Bachelor degree project in Mechanical Engineering Level G2E 30 credits Spring term 2019 Marcus Berglund Examiner: Lennart Ljungberg Bachelor degree project in Product Design Engineering Level G2E 30 credits Spring term 2019 Martin Karlgren Examiner: Peter Thorvald Supervisors: Ulf Stigh & Erik Brolin
DEVELOPING A FURNITURE TEST
MACHINE ACCORDING TO NATIONAL
STANDARDS
ENSURING QUALITY AND CREDIBILITY FOR THE SMEES IN SOUTH AFRICA
Abstract
In South Africa where the unemployment is immense, Small Micro and Medium enterprises (SMMEs) provide more than half of all job opportunities. Furntech, a non-profit organisation that works with vocational training and incubation within the furniture manufacturing sector in South Africa, wants to expand their testing laboratory with a machine to test mattresses according to local standards. The aim of this project is to develop a machine design to test innerspring mattresses by using product development methodology. Observations, interviews, and visits at companies in the furniture manufacturing sector is conducted to understand the needs from the user- and mechanical aspects. Existing and required additional parts to support the functionality for the test bedding machine has been evaluated by calculations and simulations by using for example ABAQUS and JACK.
A design is produced that meets the local standards by developing the existing table test machine in Furntech’s laboratory and is presented in a CAD-model. A scissor lift controls the vertical adjustment of the platform and an electric ball screw cylinder controls the compression of the mattresses. Instruction manuals, a graphical interface design, flowcharts and drawings of some of the parts has also been produced.
Certification
This thesis has been submitted by Marcus Berglund and Martin Karlgren to the University of Skövde as a requirement for the degree of Bachelor of Science in Mechanical Engineering and Product Design Engineering. The undersigned certifies that all the material in this thesis that is not my own has been properly acknowledged using accepted referencing practices and, further, that the thesis includes no material for which I have previously received academic credit.
Marcus Berglund
Skövde 2019-06-07
Institutionen för Ingenjörsvetenskap/School of Engineering Science
Martin Karlgren Skövde 2019-06-07
Acknowledgements
We would never have thought when we first applied to the University of Skövde, that we three years later, would end up in Cape Town, South Africa, doing our Bachelor degree project. We are forever grateful to you who made this possible and we want to address a special thanks to: Mikael Hultberg
For helping us get in contact with Furntech and making all of this possible.
Michael Reddy, Iegshaan Ariefdien, Maxwell Jaca and everyone else at Furntech. We will remember our stay with joy, and we hope we will meet you again soon. Frida Lindgren
For all your support during our MFS application.
Ulf Stigh, Erik Brolin, Peter Thorvald and Lennart Ljungberg at the University of Skövde For helping us completing this project.
Table of contents
1. INTRODUCTION 1 1.1 BACKGROUND 1 1.2 PROBLEM 1 1.3 FURNTECH 2 1.4 BRIEF 2 1.5 AIM AND OBJECTIVES 2 1.6 RESTRICTIONS 2 1.7 TARGET GROUP 3 1.8 METHODOLOGY 4 1.9 SUSTAINABLE DEVELOPMENT GOALS 4 2. PRELIMINARY STUDY 6 2.1 STANDARDS AND ITS PURPOSE 62.2 INNERSPRING MATTRESSES SANS 1005:2009 6
2.2.1 Performance test for spring units 6 2.2.2 Endurance test for mattresses 7 2.3 ERGONOMICS 8 2.3.1 What is ergonomics? 9 2.3.2 Physical ergonomics 9 2.3.3 Cognitive ergonomics 10 2.4 FIELD STUDY 12 2.4.1 Benchmarking 12 2.4.2 Furntech’s laboratory 13 2.4.3 Technology station of clothing and textiles 14 3. REQUIREMENT SPECIFICATION 15 4. METHOD 18 4.1 FUNCTION ANALYSIS 18 4.2 GENERATION 20 4.2.1 What are easy products? 20 4.2.2 Idea generation 20 4.2.3 Concept development 21 4.2.4 Three concepts 21 4.3 CONCEPT EVALUATION 24 4.3.1 Existing parts 24 4.3.2 Ergonomic evaluation 30 4.3.3 Prototyping 37 4.3.4 Summarizing the evaluation phase 38 5. RESULTS 39 5.1 POSITIONING 40 5.2 TOOL 42 5.3 MEASUREMENT 43 5.4 COMPONENTS AND PARTS 43 5.4.1 Cylinder 43 5.4.2 Mattress Tool 44 5.4.3 Pressure disc 45 5.4.4 Sliders and profiles 45 5.5 TEST PROCEDURES 46 5.5.1 Spring test 46 5.5.2 Mattress test 48 5.6 RECONCILIATION WITH THE REQUIREMENT SPECIFICATION 50 6. DISCUSSION 54 6.1 MATTRESS MANUFACTURER 54 6.2 LAB TECHNICIAN 54
6.3 TECHNICAL ISSUES 55
6.4 ERGONOMICS AND USABILITY 55
6.5 FURTHER WORK 55
6.6 TECHNOLOGY, SOCIETY AND THE ENVIRONMENT 56
7. CONCLUSION 57 REFERENCES 58 APPENDIX 1. WORK BREAKDOWN AND TIME PLAN 61 APPENDIX 2. THE GENERATION OF EASY PRODUCTS AND HOW THEY ARE DESIGNED ACCORDING TO NORMANS (2013) DESIGN PRINCIPLES. 62 APPENDIX 3. IDEAS ON EACH SUB-FUNCTION FROM THE BRAINSTORMING SESSION. 63 APPENDIX 4. HOW THE 15 DIFFERENT MAIN AREAS WAS CONNECTED BY THE METHOD MORPHOLOGIC MATRIX. 64 APPENDIX 5. THE FIVE CONCEPTS FROM THE MORPHOLOGIC MATRIX THAT WAS EVALUATED BY VOTING. 65 APPENDIX 6. FIRST USER MANUAL DESIGN (SPRING TEST) 66 APPENDIX 7. FIRST GUI DESIGN (SPRING TEST) 67 APPENDIX 8. FIRST USER MANUAL DESIGN (MATTRESS TEST) 68 APPENDIX 9. FIRST GUI DESIGN (MATTRESS TEST) 69 APPENDIX 10. QUESTIONNAIRE FOR SATISFACTION 70 APPENDIX 11. SPRING TEST FLOWCHART 71 APPENDIX 12. MATTRESS TEST FLOWCHART 72 APPENDIX 13. DRAWINGS MATTRESS TOOL 73 APPENDIX 14. DRAWING PRESSURE DISC 76 APPENDIX 15. PROTOTYPE OF AID TOOL 78
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IST OF FIGURESFIGURE 1. ACTIVITIES THAT ARE INCLUDED IN THE FOUR PHASES ACCORDING TO CROSS (2008) METHODOLOGY. ... 4
FIGURE 2. THE 17 SDGS IN AGENDA 2030. ... 5
FIGURE 3. MEASURING POINTS FOR THE DOUBLE CONE SPRING UNIT TEST. ... 7
FIGURE 4. MEASURING POINTS (X) ON A MATTRESS. ... 8
FIGURE 5. PICTURES OF THE ALREADY EXISTING FURNITURE TESTING MACHINES AT FURNTECH. ... 13
FIGURE 6. THE ALREADY EXISTING TABLE TEST MACHINE, THE TWO HORIZONTAL CYLINDERS (B1-B2) AND THE VERTICAL CYLINDER (A1) ... 14
FIGURE 7. HOW THE VERTICAL CYLINDER IS ATTACHED BY SCREWS INSERTED IN THE PROFILES TRACKS ... 13
FIGURE 8. HOW THE TRANSVERSE PROFILE IS CONNECTED TO THE SLIDERS ... 13
FIGURE 9. THE POSITIONING SENSORS THAT SHOULD READ THE END POSITIONS FOR THE ROD. ... 13
FIGURE 10. THE DIFFERENT TEST EXPRESSED IN MAIN FUNCTIONS. ... 18
FIGURE 11. HOW THE MACHINE IS SPLIT UP IN THREE MAIN AREAS POSITIONING, TOOL AND MEASUREMENT AND THE SUB -FUNCTIONS. ... 19
FIGURE 12. CONCEPT 1. ... 22
FIGURE 13. CONCEPT 2. ... 22
FIGURE 14. CONCEPT 3. ... 23
FIGURE 15. INVESTIGATION IF A CENTRING CHUCK FIXATION COULD BE USED FOR ALL MATTRESSES, IF ALL MATTRESSES ALWAYS WERE TO ORIGINATE FROM A MATCHING CENTRE POINT IN THE MACHINE. ... 27
FIGURE 16. A COORDINATE SYSTEM WHERE ALL MATTRESSES ORIGINATE FROM THE SAME CORNER "S". THE POINTS REPRESENT ALL THE DIFFERENT CENTRE POINTS FOR THE 17 MATTRESSES. THE BRIGHTER BLUE RECTANGLE IS THE TOOL POSITIONED FOR MATTRESS 2000 X 1830 MM. ... 27
FIGURE 17. A CAD-MODEL OF THE MATTRESS TOOL IN COLORED POLYCARBONATE PLASTIC. ... 29
FIGURE 18. THE PICTURE TO THE LEFT ILLUSTRATES THE APPLIED PRESSURE TO THE BOTTOM CORRUGATED SURFACE AND BOUNDARY CONDITIONS IN ITS MIDDLE FOUR HOLES. THE PICTURE TO THE RIGHT ILLUSTRATES THE MESHING OF THE PART. ... 29
FIGURE 19. THE FE ANALYSIS RESULT. THE HIGHEST STRESSES CAN BE FOUND IN THE 4 HOLES IN THE MIDDLE. ... 30
FIGURE 20. ILLUSTRATION FOR THE LONGEST DISTANCE AND WORST DISTANCE THE USER MUST REACH DURING THE MATTRESS TEST. ... 31
FIGURE 21. ILLUSTRATION OF THE PLATFORM TEST WITH LBA RESULT FOR WORST POSITION. ... 32
FIGURE 22. ILLUSTRATION FROM PLATFORM TEST WITH OWAS RESULT. ... 33
FIGURE 23. PLACING DISC WITH 35 CM AID HANDLE. ... 34
FIGURE 24. ILLUSTRATION OF THE MANIKINS RIGHT AND LEFT EYE DURING THE PROCEDURE. ... 34
FIGURE 25. ILLUSTRATION FROM TOOL CONNECTION ANALYSIS. ... 35
FIGURE 26 FINAL CONCEPT FOR THE MATTRESS TESTING MACHINE. ... 39
FIGURE 27. THE LEFT PICTURE ILLUSTRATE THE SCISSOR LIFT AND THE RIGHT PICTURE THE PLATFORM. ... 40
FIGURE 28. THE LEFT PICTURE INDICATES WHERE TO PUT THE TEST UNIT. THE RIGHT PICTURE ILLUSTRATES THE FIXATION OF THE MATTRESSES. ... 40
FIGURE 29. BOSCH ECOSLIDES AND HANDLE FOR LOCKING FUNCTION. ... 41
FIGURE 30. THE LEFT PICTURE ILLUSTRATES THE CENTRUM LASER FOR THE SPRING TEST, AND THE RIGHT PICTURE ILLUSTRATES THE AID TOOL. ... 41 FIGURE 31. THE STANDARD MARKINGS FOR LENGTH AND WIDTH FOR THE MATTRESS TEST. ... 41 FIGURE 32. SHELF FOR TOOL STORAGE AND THE TEST NAMES ON THE TOOL AND SHELF. ... 42 FIGURE 33. CONCEPT OF THE QUICK CONNECTION COUPLING. ... 42 FIGURE 34. THE MATTRESS TOOL WITH INTEGRATED SENSORS THAT BOTH INDICATES AND MEASURES SIX POINTS ON THE MATTRESS AUTOMATICALLY. ... 43
FIGURE 35. THE FIRST PICTURE FROM LEFT ILLUSTRATE THE ELECTRIC BALL SCREW CYLINDER, THE SECOND ILLUSTRATE THE SERVO MOTOR AND THE THIRD PICTURE ILLUSTRATE THE AXIAL SUPPORT KIT. ... 43
FIGURE 36. A CAD-MODEL OF THE MATTRESS TOOL AND ITS PARTS. ... 44
FIGURE 37. AN ASSEMBLY OF THE MATTRESS TOOL TO THE CYLINDER, SERVO MOTOR AND AXIS SUPPORT. ... 44
FIGURE 38. CAD MODEL OF THE PRESSURE DISC MADE IN ALUMINUM ... 45
FIGURE 39. THE FIRST PICTURE FROM RIGHT ILLUSTRATE THE 90X90 MM ALUMINIUM PROFILE, THE SECOND ILLUSTRATE THE 45X45 MM PROFILE AND THE THIRD PICTURE ILLUSTRATE THE ECOSLIDES WITH THE LOCKING HANDLE. ... 45
FIGURE 40. THE USER MANUAL FOR THE SPRING TEST. THIS NORMAL FORMAT IS IN THE SIZE A3. ... 46
FIGURE 41. SELECT TEST DISPLAY . ... 47
FIGURE 42. THIS DISPLAY WILL REMIND THE USER TO FOLLOW THE MANUAL. ... 47
FIGURE 43. WHERE THE USER CLICKS TO TYPE IN THE HEIGHT. ... 47
FIGURE 44. THE KEYPAD FOR TYPE IN MEASUREMENTS. ... 47
FIGURE 46. REMINDER DISPLAY FOR THE USER TO FOLLOW THE MANUAL. ... 47 FIGURE 47. TEST START DISPLAY. ... 48 FIGURE 48. DOUBLE CHECK DISPLAY. ... 48 FIGURE 49. PROGRESSION DISPLAY. ... 47 FIGURE 50. TEST FINISHED DISPLAY AND REMINDER TO FOLLOW THE MANUAL. ... 47 FIGURE 51. DISPLAY FOR CLICK ON RESULT. ... 47 FIGURE 52. RESULT DISPLAY. ... 47
FIGURE 53. THE USER MANUAL FOR THE MATTRESS TEST. THIS NORMAL FORMAT IS IN THE SIZE OF A3. ... 47
FIGURE 54. TEST SELECTION DISPLAY. ... 49
FIGURE 55. THIS DISPLAY WILL REMIND THE USER TO FOLLOW THE MANUAL. ... 49
FIGURE 56. TIME LEFT FOR THE MATTRESS FIRST 12 HOUR REST. ... 49
FIGURE 57. THE USER SHOULD CLICK ON MEASURE TO START THE MEASURING PROCESS. ... 49 FIGURE 58. NUMBER OF MEASURMENTS THAT IS LEFT TO STORE PROPERLY. ... 49 FIGURE 59. REMINDING DISPLAY FOR THE USER TO FOLLOW THE MANUAL. ... 49 FIGURE 60. TEST START DISPLAY. ... 50 FIGURE 61. DOUBLE CHECK DISPLAY. ... 50 FIGURE 62. PROGRESSION DISPLAY. ... 50 FIGURE 63. TEST FINISHED DISPLAY AND REMINDER TO FOLLOW MANUAL. ... 50 FIGURE 64. DISPLAY FOR CLICK ON RESULT. ... 50 FIGURE 65. RESULT DISPLAY. ... 50
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IST OF TABLES TABLE 1. STANDARDS THAT HAVE BEEN ASSESSED DURING THIS PROJECT. ... 3 TABLE 2. STANDARD SIZES OF INNERSPRING MATTRESSES. ... 7 TABLE 3. REQUIRED STEPS TO BE PERFORMED BY THE USER DURING THE TWO TESTS. ... 8 TABLE 4. THE REQUIREMENT SPECIFICATION. ... 15TABLE 5. PREPARATION FOR IDEA GENERATION WHERE MAIN FUNCTIONS AND SUB-FUNCTIONS WERE COMPILED INTO A TABLE. ... 18
TABLE 6. ROD MOVEMENT AND SPEED REQUIRED DEPENDING ON MATTRESS HEIGHT. ... 26
TABLE 7. FE ANALYSIS RESULT AFTER THREE REFINEMENTS OF THE MESH SIZE. ... 30
TABLE 8. ANTHROPOMETRIC DATA FROM SANHANES-1. ... 31
TABLE 9. COMPILED DATA FROM PLATFORM SIMULATION. ... 32
TABLE 10. COMPILED DATA FROM DISC AND VISION ANALYSE. ... 33
TABLE 11. COMPILED DATA FROM TOOL CONNECTION ANALYSES. ... 35
TABLE 12. THE MEASUREMENT THAT HAS BEEN ADDED TO REQUIREMENT SPECIFICATION AFTER ERGONOMIC SIMULATIONS. ... 35
TABLE 13. THE DIFFERENCE OF TIME AND ERRORS MADE, FIRST AND SECOND TEST FOR THE SPRING TEST. ... 36
TABLE 14. THE DIFFERENCE OF TIME AND ERRORS MADE, FIRST AND SECOND TEST FOR THE MATTRESS TEST. ... 36
TABLE 15. ERRORS AND COMMENTS FOR THE SPRING TEST (MANUAL AND GUI) DURING THE USABILITY TEST. ... 36
TABLE 16. ERRORS AND COMMENTS FOR THE MATTRESS TEST (MANUAL AND GUI) DURING THE USABILITY TEST. ... 37
TABLE 17. THE SATISFACTION SCORE FOR THE GUI DESIGN (LEFT TABLE) AND THE USER MANUALS (RIGHT TABLE). ... 37
1. Introduction
This project aims to develop a machine to test mattresses according to South African standards and to expand the furniture test laboratory at Furntech’s facilities in Cape Town, South Africa. In the future, Furntech has an ambition of achieving an accredited test laboratory which in turn will help the Small Micro and Medium Enterprises (SMMEs) that works within their facilities to be more competitive on the market.
A necessity for this project to be carried out in South Africa was the financial support of the Swedish International Development Cooperation Agency (SIDA) through a scholarship called Minor Field Studies (MFS). Requirements to be eligible for the scholarship is that the subject of the project addresses issues in the country that is of importance, for example, health, jobs, economic growth etcetera. The project should also have a connection to the Sustainable Development Goals in Agenda 2030.
The first chapter will describe the background to this project along with the purpose, restrictions, and methodology.
1.1 Background
South Africa is with its 50 million citizens, the largest economy in Africa seen by GDP per capita. Years of economic growth has made South Africa a country with a prosperous middle class. Despite this, the country still faces a lot of problems; a divided population as a result of the former policy on racial segregation, social- and political tensions, and an increasing number of unemployed citizens (Höglund, 2016).
In July 2011, the website Leader wrote an article 9 major problems facing South Africa - and
how to fix them. The first bullet point on that list is “Too few South Africans in work”
(Leader.co.za, 2011). The unemployment is a big issue for South Africa, and for the second quarter of 2018, the unemployment rate was 27.7%, which is about 6.08 million people of the population according to Moya (2018). But, depending on the perspective this number differs a lot. The Economist (2018) states “Unemployment has ballooned to a frightening 37.2% using an expanded definition that includes people that simply has given up looking for work”. While Sharpe (2011) writes in answer to the article 9 major problems facing South Africa - and how
to fix them “(...) South Africa’s unemployment rate is closer to 8% rather than 25%”, meaning
that if all the informal employments are fully accounted for the actual percentage is significantly lower. However, even if this is the case, and millions of people are incorrectly labelled as “unemployed”, all these people are making a living without paying taxes or adhering to labour laws. So regardless of whether South Africa’s unemployment rate is 8% or 37%, it is obvious that the country must find a solution to this problem.
In South Africa, Small Medium and Micro Enterprises (SMMEs) provide more than 50% of all
the employment opportunities and 45% of the country’s GDP.But statistics show that there is
only a 37% chance for SMMEs to survive more than four years and only 9% to survive for more than ten years. Between 70- and 80% of all SMMEs in South Africa fail during their first year of operation (Business Report, 2014).
1.2 Problem
Technical and industry-specific competencies in SMMEs are often ignored even though these are essential due to their direct effect on sustainability. Business operation skills are often acquired through experimental learning, and for a start-up business technical skills are required (Urban & Naidoo, 2012). Finding ways in helping small businesses in the SMMEs sector to survive and grow can, in the long run, give a lot back to South Africa (see Sustainable
development goals under section 1.9). Some key areas of support to SMMEs will include; access to advice, access to training, access to premises, and access to appropriate technology (Visagie, 1997).
1.3 Furntech
Furntech is a non-profit organization that works in the fields of vocational education and business incubation in the furniture manufacturing industry. Furntech was established in the year 2000, and the Tibro Training Centre (TTC) was a key partner in the development of the organization. Today Furntech has seven centres located around South Africa. In these centres, 6919 students have been educated, 396 new SMMEs has started their operations, and this has until now created 935 new jobs (Furntech, 2019). As part of Furntech’s contribution to the development of the SMMEs sector in South Africa, Furntech has established a furniture testing laboratory. The laboratory consists of machines to test tables, chairs, and hinges.
1.4 Brief
This project will focus on developing appropriate technology for SMMEs in the furniture manufacturing sector. Where Furntech’s testing facility will be expanded with a machine to test mattresses. This machine will conduct the necessary steps to test innerspring mattresses and will be designed by assessing the local standards relating to the bedding industry. Furntech is working on getting an accredited testing laboratory according to South African standards that can help improve the SMMEs competitive advantage on the market.
1.5 Aim and objectives
This project has been designed to investigate the possibility of implementing the two tests (endurance and performance) specified in the standard SANS 1005:2009 for innerspring mattresses in the already existing table test machine at Furntech’s laboratory. A central focus for this project is to investigate how the mattress test machine can be designed by using already existing parts. Another focus is to design the machine from a usability perspective as the table test machine is difficult to manage today; this includes both physical and cognitive ergonomic aspects. Due to limited time on site, the test-bedding machine will not be installed during this project. The main objectives are to:
● Design a test bedding machine by assessing the standard SANS 1005:2009. ● Use existing parts of the table test machine if possible.
● Present the final machine design in a CAD-model with functional parts. ● Describe the test procedures and how the machine should be operated. ● Present technical drawings of parts.
1.6 Restrictions
Mattresses come in many sizes and different fabrics, for example; foam mattresses, innerspring mattresses, adult- or cot size mattresses, foam mattresses for hotel or hospital use and so on. For all these different mattresses, there are different criteria to fulfill. These criteria are written in standards, which in South Africa is called South African National Standard (SANS).
The standard that has been the foundation for this project is the standard for innerspring
mattresses (SANS 1005:2009). It includes twotests for performance and endurance. One test
for spring units and one test for testing the complete mattress (these procedures will be described under section 2.2). Besides these tests, SANS 1005:2009 also connects to standards for fabrics and foams.
The standards that have been assessed in this project are presented in Table 1. To separate these standards, they have been split up into three groups; Fabrics, Foams, and Bed. The standards
for fabrics used on a bed/mattress requires specific machines to test colour fastness, bursting- and tensile- strength. The standard for bed bases (SANS 1420:2017) is also connected to the standards for fabrics. An endurance test exists for bed bases as well, which uses the same tool as for innerspring mattresses. There should be a possibility to implement this test as well in the machine. However, this will not be part of this project due to limited time.
The standards for Foams are more complex. Two of the standards (SANS 1291-2:2014 and CKS 615:212) only mentions standard sizes and general requirements but not how they should be tested. The third one (SANS 5999:2007) mentions several test methods but are referring to a large number of other standards. Therefore, further research is needed in this category.
Table 1. Standards that have been assessed during this project.
1.7 Target group
The SMMEs that already work at Furntech’s incubation centres will be the main target group for this project. Furntech also plans on doing tests for external companies, which will be the secondary target group.
The user for the test machine is difficult to define. According to the company, the user will probably be a South African male or female, from 16 to 65 years old. Another aspect to have
in mind is that the user may not have primary education. Focus in this project will therefore be to design the test-bedding machine according to anthropometric data from the South African population with a usability perspective in mind. The machine will be placed inside the same room as the already existing laboratory (see section 2.4.2).
1.8 Methodology
The project and its included activities will be divided into four phases, according to Cross (2008) methodology; exploration, generation, evaluation, and detailed design, Figure 1. Cross (2008) also talks about communication as a fifth phase, which will be an ongoing phase during the entire project between all participants. Even though the other phases have more distinct starting- and ending points, it does not mean that looping back and iterate a previous phase is impossible. Combining expertise from two engineering perspectives (design- and mechanical engineering) in the project will help broaden the scope. Different knowledge and different aiming points on what is important will likely help to find better solutions. Simultaneous engineering, where members from different job functions collaborate early and regularly, is an approach in which issues can be identified and solved sooner by working together as a team and increase the efficiency when members can work on parallel tasks at the same time (Lichtman, 2016). The methodology can however be the same but have different outcome purposes. In the exploration phase, market research will be done on already existing test machines, for example, with interviews, observations, and benchmarking. In this research, the design engineer will have more focus on design, ergonomics, and functions while the mechanical engineer will focus on how the machines are constructed and assembled.
1.9 Sustainable development goals
The UN adopted the historical resolution of Agenda 2030 for sustainable development in September 2015 which says that all member states are committed to work towards; abolishing extreme poverty, reducing inequalities and injustice in the world, promoting peace and justice, and to solve the climate crisis before 2030. To do this, the Agenda 2030 consist of 17 Sustainable Development Goals, also known as SDGs or Global Goals (see Figure 2) as well as 163 sub goals (Agenda 2030-delegationen, 2019). Africa has apart from Agenda 2030 also committed to achieve African Union Agenda 2063, which strives to get a more prosperous Africa in 50 years. United Nations development program (UNDP) works in about 170 countries and territories and supports nations efforts to reach the Global Goals. The UNDP program in South Africa is focusing on four key priority areas. Priority area one is enhancing inclusive
growth and decent work, which aims to support the South African government to undertake the
triple threat of poverty, unemployment, and inequality (UNDP in South Africa, 2019).
The issue with unemployment can be connected to several of the SDGs set by the UN. For example, quality education (goal 4), decent work, and economic growth (goal 8) and promote sustainable industrialization (goal 9). By working towards these goals, unemployment has a chance to decrease.
Developing the test machine for Furntech’s laboratory will help support sub goal (9.b) domestic technical development, research, and innovation in global goal 9. As well as providing information, communication, and technical skills relevant to their occupation (sub goal 4.4 in global goal 4). It may also have a negative effect on the climate when new parts need to be developed, manufactured, and transported. To affect climate change as little as possible, this project will aim to use existing parts of the machine and to buy new parts from local companies (global goal 12 and 13).
2. Preliminary study
The preliminary study section describes findings of literature reviews and field studies. Information regarding standards and why they exist along with the test procedures for innerspring mattresses will be described in the first part of this section before findings within physical- and cognitive- ergonomics are explained. The second part contains observations made at different companies and information on how the laboratory at Furntech is built today.
2.1 Standards and its purpose
Standards are a voluntary tool that can be used as an aid to follow the legalization. It is an important basis for a successful global market. The purpose of standards is to create routines and similarities that members agree about. For a recurrent problem, these routines and similarities are mutual solutions to solve it (Swedish Standards Institute [SIS], 2019). The companies can use standards to develop their products, services, and systems for saving time, labour, and to use it for facilitating international trade (International Organization for Standardization [ISO], 2019).
There is one member per country that represent ISO and takes part in influencing the ISO system. South Africa’s representative member is called the South African Bureau of Standards (SABS). SABS is the institution authorized to develop, promote, and maintain South African National Standards (SANS) to promote quality for products and services. SABS also provides necessary conformity assessment services (SABS, 2019).
To get accredited products according to its specific standard within the country, it is important to follow the specifications written in the standards. If it can be proven that the product fulfills the standard requirements, a company will get a certification which proves product quality.
2.2 Innerspring Mattresses SANS 1005:2009
The standard SANS 1005:2009 explains all steps in which the spring unit and the complete mattress should be tested, from necessary parts in the apparatus along with performing requirements such as compressing rates. A summarization of what the standard requires of the machine and how the tests should be performed will be described below.
2.2.1 Performance test for spring units
The machine should consist of two platens, one stationary and one compressing. The stationary platen is from now on referred to as platform and the compressing platen as tool in order to facilitate the communication in this report. The distance between the platform and tool should be adjustable to be able to perform initial compression and accommodate different sizes of spring units.
Preparation of spring test
An innerspring mattress can either consist of a Double-cone spring unit or an Interlinked formed-wire spring unit. For the double-cone spring units a section of 16 springs in total, i.e., four rows that each contains four springs, should be cut out. This section of springs is now referred to as test unit. On the unit, six markings are made, four markings “A” on each of the centre four springs, and two markings “B” at the upper lacing wire (see Figure 3). The height of the springs is measured at the respective A-points as well as the distance between the two B-points to the nearest 2 mm.
Figure 3. Measuring points for the double cone spring unit test.
The preparation for the Interlinked formed-wire unit is very similar. The difference is that the section should be cut to a specified size (rather than a number of springs), approximately 430 x 330 mm, and the four markings “A” are to be put in the centre to form a square of approximately 100 x 100 mm. The markings “B”, as well as the measurements, are performed as described above.
The procedure of spring test
The unit is to be placed on the platform of the apparatus centrally positioned under the tool. Initial compression of 20% of the free height of the specimen is to be made by adjusting the distance between the platform and the tool. The stroke length is then to be adjusted to give a 65% compression of the free height and perform 5000 cycles at a rate of 60 cycles per minute. When the test is over, lower the platform and check the unit for breakage or loosening of springs or connecting wires, then measure the marked points and calculate the deviation in height and length expressed in percent. If the loss in height or permanent stretch is more than 5% or if finding breakage or loose connections, the specimen has failed the test.
2.2.2 Endurance test for mattresses
The apparatus needed to perform the endurance test is similar to the apparatus for spring units. The platform however must be large enough to support the whole mattress (there are 17 different sizes of standard mattresses, see Table 2). The apparatus should also have a compressing tool, but of different size and shape compared to the spring unit test tool.
Table 2. Standard sizes of innerspring mattresses.
Mattress Size Length (mm) Width (mm)
Adult 2000 1930 1880 1830, 1520, 1370, 1070, 915, 760 915, 760 1830, 1520, 1370, 1070, 915, 760 Juvenile 1625 760 Cot 1320 1220 760 610
Preparation of mattress test
The mattress to be tested should be placed on a solid plane horizontal base for at least 12 hours. When this time has passed, a flat pressure disc, weighing 2 kilograms, is to be placed on six different locations on the mattress. These points always originate from the centre regardless of mattress size (see Figure 4). The pressure disc is to be lowered slowly and without shock on to each of the six locations and be allowed to rest for at least 10 seconds before the height are measured and noted on all six points.
Figure 4. Measuring points (x) on a mattress.
The procedure of mattress test
The tool is to be placed vertically above and in the centre of the mattress with its longitudinal axis parallel to the longitudinal axis of the mattress. Before the test starts, the mattress needs to be secured against horizontal movement. The tool should compress the mattress to 67% of its free height and then release it at a rate of 60 cycles per minute for 60000 cycles. After the completed test, the mattress should be allowed to rest for another 12 hours before measuring the same six locations as described in the preparation section. For each of the six points, the loss in height expressed in percent should be calculated. If loss in height exceeds 5%, the mattress has failed the test.
2.3 Ergonomics
As an objective for this project is to make the machine easy to use, defining when the user needs to interact with the machine or perform different tasks are important. The required steps to be performed by the user during the two tests are presented in Table 3 below.
Table 3. Required steps to be performed by the user during the two tests.
Spring test Mattress test
Cutting out the spring unit specimen Place mattress on the platform
Marking and measuring the unit Marking, placing pressure disc and measuring the mattress
Place the unit on the platform Mount the mattress tool
Mount the spring unit tool Adjust platform and tool in the correct position Adjust platform and tool in the correct position Start the test
Start the test Check the unit for breakage or loosening of springs
Check the unit for breakage or loosening of springs
Measure the marked points Measure the marked points Calculate the deviation Calculate the deviation
This is done to find potential areas where the user may need aid tools in performing some of the tasks. Also, if there are potential areas where the user will be exposed to more demanding physical moments and repetitive actions. The spring test can be performed four times during an 8-hour working day. This means that for example, the measuring procedure of the spring test can be performed up to 40 times during a working week. Whereas the mattress test can only be performed once a week. Even if the mattress test is not as repetitive in terms of user interaction, the changing of the tool can be physically demanding depending on its weight. Another aspect is also to see if the user can reach necessary points. The machine should be able to be managed by only one person. However, one step where two persons may be needed is when placing bigger mattresses on the platform. Research within different areas of ergonomics has been done to reach the goal of making the machine easy and safe to use.
2.3.1 What is ergonomics?
Ergonomics and human factors engineering aim to improve human interaction with systems by enhancing: Safety, Performance, and Satisfaction. It is about interaction between people, objects, and the environment they live in (Lee, Wickens, Liu, & Boyle, 2017). To achieve these elements and improve the interaction between people and objects, ergonomics is divided into different compartments:
● Physical ergonomics
● Cognitive ergonomics
● Organization/social ergonomics
This project will focus on two of these areas, physical and cognitive ergonomics. The physical area evaluates manual handling, the repetitions of work, work postures, and movements. While the cognitive area focuses on the user’s perception and interpretation with the machine (Ahlin
& Pettersson, 2019).
Anthropometry can be described as knowledge and research into human measurements. The human body has different dimensions depending on age, health conditions, sex, race or ethnic group, occupation, and so on. The dimensions and variations of the human body are important implications during the design process. This is the reason why it is important to define the user or target group for the product or system (Pheasant, 1996).
2.3.2 Physical ergonomics
Uncomfortable working postures, physical loads, and heavy lifting are common examples of physical ergonomics. Another type of physical ergonomics is local and repetitive work postures, for example working with computer and keyboard every day can cause damages in hands and wrists (Holmström & Ohlsson, 2014). The human body is still made for work at a moderate level of physical movement, loading, and recovery. Which means that both a high or a low dose of effort can give negative consequences. Reducing heavy loads by aids and make hand tools more lightweight have been implemented for reducing physical loads on the human body at workstations. To eliminate the duration and frequency damages variation of loads with alternately heavy and easy loads is an important aspect to think about during a workstation development (Holmström & Ohlsson, 2014). This is why it is important to be able to evaluate a work station according to lifting tasks and movements. Holmström & Ohlsson (2014) also says that a good working posture is when the human can use their back in an upright position during a lift or movement. The working height is dependent on the type of work, the size and weight of load are examples of these types.
The most common work-related musculoskeletal disorder in the industry is low-back pain at the disc between the fifth lumbar and the first sacral vertebrae (called the L5/S1 lumbosacral disc) (Lee, Wickens, Lie, & Boyle, 2017). National Institute for Occupational Safety and Health
(NIOSH) is a US governmental organization that works to implement work-related health and safety prevention for the general industry and have developed limit values for the lower back load. To assist ergonomics and occupational safety and health in the industries, a method called OWAS has been widely used. It has been used since the 1970s and is based on sampling from typical working postures for the human body. This method uses a four-digit code to describe various postures and force combination that can be harmful to the body (Lee & Han, 2013). This lower back and posture analysis can be simulated in the Digital Human Modelling (DHM) software Jack (Siemens, 2019). This software uses manikins that can be manipulated into a wanted posture and has a skeleton like a real human. The Jack software is programmed with Task Simulation Builder (TSB) that makes it possible to simulate the required tasks for evaluations of the manikin’s work. Task Analysis Toolkit (TAT) are preprogrammed in the Jack software for posture and lower-back analysis (Delleman, Haslegrave, & Chaffin, 2004).
2.3.3 Cognitive ergonomics
The word cognition has since the mid-1970s generally been used without much precision and in many ways. Hollnagel (2003) mentions these as a range from cognitive ergonomics, cognitive systems engineering, and cognitive work analysis to cognitive tools, cognitive task analysis, and cognitive function analysis- to mention just a few. He also describes the word cognition and how it is used to describe how the human brain interprets, organizes, and uses acquired knowledge.
To apply cognition in ergonomics issues, Hollnagel (2003) explains it in three key problems: • Explaining and understanding human thinking and knowledge.
• Find the relationship between this knowledge and human performance.
• Training required for safe, reliable, and effective performance and supporting the design of tasks and interfaces.
It could, in other words, be explained as a relationship about a humans ability to see, hear, understand, and act (Hollnagel, 2003). Norman (2013), on the other hand, explains it more simply as the words good or poor design. He explains that it is easier to notice poor design than good. In part, because good design is invisible, it fits the user's needs that make the product smooth and easy to use.
Therefore, this project will put much focus on how a good design can create a mutual interface between the user interaction, how users understand it, see it, and acts during the test procedures. Usability
Usability is a word that is a part of the cognitive ergonomics. It is an attribute about how easy the user can; implement a task, how quickly they can perform a task, remember the features, how many errors they can make and how appealing the design of the product is (Nielsen, 1993). Norman (2013) describes the usability design in 7 design principles that can be implemented in this project.
• Visibility - Make functions visible helps the user know what actions are available. • Feedback - When an action has been done, the user receives information about what
has been accomplished, this could, for example, be a vibration or a sound.
• Conceptual model - A mental model that most people know how it works based on experience from previous products.
• Affordance - It allows people to know how it should be used to make the desired action possible.
• Signifiers - It ensures discoverability and that the feedback is well understandable. • Mappings - Relationship between the controls and the product.
• Constraints - Reduces the probability to do errors. By physical constraints where the user can not do wrong, e.g. insert a USB-cable in the wrong direction. It can also be by logical constrains, e.g. discolour menu option in a computer program. It is still
possible to click on it, but the program will not answer if that happens.
User testing is a useful method to test the usability of a product. By using representative users and ask them to perform a task with the design. Then observe and have a conversation where the user talks about the different components that are mentioned above (Nielsen, 1993). According to Ward & Hiller (2005) the goal with user testing is to provide data about the effectiveness of the product by observing; how users accomplish a task, how they do it in a reasonable time and effort (efficiency), show how it is done (context) and finally their satisfaction by observing the reaction to the product. Nielsen (1993) describes these as five components for measuring usability:
● Learnability - The simplicity for the user to accomplish basic tasks the first time.
● Efficiency - How quickly the user can perform the task when they have learned it
● Memorability - How easily can the user re-establish proficiency after returning to the
design after a period of not using it.
● Errors - Describes how many errors the user do during the test, how serious the errors
are, and how easy they can recover from it.
● Satisfaction - The users appealing to use the design.
Design interfaces
According to Westerholm & Åström (2002), an interface can be described in three types of systems: Mechanical interface, Information interface, and User interface. The mechanical interface is about the interaction between components that constitutes functionality, for example, the parts in a clockwork. It creates a mechanical interface with a detailed description in the form of time. Information interface can be described in terms of orientation, for example, in this project, information about how the functions of the test procedures will act and how the outcome value should be interpreted. Most focus is usually put into the user interface. It is the interface where machine and human interact. The user interface is most of the time a surface of contact in forms of buttons or a display, and information provided by a computer that can be seen, heard or touched (Westerholm & Åström, 2002).
These three different areas can also be described as a part of the cognitive working environment and are important to have knowledge about during a working station development process to avoid cognitive working environment problems. A concept called KAMP was proposed by Lind, Sandblad, and Nygren (1991) to give understanding about working environment problems related to stress, actuation, and limitations that can occur during the interaction between humans and technical interfaces. Lind, Sandblad, and Nygren (1991) also identified important classification according to design- and construction methods. This survey is possible to consider during the design process of the interface process.
• Interruption in the mindset - The user has incomplete focus of the actual task because the user is forced to put too much information into the interface.
• Orientation problem. - The user gets lost in the system. It is hard for the user to understand where in the system they are.
• Stress in short term memory - The short-term memory has a limitation of 5-8 units of information at the same time and have a short decay time. It is also easy to interrupt short time memory.
• Unnecessary cognitive effort - The user has problem to collect information automatically. Pattern recognition makes it easier for the user to understand the
interface automatically. Colours, forms, and text interface are other aspects that can affect the cognitive effort.
• Coordination problem of time and values - It is important to be able to associate a process and values to time. It is also important for the user to be able to identify the status of the process, to simplify the planning and exchange of working tasks.
2.4 Field Study
During a product developing process, it is important to understand and know the environment, but also building empathy with the people it should be designed for. Spending time with people engaged in real-world activities is a helpful approach to increase knowledge regarding specific behaviors and to collect relevant data (Kumar, 2012). According to Eikhaug & Gheerawo (2010), there are different approaches in which this can be done, for example, natural observations or controlled observations. The natural observations are defined as low contact with people, where just by looking, discovers behaviors and surroundings, while controlled observations are in a level of higher contact, where people (users) can be presented with a task or design while observing how they complete or interact with it. Another way to achieve higher contact and deeper understanding about the user and their needs is by interviews. In unstructured interviews, the questions are stated in a way that allows the interviewed person to speak more openly about the subject. In this case, the interview can take different courses. Another kind of interview is where direct questions are asked. A specific topic area or detailed technical information about the subject is then the purpose of the interview, and the course of the interview is already set. When choosing interview approach, it could be useful to know the advantages and disadvantages with the different approaches, for example, in widespread interview advantage can be that information that would not otherwise get through can do so compared to the direct interview approach (Eikhaug & Gheerawo, 2010).
A combination of these methods will compose the field- and preliminary study. It will give honest and insightful information, good and in-depth information about technical aspects, and a good understanding of the natural context in the user’s environment. This information will form part as requirements and needs in the requirement specification for the machine.
2.4.1 Benchmarking
Benchmarking is a word for investigating the already existing market and is a way to see how a design or technical solution for a machine is developed today or also if there are any blanks to fill in. Another important aspect is to explore if already existing solutions for testing machines can be combined and be applied for this project (Ulrich & Eppinger, 2014).
To explore how a furniture testing laboratory can be constructed and used, a visit to Kinnarps AB, one of Europe’s leading supplier of office furniture was made. At this early stage of the process, the knowledge about the subject was very low. In this case, Milton and Rodgers (2013) recommend the use of an unstructured interview, which is recommended to use when the subject is still ill-defined for the designer and the questions in the interview have no specific set. The interview has still certain topics to cover, but the conversation flow is more like a daily conversation and has more chance to be more open-ended (Milton & Rodgers, 2013). The main topic with this interview was how Kinnarps AB works with standards and how much it affects the company’s position on the market, also how the standards affect the design for the different testing machines. This visit helped increase the knowledge about standards and why a testing laboratory is essential for a furniture manufacturer. For example, it turned out that testing the products according to Swedish standards reduces the furniture production cost because of the ability to test parts of products early on during the product development. It also turned out that the standards disclose the main functions and procedures for the machines.
2.4.2 Furntech’s laboratory
Furntech’s testing facility consists of five different testing machines (see Figure 5). All machines are driven by pneumatic cylinders as well as additional control equipment provided by Festo. A central compressor provides air to the machines. It can provide up to 10 bars in total. The cylinders apply pressure on either chairs or tables or perform a linear motion to open and close drawers for a certain period of cycles to determine if they pass the endurance tests. Aluminium profiles form the base and framing for all machines (BOSCH Rexroth).
The table testing machine
The table testing machine has a length and width of 2650 mm and is 2100 mm tall. It is built of 90x90 mm aluminium profiles (Bosch Rexroth) and has one vertically and two horizontally installed Festo cylinders (see Figure 6). The vertical cylinder is attached to a vertical profile, which in turn are attached to a transverse profile by screws in its tracks (see Figure 7). The transverse profile is then connected to two sliders at each end, so it can move in one direction (see Figure 8). A platform consisting of three iron plates with a thickness of about 10 mm forms the base. All cylinders are connected to load cells which are connected to a computer by Bluetooth. The load cells are unable to communicate to the PLC (Programmable Logic Controller) thus, it can only interpret the pressure applied and convert it to, for example, kilograms. As a consequence, the computer can say if a test has failed when the load cell notices a value outside the set boundaries, but the machine will continue performing the test without knowing that the test specimen already failed. On the cylinders are however positioning sensors installed that should read the end positions for the rod motion (see Figure 9). So, if a table surface would break, the rod would theoretically move outside its allowed distance and stop. A test was made to see if this was the case. After a couple of cycles, the cylinder was pushed away from the table to illustrate a failure but the machine did not stop, the rod continued its movement downwards and the emergency stop had to be pushed before the cable connected to the load cell broke. In the Graphical User Interface (GUI) it is only possible to adjust the amount of bar going into the cylinders. Therefore, a lot of trial and error had to be made before the actual test could start. This to see what amount of bar is required to apply the correct kilograms and adjust the sensors to correct movement for the rod.
Figure 6. The already existing table test machine, the two horizontal cylinders (B1-B2) and the vertical cylinder (A1).
2.4.3 Technology station of clothing and textiles
As mentioned in section 1.4, the fabrics for the innerspring mattresses should also be tested according to certain standards. A field visit was made to the Technology Station in Clothing and Textiles (TSCT) located at Cape Peninsula University of technology in Cape Town. TSCT is working on getting an accredited testing facility for testing fabrics and the purpose of this visit was to see if TSCT could provide the necessary machines to perform the tests described in SANS 1005:2009. A collaboration between Furntech and TSCT would then be an alternative for Furntech to still be able to provide the necessary tests without having to invest in their own fabric testing machines. To mention a few examples of available technology at TSCT’s laboratory are; burst strength tester, tensile tester, and Xenon arc light and weather fastness tester. Which all falls under the tests required for the innerspring mattresses in SANS 1005:2009. So, there is a possibility to perform the fabric tests if Furntech and TSCT agree to work together.
A1
B1 B2
Figure 7. How the vertical cylinder is attached by screws inserted in the
profiles tracks.
Figure 8. How the transverse profile is connected to the sliders.
Figure 9. The positioning sensors that should read the end positions
3. Requirement specification
To document all collected information, a detailed requirement specification has been compiled. It contains measurements of the existing table test machine, all necessary data from the standards as well as continuous findings in research considered essential for the machine. The requirement specification is split up as demands and requests for the machine and could be changed during the project to be more precisely specified if it corresponds with the demands from the company and in this case the local standards. It could be used in two ways, as guidelines and as a record at the end of the project (Österlin, 2003). All the requests are prioritized according to pre-study and literature, from 1-3 where 1 is most important.
Table 4. The requirement specification.
No. Specification
Demand
Request
Unit
Source
Prio
Spring test
1 Velocity 60±5 Cycles/min SANS 1005:2009
2 Adjustable stroke (Rod movement) From 75 to 150 mm SANS 1005:2009
3 Minimum space between tool and platform From 0 to 650 mm
SANS 1005:2009 and
anthropometry
4 Size platform 500x500 mm SANS 1005:2009
5 Size tool 230x150 mm SANS 1005:2009
6 Radius on tool 6 mm SANS 1005:2009
7 Cycles calculator 1 Pcs SANS 1005:2009
8 Compression cycles 5000 no. SANS 1005:2009
Mattress test
9 Compression height 67 % SANS 1005:2009
10 Velocity 60±5 Cycles/min SANS 1005:2009
11 Platform length 2020 mm SANS 1005:2009
12 Platform width 1850 mm SANS 1005:2009
13 Securing mattress in horizontal direction 0 mm
14 Compression cycles 60000 no. SANS 1005:2009
15 Dimension tool See Appendix 13 mm SANS 1005:2009
Additional equipment
16 Able to measure distance From 100 to 1650 mm SANS 1005:2009
17 Pressure disc 1 pcs. SANS 1005:2009
18 Pressure disc weight 2±0.2 kg SANS 1005:2009
19 Pressure disc diameter 300±2 mm SANS 1005:2009
MACHINE DESIGN Measurements
20 Height 2100 mm Field study 1
21 Width 2650 mm Field study 1
Material
23 Aluminium profiles 90x90 mm Field study 1
24 Aluminium profiles 45x90 mm Field study 1
25 Aluminium profiles 45x45 mm Field study 1
26 Iron plates 10 mm Field study 1
27 Aluminium profile for cylinder 1000x90x90 mm Field study 1
Cylinder (DSBC-Q-80-500-PPSA)
28 Cylinder width 90 mm Field study 1
29 Cylinder length housing 628 mm Field study 1
30 Cylinder slot 542 mm Field study 1
31 Rod movement 500 mm Field study 1
32 Threads M20x1.5 Field study 1
Physical
33 User age 18-65 year Field study
34 User gender Male and female gender Field study
35 Adjustable height platform From 200 to 900 from 100 mm Ergonomic simulation
36 Connection height (Floor->Cylinder) From 1450 to 1650 mm mm Ergonomic simulation
37 Storage height 900 mm Ergonomic simulation
38 Connection Diameter 40 mm Peoplesize
Sustainable development
39 Use already existing material on site Yes Furntech 2
40 Buy new material from local companies Yes Furntech 2
GUI interface
41 Units of information on one display From 1 to 8 From 1 to 5 pcs. Literature
42 Orientation map Yes Yes/No Literature
43 Patterns From 1 to 2 1 pcs. Literature
44 Text interface From 1 to 2 1 pcs. Literature
45 Text size From 12 to 24 pkt. Literature
46 Different colours From 1 to 3 pcs. Literature
47 Calculate cycles From 0 to 60000 no. Literature 2
48 Calculate time From 0 to 40 hours SANS 1005:2009
User Manual
49 Paper size Over A5 A3 size Literature 1
50 Text size From 11 to 30 pkt. Literature
51 Picture size From 20 to 100 mm Literature
Usability (machine)
53 Switch tool From 60 to 300 seconds Supposition 2
54 Place test unit From 20 to 120 seconds Supposition 2
55 Securing mattress in horizontal direction From 120 to 300 seconds Supposition 2
56 Adjust platform (bottom -> highest) From 120 to 300 seconds Supposition 2
57 Lock tool in position From 120 to 180 seconds Supposition 2
Usability (GUI & user manual)
58 Task time (spring test) 120 to 300 seconds Supposition
59 Task time (mattress test) From 120 to 240 seconds Supposition
60 Task errors Under 4 0 no. Supposition
61 Satisfaction (GUI) Over 4 5 Points Supposition
62 Satisfaction (User manual) Over 4 5 Points Supposition
4. Method
This section of the report will describe the methodology used in the project and how the design process was performed. It includes function analysis, idea and concept generation, and concept evaluation.
4.1 Function analysis
The idea with a function analysis is to express the product, in this case, the test machine, in functions instead of actual solutions. The function analysis should be structured in main, sub, and support-functions where the main functions are the required properties a product must implement. The main function consists of different sub-functions that make it operational (Österlin, 2003). The purpose of the function analysis is to split up the requirement specification in required functions to generate ideas and solutions for these. The machine will be optimized to implement two different tests. To make it easier to see the functions and for what test it belongs to, this analysis is split up in spring test and mattress test and machine categories. The first step was to express the machine in functions, see Figure 10.
Figure 10. The different test expressed in main functions.
To prepare for the Brainstorming session, the main functions were further split up into sub-functions. These sub-functions will, in summary, describe what the purpose for the specific machine actions should be. In the same table are queries for each function specified, to have a framing of questions to start the brainstorming. Some of the main functions are already existing in the table test machine today, see Table 5.
Table 5. Preparation for idea generation where main functions and sub-functions were compiled into a table.
Main functions Sub-functions Existing Queries TO-DO
Rod movement Press in cycles x How is it today? Ask Furntech
Air driven x Pressure? Capacity? Ask Furntech
Specific speed x Capacity? Speed today? Ask Furntech
Is it possible to program for
different heights? Ask Furntech
Adjustable distance
Place test part Important heights? Anthropometric
data and loads
Free height Are standards available
Tool-switch Best height for tool-switch? Anthropometric data and loads The positioning
of the test specimen
Matching point of zero
How? Brainstorming
Measure length and
height Marking
Is it possible to facilitate the
marking process? Brainstorming
Measure the test
part (height and length)
Is it possible to facilitate the
measuring process?
Brainstorming
Tool Connection x How connect
to the cylinder?
Brainstorming
Switch Manually/Automatic? Brainstorming
Attachment for
connection
x How attach the connection
on the tool?
Brainstorming
Selection of a
tool How to select the correct tool for the test Brainstorming
Storage
of the tool
How to store the tools? Brainstorming &
Anthropometric data
Displacement
of the tool
How to move the tool? Brainstorming
The positioning of the cylinder
Adjusted sideways
Customise for the correct
test?
Brainstorming Instructing test
procedure Start x Automatic? Manual? Brainstorming
Choose a test Mapping? Brainstorming
Cancel test x Cancel if error? Brainstorming
Manual
for the procedures
x Explain the procedure? Brainstorming
The machine has now been split up in three different main areas that include different sub problems to solve. They have been selected as the most important areas according to the requirement specification and for that reason had the highest priority during the generation process (see Figure 11). According to Cross (2008) summarising the problem formulation and partially prioritise it, is an important step for a successful design.
Positioning
Adjustable
platform Positioning of unit Positioning of
cylinder
Tool
Storage Connection Selection
Measurement
Marking Height and length Analysis
4.2 Generation
Both convergent and divergent approaches are important for a successful design. This phase of the design process is overall, a divergent approach, which means that the designer is more open and creative minded to create new ideas. Instead of the convergent way where the designer is more critical and analyses the ideas (Cross, 2008).
A lot of sub-functions for the machine now needs solutions, and solutions require ideas. This phase of the idea generation was a combination of brainstorming, braindrawing, and brainwriting. According to Wikberg-Nilsson (2016), these three methods are similar to each other and usually have a big result outcome. The purpose was to think wide, in the beginning, to come up with lots of ideas that could be combined with multiple different solutions for the functions.
4.2.1 What are easy products?
According to Ulrich & Eppinger (2014), already existing solutions of a problem is useful during a product development process. Have solutions in mind and develop new ideas from them, maybe by combining two or more solutions to one unique. Because of the demands in simplicity and usability from Furntech a generating session for existing “easy products” was the first to do. One purpose was to analyse how these products are designed according to Norman’s (2013) seven design principles, and if any solutions could be usable in this project (see Appendix 2). Another purpose was to define what attributes in these products that people recognized as easy to use. The idea was always to have usability close in mind, and create a mind map that could be used during the idea generation, as a reminder of the seven design principles and how to find them in other products.
4.2.2 Idea generation
The three main areas that have been divided into sub-functions should now be combined and in the end, create the final machine design. A big session was started where each sub-function was brainstormed individually. The issue and purpose for each function were discussed before the start of respective session to make sure the objective was clear for all participants. According to Cross (2008), one of the working methods that make the designer successful is to work with clarified requirements, by focusing on the problem structure with sets of related questions from a project leader. Another working aspect that Cross (2008) writes about is that successful designers tend to follow through all ideas. It is important not to suppress any initial solution ideas. In other words, save all the upcoming ideas and iterate back to them during the process, instead of throwing them away. All ideas were saved during this first step of the generation session (see Appendix 3). This first part of the generation resulted in a lot of different ideas for each sub-function, both from a mechanical and design perspective. These ideas will now be randomly put together into 15 different solutions for the main areas (Positioning, Tool, and
Measurement) independent from each other and combined into different machine concepts.
To still have the wide-spread and convergent design thinking, this part of the process is produced by the method Morphological Matrix. Morphologic or morphogenetic is the study behind structures, shapes, and forms that a product or machine might take. This is a method for combining novel combinations of elements or components. The purpose of this method is to widen the search for potential new solutions (Cross, 2008). As in many other methods it is important to not think about physical components for the product during a Morphological Matrix session, instead think of the functions that the components serve. It is also important that the ideas in the matrix list is of the same level of generality and should be independent of each other to be able to unite into completely new solutions (Cross, 2008). This session starts with the 15 independent solutions for the main areas (see Appendix 4). With the method
morphologic matrix, with an open-minded perspective, created five different concept solutions for the machine that now can be evaluated in a more convergent perspective.
4.2.3 Concept development
To start this more convergent evaluating session for the five concepts, pros and cons were discussed according to design and mechanical aspects. Wikberg Nilsson, Ericson & Törlind (2016) describe this as a simple and fast method to evaluate a lot of ideas with democratic and fair voting. The purpose was to quickly take away ideas and concepts that were not relevant to this project. Every concept and idea was explained and discussed between the participants, before minus and plus were positioned on each function in each of the concepts that gave the concepts a rating (see Appendix 5).
Three concepts were the result of the voting session. Cross (2008) describes a successful design process when the designer can iterate between all the phases. Therefore, these three concepts were disassembled and put into a new divergent process.
This creative phase is like what Wikberg Nilsson, Ericson & Törlind (2016) describe as the method called Scamper. This is a method that can support the idea generation by asking questions about how ideas or concepts can be substituted, combined, adapted, modified, put to
other use, eliminated, or reversed. Out of this, new ideas were generated and evaluated, and the
outcome was three new concepts that included ideas from previous concepts as well as completely new ideas. These three concepts were investigated further and were evaluated against the demands and requests from the requirement specification.
4.2.4 Three concepts
Communication is a word that could be interpreted in different ways. The designer communicates with many people during a design process, and it can be done in several manners. It can mean communication with a client, buyer, test person, or between participants in the design team. The way to illustrate depends on who the designer communicates with. For example, drawing, that is the most widely used form, to communicate artefacts of solutions, how it works and looks (Cross, 2008).
Sketching or drawings could be executed in different categories of skills as well. Cross (2008) describes these in different stages depending on the purpose of the outcome. Thumbnails sketches is a way to communicate quickly, for example, in the braindrawing session (see Appendix 3). The second way is more rendered sketches that could be a tool to communicate shapes, solutions, and ideas in the team. This could also be an aid for thinking and discussion (Cross, 2008). In this stage of the project, the purpose was to communicate the concepts for the different main areas of the machine in a more extensive manner.
Below are the three concepts communicated as rendered sketches, images and text (see Figures 12 to 14), that should be further investigated relative to functionality, usability, ergonomics, and mechanical aspects according to the requirement specification. The concept tables are split up into the three main areas from top: Positioning, Tool, and Measurement.
Figure 12. Concept 1.
Figure 14. Concept 3.
The chosen solutions for each of the concepts were motivated a lot from a simplicity point of view, meaning both construction wise and operation wise. With today’s technology, a lot can be made automatic, where the platform, cylinder and measurements will be performed with just a push of a button. That is simple from a user perspective, but only when it works, and from a construction perspective that would require a lot more expertise and money. Therefore, a lot of aid tools were chosen for both positioning and measuring the mattresses, to keep existing parts of the machine where possible and instead improve for example tool connection and fixation of cylinder. Clamps, Gardena connection and track locks are examples of that. These three concepts were the results from the generation phase and was decided to be evaluated more thoroughly in the next phase.
