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SMART

AUTOMATION

SEVEN METHODS FOR FINAL ASSEMBLY

Åsa Fast-Berglund Sandra Mattsson

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Art. No 43421 ISBN 978-91-44-14135-0 First edition 1:1 © The Authors and Studentlitteratur 2021 studentlitteratur.se Studentlitteratur AB, Lund Translation: Richard Ehnsiö Cover design: Francisco Ortega Cover illustration: Jonny Hallberg Layout: Lyth & Co Printed by Eurographic Group, 2021

TABLE OF CONTENTS

Monologues 7 Preface 9 Acknowledgements 10 Acronyms 11

Step 6: Identify important operations 41 Step 7: Generate and test hypothesis 41 Industry example: Production line for painting 42 Tips for further reading 46 4 Competency matrix 47

Part I Methods 1 Introduction 15 Reference management 17 Detailed user material 17 2 Design for automatic assembly (DFAA) 19 Background 19 Description 20 Analysis at product level 21 The Seven areas exemplified through the gearbox 21 Analysis at component level 25 Industry example: Improving the DFA index by redesigning components 30 Tips for further reading 31 3 Hierarchical task analysis (HTA) 33 Background 33 Applications 34 Description 34 Step 1: Determine the goal of the task 35 Step 2: Determine common target values 36 Step 3: Identify sources of information and select method for data collection 37 Step 4: Break down the goal into intermediate tasks 38 Step 5: Validate the division of the tasks 41 © T H E A U T H O R S A N D S T U D E N T L I T T E R AT U R

Background 47 Applications 47 Description 48 Step 1: Document operations 48 Step 2: Document operators 49 Step 3: Rank operators based on experience and knowledge 49 Step 4: Rate operations on the basis of necessary knowledge levels (KSRK) 51 Tips for further reading 53 5 Information overview 55 Background 55 Applications 55 Description 56 Level 1: Information overview at operation level 56 Level 2: Information overview at system level 60 Tips for further reading 61 6 Design principles for information presentation (DFIP) 63 Background 63 Applications 63 Description 64 Step 1: Selecting operation where the information presentation is to be improved and breaking down the operation into tasks 65

TA B L E O F CO N T E N T

Step 2: Identifying and supporting the cognitive processes in the tasks in the operation 66 Step 3: Analyzing the tasks based on how the operator perceives his or her environment 67 Step 4: Analyzing the tasks with regard to mental limitations 68 Step 5: Analyzing the tasks based on individual differences and preferences 70 Step 6: Analyzing the tasks regarding the location of content and information carriers 71 Tips for further reading 72 7 Complexity index (CXI) 75 Background 75 Applications 75 Description 76 Step 1: Choosing a station or area to be analyzed 76 Step 2: Distributing the questionnaire 76 Step 3: Analyzing questionnaire responses 77 Step 4: Proposing improvements 78 Industry example: Vehicle manufacturing 79 Tips for further reading 81 8 Dynamic automation strategies (DYNAMO++) 83 Background 83 Applications 83 Description 83 Phase 1: Analyzing the present situation 85 Phase 2: Measuring 86 Measuring physical automation 87 Measuring cognitive automation 88 Phase 3: Analysis 92 Phase 4: Implementation and follow-up 95 Tips for further reading 96

9 Automation strategy – a combination of different methods 97 Background 97 Industry example 1: Focus on quality 97 Industry example 2: Focus on cost 99 Tips for further reading 103 Part II Theory 10 Automation 107 Background 107 Physical automation 109 New parameters to consider in assembly 4.0 112 Cognitive automation 114 Tips for further reading 117 11 Complexity 119 Background 119 The complex assembly 119 Objective complexity 121 Subjective complexity 122 Complexity elements 122 Tips for further reading 123 List of figures 125 References 127 Appendix 1 135 Appendix 2 137 Appendix 3 147 Appendix 4 149 Index 157

Part I Methods

Illustration: Shutterstock.com/PlusONE

Introduction

Experiences from research projects1 show that there are several reasons why the industry does not use structured methods for measuring and analyzing their production systems when undertaking changes. The reasons for this can be divided into four main groups:

■ Complex and theoretical methods. One explanation is that people

working in the industry often are unfamiliar with methods used for task allocation and design of instructions. The methods are also often overly theoretical and difficult to use and might be presented in scientific papers that takes too long to comprehend. The methods in this book will therefore be presented in a practical and short way and hopefully it is easy to get started. ■ Lack of operational management in automation projects. If management is not aware of these methods or has not prioritiezed methods before, nor will the rest of the organization. The methods is mainly aimed for people that handles design of shop-floor work stations, for example production engineers. ■ Strategic work is often experience-based. Employees working on improving the production system may find that they do not have the time to work with “yet another method.” This view indicates that they do not see the usefulness of the method at hand (i.e., they rely more on experience than figures and structured work). An experience-based approach means that the work is based on existing 1

DYNAMO (SSF), ProAct (Vinnova [http://www.vinnova.se/upload/dokument/vinnova_nytt/ vinnovanytt1_08.pdf, p. 13]), Framtidsoperatören (Vinnova) (https://www.chalmers.se/sv/ projekt/Sidor/Framtidsoperat%C3%B6ren.aspx); Komplex produktion: Stöd för optimering av direkt och indirekt arbete, kompetens och information (COMPLEX), DYNAMITE (Produktion2030.se)

Pa r t I M eth o d s

conditions and technology. This may result in people having in tunnel vision and a decreasingly proactive production system. ■ Resistance to measuring work in relation to performance-based compensation. There is still opposition to studies of workers’ quantative performance, as this was previously linked to performance-based salaries (the faster you work, the more you get paid). Due to today’s high demands on productivity it is however necessary to optimize and improve our production systems (from both an efficiency and health perspective, but without reintroducing performance-based compensation). This book presents seven methods that hopefully are easy to use and give structure and help to create efficient station designs. Furthermore, many chapters present an industry example, intended to offer a more practical understanding of the utility of these methods. By using the methods presented herein, it is possible to create and develop lists of priorities and possible solutions linked to measurable results in the form of KPIs, which in a practical situation make it easier to justify their use for decision-makers in companies. The methods are presented in an order that may be suitable to follow when designing or improving a production system or when creating an automation strategy in relation to a given product. The purpose and background (history and use) of these methods are described, as well as their respective applications. For those wanting to immerse themselves in this topic, we also offer tips for further reading. The methods are exemplified through a LEGO gearbox that has been used in education and research at Chalmers for many years. A component list and further information and instructions of the gearbox is collected in Appendix 1, p. 135. The gearbox is mainly used in methods 1, 2 and 5. The seven methods presented in this book are: 1 Design for automatic assembly (DFAA). This method provides

guidelines for product designers and production engineers in order to design products that are more automation-friendly and flexible for both manual and automated assembly. 2 Hierarchical task analysis (HTA). This method offers a flow structure and a plan for how to divide an operation into shorter and defined tasks in order analyse the need for cognitive support and re-balancing of tasks. 3 Competence matrix. This method provides guidelines for how to get an overview of skillsets in order to prioritize and offer the right

1 I nt r oduction

6 7

support to the operator and in order to have an effective resource planning. Information mapping. This method aims to achieve an overview of the information systems used as well as how and by which technologies this information is presented. Design principles for information presentation (DFIP). This method provides guidelines on how to present information in a way that is easily absorbed and understood by the operator. Complexity index (CXI). This method offers an index of how operators perceive the complexity of their workstations. Dynamic automation strategies (DYNAMO++). This method provides support and description for measuring and analyzing cognitive and physical automation.

In the concluding chapter, we present examples where several methods are combined in order to analyze some of the most common measurable factors, such as increased quality and reduced cycle times.

Reference management Our aim is that this book should be easy to read and understand, which is why we do not present any references in the body text. Instead, a selection of references is gathered under the heading Tips on further reading in each chapter. All references are collected at the end of the book, linked to each chapter.

Detailed user material Each method has its own material for a more detailed use of the method. These questions and surveys are gathered in the back of the book as appendix.

Pa r t I M eth o d s

Design for automatic assembly (DFAA)

Background There are several methods to use when designing products that are easy to manufacture and assemble. These methods are classified under the umbrella term DFx, Design For x. The most famous is Boothroyd-Dewhurst’s DFMA method, where MA stands for Manual Assembly. The DFMA method was developed in the United States during the 1990s and it is based on the MTM1 studies carried out in the 1960s and 1970s, this will be brought up further in chapter 3. A further development of the DFMA was the Design for Assembly and the latest development, in the late 1990s, is the DFAA. Design For Automated Assembly (DFAA) is adding fixtures and robot interaction more than the earlier development. A Design For Automatic Assembly, (DFAA) analysis is important and should be performed at an early stage to get rid of unnecessary components or to integrate components with each other. The goal is to make the product more assembly-friendly and flexible so that both humans and robots can assemble the product. This chapter describes DFAA which is more practical and easy-to-use method. The method aims to offer a clear picture of which components and tasks should be prioritized in order to increase the level of automation. If applied correctly, this method can also lead to increased cooperation between design and manufacturing departments, which may potentially eliminate assembly-related problems already during the design phase. The method can also be used in order to determine what type of gripper (end-effector) to use if the task is to be automated, this will be further explained in chapter 8.

The acronym for Methods-Time Measurement, a method used for optimizing movements and determining the time needed for different tasks.

Pa r t I M eth o d s

Description There are thirteen rules of thumb in a DFAA analysis, all of which aim to create a more assembly-friendly product. These rules of thumb can also be used to automate the actual assembly (e.g., fixtures, base component and direction of assembly). The first two rules can be connected to assembly time and number of tasks. The number of components are also closely connected to inventory and standardization of components. The base component is the most important component since most of the fixtures and the order of the assembly is decided based on this component, so this needs some extra thought. It is also important to adapt the rest of the component to the selected way of assembly. This can be done by starting to sort the components into subgroups and then do a precedence graph of the order of the assembly, see Figure 2.3. For higher levels of automation – such as robots – gripping, grasping and placing become vital as well. These are the thirteen rules of thumb: 1 2 3 4 5 6 7 8 9 10 11 12 13

Minimize the number of components. Minimize the number of attachment points. Select a suitable base component. Ensure that the base component does not have to be reoriented. Select an effective assembly fixture. Ease the access to the component. Adapt components to selected assembly procedure (e.g., manual, robot, collaborative station, special machine). Seek to use symmetrical components. Seek to use components that are symmetrical in the direction of assembly. If asymmetric components exist, let these be clearly asymmetric. Seek to create assembly from one direction that is linear. Take advantage of beveling, guidance and elasticity for easier fitting. Maximize accessibility during assembly.

Background illustration: Shutterstock.com/EtiAmmos

2 Design fo r automatic assembly (DFAA )

In order to create a structured way of dealing with these thirteen rules of thumb, twenty-three questions or statements have been developed to have a more quantitative why of comparing different products and components, the questions are to be found in Appendix 1. The method is carried out in two steps: first, the product itself is analyzed, after which the various components are analyzed in relation to each other.

Analysis at product level The analysis at the product level is intended to assess a product’s potential for improvement and whether early changes can be made. The analysis is performed in relation to seven areas, each of which contains a key question to be answered and evaluated (see Appendix 2). These answers are ranked according to a points system, where 1 represents an undesired solution, 3 is a decent solution and 9 is the best solution. This ranking clearly shows whether a product or component has a desired or undesired solution. A maximum of 63 points is possible at the product level and everything below this number is to be seen as potential for improvement in terms of automation.

Product level

(questions per product/module) Reduce the number of components Unique components Base object Design base object Directions of assembly

Figure 2.1 The seven areas of analysis at the product level. Source: Axelsson & Rapp, 2002

Parallel operations Tolerance chains

The Seven areas exemplified through the gearbox Minimize the number of components is addressed in two of the seven areas. The number of components is to be minimized and, if possible, remain the same throughout the entire product family. Everything from bolts and nuts to O-rings and the like is included and thus need to be counted. If the number of components becomes too large, the costs for inventory and logistics go up. Replacing compo© T H E A U T H O R S A N D S T U D E N T L I T T E R AT U R

Pa r t I M eth o d s

nents or updating a product becomes more difficult if the product contains unique components. The analysis contains two questions that take the overall number of components and the number of unique components into account. To constitute an optimal solution, the product (or subproduct) should contain no more than 20 components and the ratio between the number of unique components and the total number of components should be less than 40 percent. The gearbox has 21 components in total and a total of 13 unique components, illustrated in Figure 2.2.

Figure 2.2 The gearbox. Photo: Dan Li

The choice of base component and associated fixtures is key in relation to all forms of assembly. As said before, this is a very important step in the methodology. A base component is important for being able to implement an automated process. The term base component refers to a component constituting the core of the product. A base component is optimal if it is possible to easily assemble components from above or from the side (so-called sandwich or hamburger assembly2). Figure 2.3 shows how four smaller components are assembled to the base component from above. An optimal assembly is performed in one direction of assembly to minimize the number of different orientations of the base component. Furthermore, designing fixtures is facilitated if there is only one base component and one direction of 2

Assembly is always performed from above or the side.

2 Design fo r automatic assembly (DFAA )

Figure 2.3 The large plate is an example of a so-called base component. Photo: Åsa Fast-Berglund

assembly. The goal is to develop the base component so that only one fixture is required and that the remaining components serve as fixtures for each other. Parallel operations can be used when the direction of assembly differs from the base component or in order to prevent rotation (i.e., if the components cannot be assembled from above or the side but first need to be assembled in a different way). Parallel operations are also used if there is an imbalance in cycle times, since the total lead time may then be reduced. In cases of several parallel flows, however, many logistics points may represent a problem. It may also be difficult to get an overview of the flow. The best way to get started on the graph is to cluster the components into subgroups and then divide them into stations. The next step is to understand in what order the subgroups can be assembled onto the base component. The gearbox has four clear subgroups if the base component is excluded (illustrated in Figure 2.4). The next step is to do pre-assembling of the subgroups and measure cycle time and analyze difficulties in the pre-assembling. By doing a pre-assembly, a precedence graph can be designed in order to see how many parallel stations there are, this is brought up in chapter 3 when a task analysis is done.

Åsa Fast-Berglund is a professor in smart automation in production systems at the division IMS at Chalmers university of technology. Her research focuses on how automation (cognitive and physical) can support humans in order to achieve flexible and adoptable workplaces. She is an operational manager at the national testbed Stena Industry Innovation Lab (SIILab). Sandra Mattsson was awarded her PhD in production systems in 2018 with a focus on perceived complexity in assembly. Since then, she has worked as a researcher at RISE (Research Institutes of Sweden), supporting small and medium-sized companies regardingdigitalization, robotics and other types of changes linked to human-technologyorganization.

SMART AUTOMATION SEVEN METHODS FOR FINAL ASSEMBLY Smart Automation – Seven Methods for Final Assembly is a manual presenting seven methods guiding the reader when it comes to smart ways of choosing the appro priate level of automation. The book presents new perspectives on automation by combining older methods with new ones, thus presenting a broad picture of automation strategies. The book has a practical focus. The first part describes the various methods, while the second and final part presents the reader with the theoretical foundation of the different methods. The target group includes students in the fields of production engineering, mechanical engineering, mechatronics, design and industrial management. The book is also wellsuited for professional training, such as production engineers.

Art.No 43421

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