The aim of these tools is to analyse the risk factors that may lead to overload the operator and eventually to occupational diseases.
The need to identify the degree of exposition to biomechanical load has led at the beginning of the new millennium to the development of specific ergonomic risk screening tools; aim of these tools is to analyse the risk factors that may lead to overload the operator and eventually to occupational diseases. As always, the final goal is the redesign of the work system so that the any risk can be minimized and the performance eased.
The basis of every ergonomic risk screening tool is to estimate the correlation between the task ergonomic characteristics (force, frequency, postures, etc.) and the probability to cause an occupational disease. The main difficulty is to establish how the different factors interact and lead to work related troubles or diseases.
Certainly the best approach is the prevention of the risk in the design phase of the work system (preventive ergonomics); if the product and/or the process is already defined, changes may be too costly and less efficient (corrective ergonomics).
For a quantitative ergonomic risk evaluation of a specific working sequence, generally two evaluation levels are used:
First level tools: risk screening tools which require a quick checklist.
Second level tools: risk evaluation tools which require a detailed analysis with index calculations. They are applied where a possible risk has been already detected by a 1st level system and the “risk generator” is not yet well identified.
The aim of First level tools is to get a very quick mapping of the different risk areas and to concentrate all the efforts on a rapid redesign. With the Second level tools specific loads are analyzed in detail, since the first level corresponding tool was insufficient to identify the origin of the risk.
Though the EAWS is presented as First level tool, it is quite analytical and it always identify the origin of the risk.
In the following table the risk areas, the correlated standards and the most common ergonomic tools are summarized.
The needs to comply with the standards pushed the companies to have at their disposal a 1st level ergonomic analysis system to evaluate the biomechanical load in its components (postures, forces, etc.) for the whole body. The EAWS meets these requirements. During its development in particular the following design criteria were taken into account:
The tool had to be accepted and considered exhaustive by:
Applicator deviations – e.g. the gap between the analysis results of different applicators – had to be minimized, rendering the identification and measuring of technical actions, awkward postures and forces at maximum objective.
The tool should have the capability to be used during the planning of the product/process as well as in the production process.
The main aims of the development of the EAWS system were:
EAWS is originally an extension of the Automotive Assembly Worksheet (AAWS) developed by the IAD (Institut of Ergonomics at the Darmstadt University of Technology) on the basis of the “New Production Worksheet”, initiated 1997 by General Motors Europe (GME), and the “DesignCheck”, realized at the same time at Porsche. The development of the EAWS was carried out between 2006 and 2008, by occupational health, biomechanical and industrial engineering international experts from all over the world, coordinated by the IMD (International MTM Directorate).
The field test was run in multinational companies that allowed the team to analyze relevant processes that represented different production contests. In this way all the necessary tests were performed before the last release of the tool (Field Application Group).
In addition, software companies were involved during EAWS development in order to implement and develop specific software solutions based on EAWS structure (Engineering Application Group).
IMD and national MTM Associations, together with the experts that worked with the team, gave all the tests results to the reference teams that represent the EAWS users main process partners (Reference Groups). The general project organization during the development phase was the following:
FIAT auto, Mirafiori Torino Plant
BOSCH Diesel Technologies and Breaking Systems (BA)
WE: Whirlpool Europe (Home Appliances), Amiens plant, France
IVECO: commercial vehicles, Suzzara plant
Volkswagen: automotive (IAD)
EAWS is an ergonomic tool for measuring the workload generated in a workstation by a given working method (motion sequence, workplace geometries, postures, equipment, parts, conditions) executed according to a given production plan (quantity and production mix) with a given work organization (shift duration, pauses).
EAWS can also be used as a an ergonomic 1st level risk screening tool providing an overall risk evaluation, where the risk is due to any biomechanical load. Up to a certain extent EAWS can also be used as 2nd level analysis tool, since it is quite analytical and detailed; EAWS gives the necessary information to redesign the work task, making the second level systems seldom necessary.
The risk assessment model is defined more comprehensive in the International Standard ISO 11228 Part 2 (Pushing and Pulling) at page 3.
The structure of the analysis is as follows:
Macro-Section “Whole body”:
Macro-Section “Upper limbs”:
Whole body and upper limbs scores are evaluated on the same scale.
The EAWS system can be used in two different modes, which differ in scope and calculation procedure:
For a quick ergonomic risk assessment on an observed specific worker performing the work task on the shop-floor (observational method)
Paper & pencil tool à two double-sided A4 sheets with interpolation
Analysis refers to observed work task and operator (deviation risk from planned method)
Risk factors estimated by users (forces, durations, frequencies, etc…)
Quick workstation re-design
ergonomic risk assessment of the workstation on a generic worker performing the standard work task (MTM method)
Software tool: IVGA (Excel based)
Useful to assess the ergonomic impact of method improvement opportunities
For a preventive and analytic ergonomic risk assessment on an anthropometric group of operators performing a work task (MTM method)
Software tool: TiCon – MTMergonomics®
MTM task analysis
Production plan for frequencies calculation
MTM codes ergonomic characterization (geometries, forces, weights, etc…)
Production flow macro-geometries (heights) and product positions (high, low, etc…)
The basic EAWS form structure is the following: