Production Systems for Manual Repetitive Jobs. Effects on Autonomy and Variety of Work and Prevalence of Musculoskeletal Disorders in Upper Limbs

The aim of this thesis is to improve workers\u27 conditions and it deals particularly with companies in the engineering industry. In many of these companies, production systems are designed to have manual repetitive jobs. Many such jobs are characterized by static work positions and repetitive motions, which are considered to be risk factors for musculoskeletal disorders in the upper limbs. There is a lack of knowledge of how to prevent the development of such disorders, but a variety of tasks and muscular activities are viewed as a means for preventing musculoskeletal disorders in upper limbs. Autonomy can be seen as a prerequisite for variety. In this thesis, the overall objective was to gain better knowledge of how to design production systems for manual repetitive jobs. A first purpose was to analyze how manual repetitive jobs in the engineering industry were in fact designed. A second purpose was to study interrelationships between work roles, work behavior, work-related stress and the prevalence of musculoskeletal disorders in the upper limbs, as well as how individual worker characteristics influence these relationships. The work has thus been explorative. Four case studies were made in two companies where the methodology mainly involved interviews, medical examinations, observations of work, use of questionnaires and video recordings. Three reference case studies were also carried out. All case studies focused on work groups. The thesis work emerged in a number of stages. Initially, a method for detailed analyses of hand and arm movements was developed on the basis of technical and medical methods. The so called Hand-Arm-Movement-Analysis (HAMA) method was used to analyze assembly tasks and illustrate work methods and work positions in the first case study. Using theories and empirical data, three theoretical models were successively developed during the thesis work. The models were used as a frame of reference in the analysis of the production systems studied. One model treats relationships between work role, work behavior, work-related stress and influence of individual worker characteristics, while the two other models treat the design of and factors influencing the design of production systems. Briefly, a production system is described as consisting of a social and a technical system. The results of the case studies show that manual repetitive jobs were designed differently, with different task contents, both within and between the companies studied. This especially concerned the extent to which workers were given autonomy and variety in their work, which differed between the work groups as well as the different work roles. The results show that workers differed greatly as regards work behavior (i.e. work method, work pace, work position and work-rest patterns) even when carrying out the same task. The prevalence of musculoskeletal disorders in the upper limbs was highest in the company in which workers were given higher autonomy as regards the technical system, more limited autonomy as regards the social system, high object variety and limited motor variety. The conclusion arrived at in this thesis is that there are many aspects of autonomy and variety that should be considered when production systems are designed, as autonomy and variety were found not to be one-dimensional concepts. More research is needed to analyze the importance of different aspects of autonomy and variety for the risk of musculoskeletal disorders in the upper limbs.More research is also needed to validate the theoretical models presented

Production Systems for Manual Repetitive Jobs. Effects on Autonomy and Variety of Work and Prevalence of Musculoskeletal Disorders in Upper Limbs

The aim of this thesis is to improve workers\u27 conditions and it deals particularly with companies in the engineering industry. In many of these companies, production systems are designed to have manual repetitive jobs. Many such jobs are characterized by static work positions and repetitive motions, which are considered to be risk factors for musculoskeletal disorders in the upper limbs. There is a lack of knowledge of how to prevent the development of such disorders, but a variety of tasks and muscular activities are viewed as a means for preventing musculoskeletal disorders in upper limbs. Autonomy can be seen as a prerequisite for variety. In this thesis, the overall objective was to gain better knowledge of how to design production systems for manual repetitive jobs. A first purpose was to analyze how manual repetitive jobs in the engineering industry were in fact designed. A second purpose was to study interrelationships between work roles, work behavior, work-related stress and the prevalence of musculoskeletal disorders in the upper limbs, as well as how individual worker characteristics influence these relationships. The work has thus been explorative. Four case studies were made in two companies where the methodology mainly involved interviews, medical examinations, observations of work, use of questionnaires and video recordings. Three reference case studies were also carried out. All case studies focused on work groups. The thesis work emerged in a number of stages. Initially, a method for detailed analyses of hand and arm movements was developed on the basis of technical and medical methods. The so called Hand-Arm-Movement-Analysis (HAMA) method was used to analyze assembly tasks and illustrate work methods and work positions in the first case study. Using theories and empirical data, three theoretical models were successively developed during the thesis work. The models were used as a frame of reference in the analysis of the production systems studied. One model treats relationships between work role, work behavior, work-related stress and influence of individual worker characteristics, while the two other models treat the design of and factors influencing the design of production systems. Briefly, a production system is described as consisting of a social and a technical system. The results of the case studies show that manual repetitive jobs were designed differently, with different task contents, both within and between the companies studied. This especially concerned the extent to which workers were given autonomy and variety in their work, which differed between the work groups as well as the different work roles. The results show that workers differed greatly as regards work behavior (i.e. work method, work pace, work position and work-rest patterns) even when carrying out the same task. The prevalence of musculoskeletal disorders in the upper limbs was highest in the company in which workers were given higher autonomy as regards the technical system, more limited autonomy as regards the social system, high object variety and limited motor variety. The conclusion arrived at in this thesis is that there are many aspects of autonomy and variety that should be considered when production systems are designed, as autonomy and variety were found not to be one-dimensional concepts. More research is needed to analyze the importance of different aspects of autonomy and variety for the risk of musculoskeletal disorders in the upper limbs.More research is also needed to validate the theoretical models presented

Evaluation of ergonomics in a virtual manufacturing process

This paper presents a study of the evaluation of ergonomics using virtual tools in a pre-production phase when verifying the manual assembly of the XC90 car model at the Volvo Car Corporation. The case study focused especially on the verification of visual demands in assembly work due to its complexity. The virtual development process was mapped in observations of the use of virtual tools and interviews with actors involved in the verification. Results show that computer manikins are viable tools in verifying ergonomics early in a development process and that they help to detect many problems prior to physical pre-series. There are, however, substantial improvement potentials, both in the software itself and, even more, in the process of using virtual tools. The study identified several factors that can increase the reliability of the results of computer manikin simulations (e.g. participative ergonomics and documentation issues). The special focus on visual demands shows the need of basic knowledge about human behaviour for making valid simulations. This case study stresses the need for knowledge about simulations in both analysis and interpretations in order to achieve maximum output from a virtual manufacturing process

Utv\ue4rdering av ErgoSAM. Handbok. Utf\uf6rd vid vid Volvo Personvagnar AB i samarbete med Arbetslivsinstitutet V\ue4st, G\uf6teborg, Sverige.

SammanfattningErgoSAM \ue4r en produktionsteknisk metod avsedd att anv\ue4ndas av tekniker med viss belastningsergonomisk kompetens. Metoden \ue4r baserad p\ue5 systemet Sekvensbaserad Aktivitets- och Metodanalys, SAM och har ut\uf6kats med information om arbetsomr\ue5de (zon) och vikt p\ue5 hanterade f\uf6rem\ue5l. Syftet med ErgoSAM \ue4r att f\ue5 en f\uf6rsta indikation p\ue5 den fysiska belastningsniv\ue5n f\uf6r ett arbete, inte att f\ue5 en detaljerad och fullst\ue4ndig belastningsergonomisk analys. Metoden \ue4r speciellt t\ue4nkt att anv\ue4ndas i en utvecklings- eller f\uf6r\ue4ndringsfas av en arbetsplats, d\ue4r sj\ue4lva arbetsplatsen \ue4nnu inte existerar fysiskt, f\uf6r att tidigt uppt\ue4cka eventuella brister i arbetsplatsutformningen som medf\uf6r h\uf6ga fysiska belastningsniv\ue5er f\uf6r de som skall utf\uf6ra arbetet. Metoden \ue4r utformad som ett Excel-program.ErgoSAM har utvecklats vid Lindholmen Utveckling AB i samarbete med Volvo Cars, Torslanda, och ITT Flygt AB. Tv\ue5 utv\ue4rderingar har tidigare genomf\uf6rts av ErgoSAM, vilka har visat att metoden \uf6verensst\ue4mmer v\ue4l med resultat fr\ue5n andra ergonomiska metoder. Dock fanns behov av ytterligare en utv\ue4rdering innan en vidare anv\ue4ndning medges vid olika f\uf6retag. Denna rapport beskriver resultatet av denna tredje utv\ue4rdering.Utv\ue4rderingen genomf\uf6rdes f\uf6r fem arbetsuppgifter (s\ue5 kallade balanser) vid Volvo Cars monteringsfabrik i Torslanda. Totalt analyserades 28199 TMU (17,4 min). De fem balanserna representerar b\ue5de fysiskt l\ue4ttare och tyngre arbetsuppgifter. F\uf6r respektive balans gjordes analyser med ErgoSAM av en erfaren produktionstekniker. Dessutom gjordes belastningsergonomiska analyser f\uf6r de fem balanserna enligt Volvo Cars ergonomiska kravspecifikation (koncernstandard). De ergonomiska analyserna utf\uf6rdes, f\uf6r varje SAM aktivitet, av en erfaren ergonom vid Celero Support AB.Resultaten visar att ErgoSAM \ue4r en bra metod, med vilken man enkelt kan analysera en arbetsplats f\uf6r att bed\uf6ma den fysiska arbetsbelastningen. Metoden tar inte h\ue4nsyn till alla belastningsergonomiska parametrar, men ger en ganska bra bild av belastningen f\uf6r ett analyserat arbete. De belastningsergonomiska analyserna visade generellt en n\ue5got h\uf6gre arbetsbelastning j\ue4mf\uf6rt med ErgoSAM. Den viktigaste f\uf6rklaringen till detta \ue4r att 28 ergonomiparametrar anv\ue4nds i bed\uf6mningen med Volvos belastningsergonomiska kravspecifikation j\ue4mf\uf6rt med tre parametrar i ErgoSAM. Detta inneb\ue4r en st\uf6rre noggrannhet vid bed\uf6mning med anv\ue4ndning av Volvos kravspecifikation. ErgoSAM i dess nuvarande utformning tar ej h\ue4nsyn till:•arbetsst\ue4llning och arbetsr\uf6relser f\uf6r nacke, armb\ue5gsleder, hand- och fingerleder, h\uf6ftleder, kn\ue4leder, fotleder och i vissa fall axeln och ryggen•typ av handgrepp (\uf6ver/underhandsgrepp respektive enhands-/tv\ue5handsgrepp) och greppbarhet•den belastnings\uf6kning som uppst\ue5r vid statiskt arbete•Volvos belastningsergonomiska kravspecifikation f\uf6r tex. clips och handmaskiner.En f\uf6rdel med metoden \ue4r det diagram som skapas som resultat av en analys, vilket g\uf6r att det \ue4r enkelt f\uf6r andra att ta del av analysen, \ue4ven f\uf6r personer som inte beh\ue4rskar SAM eller ergonomi. Med de resultatniv\ue5er som f\ue5s (kubv\ue4rden) \ue4r det l\ue4tt att dela in i belastningsniv\ue5erna i tre omr\ue5den, Gr\uf6nt - OK, Gult - Acceptabelt, R\uf6tt - D\ue5ligt. ErgoSAM kan d\ue4rf\uf6r anv\ue4ndas i f\uf6r\ue4ndringsprojekt f\uf6r att \ue5stadkomma en \uf6kad f\uf6rst\ue5else bland mont\uf6rer/operat\uf6rer och andra som p\ue5verkas av en arbetsplatsf\uf6r\ue4ndring.I rapporten ges f\uf6rslag till vidare utveckling av ErgoSAM samt rekommendationer f\uf6r fortsatt anv\ue4ndning av ErgoSAM generellt och specifikt inom Volvo Cars

ErgoSAM - en produktionsteknisk metod f\uf6r tidig identifiering av belastningsergonomiska problem

ErgoSAM is a production technology method designed for use by SAM-authorized engineers with a certain level of proficiency in load ergonomics. The method is based on Sequence-Based Activity and Method Analysis (SAM) and has been expanded with the addition of information about working area (zone) and weight of objects handled. The method is intended specifically for use during a phase of development or change of a workplace where the workplace itself does not yet exist physically to identify at an early stage any shortcomings in the workplace design that will create high levels of physical stress for the person who is to perform the work. ErgoSAM has been validated twice previously in association with ITT Flygt AB and Volvo Cars, Torslanda. A third, and wider-ranging validation was conducted at Volvo Cars during 2001 and is reported on here. This validation analyzed five separate working operations for assembly using ErgoSAM and Volvos specification of load ergonomic requirements. The ErgoSAM analyses were performed by an experienced production technician and the load ergonomic analyses by an experienced ergonomist. The results show that ErgoSAM is an effective method that may be used for simple analysis of a workplace, in order to assess the physical workload, and it is recommended for continued use. Today, the method does not take all load ergonomic parameters into account and could therefore be expanded by the addition of a number of simple checklists to obtain a more comprehensive assessment of the physical workload

Evaluation of ErgoSAM. Handbook. Performed at Volvo Car Corporation in cooperation with the National Institute for Working Life West, Göteborg, Sweden.

Sammanfattning ErgoSAM är en produktionsteknisk metod avsedd att användas av tekniker med viss belastningsergonomisk kompetens. Metoden är baserad på systemet Sekvensbaserad Aktivitets- och Metodanalys, SAM och har utökats med information om arbetsområde (zon) och vikt på hanterade föremål. Syftet med ErgoSAM är att få en första indikation på den fysiska belastningsnivån för ett arbete, inte att få en detaljerad och fullständig belastningsergonomisk analys. Metoden är speciellt tänkt att användas i en utvecklings- eller förändringsfas av en arbetsplats, där själva arbetsplatsen ännu inte existerar fysiskt, för att tidigt upptäcka eventuella brister i arbetsplatsutformningen som medför höga fysiska belastningsnivåer för de som skall utföra arbetet. Metoden är utformad som ett Excel-program. ErgoSAM har utvecklats vid Lindholmen Utveckling AB i samarbete med Volvo Cars, Torslanda, och ITT Flygt AB. Två utvärderingar har tidigare genomförts av ErgoSAM, vilka har visat att metoden överensstämmer väl med resultat från andra ergonomiska metoder. Dock fanns behov av ytterligare en utvärdering innan en vidare användning medges vid olika företag. Denna rapport beskriver resultatet av denna tredje utvärdering. Utvärderingen genomfördes för fem arbetsuppgifter (så kallade balanser) vid Volvo Cars monteringsfabrik i Torslanda. Totalt analyserades 28199 TMU (17,4 min). De fem balanserna representerar både fysiskt lättare och tyngre arbetsuppgifter. För respektive balans gjordes analyser med ErgoSAM av en erfaren produktionstekniker. Dessutom gjordes belastningsergonomiska analyser för de fem balanserna enligt Volvo Cars ergonomiska kravspecifikation (koncernstandard). De ergonomiska analyserna utfördes, för varje SAM aktivitet, av en erfaren ergonom vid Celero Support AB. Resultaten visar att ErgoSAM är en bra metod, med vilken man enkelt kan analysera en arbetsplats för att bedöma den fysiska arbetsbelastningen. Metoden tar inte hänsyn till alla belastningsergonomiska parametrar, men ger en ganska bra bild av belastningen för ett analyserat arbete. De belastningsergonomiska analyserna visade generellt en något högre arbetsbelastning jämfört med ErgoSAM. Den viktigaste förklaringen till detta är att 28 ergonomiparametrar används i bedömningen med Volvos belastningsergonomiska kravspecifikation jämfört med tre parametrar i ErgoSAM. Detta innebär en större noggrannhet vid bedömning med användning av Volvos kravspecifikation. ErgoSAM i dess nuvarande utformning tar ej hänsyn till: • arbetsställning och arbetsrörelser för nacke, armbågsleder, hand- och fingerleder, höftleder, knäleder, fotleder och i vissa fall axeln och ryggen • typ av handgrepp (över/underhandsgrepp respektive enhands-/tvåhandsgrepp) och greppbarhet • den belastningsökning som uppstår vid statiskt arbete • Volvos belastningsergonomiska kravspecifikation för tex. clips och handmaskiner. En fördel med metoden är det diagram som skapas som resultat av en analys, vilket gör att det är enkelt för andra att ta del av analysen, även för personer som inte behärskar SAM eller ergonomi. Med de resultatnivåer som fås (kubvärden) är det lätt att dela in i belastningsnivåerna i tre områden, Grönt - OK, Gult - Acceptabelt, Rött - Dåligt. ErgoSAM kan därför användas i förändringsprojekt för att åstadkomma en ökad förståelse bland montörer/operatörer och andra som påverkas av en arbetsplatsförändring. I rapporten ges förslag till vidare utveckling av ErgoSAM samt rekommendationer för fortsatt användning av ErgoSAM generellt och specifikt inom Volvo Cars