Acceptable peak forces and impulses during manual hose insertions in the automobile industry (original) (raw)
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Human Factors: The Journal of the Human Factors and Ergonomics Society, 2009
Simulated rubber hose insertion tasks were performed in a laboratory study to measure the required clearance around the flange during the insertion. The objective was to determine what effect different insertion methods had on the clearance requirements. Six participants performed 16 insertions using three methods -straight push, oscillate, and rotate -as observed in a field study of automotive truck assembly operations. The participants also performed the task using their own preferred method. The simulated insertions were conducted over two levels of required force. Results showed that the oscillation method required the most clearance around the flange, while the straight push required the least. The data also showed practical increases in the grasp envelope for all methods for the condition of higher required insertion force. When using their own preferred method of insertion, the participants' required clearance levels were similar to a combination of the rotate and oscillate methods. These findings suggest that engineers should consider insertion method when designing clearance levels in an assembly task. They must also consider the required insertion forces and add clearance at higher force levels.
Maximal acceptable forces for manual insertions using a pulp pinch, oblique grasp and finger press
International Journal of Industrial Ergonomics, 2006
The purpose of this study was to investigate the human limitations for electrical connector tasks common to automotive manufacturing. The study employed a psychophysical and biomechanical methodology and included 24 female participants from a wide range of working ages. Each participant was provided with a total exposure of 27 h to a variety of simulated electrical connector tasks, with at least 18 h of training before final testing. The independent variables in this study were grip type (Oblique Grasp, Finger Press, Pulp Pinch), insertion frequency (2, 7 and 12/min) and wrist posture (Extended, Neutral, Ulnar Deviated). For each trial, participants were asked to exert the maximal force that they would find acceptable at the tested frequency for full eight hour work day. For each trial, the dependent variables were maximal acceptable peak force and impulse. There was a main effect of grip type and frequency for both variables, with no significant effects of wrist posture or age. Oblique Grasps had higher acceptable efforts than both the Finger Press and Pulp Pinch, and the acceptable efforts were observed to decrease with increasing insertion frequency. At the lowest frequency (2/min), the recommended peak force TLVs for Oblique Grasp, Pulp Pinch and Finger Press were 41.7, 28.2 and 26.0 N, respectively. On average, participants selected acceptable peak forces that were 62-63% of their absolute maximum for Pulp Pinch and Finger Press grips and 48% of maximum for the Oblique Grasps.
Strength Capabilities and Subjective Limit of Repetitive Manual Insertion Task
Manufacturing industry sector is one of industrializing parties that gives significant contribution in achieving the vision of 2020 in Malaysia. The ability of human works is compulsory in letting the industry to be successful in producing products. Unfortunately, many of painful afflictions of musculoskeletal system as Musculoskeletal Disorders (MSDs) are associated with the working posture. Ergonomic play an important role to give comfort ability to the workers who work at any manufacturing industry. Nowadays, there are so many companies that ignore about the ergonomic of their workers. They tend to push the worker to achieve the output of the company rather than think about comfort ability to the workers on the workstation. This project is conducted to investigate the subjective limit for repetitive manual handling tasks according to workstation area and body posture for workers and the pain or discomfort experienced by the workers while undertaken the task. Also the improvement ...
International Journal of Industrial Ergonomics, 2000
The purpose of the current study was to use a psychophysical methodology to establish acceptable impact severity levels for this automotive trim installation. Two studies were conducted. In the first study, 17 male and 12 female subjects (6 assembly line workers and 23 students) performed 5 hand impacts/min on a device that simulated the process of seating push pins during door trim panel installation. In both studies, subjects were asked to impact the simulation device as hard as they found acceptable without causing injury, numbness or pain. Subjects were trained for 11 h. Force and hand acceleration time-histories were recorded from the simulation device and a hand-mounted accelerometer, respectively. The magnitude of each impact was quantified with eight dependent measures: peak, time-to-peak, load rate and impulse, from both the force and acceleration transducers. Statistics were used to determine the effects of gender, skill level and impact location on acceptable impact severity. In the second study, 8 male and 8 female subjects performed repeated hand impacts on a wall-mounted force plate at three different frequencies (2, 5 and 8 impacts/min) over three separate sessions. Force measures and statistics were the same as in Study 1. In the first study, impact location did not appear to have a consistent effect on the acceptable impact severities and there was no significant differences observed between male and female values. For both force and acceleration, impulse was the most reliable variable followed by the peak. In the second study an increase in impact frequency was observed to result in a significant decrease in the acceptable levels of peak force and force impulse. This effect was largest when going from 2 to 5 impacts/min and was less pronounced when going from 5 to 8 impacts/min (especially for force impulse). Male subjects demonstrated significantly higher acceptable impulse levels. Based on the combined results from both studies, acceptable limits were recommended for peak force and impulse that would be acceptable to 75% of the population for a range of frequencies. These limits were observed to range from 181 (8/min) to 259 N (2/min) for peak force and 2.53 (8/min) to 3.52 N s (2/min) for force impulse. It was concluded that force impulse and peak force were the variables most likely being controlled by the subjects.
This paper presents an evaluation of torque strength and on the perceptual aspects of the use of faucets. We evaluated 180 subjects (18-29 years old = 30M and 30F; 30-55 years old = 30M and 30F; >55 years old = 30M and 30F). A digital dynamometer, a static torque transducer, five different models of handles (faucets) and other complementary tools were used for data collection. The procedures were standardized, based on ethical recommendations and biomedical criteria. The data analysis was based on descriptive statistics and included the application of tests for verification of significant differences. The results show the male performed torque significantly higher (p≤0.05) than the female subjects and the forces applied by the age group above 55 years old were the lowest (p≤0.05). With the lever-type handle was possible to achieve the highest magnitude of torque to all groups of subjects and these differences were significant (p≤0.05) in all comparisons. The lever-type handle was considered the easiest to use and the spherical handle was the hardest.
Development of a Kinematic Hand Model for Study and Design of Hose Installation
Digital Human Modeling, 2009
Kinematic hand models can be used to predict where workers will place their fingers on work objects and the space required by the hand. Hand postures can be used to predict hand strength. Kinematic models also can be used to predict tissue stresses and to study work-related musculoskeletal disorders. Study and design of manual hose installation is an important application for kinematic hand models. Hoses are widely used in many mechanical systems such as autos, aircraft and home appliance, which are all mass-produced on assembly lines. Studies of automobile assembly jobs show that hose installations are one of the most physically demanding jobs that workers perform. Hoses are a good starting point for kinematic model development because they can be characterized as simple cylinders.
A biomechanical and psychophysical examination of fastener initiations in automotive assembly
International Journal of Industrial Ergonomics, 2006
A psychophysical and electromyographical methodology was utilized to examine 24 female subjects while performing fastener initiation (FI) tasks on a simulation device. Three wrist postures (neutral, flexed and extended) and two fastener sizes (large: 10 mm depth  20 mm diameter; small: 5 mm  10 mm) were examined. The number of FIs per minute and the number of efforts per FI were the kinematic dependent variables, and posture and fastener size were found to have significant effects on both (po0:05). Maximal acceptable frequencies (MAF) of FI were calculated to be those acceptable to 75% of the female subjects. These ranged from a low of 6.1/min (extended wrist, small fastener) to a high of 7.4/min (neutral wrist, large fastener). EMG data showed a significant effect of posture for the FCU and Thenar muscles. The ECU was found to have the highest activity of all muscles regardless of the condition.
Evaluation of perceived and self-reported manual forces exerted in occupational materials handling
Applied Ergonomics, 1996
The main objective of the study was to evaluate the ability of workers to reproduce simulated manual work forces correctly and to quantify these forces in Newtons (N) by means of selfreports. Fourteen male and 14 female workers participated in the study. Three experiments were carried out. In the first experiment, the ability to reproduce the magnitudes of simulated manual forces occurring in daily work and to estimate these forces in Newtons was tested. A specially designed force-measuring device was used for this purpose. In the second experiment, the subjects estimated the weights of five boxes ranging from 1 to 30 kg. In the third experiment, the subjects were asked to produce five predetermined push and pull forces ranging in magnitude from 10 to 300 N on to the handle of the force-measuring device. The ability to reproduce the magnitudes of manual forces when simulating four familiar work tasks was good (the intraclass correlation coefficients ranged from 0.75 to 0.95). The ability to quantify these forces in Newtons was not as good (the product moment correlation coefficients ranged from 0.21 to 0.69). When the subjects estimated the weights of boxes they underestimated the weights. When they produced predetermined push and pull forces they exerted higher forces than expected when low force levels were requested, and lower forces when high force levels were requested. However, the forces were correctly ranked. In summary, simulation of the manual push/pull forces used in familiar work tasks seemed to offer sufftcient reproducibility to be worth testing for validity. Self-reports, used without previous training or without known 'reference forces', seemed to be very rough when the aim was to estimate in kg or Newtons. However, the fact that individuals could rank the forces correctly opens a potential for refinement of self-reports as a method for quantifying manual forces in objective terms, e.g. kg or Newtons.
Applied Ergonomics, 2010
Using psychophysics, the maximum acceptable forces for pushing have been previously developed using a magnetic particle brake (MPB) treadmill at the Liberty Mutual Research Institute for Safety. The objective of this study was to investigate the reproducibility of maximum acceptable initial and sustained forces while performing a pushing task at a frequency of 1 min À1 both on a MPB treadmill and on a highinertia pushcart. This is important because our pushing guidelines are used extensively as a ergonomic redesign strategy and we would like the information to be as applicable as possible to cart pushing. On two separate days, nineteen female industrial workers performed a 40-min MPB treadmill pushing task and a 2-hr pushcart task, in the context of a larger experiment. During pushing, the subjects were asked to select a workload they could sustain for 8 h without ''straining themselves or without becoming unusually tired, weakened, overheated or out of breath.'' The results demonstrated that maximum acceptable initial and sustained forces of pushing determined on the high inertia pushcart were 0.8% and 2.5% lower than the MPB treadmill. The results also show that the maximum acceptable sustained force of the MPB treadmill task was 0.5% higher than the maximum acceptable sustained force of . Overall, the findings confirm that the existing pushing data developed by the Liberty Mutual Research Institute for Safety still provides an accurate estimate of maximal acceptable forces for the selected combination of distance and frequency of push for female industrial workers.
Safety and Health at Work, 2016
The purpose of this review is to name and describe the important factors of musculoskeletal strain originating from pushing and pulling tasks such as cart handling that are commonly found in industrial contexts. A literature database search was performed using the research platform Web of Science. For a study to be included in this review differences in measured or calculated strain had to be investigated with regard to: (1) cart weight/ load; (2) handle position and design; (3) exerted forces; (4) handling task (push and pull); or (5) task experience. Thirteen studies met the inclusion criteria and proved to be of adequate methodological quality by the standards of the Alberta Heritage Foundation for Medical Research. External load or cart weight proved to be the most influential factor of strain. The ideal handle positions ranged from hip to shoulder height and were dependent on the strain factor that was focused on as well as the handling task. Furthermore, task experience and subsequently handling technique were also key to reducing strain. Workplace settings that regularly involve pushing and pulling should be checked for potential improvements with regards to lower weight of the loaded handling device, handle design, and good practice guidelines to further reduce musculoskeletal disease prevalence.