Kin 420 Project Report

7/28/2019 Kin 420 Project Report

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J ob Analysis of Laser CellOperator

KIN 420: Occupational Biomechanics

Instructor: Dr. Andrew Laing

Teaching Assistant: Colin McKinnon

April 4th, 2013

Time: 2:30 pm

Group #5

Brandyn McCarthy (20%), Jake Tennant (20%), Jonathan Park (20%), Inhan Song(20%), Michael Wulff (20%)


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Executive Summary

Injury risk factors were determined qualitatively and quantitatively of a Laser Cell

Operator. 3DSSPP, RULA, NIOSH lifting equation, Energy Expenditure Calculation, and

CCOHS hand tool guidelines were used. Recommendations and strategies to implement and

minimize injury risk factors were determined. Essential Tasks 1 and 4: Stoop lift, forward reach,

energy inefficiency, and tripping hazard were observed risk factors. 3DSSPP found 26%-67% of

the female population had strength capabilities at the ankle, knee and hip. Only 60%-70% of the

male population had strength capabilities at the ankle and knee. RULA determined the need for

further investigation, and change soon. NIOSH indicated minimal risk associated.

Recommendations involved installations of a steel bin raiser and rotator, to minimize horizontal

reach distance and stoop posture. Ramp installation to overcome the step would eliminate the trip

hazard and reduce overall required energy expenditure. Essential Tasks 2 and 3: Working at

shoulder height was an observed risk factor. 3DSSPP showed 67% of the 50th percentile female

population was capable of performing the task. The 50% men all had strength capabilities in the

90th percentile. RULA determined the need for further investigation, and change soon. NIOSH

indicated minimal risk associated. Recommendations involved job rotation and engineering

provision of a ramp to reduce working height, improve upper limb postures, and accommodate

greater working population. Essential Task 5: Ulnar deviation was an observed risk factor.

RULA determined that further investigation may be needed. Grinder dimensions adequately

met CCOHS guidelines. Provision of a new grinder with compressible handle material angulated

head tool, and trigger relocation may improve performance and minimize injury risk. Board of

Directors, Occupational Health and Safety Personnel, and workers are needed in successful

implementation of interventions and agreement.


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Table of Contents

Introduction....................................................................................................................................1

Material and Methods...................................................................................................................3

Results.............................................................................................................................................6

Discussion........................................................................................................................................8

Recommendations........................................................................................................................12

Implementation Strategy.............................................................................................................15

Conclusion ....................................................................................................................................15

References.....................................................................................................................................17

Appendix A - Physical Demands Analysis Summary...............................................................19

Appendix B - Analysis Before Recommendations ...................................................................28

Appendix B1 3DSSPP .............................................................................................................28

Appendix B2 RULA ................................................................................................................30

Appendix B3 NIOSH Lifting Equation ...................................................................................33

Appendix B4 Energy Expenditure Calculation .......................................................................34

Appendix C - Analysis After Recommendations......................................................................35

Appendix C1 - 3DSSPP ............................................................................................................35

Appendix C2 - RULA ...............................................................................................................37

Appendix C3 - NIOSH Lifting Equation ...................................................................................40Appendix C4 Energy Expenditure Calculation .......................................................................41

Appendix D - Additional Tables...................................................................................................4

Appendix E - Additional Figures for Proposed Products..........................................................4


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Introduction

With dire implications of work-related musculoskeletal disorders (WMSD) to the

economy, health care, and most importantly the worker, it is imperative that jobs at-risk for

WMSD be assessed and analyzed so that interventions can be implemented to minimize the risk

of WMSD. We analyzed the tasks performed by the Laser Cell Operator (LCO) within Magna

International Formet Industries automotive manufacturing plant in St. Thomas, Ontario.

The purpose of the Laser Cell Operator (LCO) is to prepare JK Uppers for further

utilization in car frame manufacturing. The task cycle begins with the LCO retrieving two raw

JK Uppers from the steel bin. The LCO carries the JK Uppers and is required to climb up one 21

cm step to reach the platform of the laser cell machine (LCM). The LCO mounts them into the

LCM tooling, where specific cuts are made. The LCO mounts and dismounts the JK Uppers at

approximately shoulder height. The LCO climbs down the 21 cm step and carries the fabricated

JK uppers back to the workstation bench for grinding purposes. The LCO uses an air-powered

grinder to eliminate burrs caused by poor quality cuts from the LCM. The LCO places the

finished fabricated JK uppers into their appropriate steel bins. The total cycle time for the task is

2 minutes and 30 seconds and is dictated by the pace of the laser cell machine.

Risk factors were analyzed based on the retrieving, placing, mounting, dismounting, and

grinding the JK uppers. Essential tasks 1 and 4 (placement and retrieval of the JK Uppers to and

from their appropriate steel bin) required extreme postures of the upper limbs and torso (i.e.

stoop lifts and forward reaches), which may cause increased load moments on the spine to

oppose the stoop posture while placing and retrieving the JK Uppers. As a result, Tichauers

prerequisites of Avoid Covert Lifting Tasks were violated (Tichaeuer, 1976).

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Essential tasks 2 and 3 (mounting and dismounting the JK Uppers) posed hazardous risks

to the LCO because the working height was occurring at approximately shoulder height and

forward reach was required to mount and dismount. The implications of the height required to

operate the LCM forces extreme shoulder postures, potentially causing accelerated fatigue and

increased risk of injury. Tichauers prerequisites of Keep Forward Reaches Short and Keep

Elbows Down & In were violated (Tichaeuer, 1976).

The LCO must climb the 21 cm step up and down once each cycle. This results in the

LCO required to climb up the step approximately 174 times and down the step 174 times

throughout their entire shift. This creates a dangerous trip hazard as well as potential for energy

inefficiency. Increased energy expenditure involved in repeatedly climbing the step may result in

decreasing tissue tolerance, potentially resulting in increased risk of injury.

Lastly, the design of the grinder was investigated for essential task 5 (using grinder)

because using the grinder may result in excessive biomechanical stressors, such as: vibration

produced from the grinder, and exposure to poor design of the powered hand tool eliciting

increase grip force. This violates Avoid Compression Ischemia and Avoid Stress

Concentrations on Small Anatomical Parts of Tichauers prerequisites (Tichaeuer, 1976).

These potentially hazardous exposures may cause obstructed blood circulation in the hand,

decreased performance, and increased risk of injury (e.g. tenosynovitis) due to muscular fatigue.

In addition, the LCO described that the trigger for the grinder is located on the right side of the

handle, making it difficult to use for left-handed or ambidextrous workers.

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Materials and Methods

Quantifications of the work environment and machine interface dimensions were directly

measured using a measurement tape. Video recording of the entire task was captured. Duration

and frequency of essential tasks were observed and recorded with simultaneous video viewing

and stopwatch use. The software, assessments, and guidelines used were: 3D Static Strength

Prediction Program (3DSSPP), National Institute for Occupational Safety and Health (NIOSH)

lifting equation, Rapid Upper Limb Assessment (RULA), Energy Expenditure Calculation, and

the Canadian Centre for Occupational Health and Safety (CCOHS) hand tool guidelines.

Essential tasks 1 and 4 (placing/retrieving) and 2 and 3 (mount/dismount) were assessed

with 3DSSPP, RULA, NIOSH lifting equation, and Energy Expenditure.

The LCO alternated between a stoop lift and a one-handed lift with their opposite hand

supporting part of their body weight while performing tasks 1 and 4. Thus, an assumption was

made that the LCO only performed stoop lifts. In addition, the LCO was assumed to perform

tasks 1 and 4 with elbow and wrist joints kept straight.

3DSSPP was used to predict the load moments, static strength requirements, and enabled

mannequin simulations of the tasks the LCO performed. By inputting posture data, hand loads

and anthropometry, this provided outputs of static strength requirements about the major joints

such as: the elbow, shoulder, torso, hip, knee, ankle and the population capable of performing the

described job. Furthermore, 3DSSPP enabled us to determine if the recommendations made for

the essential tasks improved the percentage of the population capable and reduced the risk of

injury. Anthropometrics and static strength data of the 50th percentile male and female were

used because we assumed this would represent the majority of the working population within the

factory.

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RULA was used to qualitatively assess the exposure of the LCO to risk factors associated

with WMSD of the upper limb. Body posture diagrams and three scoring tables were used to

indicate the level of loading experienced and the exposure to risk factors (i.e. number of

movements, static muscle work, force and postures) (McAtamney & Corlett, 1993). The final

score obtained was used to compare it to the categories outlined in the RULA (Refer to

Appendix B2 ) and provided inference to which task required modifications to minimize risk of

injury (McAtamney & Corlett, 1993). Body postures were determined by assuming those which

qualitatively appeared to pose the highest risk of injury. Because the high risk postures for Tasks

1 & 4 were virtually identical both tasks were assessed with one RULA. The same was done for

tasks 2 & 3. Also, both hands shared the work equally so only one RULA was needed for both

hands of tasks 1 & 4 and of tasks 2 & 3.

NIOSH lifting equation was used to identify any lifting hazards present within each

essential task. Direct measurements of several variables (e.g. horizontal distance, frequency of

lifting) related to the task were taken at the facility and used to determine multiplier factors (e.g.

horizontal multiplier factor). The recommended weight limit (RWL) was calculated and used to

determine the lifting index (LI). If the LI was greater than 1, the lifting task was deemed

hazardous and the factor contributing the highest risk was identified to guide strategies to reduce

the LI to less than 1 and minimize risk of injury. Presence of asymmetry is not definite in all the

tasks, and if it was present, it would have been negligible. Therefore, the value of asymmetry is

assumed to be 0. Coupling was assumed to be fair because the worker was able to easily grab the

JK Uppers, despite the lack of handles. In addition, the maximum horizontal distance for the task

performed was assumed to be 63 cm because the horizontal multiplier value becomes 0 after the

reach distance exceeds 63 cm, making the RWL value 0 as well. Thus, the horizontal distance

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that was possible for the LCO to perform the task was assumed to be 63 cm. It is also assumed

that the worker/floor surface adhesion provides at least a 0.4 coefficient of static friction between

the shoe sole and the working surface (Waters et al., 1993).

An Energy Expenditure Calculation was used to determine the physiological effects of

the entire job on the LCO, with and without climbing the 21 cm step. The value obtained was

compared to published guidelines by researchers in the field. We determined if recommendations

to eliminate the step would prove to reduce energy expenditure by the LCO.

To evaluate essential task 5, RULA and CCOHS hand tool guidelines regarding different

aspects (e.g. handle shape) of hand tool design and considerations for powered hand tools were

used. Dimensions (e.g. handle length) of the grinder were obtained from Occupational Health

and Safety personnel within Formet Industries. To minimize risk of injury, dimensions of the

grinder were compared to guidelines by CCOHS to identify any dimension(s) of the grinder that

could benefit from change.

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Results

Essential Tasks 1 and 4 (Retrieving and Loading Steel Bins):

3DSSPP determined the compressive load about the L4/L5 joint for 50th percentile

female and male to be 2915N and 2787N, respectively (Refer to Appendix B1). Gender specific

strength capability results are presented in Table 1.0.

Table 1.0 - 3DSSPP Results of Strength Capabilities at Major J oints for Tasks 1 and 4

Ankle Knee Hip

Female Population 26% 38% 67%

Male Population 60% 70% 95%

One RULA was performed for essential tasks 1 and 4 because the upper limb postures

adopted by the LCO were identical. RULA determined a score of 6 (Refer to Appendix B2). The

posture assessed involved 90 degrees trunk flexion. This occurred when the LCO was retrieving

and placing JK Uppers inside the partially empty steel bin.

NIOSH lifting equation determined the LI values to be 0.26 and 0.68 (Refer to Appendix

B3)

The Energy Expenditure Calculation showed that in total, the job required 3.68 Kcal/min

(Refer to Appendix B4). This value includes climbing up and down one 21cm step each cycle.

Essential Tasks 2 and 3 (Loading and Unloading LCM Tooling):

3DSSPP showed that only 67% of the 50th percentile female population could perform

the task of loading and unloading the JK Uppers with the required shoulder angle Refer to

Appendix B1). The 50% men all had strength capabilities in the 90th percentile.

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One RULA was performed for essential tasks 2 and 3 because the upper limb postures

adopted by the LCO were identical. RULA determined a score of 6 (Refer to Appendix B2). The

posture assessed involved the LCO standing upright with 90 degree shoulder flexion.

NIOSH lifting equation determined the LI values to be 0.26 and 0.68 (Refer to Appendix

B3)

Essential Task 5 (Grinding):

RULA determined a score of 3 (Refer to Appendix B2). The posture assessed involved

the LCO with wrist in ulnar deviation and neck in flexion. The LCO distributed equally the

length of time spent performing the task between their left and right hand. Dimensions of the air-

powered grinder are presented in Table 2.0.

Table 2.0 - Dimensions of Air-powered Grinder

Characteristic of Hand ToolDimensions of Grinder

Hand

Tool shape Slightly contoured

Direction of force is in-line with forearm andwrist (typically horizontal)

Pistol grip

Handle length 140 mm

Handle diameter (power grip) 35 mm

Material and texture of handlesMetallic, Fairly SmoothSurface

Tool weight (


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Discussion


According to the results from 3DSSPP, for both 50% male and females there needs to be

a change to the lower limb postures. The strength capabilities are too low and therefore the

balance is unacceptable. Although the compression load is below the NIOSH action limit by

485-613 N, it is still close and decreasing this would be beneficial. As a result, these postures

need to be corrected for in order to increase balance and minimize injury risk to the specified

joints this posture puts at risk.

With a RULA score of 6, a need for further investigation and change soon was

determined. This indicates that the upper limb and torso postures assessed are quite hazardous

and vulnerable to increased risk of injury.

NIOSH lifting equation was performed with the horizontal distance limited to 63 cm. LI

values were below 1 for tasks 1 and 4, indicating minimal lifting hazards associated with the

tasks. However, assuming the horizontal distance to be 63 cm may have resulted in

overestimation of the LI value, because distance that one can reach without supporting the upper

body weight with one hand is shorter. Tasks 1 and 4 being were completed at a rate of 0.8

lifts/min. LI values may have been overestimated because of the assumption that the LCO only

performed stoop lifts throughout the tasks, rather than the observed reality of the alternation

between a one-handed lift and stoop lift.

According the 1981 NIOSH Work Practices Guide for Manual Lifting, it was determined

that the maximum aerobic capacity of males is 15 Kcal/min. It was further determined that for

occupational tasks over an 8 hour shift shall not exceed 33% of this maximum. Overall, this

equates to a maximum energy expenditure of 5 Kcal/min (NIOSH, 1981). Compared to our

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calculated energy expenditure of 3.68 for the LCO, this job is within the recommended

guidelines. In addition, this step poses a safety hazard, as operators may trip and fall, while

carrying the sharp JK Uppers.

Essential Tasks 2 and 3 (Loading and Unloading LCM Tooling):

To begin, 3DSSPP has calculated that the posture in which the shoulder is at during

loading and unloading the machine, only 67% of the 50% female working population has the

capable strength to accomplish the task. As a result, a recommended change to the working

station is needed to decrease this strain placed on the shoulder, enabling more workers to

complete the loading and unloading task.

RULA results and interpretations were identical for the RULA obtained from tasks 1 and

4.

LI values are below 1, indicating that the lifting tasks are safe for the workers to perform.

However, our assumptions of making the asymmetry factor to be 0 and the coupling to be fair

may have resulted in underestimation of LI values.


RULA gave us a score of 3, indicating that further investigation may be needed. As in

the other tasks, this score can be applied to both hands. This posture is a relatively safe one with

only minor concerns due to ulnar deviation of the wrist.

In comparing the dimensions of the grinder to the recommended guidelines provided by

CCOHS, we found that the grinder has met most of the CCOHS guidelines. There were no

significant violations of the CCOHS hand tool guidelines and this element of the job poses

minimal risks to the LCO using the grinder (Refer to Table 3.0).

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Table 3.0 - Comparison of Grinder Dimensions to CCOHS Guidelines and Potential

Hazards

Characteristic of Hand Tool CCOHS GuidelineDimensions of

Grinder Hand

PotentialHazard(Y/N)

Tool shape Slightly contoured Slightly contoured N

Direction of force is in-linewith forearm and wrist(typically horizontal)

Bent handle Pistol grip N

Handle length>100 mm (ideally 115- 120 mm)

140 mm N

Handle diameter (power grip) 30 - 45 mm 35 mm N

Material and texture of handlesNon-slip, non-conductive materials

Metallic, FairlySmooth Surface

Y

Tool weight (


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of lifting could not have been determined with NIOSH lifting equation. Limitations of Energy

Expenditure Calculation is that it provides an indirect measure of energy expenditure (as

opposed to laboratory measurements of energy expenditure), resulting in an inaccurate value.

CCOHS guidelines provided no recommendations for trigger activation force minimal

considerations for an air-powered grinder. Although no recommendation for trigger activation

force was specifically provided, the permissible grip force across male and female populations is

90 N (Chaffin, Gunnar, & Bernard, 2006). Thus, we believe it is safe to conclude that the trigger

activation force of 0.5 kg (4.9 N) poses minimal risk.

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Recommendations


Engineering interventions include placing the bins on rotating platforms. These would

cost $2,000 - $2,100 each (Southworth Products Corp, 2013). We could use these platforms to

rotate the bin 180 degrees. This would reduce the horizontal reach because the worker would

only ever have to ever reach halfway across the bin. Platforms can raise the steel bin about 50 cm.

This will minimize covert lifting and therefore increase the balance of the worker, increase the

worker population able to complete the task (Refer to Figure 1.0) and decrease the compression

loads of L4/L5 to 2020 N for males and 1921 N for females (Refer to Appendix C1). The RULA

score decreased from 6 to 3 (Refer to Appendix C2). NIOSH LI values for initial posture of task

1 and ending posture of task 4 also decreased from 0.68 to 0.64 (Refer to Appendix C3).

Figure 1.0: Lower L imb Strength Capabilities Before and After Recommendations forRetrieving and Placing J K Uppers

0

10

20

30

40

50

60

70

80

90

100

Female Ankle Female Knee Female Hip Male Ankle Male Knee Male Hip

StrengthCapabilities(%)

Before

After

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In regards to the 21 cm step, a recommendation is to install a ramp at a 10% inclination

from horizontal. The ramp would cover 21 cm vertically and span 200 cm horizontally. This

results in an overall energy expenditure change from 3.68Kcal/min (with the step) to

3.56Kcal/min (with the ramp) (Refer to Appendix C4). In addition, the ramp reduces the

tripping hazard of the 21 cm step. To implement, this would cost approximately $100 - $200 for

supplies and labor if the ramp was made on-site. A prefabricated ramp would be around $600.

Essential Tasks 2 and 3 (Loading and Unloading Tooling):

Optimally we would like to reduce the horizontal reach, which would involve replacing

and redesigning the LCM tooling completely. This is not feasible because this would reduce

production and require rebuilding the entire machine, making it a very costly solution to the

company. An alternative solution would be to build a 20 cm removable platform with a ramp

(cost of $100-$200) in front of the tooling in order to decrease the vertical reach and allow for

mild forward bend to enable about 81% of the 50% female workers to complete the task (Refer

to Figure 2.0 and Appendix C1) (no risk of shear and compression forces).

Figure 2.0: Shoulder Strength Capabilities for 50% Female Population During Loadingand Unloading Task

0

10

20

30

40

50

60

70

80

90

100

Female Male

StrengthC

apabilities(%)

Before

After

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This recommendation does not change the risk for the 50% male population. After

implementation of this recommendation the NIOSH LI value of the ending posture of the task 2

and initial posture of task 3 would decrease from 0.68 to 0.48 (Refer to Appendix C3). The

RULA score would decrease from 6 to 3 (Refer to Appendix C2). We also recommend doing job

rotation as well so that one person is not completing the task for 8 hours a day.


Recommendations involve purchasing a new grinder with compressive handle material

(e.g. rubber, compressible plastic), rather than metal, to provide more surface friction to the

handle for better gripping and comfort (Strasser, 2007). Furthermore, angulation of the tool head

axis to be aligned with the index finger may be necessary to help maintain a neutral wrist

because the long axis of the hand grip is approximately 78 degrees from horizontal (Strasser,

2007). Lastly, orienting the trigger in the middle and anterior aspect of the handle enables the

left-hand dominant workers to use the grinder. Prices of tools that accommodate the needs of a

change in trigger and handle material range from 70$ - 155$, with the highest range providing an

angulated tool design (Northern Tool +Equipment, n.d.; Snap-On Inc., n.d.). This may help

improve performance/productivity, reduce muscular effort, and enhance operator comfort.

Postural recommendation would be to bend the tool and avoid any wrist deviation, in order to

minimize risk of injury (Tichaeuer, 1976).

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Implementation Strategy

Effective means of successfully adapting to the recommendations provided involve

implementing engineering interventions of providing a steel bin lifter, rotator, ramps, and new

grinder. This would elicit meaningful adoptions by the LCO, due to their enhanced ability to

control and change their work setting to help minimize their risk of injury and to optimize their

productivity, comfort, and efficiency.

Stakeholders involved in this project would require the work of Occupational Health and

Safety Sector, Engineering department to verify that these interventions are suitable for the work

environment. The Board of Directors would be needed to ensure these changes be implemented

and permission to be granted for funding. Lastly, the workers that are involved in performing the

job would be informed of the upcoming changes and benefits to ensure agreement on these

interventions are positive.

Conclusion

The LCO is required to perform essential tasks that may increase their risk of WMSD.

Essential tasks 1 and 4 required the LCO to perform stoop lifts and forward reach.

3DSSPP found L4/L5 joint compressive loads did not exceed the NIOSH action limit but was

near it. 3DSSPP determined within the 50th percentile female and male population strength

capabilities were: 26% and 60% for the ankle, 38% and 70% for the knee and 67% at the hip

(only females). RULA determined a final score of 6, inferring the need for further

investigation, and change soon. NIOSH lifting equation deemed tasks 1 and 4 to be safe, with

LI values of 0.26 and 0.68. Energy expenditure calculation determined to be 3.68 Kcal/min.

Recommendations involved engineered installations and provision of a steel bin raiser, rotator,

and ramps, in order to minimize horizontal reach distance, stoop posture, tripping hazard, and

decrease overall energy expenditure.

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Essential tasks 2 and 3 required the LCO to work at approximately shoulder height.

3DSSPP found that only 67% of the 50% female working population possessed the necessary

strength capabilities at the shoulder to perform the tasks. RULA determined a final score of 6,

inferring the need for further investigation, and change soon. NIOSH lifting equation deemed

the tasks to be safe, with the LI of 0.26 and 0.68. Recommendations involved engineering

provision of a ramp and platform to reduce working height and improve upper limb postures to

minimize risk of injury and accommodate greater proportion of the working population.

Administrative interventions involved job rotation.

Essential task 5 resulted in the LCO operating the grinder with an ulnar-deviated wrist.

Discomfort with the trigger location for left-handed and ambidextrous operators was noted by

the LCO. RULA determined a final score of 3, inferring that further investigation may be

needed. Grinder dimensions compared to CCOHS guidelines showed that the grinder

dimensions adequately met the CCOHS guidelines. Recommendations involved engineering

provision of a new grinder (cost of 75-150$) that provided more surface friction for improved

gripping, angulated head tool, and accommodating trigger location. Administrative and postural

interventions involved educating the need to avoid twist and bending of the wrist and to instead,

bend the tool.

Board of Directors, Occupational Health and Safety Personnel, and workers performing

the job are needed in successful implementation of interventions and agreement.

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References:

3D SSPP. (n.d.). College of Engineering Home | Michigan Engineering. Retrieved March 5,2013, from http://www.engin.umich.edu/dept/ioe/3DSSPP/

Canadian Centre For Occupational Health And Safety (2007).Calculated Recommended WeightLimit. Retrieved March 26, 2013, fromhttp://www.ccohs.ca/oshanswers/ergonomics/niosh/calculating_rwl.html

Canadian Centre For Occupational Health And Safety (2007).Assessing Relevant HandlingFactors.Retrieved March 26, 2013, fromhttp://www.ccohs.ca/oshanswers/ergonomics/niosh/assessing.html

Chaffin, Don B., Gunnar Andersson, and Bernard J. Martin. (2006).Occupational Biomechanics.4th ed. Hoboken NJ : Wiley-Interscience.

Hand Tool Ergonomics - Tool Design : OSH Answers. (n.d.). CCOHS: Canada's NationalCentre for Occupational Health and Safety information. Retrieved March 5, 2013, fromhttp://www.ccohs.ca/oshanswers/ergonomics/ handtools/tooldesign.html

McAtamney, L., & Nigel Corlett, E. (1993). RULA: a survey method for the investigation ofwork-related upper limb disorders.Applied ergonomics, 24(2), 91-99.

Middlesworth, M. (2012). Rapid Upper Limb Assessment (RULA): A Step-by-Step Guide.Ergonomics-Plus. Retrieved March 27, 2013, from www.ergo-plus.com/healthandsafetyblog/wp-content/uploads/2012/11/RULA-A-Step-by-Step-Guide1.pdf

Northern Tool +Equipment. (n.d.). Ingersoll Rand Angle Die Grinder 1/4in., Model#3101G |Air Grinders| Northern Tool +Equipment.Portable Generators, Pressure Washers, Power Tools,Welders | Northern Tool + Equipment. Retrieved March 28, 2013, fromhttp://www.northerntool.com/shop/tools/product_200342897_200342897

Occupational Health Clinics for Ontario Workers Inc.. (n.d.). Guidelines To Implementing AndPerforming Physical Demands Analysis Handbook. Retrieved March 5, 2013, fromwww.ohcow.on.ca/uploads/Resource/Workbook /pdamanualbook.pdf

Huynh, Bich.The Revised NIOSH Lifting Equation.Retieved March 27, 2012, fromwww.ergonomics.com.au/niosh.htm

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Snap-On Inc. (n.d.). Die Grinder, Mini, 115 Angle, 1/4" Quick Change Collet, 20,000 RPM.Snap-on: Hand Tools, Power Tools, Tool Boxes, Automotive Diagnostics and Shop Equipment.Retrieved March 29, 2013, fromhttp://buy1.snapon.com/catalog/item.asp?P65=yes&tool=all&item_ID=650251&group_ID=675146&store=snapon-store&dir=catalog

Southworth Products Corp (2013) PalletPal 360 Spring Level Loader.Retrieved April 1, 2013,from http://www.southworthproducts.com/content42.html

Strasser, H. (2007). Assessment Of The Ergonomic Quality Of Hand-Held Tools & Computer(Vol. 1). IOS Press.

Tichauer, E. R. (1976). Biomechanics sustains occupational safety and health.IndustrialEngineering, 8(2), 46-56.

U.S. Department Of Health And Human Services (1994).Application Manual For The RevisedNIOSH Lifting Equation.Retrieved March 28, 2013, fromhttp://www.humanics-es.com/nioshliftingequationocr.pdf

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Waters, T. R., Putz-Anderson, V., Garg, A., & Fine, L. J . (1993). Revised NIOSH equation forthe design and evaluation of manual lifting tasks.Ergonomics, 36(7), 749-776.

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http://buy1.snapon.com/catalog/item.asp?P65=yes&tool=all&item_ID=650251&group_ID=675146&store=snapon-store&dir=cataloghttp://buy1.snapon.com/catalog/item.asp?P65=yes&tool=all&item_ID=650251&group_ID=675146&store=snapon-store&dir=cataloghttp://www.humanics-es.com/nioshliftingequationocr.pdfhttp://www.humanics-es.com/nioshliftingequationocr.pdfhttp://www.humanics-es.com/nioshliftingequationocr.pdfhttp://www.humanics-es.com/nioshliftingequationocr.pdfhttp://www.humanics-es.com/nioshliftingequationocr.pdfhttp://buy1.snapon.com/catalog/item.asp?P65=yes&tool=all&item_ID=650251&group_ID=675146&store=snapon-store&dir=cataloghttp://buy1.snapon.com/catalog/item.asp?P65=yes&tool=all&item_ID=650251&group_ID=675146&store=snapon-store&dir=catalog


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APPENDIX A Physical Demands Analysis Summary

Employer: Magna International Inc. Location: St. Thomas, ONJ ob Title: Laser Cell Operator (Line

Worker)Plant: Formet Industries

Date Information was obtained: 02/20/13

Work Hours/Shifts:The usual work week is Monday to Friday, 40 hours a week. The Laser Cell Operator rotatesbetween morning or afternoon/evening shifts of 6:00am to 2:30pm or 2:30pm to 11:00pm. Thereis one 15 minute break and one 25 minute lunch provided for each shift.

J ob Purpose:Prepare JK Uppers for utilization in further car frame manufacturing

Essential Functions:1. Retrieve unfinished JK Upper from raw steel bin2. Mount JK Upper to laser cell machine for fabrication3. Dismount JK Upper from laser cell machine after fabrication is complete4. Place fabricated JK Upper into fabricated steel bin5. Grind burs from fabricated parts

Non-Essential Functions:1. Operate pump truck to mobilize steel bin2. Ensure organized and clean workspace

General Observations:The cycle time for the particular task is 2 minutes and 30 seconds in length, and is dictated by

the pace of the laser cutting machine.

Laser Cell Operator retrieves and mounts two unfinished JK Uppers (4 kg each) into a lasercell machine every cycle, where specific cuts are made to the JK Upper. In order to mount the JKUppers on the laser cell machine, the operator is required to reach the platform by climbing up one21cm step with the parts that are to be loaded. Once the laser cell machine has completed its task ofspecific cuts, the operator checks and removes any remaining debris. The operator then climbs downthe platform and to their workstation, where they are required to grind parts of the JK Uppers usingan air powered tool to eliminate burs caused by poor quality cuts from the laser cell machine. Theoperator then places finished JK Uppers into their appropriate parts bin. There is also periodic useof a pump truck to move empty or full parts bins to and from an area that is accessible by a forklift.

The work area is well lit and is normally at a comfortable temperature, although during thesummer months temperatures may rise to a point where heat reliefs are required. There are anumber of personal protective equipment (PPE) items which must be worn to perform the job:earplugs, a face mask when using the air-powered grinder, kevlar gloves (to protect from cuts), safetyglasses, and steel-toed shoes.

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Table 1A: Manual Material Handling Activities by Task Requirements for Laser Cell Operator.

Manual Material

Handling Activities

Essential Task 1

(18%/shift)

Essential Task 2

(8.5%/shift)

Essential Task 3

(8.5%/shift)

Essential Task 4

(32%/shift)

Essential Task 5

(20%/shift)

Noness. Task 1 Noness. Task 2

Lifting:23-40 85 150Beginning Heights(cm) 85 85

Ending Heights(cm) 85 150 85 23-40 96

Weights (kg) 4-8 4 4 4-8 1-4

Frequency(#/min) 0.8/min 0.8/min 0.8/min 0.8/min 0.8/min

Carrying:

Weight (kg) 4-8 4-8Distance(m) 9 14

Frequency(#/min) 0.4/min 0.4/min

Pushing:

Push Heights(cm) 150 120

Horizontal Force(kg) N/A 14-18

Frequency(#/min) 0.8/min Occasional

Pulling:

Pull Heights(cm) 150 85

Horizontal Force(kg) N/A 14-18

Frequency(#/min) 0.8/min Occasional

Reaching (4kg):

Front Distance(cm) 0-100 50 50 0-100

Vertical Height(cm) 23-40 150 150 23-40

Reach Direction Front Front Front FrontFrequency(%/shift) 5%/shift 8%/shift 8%/shift 5%/shift

Handling:

Weight of Object (kg) 4-8 4 4 4-8 1 1

Grip Force(N) N/A N/A N/A N/A N/A N/A

Diameter(cm) 7-11 7-11 7-11 7-11 7-11 0-10

Frequency(%/shift) 13 0.5 0.5 27 5 1-2/day

Fingering:

Weight of Object(lbs) 1

Pinch Force(kg) 0.5

Pinch Type 3-Point

Finger Flexion (x) x

Frequency(%/shift) 15

Noness. =Nonessential

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Table 2A: Body Posture by Type of Activity.

All values are weighted average (in percent) per shift.

Activities Essential Task 1:Retrieve JK Uppers

(18%/shift)

Essential Task 2:Mount JK Uppers

(8.5%/shift)

Essential Task 3:Dismount JK Uppers

(8.5%/shift)

Essential Task 4:Placing of JK Uppers

(32%/shift)

Essential Task Grinding Parts

(20%/shift)Back:

Straight/neutralStoop/flex

Twist/side bendTwist and stoop

Arms:Below shoulder

At/above shoulderOverhead

Legs:Sitting

Standing stillWalkingKneelingCrouchingCrawling

LyingClimbing

13% (Occasional)5% (Occasional)

0% (Never)0% (Never)

18% (Occasional)0% (Never)0% (Never)

0% (Never)

8.5% (Occasional)8.5% (Occasional)

0% (Never)0% (Never)0% (Never)0% (Never)

1% (Occasional)

7.5% (Occasional)0% (Never)

1% (Occasional)0% (Never)

1% (Occasional)7.5% (Occasional)

0% (Never)

0% (Never)

8.5% (Occasional)0% (Never)0% (Never)0% (Never)0% (Never)0% (Never)0% (Never)

7.5% (Occasional)0% (Never)

1% (Occasional)0% (Never)

1% (Occasional)7.5% (Occasional)

0% (Never)

0% (Never)

8.5% (Occasional)0% (Never)0% (Never)0% (Never)0% (Never)0% (Never)0% (Never)


0% (Never)0% (Never)

32% (Occasional)0% (Never)0% (Never)

0% (Never)


0% (Never)0% (Never)0% (Never)0% (Never)

1% (Occasional)

20% (Occasion0% (Never)0% (Never)0% (Never)

20% (Occasion0% (Never)0% (Never)

0% (Never)20% (Occasion

0% (Never)0% (Never)0% (Never)0% (Never)0% (Never)0% (Never)

**Frequency defined by the Ministry of Labour is 1-33% for Occasional, 34-66% forFrequent, and 67-100% for Constant.

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Identified Risk Factors/Potential Hazards

The identified hazardous components of the job include:

Mounting and dismounting JK Uppers from the laser cell machine because the working

height (from our observed worker; may vary depending on workers anthropometrics) is taking

place at approximately shoulder height, and forward reach is required to mount and dismount.

This results in increased load moments occurring about the elbow and shoulder joints. The

height required to operate the laser cell machine forces the operator to violate a number of

Tichauers prerequisites including Keep Forward Reaches Short and Keep Elbows Down &

In. There is also push and pull forces being exerted by the worker to mount and dismount the

parts into the laser cell machine. This results in increased muscular demand to oppose the load

moments about the shoulder and L5/S1 joint, potentially increasing risk of injury or decreasing

performance due to increasing rate of muscular fatigue.

Retrieving and placing of JK uppers into their appropriate bins requires the worker to

perform stoop lifts and forward reaches. This may cause increased load moment taking place

about the L5/S1 joint, produced by the weight of the individuals upper body segments and the

large moment arms, in addition to the weight of the JK Uppers in the workers hands. This

violates another of Tichauers prerequisites being Avoid Covert Lifting Tasks. This causes

increased muscular force required at the L5/S1 joint to oppose the load moment, increasing

fatigue and potentially decreasing performance and/or increasing risk of injury.

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The pump truck required to manually push and pull metallic part bins to a location that is

accessible by a forklift will potentially result in increased extensor/flexor load moment

production because of the pulling/pushing of the pump truck handle, located above the L5/S1

joint. This may also increase fatigue and potentially decrease performance and/or increase risk

of injury.

Using the grinder may result in over gripping due to reduced grip feedback that may result

from using the gloves as well as the vibration produced from the grinder, resulting in potential

decrease in performance and increased risk of injury due to muscular fatigue. This violates three

of Tichauers prerequisites including Consider Negative Effects of Gloves, Avoid

Compression Ischemia, and Avoid Stress Concentrations on Small Anatomical Parts.

Another point made by the worker is that the trigger for the grinder is located on the right side of

the handle, making it difficult to use for left-handed or ambidextrous workers.

Finally, there is a 21cm step which the worker must go up once and down once each cycle.

This results in the worker having to climb up the step 174 times and climb down the step 174

times throughout the entire shift. The worker is usually carrying a mass of approximately 8 kg

(two JK Uppers) while going both up and down. This creates a dangerous trip hazard as well as

energy inefficiency in contrast to without having to climb this step or having a gradual incline to

reach the platform. Increased energy expenditure involved in repeatedly climbing the step may

result in decreasing tissue tolerance, potentially resulting in increased risk of injury.

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Planned J ob Analysis ApproachOur initial assessment consists of utilizing the 3D Static Strength Prediction Program

(3DSSPP) to predict the load moments and static strength requirements by enabling approximate

simulations of the various tasks the laser cell operator performs (e.g. stoop lifts, push, pull). By

inputting posture data, hand loads, and anthropometry, this allows us to retrieve outputs of static

strength requirements about the major joints such as the elbow, shoulder, torso, and the male and

female percentile capable of performing the described job. It also outputs data that analyzes

L5/S1 compression and shear forces, and comparisons to NIOSH guidelines that we may utilize.

In addition, this program allows us to simulate the impact of any changes and recommendations

we make and compare it to current conditions to determine if strength requirements and postural

adoptions are required to be more inclusive in design.

The push and pull forces required to mount/dismount the parts from the laser cell machine

and to move the steel bin with a pump truck will be used to compare and contrast to Snook

Tables (Snook & Ciriello, 1991). We aim to determine if the estimated push/pull forces exerted

are within the recommended guidelines and what the impact of changing dimensions of the laser

cell machine and the posture necessary to perform the pushing and pulling will have.

In terms of determining load limits, we plan to use the NIOSH lifting equation. We can use

the measurements of where the hands are placed during different tasks to determine the

recommended load limit and determine if the current weight of the JK Uppers fall within this

limit, or if postures need to be changed to accommodate the part weights. We can also use this

tool to evaluate the impact of any recommendations we choose to make.

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In order to assess the impact of the step, we plan to use an Energy Expenditure. Aside from

an obvious trip hazard, we can determine the energy requirements of going up and down the step

once each cycle and determine the effect of eliminating the step on the energy requirements. This

enables us to compare the outputs we get to industry standard energy expenditures.

Finally to evaluate the grinder, we plan to use guidelines provided by the Canadian Centre

for Occupational Health and Safety. This organization provides numerous guidelines regarding

different aspects (e.g. handle shape, diameter, and weight) of power tools. We can apply our

measurements about the grinder to ensure they fall within the recommended guidelines in regards

to handle shape, handle diameter, length, and weight of the tool. We can also use these

guidelines to recommend any changes with regards to power tool design changes.

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Figure 1 Retrieving J K Uppers from Figure 2 Steel BinSteel Bin

Figure 3 Worker Mounting J K Upperto Laser Cell Machine

Figure 4 Worker Dismounting J KUpper from Laser Cell Machine

Figure 5 21 cm Step

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Figure 6 Worker Grinding Ends of J K Upper Figure 7 Grinding Tool

Figure 8 Worker Placing J K Uppers into Steel Bin

Figure 9 Pump Truck Figure 10 J K Uppers

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Appendix B Analysis Before Recommendations

Appendix B1 3DSSPP

Figure 1: 3DSSPP 50% Female Retrieving and Placing the J K Uppers (Task 1 and 4)

Figure 2: 3DSSPP 50% Male Retrieving and Placing the J K Uppers (Task 1 and 4)

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Figure 3: 3DSSPP 50% Female Loading and Unloading J K Uppers (Task 2 and 3)

Figure 4: 3DSSPP 50% Male Loading and Unloading J K Uppers (Task 2 and 3)

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Appendix B2- RULA

Table 1: RULA Score Interpretation

RULA Score Significance:

1 2: acceptable3 4: further investigation may be needed

5 6: investigation and change soon

7: immediate investigation and change

Figure 1: RULA Analysis for Retrieving and Placing J K Uppers (Task 1 and 4)

(Middlesworth, M., 2013)

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Figure 2: RULA Analysis for Mounting and Dismounting J K Uppers (Task 2 and 3)


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Figure 3: RULA Analysis for Grinding the J K Uppers (Task 5)


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Appendix B3- NIOSH L ifting Equation

Table 1: NIOSH Lifting Equation Summary Table for Measurements of Retrieving andPlacing as well as Mounting and Dismounting JK Uppers.

Table 2: NIOSH Lifting Equation Summary Table for the Results of Retrieving andPlacing as well as Mounting and Dismounting J K Uppers.

*RWL =23kg(HM)(VM)(DM)(FM)(AM)(CM) *LI =Load / RWL

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Appendix B4- Energy Expenditure Calculation

Figure 1: Sample of Energy Expenditure Calculation with Results

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Appendix C Analysis After Recommendations

Appendix C1 3DSSPP

Figure 1: 3DSSPP 50% Female Retrieving and Placing the J K Uppers (Task 1 and 4)

Figure 2: 3DSSPP 50% Male Retrieving and Placing the J K Uppers (Task 1 and 4)

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Figure 3: 3DSSPP 50% Female Mounting and Dismounting the J K Uppers (Task 2 and 3)

Figure 4: 3DSSPP 50% Male Mounting and Dismounting the J K Uppers (Task 2 and 3)

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Appendix C2 - RULA

Figure 1: RULA for Retrieving and Placing J K Uppers (Task 1&4)

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Figure 2: RULA for Mounting and Dismounting J K Uppers (Task 2&3)

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Figure 3: RULA for Mounting and Dismounting J K Uppers (Task 2&3)

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Appendix C3- NIOSH L ifting Equation

Table 1: NIOSH Lifting Equation Summary Table for Proposed Measurements ofRecommended Changes.

Task 1 Task 2 Task 3 Task 4

Initial Ending Initial Ending Initial Ending Initial Ending

Horizontal Location (cm) 13 0 0 50 50 0 0 13

Vertical Location (cm) 23 65 65 130 130 65 65 23

Lift Distance (cm) 23 65 65 130 130 65 65 23

Lifting Frequency (lift/min) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

Asymmetric Angle

(degree)0 0 0 0 0 0 0 0

Coupling Fair Fair Fair Fair Fair Fair Fair Fair

Table 2: NIOSH Lifting Equation Summary Table for the Results After ProposedRecommendations Implemented.

Task 1 Task 2 Task 3 Task 4

Initial Ending Initial Ending Initial Ending Initial Ending

HM 1 1 1 0.5 0.5 1 1 1

VM 0.85 0.97 0.97 0.84 0.84 0.97 0.97 0.85

DM 1 0.89 0.89 0.84 0.84 0.89 0.89 1

FM 0.79 0.79 0.79 0.79 0.79 0.79 0.79 0.79

AM 1 1 1 1 1 1 1 1

CM 0.95 1 1 1 1 1 1 0.95

RWL

(kg)*14.67 15.69 15.69 6.41 6.41 15.69 15.69 14.67

LI* 0.27 0.26 0.26 0.62 0.62 0.26 0.26 0.27

*RWL =23kg(HM)(VM)(DM)(FM)(AM)(CM) *LI =Load / RWL

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Appendix C4- Energy Expenditure Calculation

Figure 1: Sample of Energy Expenditure Calculation with Results After Recommendations

Kin 420 Project Report

Documents

Transcript of Kin 420 Project Report