Parámetros “Tecla 1”: 74

Practical assessment framework

3.1 Assessment framework

3.1.1 Overview of the model

The core of the model is a set of questions. As mentioned in paragraph 2.2, some questions, rules and improvement proposals were already provided, before the start of the construction of the assessment model. The two sources were De Nil (2009) and Van Goubergen and Van Landeghem (2002). Not all of the rules mentioned in these works are included in the final model. Some rules are covered in both works, others are considered less important. Only the rules which are considered necessary, are added to the rules in this thesis and included in the final framework. The complete list of questions, rules and improvement proposals is presented in appendix A, and the reader is referred to this section of the work, if he would like to study the questions in more detail. The improvement proposals are always mentioned below the (set of) rule(s) or question(s) for which they are relevant. They are preceded by a ‘+’ sign. The origin of each rule, question or improvement proposal is explained through the use of colors: black stands for the work of professors Van Goubergen and Van Landeghem, red stands for the work of De Nil, and green is the result of this thesis.

As discussed above, this work is built around a set of questions. In this section more information is provided on how this list of questions has been implemented in a practical tool. On the next page a schematic overview of the model is shown. It might give a better understanding of the structure of the tool.

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Figure 36: General structure of the model

The Excel file (EDAT-MC: Ergonomics & Design Assessment Tool – Machine Changeover) that contains the model has several sheets:

Machine Sheet:

This is the first sheet the user will see as the file opens. This sheet contains a portion of the total set of questions. Questions that have a more general nature and that cover not just one piece involved in the changeover, have been placed under this heading. The questions are divided among the 9 categories proposed by Van Goubergen and Van Landeghem (2002). The user can select whether he wants to answer a question (if it is applicable, he usually will), and he can select his answer from a drop-down menu. Additionally, he can decide to implement one of the improvement proposals that are mentioned together with each (set of) question(s). Choosing an answer results in the calculation of two scores for each question: a design/time score, and an ergonomic score. The details of the score calculation will be discussed in section 3.1.2. At the bottom of the sheet, the user has to fill out a factor (between 0 and 1). This factor indicates the importance of the design/time score vs. the ergonomic score in the calculation of a total score.

72 Parts Sheet:

This is the second sheet in the tool. It contains the questions that have a more specific nature and that are applicable to only one of the parts used, during changeover. It is developed in a similar way to the “Machine Sheet”.

Financial Sheet:

In this sheet, the user can fill out all the costs and expected yields that come with the implemented improvements. They are all split up in standard categories.

Extra info:

When completing the “Machine Sheet”, the user is sometimes referred to the “Extra info” sheet. It contains some background information that might be useful when answering a certain question. Question classification:

This sheet contains buttons. They will generate the division of the “Machine Sheet” questions among different score intervals (0-10, 10-20, …). The first button performs this function for the time scores, the second one handles the ergonomic scores.

Results Machine:

The “Results Machine” sheet contains absolute design- and ergonomic scores. It also shows a relative score and improvement potential per category, both for design and ergonomic scores. On top of that, an absolute total score and total relative score is calculated. The presence of an absolute score allows the user to estimate the importance of each category.

Results Parts:

This sheet is constructed in a similar way as the previous one. This time, however, the absolute design and ergonomic scores, as well as a relative score and improvement potential (design and ergonomic) are calculated per part. Next, a total absolute and relative score is generated, again per part. And the final graphs show a total absolute and relative score for all parts together. Results Machine and Parts:

This sheet combines “Machine Sheet” scores with “Parts Sheet” scores and compares them to the maximum score that is attainable for the questions. This feature allows the user to objectively compare changeovers on two different designs or machines.

Results financial:

This last result sheet allows the user to draw conclusions from the financial data that has been entered.

73 Numeric results:

This is a calculation sheet which is hidden for the user. It uses all the scores that are generated in the “Machine Sheet” and “Parts Sheet”, in order to generate the graphical output that is introduced in the result sheets.

Sheet settings:

A second, hidden sheet is called “Sheet settings”. It contains all possible answers for each question. Every possible answer has a design score and an ergonomic score. These answers are linked to the ones in “Machine Sheet” and “Parts Sheet” to complete the drop-down menu and to generate the score linked to the answer that is picked.

3.1.2 Essential calculations 3.1.2.1 Score calculation Scores and weights:

The score calculation is performed in “Machine Sheet” and “Parts Sheet”. The questions in these sheets are divided among the 9 categories of Van Goubergen and Van Landeghem (2002). So regardless the source of the questions (De Nil, (2009); Van Goubergen and Van Landeghem (2002); own rules), they have been placed under one of the 9 headings. Not all of the categories are equally important. Therefore a weight factor is developed. Each category has its weight, which mirrors the importance in relation to the other categories. This weighing system is used for the design/time scores as well as the ergonomic scores. A second weighing factor is used to express the importance of each question within a category. Once again this system is used for the design/time scores and the ergonomic scores per question. Note that the weights for time are based upon differences upon tasks that take minutes versus tasks that are performed within (milli)seconds. The weights for ergonomics are based upon physical or mental load.

Next to the weights, each question has its score according to the answer. To obtain a total score per question, the weights and the score are multiplied. The same way of working has been used for the improvement proposals. They get a score and have the same weights as the corresponding question. The sum of the scores per question and per improvement lead to a total design/time score and a total ergonomic score (Figure 37, Eq. 5 and Eq. 6).

It is important to know that the score allocation has been done so that the maximum score (answer score + ∑improvement score) for each question equals 100. This approach makes it very easy to generate a maximum score for all the questions that have been answered.

Design/time and ergonomic scores are treated separately for each question so far. The following text explains how the two scores are merged.

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Figure 37: Calculations of the ergonomic and design scores per category (abbriviations are explained in Table 24)

Eq. 5 𝑆𝑐𝑜𝑟𝑒𝑑𝑒𝑠𝑖𝑔𝑛 /𝑡𝑖𝑚𝑒 = 𝐴𝑛𝑠𝑤𝑒𝑟 𝑆𝑐𝑜𝑟𝑒𝑑𝑒𝑠𝑖𝑔𝑛 /𝑡𝑖𝑚𝑒 + 𝐼𝑚𝑝𝑟𝑜𝑣𝑒𝑚𝑒𝑛𝑡 𝑆𝑐𝑜𝑟𝑒𝑑𝑒𝑠𝑖𝑔𝑛 /𝑡𝑖𝑚𝑒 𝑥 𝑤𝑒𝑖𝑔𝑕𝑡 1𝑑𝑒𝑠𝑖𝑔𝑛 /𝑡𝑖𝑚𝑒 𝑥 𝑤𝑒𝑖𝑔𝑕𝑡 2𝑑𝑒𝑠𝑖𝑔𝑛 /𝑡𝑖𝑚𝑒 Eq. 6 𝑆𝑐𝑜𝑟𝑒𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 = 𝐴𝑛𝑠𝑤𝑒𝑟 𝑆𝑐𝑜𝑟𝑒𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 + 𝐼𝑚𝑝𝑟𝑜𝑣𝑒𝑚𝑒𝑛𝑡 𝑆𝑐𝑜𝑟𝑒𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 𝑥 𝑤𝑒𝑖𝑔𝑕𝑡 1𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 𝑥 𝑤𝑒𝑖𝑔𝑕𝑡 2𝑒𝑟𝑔𝑜 𝑛𝑜𝑚𝑖𝑐 Total score:

It is interesting to combine both scores into one total score that takes into account all aspects. Through multiplication factor (alpha) the importance of the design/time score is compared to that of the ergonomic score. In the calculations, the design score is multiplied with alpha and the ergonomic score with (1-alpha). The choice of this factor is up to user. This way he can choose the importance of ergonomics for his design. Calculation of the total score is shown in Figure 38 and Eq. 7.

Eq. 7

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Figure 38: Calculations of the total machine and parts scores (abbreviations are explained in Table 24)

Table 24: Explanation of the abbreviations used in Figure 37 and Figure 38

Abbreviation Explanation

Q2.1 Question score for question 2.1. One answer for both ergonomic and design part QDS / QES 2.1 Question design/ergonomic score for the answer on question 2.1

DQW / EQW Design/ ergonomic question weight within the category, to differentiate the importance of each question as opposed to the others in this category DGW / EGW Group design / ergonomic weight to differentiate the importance of each

category as opposed to another DCS/ECS Design/ ergonomic category score TMS Total machine score

TPSx Total parts score for part x

3.1.2.2 Combined compare index

Next to the individual assessment, a method of comparison between designs has been provided. Very different machines or designs can be compared, but the feature is mainly developed to compare designs that compete in the same area. One single value is linked to each design: the combined compare index.

Three compare indices are provided: one for the machine, one for each replaceable part and a combined compare index. Table 25, Table 26 and Table 27 explain the idea behind each index. The maximum possible scores, indicated by “Max”, take the questions into account that are applicable for the design. This means that the maximum possible score of questions, that are not applicable, is not added to the total sum of maximum scores.

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Table 25: Calculations needed for the (Machine and Parts) compare index and max compare index

Machine Part A Part B Part C Part D Part E Part F

Design Score Score Score Score Score Score Score

Max Max Max Max Max Max Max

Ergonomics Score Score Score Score Score Score Score

Max Max Max Max Max Max Max

Total Score Score Score Score Score Score Score

Max Max Max Max Max Max Max

Compare index 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 𝑇𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑥 𝑥 100 Max Compare index 100 100 100 100 100 100 100

Score and Max are collected from Machine sheet & Parts sheet

Design score x α + Ergonomic score x (1- α) Design max x α + Ergonomic max x (1- α) CH APT ER 3 . P RAC TICA L AS SESS M EN T FRA M EWOR K

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Table 27: Explanations for the values in Table 26: Calculations needed for the combined compare index

<value 1> The design score for M&P

= 𝑀𝑎𝑐𝑕𝑖𝑛𝑒 𝑑𝑒𝑠𝑖𝑔𝑛 𝑠𝑐𝑜𝑟𝑒 + _{𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑠 𝑡𝑜 𝑏𝑒 𝑟𝑒𝑝𝑙𝑎𝑐𝑒𝑑 𝑜𝑛 𝑡𝑕𝑒 𝑚𝑎𝑐 𝑕𝑖𝑛𝑒} 𝑎𝑙𝑙 𝑃𝑎𝑟𝑡𝑠 𝑑𝑒𝑠𝑖𝑔𝑛 𝑠𝑐𝑜𝑟𝑒𝑠 <value 2> The maximum design score for M&P _{= 𝑀𝑎𝑥 𝑚𝑎𝑐𝑕𝑖𝑛𝑒 𝑑𝑒𝑠𝑖𝑔𝑛 𝑠𝑐𝑜𝑟𝑒 +} 𝑎𝑙𝑙 𝑀𝑎𝑥 𝑝𝑎𝑟𝑡𝑠 𝑑𝑒𝑠𝑖𝑔𝑛 𝑠𝑐𝑜𝑟𝑒𝑠

𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑠 𝑡𝑜 𝑏𝑒 𝑟𝑒𝑝𝑙𝑎𝑐𝑒𝑑 𝑜𝑛 𝑡𝑕𝑒 𝑚𝑎𝑐 𝑕𝑖𝑛𝑒 <value 3> The ergonomic score for M&P

= 𝑀𝑎𝑐𝑕𝑖𝑛𝑒 𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 𝑠𝑐𝑜𝑟𝑒 + _{𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑠 𝑡𝑜 𝑏𝑒 𝑟𝑒𝑝𝑙𝑎𝑐𝑒𝑑 𝑜𝑛 𝑡𝑕𝑒 𝑚𝑎𝑐 𝑕𝑖𝑛𝑒} 𝑎𝑙𝑙 𝑃𝑎𝑟𝑡𝑠 𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 𝑠𝑐𝑜𝑟𝑒𝑠 <value 4> The maximum ergonomic score for M&P

= 𝑀𝑎𝑥 𝑚𝑎𝑐𝑕𝑖𝑛𝑒 𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 𝑠𝑐𝑜𝑟𝑒 + _{𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑠 𝑡𝑜 𝑏𝑒 𝑟𝑒𝑝𝑙𝑎𝑐𝑒𝑑 𝑜𝑛 𝑡𝑕𝑒 𝑚𝑎𝑐 𝑕𝑖𝑛𝑒} 𝑎𝑙𝑙 𝑀𝑎𝑥 𝑝𝑎𝑟𝑡𝑠 𝑒𝑟𝑔𝑜𝑛𝑜𝑚𝑖𝑐 𝑠𝑐𝑜𝑟𝑒𝑠 <value 5> The total score

= 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑐𝑕𝑖𝑛𝑒 𝑠𝑐𝑜𝑟𝑒 + _{𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑠 𝑡𝑜 𝑏𝑒 𝑟𝑒𝑝𝑙𝑎𝑐𝑒𝑑 𝑜𝑛 𝑡𝑕𝑒 𝑚𝑎𝑐 𝑕𝑖𝑛𝑒} 𝑎𝑙𝑙 𝑇𝑜𝑡𝑎𝑙 𝑝𝑎𝑟𝑡𝑠 𝑠𝑐𝑜𝑟𝑒𝑠 <value 6> The maximum total score

= 𝑀𝑎𝑥 𝑡𝑜𝑡𝑎𝑙 𝑚𝑎𝑐𝑕𝑖𝑛𝑒 𝑠𝑐𝑜𝑟𝑒 + _{𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑝𝑎𝑟𝑡𝑠 𝑡𝑜 𝑏𝑒 𝑟𝑒𝑝𝑙𝑎𝑐𝑒𝑑 𝑜𝑛 𝑡𝑕𝑒 𝑚𝑎𝑐 𝑕𝑖𝑛𝑒} 𝑎𝑙𝑙 𝑀𝑎𝑥 𝑡𝑜𝑡𝑎𝑙 𝑝𝑎𝑟𝑡𝑠 𝑠𝑐𝑜𝑟𝑒𝑠 <value 7> The value of the compare index (%)

= <𝑣𝑎𝑙𝑢𝑒 5>_{<𝑣𝑎𝑙𝑢𝑒 7>} 𝑥 100 100 The compare index is 100 at maximum = fixed value

Note that the part design scores, as well as their maximum, are 0 when not used in the Excel. Machine & Parts

Design Score <value1> Max <value2> Ergonomic Score <value3> Max <value4> Total Score <value5> Max <value6> Combined compare index <value7> Max combined compare index 100

CH APT ER 3 . P RAC TICA L AS SESS M EN T FRA M EWOR K

78 3.1.2.2 Visual Basic code in EDAT-MC

It will become clear when using the EDAT-MC Excel file, that programming has been done in Visual basic: message boxes appear when opening the file, error messages pop up when necessary, information buttons are provided,… A brief overview is given by Table 28: and in appendix C.

Table 28: Overview of the sheets that need VB-code to function

Sheet Purpose of the code Code reference

Machine sheet Information buttons Appendix C: Figure 1

Excel file: Module 3 Question Classification Design check button Excel file: Module 1 Ergonomic check button Excel file: Module 2 Question Classification

Results Parts Results Machine

Results Machine & Parts Results Financial

Safety check that indicates the questions that have not been filled in and have no indication that they are not applicable for the evaluated machine.

Appendix C: Figure 2 Excel file: <name of the sheet>

Workbook The message boxes that appear when opening the file

Excel file: This Workbook Note that most of the references refer to the Excel file. This code has not been added in the appendix since it is too extended.

3.1.3 Extra feature: Financial aspect

Another aspect of the model is the financial part. Financial data is considered to be an elementary part of an (ergonomic) intervention. Often, it is this financial facet which is determining to management. Based upon the gains the costs, management decides to implement an (ergonomic) improvement. The problem with ergonomic interventions however, is that costs are hard to quantify. An ergonomic intervention influences production in different ways and has an impact on several expenses. A standard accounting model that collects all of these expenses does not really exist. In literature, several attempts have been made to set up an accounting model that incorporates all of these expenses and that comes up with one total, correct cost (Riel and Imbeau, 1996; Hendrick, 2003; Lahiri et al., 2005; Goggins et al., 2008).

Some of these attempts cover the expenses and gains more in detail than others, but most of them go towards the same general classification. The approach that is followed in this model is very similar to the one taken by Hendrick (2003). This variant is chosen, because it covers all expenses, but remains at a level which is abstract enough. If the financial part would be more detailed, it would become hard result in a model that is very general and applicable to a wide variety of cases.

Costs and yield are divided among the categories that can be found in Table 29. The majority of them can easily be obtained at the accounting department of any firm. The same structure can be found in the “Financial Sheet” of the Excel tool.

79 The following rules have to be taken into account when filling out the form:

- numbers entered in the cost category are positive if they represent a cost - numbers entered in the cost category are negative if they represent yield - numbers entered in the yield category are positive if they represent yield - numbers entered in the yield category are negative if they represent a cost

As mentioned before, the most important expenses are covered in this framework and can be obtained with minimal effort. However, some expenses and gains are more difficult to quantify. What happens with an increase in production due to employee motivation, for instance? It is a realistic idea that employee motivation would increase thanks to the implementation of ergonomic improvements. If employees feel that their well-being is important to management, they experience that they can work in a safer environment, which is beneficial to their attitude. If employees are in a better mood and their good mood results in an increase of production, this can not be seen as a direct result of the implementation of the improvement. It is a side effect, but nearly impossible to quantify. This is a problem we are unable to solve, but is worth noticing.

Table 29: Costs and yield categories

The financial part stands on its own. It can be applied separately, or the user can decide to fill out the Machine Sheet and Parts Sheet, while ignoring the Financial Sheet. The financial output can be found in the “Results financial” sheet of the Excel tool.

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3.2 Application of the assessment framework

The model is successfully applied to a test case. The design department of Philips Lighting used the model on one of their machines. In order to do so, they read the manual (Appendix B). Appendix B briefly explains how to use EDAT-MC when assessing a machine.

3.2.1 Philips Test Case

The machine that is evaluated fabricates miniature electrodes for gas discharge lamps (the CDM lamp for shops). To give an idea: the electrodes that are produced have a length of at least 2 mm, a bar diameter of at least 150 µm and an electrode head diameter of 350 µm. One machine is equipped with several servo axles to manipulate and to construct the electrodes. It also contains two lasers for thermal treatment, two measuring cameras for production control with display interface,… One employee is responsible for the operation and changeover of 6 machines. The dimensions of the machines are: 1330 x 1000 x 2300 (l x b x h) mm. We asked the designer to fill in the Excel model and following results were obtained.

Result Machine – sheet

This graph shows the score of each category in comparison with its maximum. It also shows the differences between categories. For this design, the categories: weight, securing and machine lines are not applicable. Standardization and method on the other hand are essential. And even though the offline activities category does not seem substantial, the improvement potential is high.

Figure 39: Philips – Absolute design scores for Machine

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

Absolute total scores for Machine

Total actual score Total maximum score

81 The previous graph perfectly illustrates the share of each category compared to the others, but the risk exists of neglecting small groups. So a second graph is provided which demonstrates the percentage of potential in each area individually. Now the offline activities will not be overlooked.