Predetermined Motion Time Systems Research Articles

Regressionsbasierte Ermittlung von Ausführungszeiten in Mensch-Roboter-Kollaboration

Abstract The intensifying competitive pressures in manufacturing companies, combined with the expanding array of product variants, are propelling the integration of human-robot collaboration in operational frameworks. Effectively planning assembly processes demands particularly streamlined methods for assessing execution times, especially in the initial planning phases. While predetermined motion time systems are designed for human tasks, this contribution puts forth an approach for the time-economic analysis of robot movements without resorting to simulation.

3D standard motion time-based ergonomic risk analysis for workplace design in modular construction

As construction workers are frequently exposed to ergonomic risks, accurate ergonomic risk analysis for workplace design is needed in order to mitigate risk and, consequently, improve productivity. Researchers have sought to identify ergonomic risks of continuous motions in 3D visualizations to achieve proactive workplace designs. However, the motion time is subjectively determined by designers, leading to variable risk ratings and making it difficult to make decisions on design alternatives. This paper proposes an automated 3D standard motion time-based ergonomic risk analysis method that systematically determines motion times and accurately quantifies ergonomic risks of continuous motions for workplace design. The ergonomic risk of continuous motion is assessed using existing tools such as REBA and RULA by incorporating standard motion times determined by a predetermined motion time system. The effectiveness of the proposed method is validated in a case study of two workplace designs for manual assembly tasks in modular construction.

3D ergonomics-based motion-level productivity analysis for intelligent manufacturing in industrialized construction

In industrialized construction, accurate estimations of labour productivity and associated cycle times of repetitive operations are crucial for reliable production planning and scheduling. However, the reliability of the standardized productivity and cycle time analyses is hindered by their dependence on various factors that change with the increasing complexity of the working environment, as well as by inherent challenges involved in acquiring accurate measurements. Thus, this study proposes an automated 3D ergonomics-based motion-level productivity analysis method for intelligent manufacturing in industrialized construction that combines an existing predetermined motion–time system with ergonomic risk assessments and 3D modelling techniques. The actual and simulated cycle times and ergonomic risks of preliminary cases in the experiment are analyzed to demonstrate the feasibility and reliability of the proposed method. The proposed method can be implemented to improve occupational safety, increase the reliability of planning and scheduling, and boost the overall productivity of industrialized construction.

Measurement of Standard Time Work with the Predetermined Motion Time System Method at the Production Department in PT.PIJ Sidoarjo

Measurement of Standard Time Work with the Predetermined Motion Time System Method at the Production Department in PT.PIJ Sidoarjo

A simulation and visualization-based framework of labor efficiency and safety analysis for prevention through design and planning

Abstract Considering the physically demanding nature of manual tasks in the construction industry, an effective approach to mitigating ergonomic risks is to prevent the unsafe working conditions proactively during design and planning, also known as Prevention through Design (PtD). However, there is a lack of approaches for identifying the potential ergonomic risks of a proposed design that can effectively address designers' lack of familiarity with ergonomic risks and understanding of the PtD concept and its implementation. Furthermore, it is difficult to evaluate the impact of ergonomic interventions on productivity and vice versa using available tools. Thus, an integrated approach to PtD is proposed by developing a comprehensive framework that uses simulation modeling, coupled with Predetermined Motion Time Systems (PMTS) and ergonomic and biomechanical assessment, as well as workplace visualization, in order to incorporate both productivity and safety analysis into the design process. The results of implementing the proposed approach indicate its effectiveness in achieving optimum designs in terms of efficiency and safety by evaluating different scenarios of carrying out construction manual operations. The proposed framework also enables evaluating the relationship between safety and productivity from a physical perspective.

Towards immersive designing of production processes using virtual reality techniques

The paper provides a novel approach to the implementation of virtual reality within planning and design of manual processes and systems. The use of hardware and software that is required to perform different production -- especially assembly -- tasks in a virtual environment, using CAD parts as the interactive elements, is presented. Considering the CAD parts, the format conversion problem is comprehensively described and solved using format conversion software to overcome the present poor data connectivity between the CAD system and VR hardware and software. Two examples of work processes have been made in a virtual environment: peg-in-hole and wall socket assembly. In the latter, the traditional planning approach of manual assembly tasks using predetermined motion time system MTM- 2 have been compared with a modern approach in which the assembly task is fully performed within a virtual environment. The comparison comprises a discussion on the assembly task execution times. In addition, general and specific advantages and disadvantages that arise in the immersive designing of production processes using virtual reality are presented, as well as reflections on teamwork and collaborative man-machine work. Finally, novel technologies are proposed to overcome the main problems that occur when implementing VR, such as time-consuming scene defining or tedious CAD software data conversion.

Subjective estimates of times for assembly work

Research by Chan and Hoffmann (2013, 2016) showed that people can estimate task times with reasonable accuracy. That work included experiments on Fitts’ task, a double component movement task, pin-to-hole assembly and ballistic movement tasks. In each case, a linear relationship was found relating subjective estimates of task time and actual task times. In this research, the work has been extended to two industrial assembly tasks: assembly of a U-bolt from components and the more complex task of assembling a hacksaw. These tasks were done in an ergonomically designed work space, with components placed within the Normal Work Area and using jigs for convenience of using two-handed assembly. Actual and estimated component times were obtained from video and voice recordings. Results showed that estimated times were lower than actual assembly times, but higher than times predicted using the MODAPTS predetermined motion time system. Participants appeared to have most difficulty estimating times for task components involving fine manipulation, such as inserting and tightening screws.

Teaching Methods-Time Measurement (MTM) for Workplace Design in Learning Factories

Methods-Time Measurement (MTM) has its roots in time studies as a predetermined motion time system. It can however also be used in the field of workplace design and improvement. High amount of work effort for the creation of MTM-analyses and time-consuming trainings in MTM often lead to a decline in the use of MTM.A potential solution for the human resources management of companies could be practice-oriented trainings with MTM as a method for workplace design. A lot of job profiles (e.g. process engineer) in manufacturing do not need a complete MTM training, as they do not require the full time-study aspect of MTM. This article represents an approach for MTM workplace design training in a learning factory.

Micro-motion level simulation for efficiency analysis and duration estimation of manual operations

Abstract Due to the labour-intensiveness of the construction industry, accurate estimation of cycle time of manual activities is essential for reliable planning and scheduling of operations. Labour productivity study is used in current practice to obtain the required cycle time of manual tasks. However, the reliability of labour productivity study in estimating durations of manual activities is inhibited by its dependence on various factors which change with the different working conditions of construction jobsites and the difficulties associated with measuring productivity. This study thus investigates the use of a predetermined motion time system (PMTS) for modelling manual construction operations for cycle time estimation and efficiency evaluation. A motion-level simulation approach is developed by integrating PMTS into discrete-event simulation (DES) modelling, providing an automated and simple-to-use method of analysing manual tasks. As a case study, manual construction operations from a construction jobsite with different levels of repetitiveness are modelled, and the actual and simulated cycle times are compared and analysed. The results confirm the effectiveness of a PMTS-based simulation approach to modelling manual construction operations and its reliability in estimating the duration of manual tasks.

A Model for Complexity Assessment in Manual Assembly Operations Through Predetermined Motion Time Systems

Manual assembly processes are favoured for supporting low volume production systems, high product variety, assembly operations that are difficult to automate and manufacturing in low-wage countries. However, manual operations can dramatically impact assembly cycle times, quality and cost when the complexity of the manual operation increases. This paper proposes a method for assessing the process complexity of manual assembly operations, using a representation of manual operations based on predetermined motion time systems. The purpose of this framework is to provide a tool that can be used practically to assess, and therefore control, the complexity of manual operations during their design.

The effects of age to meet the standard production rate.

This study evaluated the energy expenditure of workers in physical work tasks in order to determine if people of different ages and gender carry out repetitive activities according to the recommended limits of energy at work. Exploring whether age is a significant factor to achieve industrial production rates and determine its possible consequences. A laboratory experiment was conducted with people age 20 to 58 years split by gender into four age groups. Oxygen consumption and heart rate were measured as variables of response to the physical workloads. When carrying out repetitive moderate load operations, women aged over 30 years exceeded the recommended energy expenditure (95% CI). For heavy activities, only men in the age groups 20-39 and 30-40 years could perform these tasks without exceeding the recommended oxygen consumption (95% CI). The industrial predetermined motion time systems do not take into account the effects of age and gender difference on energy production when obtaining cycle times in activities with significant aerobic loads. Manufacturing processes have specific standard times that might be inappropriate if they are performed by individuals who do not meet the standard energy production capacity.

Ergonomists’ and Engineers’ Views on the Utility of Virtual Human Factors Tools

AbstractA qualitative research study was conducted through explorative workshops to better understand the experiences, perceptions, needs, and expectations of the users and potential users of virtual human factors (VHF) tools. Five VHF tools were presented to ergonomists, engineers, and managers who participated in four whole‐day interactive workshops: HF enabled predetermined motion time systems (PMTS), discrete event simulation (DES), complex and simple digital human models (DHM), and virtual reality (VR). Data were collected by note‐takers, digital audio recording, and written feedback. Identified characteristics shared by the tools were organized into 9 categories that act as a motivational or deterring factor for the use of the tool: time, cost, training, difficulty of use, trustworthiness, graphics, flexibility, usefulness, and report presentation. Other tool specific areas of improvement were also identified by participants to help developers improve these design instruments.

Using a formal high-level language and an automated manikin to automatically generate assembly instructions

This paper presents an approach to automatically generate predetermined motion time system (PMTS) based assembly instruction lists from simulations within digital human modelling (DHM) software. A formal high-level instruction language is used to instruct an automated manikin to perform assembly operations. The manikin, the language and the assembled objects are composed into a discrete model. In a post-computational step, the model is used to construct PMTS instruction lists by mapping the manikin motions, assembled objects and the language instructions onto a set of PMTS keywords. The described approach is implemented in the DHM software IMMA and tested on industrial cases of manual assembly in the automotive industry.

Improving MTM-UAS to predetermine automotive maintenance times

The preventive knowledge of serviceability times is a critical factor for the quantification of after-sales services costs of a vehicle. Predetermined motion time system are frequently used to set labor rates in industry by quantifying the amount of time required to perform specific tasks. The first such system is known as Methods-time measurement (MTM). Several variants of MTM have been developed differing from each other on their level of focus. Among them MTM-UAS is suitable for processes that average around 1–3 min. However experimental tests carried out by the authors in Elasis (Research Center of FIAT Group) demonstrate that MTM-UAS is not the optimal approach to measure serviceability times. The reason is that it doesn’t take into account ergonomic factors. In the present paper the authors propose to correct the MTM-UAS method including in the task analysis the study of human postures and efforts. The proposed approach allows to estimate with an “acceptable” error the time needed to perform maintenance tasks since the first phases of product design, by working on Digital Mock-up and human models in virtual environment. As a byproduct of that analysis, it is possible to obtain a list of maintenance times in order to preventively set after-sales service costs.

Ballistic movements on data-entry keypads

Research to date on movement times on data-entry keypads has assumed that the movements are made under visual control [Drury, C.G., Hoffmann, E.R., 1992. A model for movement times on data-entry keyboards. Ergonomics 35, 129–147; Hoffmann, E.R., Tsang, K.T., Mu, A., 1995. Data-entry keyboard geometry and keying movement times. Ergonomics 38 (5), 940–950; Silfverberg, M., MacKenzie, I.S., Korhonen, P., 2000. Predicting text entry speed on mobile phones. In: Proceedings of the ACM Conference on Human Factors in Computing Systems – CHI 2000. ACM, New York, pp. 9–16]. This is often not the case; where the value of Fitts’ Index of Difficulty is low, it is likely that movements will be made ballistically. A survey of commonly used keypads on devices such as mobile phones and ATMs shows that there is a need to study movement times when these ID values are less than those for which movements are likely to be made under visual control [Gan, K.-C., Hoffmann, E.R., 1988a. Geometrical conditions for ballistic and visually-controlled movements. Ergonomics 31, 829–839]. A series of experiments on simulated and real keypads indicates that the ballistic form of movement is generally valid and may be modelled by a modification of the ballistic movement time model of Hoffmann [1981. An ergonomics approach to predetermined motion time systems. In: Australian Institute of Industrial Engineers, Proceedings, Ninth National Conference, pp. 33–47] and of Gan and Hoffmann [1988a. Geometrical conditions for ballistic and visually-controlled movements. Ergonomics 31, 829–839l; 1988b. Sequential ballistic movement. Ergonomics 31 (10), 1421–1436]. A model is developed for the time to complete sequences of number entries containing up to 5 numbers. In this model, the movement times are related to the square-root of the sum of the movement amplitudes. Relevance to industry Many industrial applications require the use of keypads for data entry. Movements may be made ballistically or visually controlled, depending on the geometry of the keypad. As the time for data entry is dependent on geometry, a model for time taken is necessary for predicting human performance.

Developing a specific predetermined time study approach: an empirical study in a car industry

Determining accurate assembly cycle times in the car industry is an integral part of efficient production, human and facility planning. Three types of methods are available for determining cycle time for manual processes, including: estimating methods, direct observation method (stopwatch), and predetermined motion time systems (PMTSs). Estimating methods cannot determine accurate times. The direct observation method cannot be used for non-existent stations; in addition, this method is very tedious. Although PMTSs are able to properly determine assembly cycle times, some problems have decreased their usage. This paper presents the results of a project accomplished in the Iran-Khodro Car Company (IKCO), the most famous vehicle manufacturing factory in Iran and the Middle East. A particular predetermined time study approach is developed in this company which covers all body shop operations. Besides, some special time tables are developed by the combination of MOST and work time table standards. Finally, an easy-to-use worksheet is designed which can be filled out by moderately educated practitioners. The potential errors will be minimised in the proposed approach to compare with existing ordinary methods.

Inserting cost effectiveness to the ergonomic equation when considering practical solutions

From a practical point of view, the cost effectiveness of ergonomic solutions is often questioned. Many times managers omit ergonomic solutions because of their high cost. This paper introduces a way to implement cost effective ergonomic solutions by coupling computer-aided design and predetermined motion time systems. This is done by generating a comparison between the operation times and body motions used in existing and safer work situations. We demonstrate using two case studies how solutions may impact operation times and stress, to which workers are subjected, which may be expressed in relaxation allowances required for resting and recovery. The ‘final product’ which may interest management the most, the ergonomic recommendations, is presented in easy to understand figures and numbers, including time to return on investment on relevant ergonomic solutions, which becomes possible when suggested improvements to work-situations are translated to time and cost.

Effect of transported mass and constant force on times for ballistic and visually-controlled movements.

A series of experiments are reported in which the effects of transferred mass and resistive/assistive forces were investigated for both ballistic and visually-controlled movements. The first experiment involved the transfer of mass in the horizontal plane so that only inertia] forces were present. This was followed by experiments in which movements were made with a purely resistive or assistive force, without the presence of increased inertia. Finally the effects of transferring mass in the vertical direction were investigated, where resistive/assistive forces were present due to gravity, as well as increased inertia force due to the transferred mass. Both theoretical and empirical models are presented for each of these cases. It was found that, for both ballistic and visually-controlled movements, the data were well accounted for simply by a component of added time proportional to the transferred mass or the magnitude of the constant force. This result is in agreement with the procedure used in some predetermined motion time systems.

Computer application of a natural-language predetermined motion time system

Most PMTS (Predetermined Motion Time Systems) in common use today employ some sort of coding system to classify various human motions. This requires fairly extensive training to determine what codes to apply to motions observed. The new computer system FAST uses a “natural language” approach to find standard times within the system, a technique called “Element Language”. This smart software just begged for a natural-language predetermined motion time system (PMTS). The author studied a number of PMTS in depth, including MTM-1, MTM-2, MTM-UAS, MSD (Master Standard Data), MOST, and MODAPTS. Although quite similar in the way that human motions were classified, each system employs a different coding system for the motions. Based on this research, a new PMTS called MST (Motion Standard Times) was developed by the author, using more self-descriptive, natural language “coding”.

Computerized predetermined motion-time systems in manufacturing industries

In recent years, a number of computerized work measurement systems have been developed. In particular, attempts have been made to computerize the manual versions of existing predetermined motion-time systems (PMTS). This can be attributed to the spread of computer technology in the last decade which may further the application of PMTS in manufacturing industries in terms of speed, ease of use, and minimization of degree of judgement on the part of the analyst in establishing time standards. The main objective of this paper is to survey the various computerized PMTS. In particular, this study will examine the computerized systems of Methods-Time Measurement (MTM), Modular Arrangement of Predetermined Time Standards (MODAPTS), and Maynard Operation Sequence Technique (MOST) due to their popular and worldwide support. The background and computer application of the aforementioned systems are discussed. Furthermore, comparative examples are given to illustrate the advantages and limitations of each system.