the one that will be conducted at the plant at Skara. The methodology in this study (see Figure 1.8)

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6 involves analysing postures directly in the production line and then replicating them in a Digital Human Modelling software to be able to use the analysis tools to find concrete data on which postures work and which don’t. The process used in the study (Gonen, Oral, and Yosunlukaya (2016)) is similar, only the software used is different.

Figure 1.8. Workflow for Gonen, Oral and Yosunlukaya (2016) study.

Last, but not least, according to Elbert, Kroemer and Hoffman (2018), there are different steps to identify or prevent ergonomic problems for designs or working stations. The setup currently being used at the assembly line of the company does not need major changes such as a complete reorganization of the production line or changes of the whole furniture. Improvements that could be needed are because of injuries that workers could experience associated with improper use of the material provided by the company. This process for the improvement of a product or a system is shown in Figure 1.9. This method was selected due to its simplicity, clarity which gives the possibilities of iterative design processes while at the same time having a rigid structure to each of its steps. Any ergonomic or product design problem can implement this method successfully and due to its simplicity, any changes can be easily implemented without compromising the process. The most important step is number 3, identifying the problem because misunderstanding the problem could cause a variation in the whole process of solving it and miss the goals (Elbert, Kroemer and Hoffman, 2018).

Figure 1.9. Steps to identify an ergonomic problem.Elbert, Kroemer and Hoffman (2018).

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7 Siemens Jack 9.0 (Jack User Manual Version 9.0, 2017) is the software that will be used in this project. The methodology used will be adapted from these four sources seen above so the implementation is much more effective than just using one methodology. Based on the previous similar studies, the flowchart to follow during this project is the following (Figure 1.10):

Figure 1.10. Workflow developed for the study.

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2. Literature review

2.1. What is ergonomics?

One theoretical and general definition for “ergonomics” is the scientific study of people and their working conditions, especially done in order to improve effectiveness”

(“ergonomics”, n.d.). But as this is part of a technical environment, a more practical definition could be according to Berlin and Adams (2017): “Ergonomics can signify anything from the physical activities and demands of the job, to how the human mind understands instructions and interfaces, to how work organization, teamwork and motivation influence human well-being and efficiency.” In layman’s terms; ergonomics is the application of human body health to any kind of activity.

Ergonomics is usually divided into three different disciplines (Berlin and Adams, 2017):

 Physical ergonomics is the study of how the human body reacts to physical load or working demands. This involves different important parts of the ergonomics as anthropometry, postures analysis and biomechanics.

 Cognitive ergonomics is the study of the interaction between humans and objects, environments, tasks, jobs and systems through their cognitive abilities. This involves such as human perception, mental workload, decision-making, memory or reasoning.

 Organizational ergonomics is also known as macro ergonomics and it is related to sociotechnical systems theory, it explores the organizational context role of ergonomics with different stakeholders and agendas.

Ergonomics can focus on different aspects; this project will focus on physical ergonomics, specifically in working postures, in which the well-being of people at the workstation of a manufacturing process is analysed.

2.2 Observations

Observing the process and documenting the postures that the workers assume while working is an essential part of the analysis of the process. The observation work done is based on checklists made by organizations like OSHA (Occupational Safety and Health Administration) that specialize in work safety (Safety and Health Topics, Ergonomics, 2020). The assessment of the poses is done by analysing the neck, back, arm and hand positions of the subject basing upon the aforementioned checklists. The observation is a crucial part of the process (The role of observation in science, 2020), as observing is innate in humans, it is the first step of the process and the one in which the early thoughts are created. During the observation step, most of the information collected should be contrasted with a certain basis, the research was done previously and with the plan made before starting.

It is important to have a participant observation taking place in a qualitative research cycle (Qu and Dumay, 2011), in which it is more important to find the

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9 information with a certain level of quality rather than ending up with redundant or useless information. The participant observation’s process involves making questions, collecting data, compiling the information, analysing it and writing a report (Jaimangal-Jones, 2014). The process requires the analyst to get involved explicitly in the working process to make descriptive observations, varying the extent of participation between the worker and the analyst (Jaimangal-Jones, 2014). Participant observation does not interrupt the professionals performing their work and can observe when the workers make decisions and why those decisions were taken, so this can provide a better understanding of the workers through the analysis of their behaviours. But participant observation is not perfect, the analyst must be careful with the assumptions made that could lead to confusion and be sure of the information’s veracity, so the method requires qualified personnel with sensitivity, creativity and the ability to translate what they see into reliable information.

2.3 Interviews

Making an interview with the workers is an essential part of the analysis, where the information comes from about their feelings and thoughts, this helps understand parts of the information that do not translate well into concrete numerical data. The way of creating an interview is going to define the type of information gotten from the interviewee. The first step is to define the goals to reach with the questioning, identify the participants and decide if the questions are going to be open or closed, depending on the structure of the interview. Having a structured interview makes the interviewer read from a script and does not allow any deviation; all interviewees answer the same questions in the same order from a list (McNamara, 2009). Otherwise, the most common situation is to have a semi-structured interview (Louise Barriball and While, 1994) in which there are prepared questions, but through the developing of the interview could appear more questions that could be useful if the interviewee answers them and elaborates further on their answers due to the interviewee feeling that the new questions are more related to them as individuals. This makes the interview more flexible, accessible, intelligible and capable of bringing to light hidden facets of the interviewee and behaviours.

The structure of the interview should be (McNamara, 2009):

1. Introduction, explain the purpose of the interview and the format of the interview, so the interviewee can ask for any question before starting the interview.

2. Simple and descriptive questions, to get to know the interviewee and make them feel comfortable with the situation.

3. More difficult and sensitive questions. With these questions, feelings and thoughts are going to be reflected.

4. Concluding questions.

After defining the structure of the interview, writing a list of all the facts or information needed about the workers and the process, avoiding general information about the individual. This step is done after the observation period so maybe some of these questions will be already solved. The questions must be comprehensible to the

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10 interviewee and the interviewer must react sensitively to the different ways that the interviewee could understand the questions and the environment around them.

Defining the type of interview could be an informal, formal, open-ended interview, or fixed-response interview. In conclusion, the interview should be informal to let the worker feel comfortable and mixing open-ended and closed questions.

Different topics can be covered during an interview (McNamara, 2009):

 Behaviours questions, their performance during working is being asked for.

 Opinions, asking about what the worker think about the process of their work in general.

 Feelings, these questions are sometimes not necessary as the interviewee usually expresses their point of view by answering other questions, not specifically those formulated to ask for their feelings.

 Knowledge, so the worker could help the interviewer to know the process better through their knowledge about the topic.

 Background, more personal questions that could help the interviewer if the interviewee is the correct person to answer the questions. These questions are usually made at the beginning of the interview.

The attitude of the interviewer is also very important, they must seem as neutral as possible, without showing surprise or very pleased about an answer because this could influence future answers. In addition to this, the interviewer must learn ways to keep the discussion going, avoid questions that suggest the end of the interview if is not the case and know when to interrupt or focus in one aspect of the interview (McNamara, 2009).

During the process, it was considered to create the list of questions after the observations because if a previous list is created, some questions will be answered during the observations and the interview could not be as complete as necessary.

Applying the theory for creating an interview and also applying what has been observed previously during the observations, the following list of questions was created:

1. How much time have you been working in the company?

2. What steps in the manufacturing process do you feel you have problems carrying out?

3. Do you have any musculoskeletal injuries?

4. What parts of your job do you feel pose a risk to your health/wellbeing?

5. How many pieces do you assemble every day?

6. Which part of the production line do you think that needs to be modified?

7. From 1 to 4, how comfortable do you feel carrying out your work?

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2.4 Taking initial data and measurements

To design a productive and healthy production line, understanding the current situation is essential (Elbert, Kroemer and Hoffman, 2018). Knowing which methods to use is also very important. There are very different approaches and using all the available methods could be a waste of time, so studying them and then deciding which to use should be more effective on the final results. This also happens with the postures to be analysed, selecting those with a high chance of causing injury will make the results more efficient. Data collection involves a quantitative approach, which looks for measurements, or a qualitative approach, which involves interviews and observations that look for understanding the process and for reliable and useful information that cannot be measured with values (King Horrocks and Brooks, 2018). For analysing the assembly line, the documents that could be helpful can include the blueprints of the sealing applicator for the simulation, blueprint of the workplace and measurements of the objects used during the process, as tables or chairs.

Measurement is essential for empirical research and in this case, for the rear analysis of the postures of the workers. In ergonomics, measurements of body parts are an important part to be considered and should be taken carefully, following the correct instructions. Berlin and Adams (2017) establish: “Anthropometry is the study of statistical variation of human body dimensions and its implications on design. This concerns everything from workplaces, tools, vehicles and medical packaging to clothing.” (p.66).

From this research, the different body dimensions will be selected to measure them on the workers. All the dimensions that could be considered can be seen below, however, not all of them are used at the same time, and it depends on what part of the body or what postures are being studied (see Figure 2.2).

Figure 2.2. Different measurements for analysis. Pictures were taken from www.antropometri.se

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12 The measurements taken are going to be used only for the first part of the initial analysis. The control subject that is going to be measured at the assembly line will be used to represent the worker during the initial analysis and its simulations and will be the basis for further improvements of the postures. Measurements of the manikins for the posture improvements will be made by using a confidence ellipse based on the statistics of the Swedish population published on the website www.antropometri.se. The measurements taken from the confidence ellipse will be used to make sure that the solutions apply to a great majority of the people that decide to work in that position.

2.5 Manual methods for analysis

According to Berlin and Adams (2017), there are different established methods for analysing physical loading:

 Posture-based analysis o Lower Back Analysis

o Rapid Upper Limb Assessment (RULA) o Rapid Entire Body Assessment (REBA) o Ovako Working Posture Analysis (OWAS) o Hand Arm Risk-assessment Method (HARM)

 Biomechanics-based analysis o NIOSH lifting analysis

o Liberty Mutual manual materials handling tables

 Analysis based on a combination of environmental factors.

o Job Strain Index (JSI)

o Key Indicator Method (KIM)

o Ergonomic Assessment Worksheet (EAWS)

o Risk Assessment and Management tool for manual handling Proactively (RAMP)

The methods that are going to be used are REBA (McAtamney, Hignett and Hignett, 2004) and OWAS (Karhu, Kansi, and Kuorinka, 1977). REBA analysis method works by evaluating the entire body posture using the angle of each joint in the body to numerically evaluate risks associated with posture. RULA works similarly but without taking into account lower body angles. That is why REBA is the method selected instead of RULA as it includes also the analysis of the lower part of the body. OWAS is a similar analysis tool, also a very complete method and gives very reliable results, however, its focus is broader as it works in the entire posture and not on each joint and limb (Berlin and Adams, 2017).

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2.6 Virtual method for analysis: Siemens Jack 9.0

Siemens Jack 9.0 is a human simulations software developed presently by Siemens. The software simulates human interactions with objects by using human proportioned manikins that are manipulated or animated to create postures to analyse using the built-in tools (Jack User Manual Version 9.0, 2017). The manikin can also interact with objects imported from a CAD program to better simulate actions in an industrial setting, for example, the assembly of a piece of equipment. Siemens Jack 9.0 uses analysis methods that can also be performed manually; however, the data is taken directly by the program from the positions of the model, making the margin for error much smaller. The simulations work by using a manikin with the dimensions outlined either in the initial measurements or afterwards using the confidence ellipse. The postures are then simulated according to the reference pictures taken and the theoretical knowledge used to find how a person should work to prevent strain on the back, neck and joints. These postures can then be analysed using the following tools (Jack TAT Manual v9.0, 2017):

 Fatigue Analysis

 Lower Back Analysis

 Manual material handling

 Metabolic energy expenditure

 NIOSH Lifting analysis

 Ovako Working Posture analysis

 Predetermined time standards

 Rapid upper limb assessment (RULA)

 Static Strength prediction

 Force Solver

Depending on the results of the analysis the postures can be changed and adjusted accordingly. Siemens Jack 9.0 is a very specialized tool used to analyse ergonomics and therefore can be very effective when it comes to analysing and implementing changes to postures and working environments.

2.7 Posture improvements

Postures while working are usually adopted because the influence of the environment around the subject, so once the correct postures range is set, all the objects that the worker uses, are going to be converted into the new dimensions as much as they allow it to be performed. During the step of analysing the possibilities of posture improvements, the data managed is going to be the one provided by the confidence ellipse with 90th percentile, chosen as a measure of reliability due to a higher percentile being used commonly in engineering (Chakraborti and Li, 2012). The 90th percentile gives the information about almost all the Swedish population measurements, also taking into account the extreme values and making the postures relatively comfortable for these extremes, all the average humans will be covered. The variables to take into account when designing a working place are the anthropometry of the worker, the

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14 requirements of the job (visual or manual) and the dimensions of the workspace (Delleman, Haslegrave and Chaffin, 2004).

There are different parts of study in the human body when well-being postures are developed: head and neck, trunk, pelvis, leg and foot, shoulder girdle and upper arm, forearm and hand. The images that are going to be used to explain this theory part are taken from Delleman, Haslegrave and Chaffin (2004). When analysing the head and neck, the first element to think about is that neck pain is a common musculoskeletal health problem in working society (Hush, Maher, and Refshauge, 2006), so neck posture must be cared for. There are three different concepts to take into account: trunk inclination, head inclination and neck flexion, shown in Figure 2.3.

(Delleman, Haslegrave and Chaffin, 2004).

Figure 2.3. Trunk inclination, head inclination and neck flexion. Delleman, Haslegrave and Chaffin (2004).

According to Lee, Waikar, Aghazadeh and Tandon (1986), a study of electromyographic activity was done to investigate the peripheral nervous system and how the muscles are stimulated with different head inclinations, 25º, 45º and 65º to diagnose neuromuscular diseases, as well as determining their intensity and origin.

Figure 2.4. shows the results and it can be appreciated that for angles less than 25º there is not pain increasing, so angles below this quantity are safe for working postures.

Figure 2.4. Electromyographic activity in the cervical region for different inclinations over time.Delleman, Haslegrave and Chaffin (2004).

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15 The combination of trunk inclination and neck flexion leads to head inclination, some combinations are less harmful than others. While a human is standing, being straight without bending trunk or head is the appropriate posture, and having the trunk upright and the head inclined forward is better than inclining the trunk backwards and also the head. So, having the trunk straight is the healthier option (Delleman, Haslegrave and Chaffin, 2004).

According to Kroemer and Hill (1986), recommendations on gaze inclination roughly range from 15º above to 45º below the horizontal of eye height. The most favourable visual target height is 10 cm below eye height for an upright backrest. If the human is seated it is recommended to adjust the chair backrest between the upright position and one inclined between 10º and 15º backwards. Moreover, according to Snijders, Hoek van Dijke and Roosch (1991), neck twisting must be 20º or less because twisting beyond 35º causes neck muscle forces that cause pain and injuries in time.

In the trunk, Lower Back Pain (LBP) is the most common work-related health problem in the working world (Andersson, 1999), it is estimated in at least 70% of the population and 90% in the population exposed to physical loads at work, but with treatment, these complaints are reduced in 85% of cases and 4% become chronic. The trunk can be oriented in the three axes; laterally bent, forward bent and twisted. The range of motion of the trunk bending forward is 70º. This amount is inside the interval for working, and even this value is usually high for some activities. The range of lumbar trunk motion in lateral bending is 30º in young people and 20º in those older than 65 years old. The twisting range of motion in the lumbar area is limited to about 15º to avoid any risk of injury.

The pelvis is a part of the body that is important for sitting postures. To have the pelvis parameter correctly set, the sitting behaviour must be controlled. Some parameters that influence this are the perception of comfort, workstation layout, anthropometric measurements and training (Delleman, Haslegrave and Chaffin, 2004).

Efficiency could be improved and fatigue reduced if a worker does their job sitting instead of standing because standing requires static muscular effort to maintain a position that is reduced while sitting. Many assembly workers tend to sit in a forward position, avoiding the backrest because they are usually moving and applying force while working; they tend to do what is called “dynamic sitting”. The adjustments for a correct sitting-workplace are based on the health of the worker, the subjective preference and biomechanics of sitting, giving priority to subjective preference and hope to fit with biomechanics because workers health is a difficult task to measure. The body posture sitting should be with a trunk-thigh angle of at least 105º to place the pelvis in a neutral position and also set the spinal posture correctly (Delleman, Haslegrave and Chaffin, 2004).

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16 Adding a footrest to the workplace while sitting reduces anterior pelvic tilt, makes the supporting leg straighter and increases the plantarflexion of the supporting foot. If the footrest is also used while the worker is standing it reduces lumbopelvic constraint and helps to prevent discomfort in this region. A correct position for the footrest could be from 100mm to 250mm height in a net posterior rotation of the pelvis of 4º to 6º, tilting the platform about 15º. It is also very important to have enough toe space because the lack of it could cause the workers to deviate from neutral sitting or standing position, leaning forwards that means pelvis tilting and lumbar flexion that cause more stress on the spine (Delleman, Haslegrave and Chaffin, 2004).

Referring to the lower body, standing on a soft floor is less harmful than standing on a hard floor, this could signify a big change to people that work an extended period standing (Delleman, Haslegrave and Chaffin, 2004).

The upper arm’s, as it has previously said, the correct backrest inclination is about 15º and this inclination makes the upper arm be flexed by 5º more comparing a posture with anyone without inclination in the backrest. The correct angles are 25º or less for flexion angle and 15º to 20º or less for an upper arm abduction angle. Studies recommend arm flexion to be less than 15º and arm abduction less than 10º (Chaffin and Andersson, 1984).

Finally, forearm and hand posture, depending on the tool handle, the human body can apply different amounts of forces to use the tool. Power grasp involves digital and palmar opposition. This means that as much more precision that is needed, less force needs to be applied and vice versa, this is shown in Figure 2.5, obtained from Delleman, Haslegrave and Chaffin (2004).

While analysing forearm and hand postures, different terms are going to be used, in Figure 2.6, obtained from Delleman, Haslegrave and Chaffin (2004), these terms are visualized.

Figure 2.5. Comparison of force and precision in tool handling. Delleman, Haslegrave and Chaffin (2004).

Figure 2.6. Different terms in forearm postures.

Delleman, Haslegrave and Chaffin (2004).

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17 The posture in which the hand applies the maximum force is at 35º of wrist extension with a margin of 2º and 7º of wrist ulnar abduction also with a margin of 2º.

The elbow flexion for a correct working posture is 65º to 100º, so the working surface should be about 3 to 5 cm above elbow level (at 90º) (Delleman, Haslegrave and Chaffin, 2004).

The seat height (see Figure 2.7) is another measurement to keep in mind for sitting postures; it will define knees and feet angles. For an adjustable seat height, it will vary between 51 and 66cm height (G). Considering these measures, a space of 20 cm must be free between the working surface and the seat height in the meaning of the leg’s width (F) (Delleman, Haslegrave and Chaffin, 2004). In the following picture, these measurements can be easily understood and other measures are also explained:

Figure 2.7. Different measurements that can be changed in the workplace. Delleman, Haslegrave and Chaffin (2004).

2.8 Summary of literature review

When designing a workspace to promote good posture, anthropometry is a very important resource. It must consider measurements of all the population that work there, in this case, is the Swedish population of working age (15 to 64 years old), the postures involved in the work tasks and their safety.

The information outlined during the literature review in section 2.1. will be used to perform the analysis for the postures. The analysis using the data will be performed during the hypothesis when analysing the data with the manual and virtual methods and finally to design the potential solutions and advice to the stakeholders. It is also important to mention the useful material needed in a workstation, owning an adjustable chair and an adjustable table could be very useful for the ergonomic study, as they give the analysis a different point of view because you can adapt the workstations you have to the different humans. Plant layout improvements are not planned for this stage of the study, however, the suggestions and solutions posed can be applied to the results, and they are not limited to the current layout only.

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3. Initial data collection

During this part of the project, the information for the analysis is going to be taken, starting from the observation point to having interviews and taking measurements of the space, objects and humans (see Figure 3.1). The entire production process will be observed and documented using pictures, video as well as notes.

During the initial data taking the poses that the test subject maintains for long periods will be noted to analyse further on in the process. All of the data taken during the observation phase will be used to hypothesise and analyse on a list of the most problematic positions and to find the solutions to them. The interview will be performed after the observations to base its content in the information gathered on it.

Figure 3.1. Workflow for data collection.

3.1 Observations

During the first day of the visits to the plant, the entire facility was shown. The main focus was the assembly area of the sealant applicators that would be studied as well as the workers that were to be assessed directly. The first day consisted of observing and documenting the production process of one of the sealant applicators from start to finish. The subject, one of the senior members of the plant and also the one in charge of the sealant applicator assembly was the main focus of this day as the worker is the one who performed all of the tasks and explained the details of the production process and area itself. One important aspect to point out is that the assembly process is performed in stages, therefore in some days, some steps of the process are not done.

Each step of the assembly process was explained in detail and each posture that the worker took while performing it was documented through pictures and notes.

Every step that involved maintaining postures for long periods or those requiring large forces to be exerted were noted as of special importance to the analysis as more than likely these would be the ones that the project would focus on. Although the objective of the study does not cover workplace design the following factors are important to add, as they were mentioned during the observation and interview process. The electronics and soldering area does not have an industrial fume extractor, the only system present is a small fan. Observations suggest it might not be enough because a production line must always be well ventilated, especially one that involves hand soldering electronics. In addition to this, the lighting of the space seemed correct due to the orientation of the building, the abundance of windows, and the working hours which even in winter all include daylight, therefore, no additional lights are needed apart from those already present.

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3.2 Interviews

Interviewing the workers helped to understand what the real situation in the assembly line is because in this way the worker’s feelings and thoughts were expressed directly. Assumptions were made using the data gathered, but gathering information directly from the people who experience the problems of the work area could be a very valuable tool when relating it to the theoretical knowledge gathered previously. The interview was focused on a semi-structured one, there are prepared questions and if any new question occurs, it will be questioned (McNamara, 2009). The list of questions is not that long because people in the company were working so some important questions have been prepared to give the option of having new ones to ask the workers, just in case.

3.2.1 List of questions

The following table shows (Figure 3.2) the different questions prepared that were asked to the operator and their answers.

Figure 3.2. Interview results.

3.2.2 Initial conclusions

The interview was performed with the worker in charge of this assembly line after a couple of days of getting used to the process and the workers in the plant. This was done to let the worker be relaxed during the interview so the worker could answer the questions without any pressure and feeling free to make the answers longer or to explain any situation properly. During the interview, the worker showed some parts of the assembly working area that were not noticed before, such as the small fume extractor for the soldering area and the initial planning to move all the workspaces to make a continuous production line that could improve productivity. These answers were the ones looked for, to acquire more information about the process that could not

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20 be noticed during the observations and that will be needed for future improvements of the plant. This information gives the interviewer the point of view of the worker while doing their job and helps to get immersed into the real situation in the company.

3.3 Measurements

Measurements were taken during the second visit to the plant in Skara. These measurements were needed for later analysis, for creating the simulations in Siemens Jack 9.0 and analysing the postures, and to develop possible solutions, for these postures, that could be implemented. The measurements shown below were taken using two measuring tapes, a 50-meter tape used for measures for the blueprint and the other one, a 3-meter tape used for shorter distances and to measure the control subject and posture components. The area for the sealing applicators was the only one that was analysed in detail as that was the main focus of the study. The production line is only limited to this space at the plant for organizational purposes. All of the storage, tools, and work areas for the production of the sealing applicators are located here. The area itself has already been marked and separated by painting a rectangle in visible colours on the floor, making the process itself much easier.

3.3.1 Spaces

These space measurements are related to the working area and the objects the workers use during the assembly process. The dimensions of the objects are essential for the simulations and the analysis of the postures that the workers adapt, as well as for studying the possibilities and the range of work of the solutions, so the proposals do not make the company change the assembly line radically and these changes are reasonable with the material they have available. Measurements of the working table (Figure 3.3) and the complete working area (Figure 3.4) were taken.

Figure 3.3. Table measurements (cm) Figure 3.4. Working station blueprint (m)

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21 A technical datasheet was supplied with all the dimensions of the sealing applicator so it could be recreated for the analysis.

Figure 3.5. Sealing applicator dimensions (mm)

This information in Figure 3.3 and Figure 3.5 will be used for the simulation of the postures in Jack 9.0; a simplification of the object will be done.

3.3.2 Humans

These human measurements (see Figure 3.6.) were taken for the analysis of the postures taken during the assembly process, to determine which postures are potentially dangerous and which ones are not. The solution proposals will be based on the confidence ellipse to take into account the complete working Swedish population (15-64 years old).

Fig. 3.6. Model made based upon the measurements taken of the worker who demonstrated all of the tasks.

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3.4 Initial Postures

The following postures shown are the ones that during the observation process were seen as potentially problematic. The postures were divided into three categories as a hypothesis based on the research done previously, divided into levels of risk, how harmful they could be and if they are, in terms of ergonomics, correct or not. The initial assessment was made based on the angles of the arms, back and neck as these factors are usually the main focus of the analysis methods. The hypothesis (see 3.4.1, 3.4.2 and 3.4.3) represents an initial assessment and in no way will influence the final results;

some of the postures may probably seem riskier than they are once the analyses are performed. Each number represents a potential risk level for the user performing the posture, 1 being the least dangerous and 3 being the most. The postures were divided in such a way for classification purposes and to create an organized list of postures.

The 14 postures seen below are the ones that will be analysed using the methods outlined in the previous chapter. Each posture will be analysed using the manual methods and the results will be compared to the analysis done to a virtual model of the posture made in Siemens Jack 9.0.

3.4.1 Level 1

Posture 1. Screwing down the needles and their

packing spacer using a common precision screwdriver. Posture 2. Placing and screwing down the three housing cover plates with a common precision screwdriver

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3.4.2 Level 2

Posture 3. Ducking down to grab a

screwdriver from the other work area. Posture 4. Inserting the needle packings using a specialized tool to grab and insert them due to their small size and the precise tolerances of this part of the sealing applicator.

Posture 5. Inserting and pressing in the cylinder packing into the central body of the applicator.

Posture 6. Screwing down the three pre-assembled solenoid valve assemblies on the swivel housing using a common precision screwdriver.

Posture 7. Assembly of the electronics housing.

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3.4.3 Level 3

Posture 8. Hammering in the spray head locating

pins into the central body using a hammer. Posture 9. Assembling and labelling the wiring for the swivel body using plastic labels.

Posture 10. Preparing the wires for the swivel body using a wire stripping tool.

Posture 11. Tightening the connection points for the inlet and return of material to the applicator using a wrench.

Posture 12. Fastening the swivel lock to the central body and swivel housing while applying moderate force.

Posture 13. Inserting the nozzle head into the central body using moderate force with hands.

Posture 14. Inserting and removing the central body from the testing machine by inserting and tightening considerably three screws.

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4. Analysis and solution generation

The project involves an analysis of a situation along with an analysis of a working station, so the methods for solution generation cannot be the same as in a product design project. In this kind of project, the way of thinking must be different, although similarly, the process is also a convergent and divergent process, after searching for all the information needed for the analysis, the most valuable information has to be selected. Once the information is clear and organised, you look for ways of analysing it and how to get the results (see Figure 4.1). After analysing all the data with the methods selected, the interpretation of the results makes the analyst respond with ideation of the possible solutions for the problem and recreate them. If these ideas come to reality, they could become solutions, if not, this is a cyclical process in which many ideas can be tried and discarded before the final idea comes to be.

Figure 4.1. Workflow for solution generation.

4.1 Initial posture analysis

In this step of the process, all the postures performed and documented previously are going to be analysed. The analysis will be performed using the manual OWAS (Karhu, Kansi, and Kuorinka, 1977) and REBA (McAtamney, Hignett and Hignett, 2004) worksheets to find the initial data. The virtual method will be made using Siemens Jack 9.0 using a lower back analysis, REBA; as a point of comparison between the manual and virtual methods, and finally; the comfort assessment only on the sitting postures. The solution generation process will apply the theory to adapt each posture to a less risky position that should not cause injuries in the future. Risk, in this case, refers to postures that once analysed receive a fail mark with the assessment tools; red in the case of OWAS or lower back analysis, and a number equal or between eight and fifteen in REBA. On the riskiest postures equipment or tools might be added to the environment to create a more favourable outcome.

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4. 1.1 Environmental factors

During the posture analysis, the environmental aspects were analysed as well, lighting and ventilation are also aspects that have to be addressed as they can also affect the workers by creating potential strain and vision problems as well as respiratory issues respectively. These two aspects may need an entire study to analyse how lightning and ventilation affected the workers' postures because they could be a reason for some posture issues. Otherwise, the entire work area was well lit and more specialized light sources were also available for detailed tasks such as those related to electronics. The ventilation aspect is the most important when it comes to the handling and inhaling fumes from soldering in the electronics area. The main problem that was found was that the soldering area does not have a big enough fan to accommodate the amount of soldering that is done, therefore causing the workers to inhale excess amounts of solder fumes. While all this is not completely related to the research being conducted during this project, it is an important part to mention. Expansion of the production area is being presently planned at the plant and aspects such as these should be taken into account.

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4.1.2 Manual analysis methods

The methods used to analyse almost every posture are Rapid Entire Body Assessment (REBA) and Ovako Working Posture Analysis (OWAS).

REBA (McAtamney, Hignett and Hignett, 2004) is a whole-body posture analysis which divides the body into different parts to analyse them independently, according to the angles each part take in comparison to the coordinates system. The final score achieved is from one to fifteen, from less to maximum risk, divided into five levels of risk so they exist thousands of possible combinations. The worksheet that ergonomists use to perform the analysis based on the method and also the one used for this study is the one in Figure 4.2.

Figure 4.2. REBA Employee assessment sheet (McAtamney, Hignett and Hignett, 2004).

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28 OWAS is also a whole body posture analysis which is divided into analysing legs, trunk, arms and the load that take part in the posture (Karhu, Kansi, and Kuorinka, 1977). The results of the analysis are divided into three groups, separated by colours (green, yellow, orange and red) that give the importance of changing the working posture. The worksheet that ergonomists use to perform the analysis based on the method and also the one used for this study is the one in Figure 4.3.

Figure 4.3. OWAS Employee assessment sheet (Karhu, Kansi, and Kuorinka, 1977).

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29 A summary of the results obtained in the analysis is developed in the following table:

Completed sheets for the REBA analysis are attached to the “Appendix 1”

Figure Picture REBA OWAS

1 4, medium risk, further investigation, change soon.

1121

2121

3 8, high risk, investigate and implement

change.

4141

2121

5 3, low risk, change may be needed. 1121

3121

7 1, negligible risk. 1121

8 3, low risk, change may be needed. 1121

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30 9 6, medium risk, further investigation,

change soon.

2111

1111

11 8, high risk, investigate and implement

change.

2121

2221

14 10, high risk, investigate and

implement change.

4141

Table 4.4. Manual analysis results, REBA and OWAS.

The initial assessment shown previously is the first look into the results for the analysis and gives an idea of which postures require more attention than others. These results also show how different the analysis was from the risk level assessment made in the beginning and used as a hypothesis. The hypothesis made in the beginning was not correct; some postures that were at a lower risk initially, when they were hypothetically divided into three levels of risk, showing much higher risks at this point and from now on they will be treated without levels, just focusing in the results of the analyses, as the least and most risky ones. From this point, another assessment can be made as to what the results of the virtual analysis could be. Further ahead, when the analyses with Siemens Jack 9.0 are done, a comparison with both methods is going to be done.

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4.1.3 Simulations in Jack 9.0

Simulations in Jack are performed to create a base from which concrete improvements can be made, to take the environments created to analyse the initial postures and apply them. Moreover, the virtual environment makes it so that the analysis can be made directly on the simulations and without extra methods, increasing accuracy. Tools and results from analysis methods such as OWAS can be compared to the manual methods as well to give more credibility to the results. To simulate the postures a simplification of the sealing applicator that focuses on the most important measurements for the study has been modelled (see Figure 4.5) to be able to model the postures as close to reality as is possible. With the measurements taken from the assembly line, a table has been also simulated (see Figure 4.6.).

The analyses were performed using the Analysis Toolkit function on the software after the postures are modelled. For every posture, a Lower Back Analysis and OWAS analysis have been made. For the sitting postures, a Comfort Assessment analysis has been applied.

 The Comfort Assessment analyses seated postures and helps determine if the simulated human is in a comfortable posture. This tool analyses individual joint angles in real-time so any joint can be changed and set to be a useful option based on the analysis (Jack User Manual Version 9.0, 2017).

 Lower Back Analysis helps evaluate the spinal forces acting on the simulated human’s lower back. This tool evaluates jobs in real-time and determines low back compression and anterior, posterior and lateral shear forces (Jack User Manual Version 9.0, 2017).

 OWAS (Ovako Working Analysis System) analysis gives a quick check of the comfort of a working posture, analysing angles of back, arms, legs and load, and determines the urgency of changing or not that working posture. It shows a score from 1 to 4 the risks for potential injury and therefore changes in posture that are needed (Jack User Manual Version 9.0, 2017).

Figure 4.5. Sealing applicator simplification Figure 4.6. Working surface simplification

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32 The following pages will show the postures that obtained the highest potential risks in the analyses, which are shown with yellow and red colours. A brief description of the results is also included. The postures that have obtained mostly green results are located in Appendix 2.

Posture 2

The principal issue of posture 2 is the bent back; this gives the OWAS analysis the yellow colour with the aspect of the human being standing instead of sitting.

Giving a solution to the bent back will give another face to the results of the analysis.

The loads the user is subjected to are low, causing low compression and therefore a low result in the lower back analysis.

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33 Posture 3

Posture 5 has lots of things to improve, the back is over bent and twisted due to the height of the table and the depth of the table and the human is standing with his knees bent. Maybe having the tools in easier access will solve the problem. The compression on the back is higher due to the torque on the back; however, the parameters don’t reach a problematic level as the user is not carrying any heavy loads around.

Posture 6

The back of the human is over bent and twisted due to the need to applying force to perform the activity. This is shown in the high numbers of the results of the OWAS analysis. The posture could cause injuries if it is used in long periods. The loads the user is subjected to are not that high, which is why the lower back analysis shows up in green.

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34 Posture 9

The results of the OWAS analysis show that the back is again over bent and twisted, in this case, is because the tool needed is far away from the working area of the worker. This working area is the range of space that the human covers reaching the arm out without bending the back. In comfort assessment there are some joints with a yellow result, they must be corrected.

Posture 11

Again, posture 11’s issue is that the back is over bent and twisted because of the need for applying force during the activity, the lower back analysis loads are high due to the torque on the back, but not high enough which is why it is green. Moreover, the neck is also bent and this could cause serious problems in the long term when working in this posture.

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35 Posture 12

On position 12, the neck is once again too bent, in not only a forward angle, but also crooked to the left, which will eventually cause further problems for the user. The back is also at a prone position due to the height of the table which causes low visibility on the part that is being assembled.

Posture 13

The main issue with posture 13 is the angle of the neck. The OWAS evaluation shows trouble because of this. The angle of the back is also worrying and will need to be addressed as that might also be the cause of the compression on the back as well, however, the compression may be this low due to the subject not carrying any loads.

The main cause of this could be the low position of the table which is causing the user to slouch down.

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36 Posture 14

Posture 14 has many problems which could eventually cause damage to the user’s neck and back. The OWAS posture analysis shows very high numbers on the bending of the neck and the position of the legs. The lower back analysis also shows high compression, however, since the subject is not lifting any significant loads the analysis has stayed green. This position will be more complicated to solve as it relies completely on the shape and position of the parts of the testing rig itself.

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4.1.4 Comparing manual OWAS and Jack 9.0 OWAS results

Posture Manual OWAS

result

Jack 9.0 OWAS result

1

2

3 4 5 6 7 8 9 10 11 12 13 14

Figure 4.7. Table comparing OWAS results in manual and virtual methods.

As shown in the comparison of manual and Jack 9.0 methods (see Figure 4.7), almost all the postures have the same results between the manual methods and the simulations, besides the two postures that have differences in their results (postures 4 and 6). For further analysis, the most problematic postures were considered. In general, the worker has worked out his postures over the years so that they are not as problematic as initially thought. The worker’s method for finding his working postures is mainly empiric which can work in some cases; however, yellow results suggest making changes soon. Of fourteen postures that were analysed only two were cause for major concern, these being postures 3 and 14, and both postures are outliers in terms of how the worker positioned himself at the moment the actions were performed.

The postures that are shown in yellow are mainly due to a bad back or neck position. These postures along with the two shown in red will be the main focus of the posture improvements. The improvements will work primarily by implementing ergonomic changes which can be done through the proper use of tools such as the adjustable tables which are already found at the facility as well as changes on how the detailed work is performed. The solutions should be easy enough so that they can once again work empirically to make the workers adapt easily to these new changes, there is no point in implementing changes if these are too complicated or impractical to implement.

ERGONOMIC CASE STUDY OF AN ASSEMBLY LINE AND SOLUTION IMPLEMENTATION IN ECCO FINISHING / CARLISLE FLUID TECHNOLOGIES (CFT)

Bachelor Degree Project