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CTD Risk Index and Reducing Injuries by Tool Re-design

Info: 2451 words (10 pages) Dissertation
Published: 12th Oct 2021

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Executive Summary

ClipCo is currently experiencing issues regarding a large number of cumulative trauma disorders (CTDs) with their workers in their Wilkes Barre plant in Pennsylvania. The annual cost of these injuries is currently exceeding $1 million. The goal of this paper is to determine if the job can be redesigned to reduce the number of CTD injuries, hence lowering both medical costs and missed workday for recovery. To gauge how "safe" a job is, the job will have its risk index for CTDs evaluated. To be considered safe or low impact, CTD index must be below 1. The current job's CTD index was found to be 1.47, with the largest contributors to the high CTD index be the tools used. This issue was alleviated by using a new wire cutter with a handle twice as long as the initial one with a smaller grip span, cutting the CTD index down to 1.11. However, ClipCo also desired an increase in productivity of 20% for the production to remain in the plant. To do so, increasing frequency alone boosts the number of motions that workers perform per day. It brought the final CTD index for the job to 1.209. The results showed that the production of the flashlights should be moved to Mexico where ClipCo will benefit from both lower cost of labor and less responsibility for their workers' CTDs. However, it is still recommended that when moving production to Mexico ClipCo should consider using both the redesigned wire cutters and workstation to maintain the industrial engineering ethics and integrity.


A manufacturing company named ClipCo has encountered a recent problem in one of their facilities in Pennsylvania. 29 of the 200 assemblers have cumulative trauma disorders (CTDs) and were removed from their job for at least one day. 10 of the 29 diagnosed required carpal release surgery, resulting in at least 8 missed weeks of work per worker. These CTDs have costed the company a significant amount of money (average $1 million a year just for workers compensation) and greatly cut off its productivity. Due to the loss of productivity and damage to profits the company is considering moving its facility from Pennsylvania to Ciudad Juarez, Mexico. Moving to Mexico will allow ClipCo to pay their workers at the rate of $0.60/ hour instead of up to $9/hour. It will also remove itself from the health care responsibility for its workers. Even though it's certain that moving the job will gain the company more profit, it will also create a substantial loss on Wilkes Barre tax base as well as an unexpected boost on the unemployment rate.

Hence, this paper is dedicated to find out if the problem can be alleviated by assessing the CTD risk index of the job, redesigning tools and work design, and evaluating if increasing frequency by 20% can salvage the productivity as well as cover the compensation costs. If these goals can be accomplished, then production will stay in PA. Otherwise ClipCo should move the job to Mexico.


- Evaluate the present job on its CTD Risk Index

- Redesign the tools and workstation to reduce the risk of CTDs and increase productivity

- Evaluate the CTD Risk Index for redesigned process

- Evaluate the CTD Risk Index of increasing productivity by increasing frequency by 20%

- Discuss if the company should move the plant to Mexico


The current job process was analyzed by watching a video of a worker complete one cycle (i.e., finish assembling one flashlight). The job was evaluated for its CTD Risk Index to find out which factors contribute the most to the CTD injuries. Then, the tools (wire cutter and screwdriver) and workstation were evaluated to find room of improvement.

The tools and workstation were then redesigned to reduce the cumulative trauma to workers and increase the productivity to eliminate any unnecessary movements. The new process was then evaluated for CTD Risk Index again to demonstrate the improvement. In addition, an evaluation for CTD Risk Index was also done on increasing the productivity by only increasing the job frequency by 20%.


The results of all evaluations and the redesigns can be found in the Appendix, Figure 1. Figure 4 showed that initially the task had a CTD risk index factor of 1.47, almost 47%, higher than the limit value of 1. It can be concluded that the job is high in risk of CTD injuries to workers. These results came from a frequency factor of 1.69, a posture factor of 1.1, and a force factor of 2. For the miscellaneous factor in the CTD Risk Index form the team decided that the only risk here was due to sharp objects such as striped wire and the wire cutter's teeth.

For the tools and workstation, as their evaluations were shown in Figure 1 to 3, we determined that the present tools required too much ulnar deviation and is difficult to use for an extended period of time. The workstation was also found to be highly unorganized and required many unnecessary movements to get access to the tools.

A redesign for the wire cutter and workstation was proposed (see Figure 5 and 6). First, the wire cutter was made to double its arm length with a reduced in grip span, hence cutting the force factor from 2 to 1. Second, the workstation was designed to reduce the frequency and angle of shoulder flexion as well as any probable should abduction. Particularly, we replaced all the holders on the table with inclined gravity bins and arranged them in a circle. Note that these new holders are open top to minimize the hand deviations for the workers. On the table, we also created a rectangular slot into the table to not only lower the wooden assemble box but also hold the tools (wire cutter and screwdriver, for example). Furthermore, we also added in a new incline next to the wooden assemble box to hang the hammer and better position the glue guns. Finally, we added a hole on the table, with the recycle bin right beneath it to allow workers to dump trash without shoulder abduction and trunk twisting. The new design was then evaluated for its CTD Risk Index (see Figure 7) and found to be 1.11.

Finally, the original process with 20% increase in frequency (note the shorter cycle time) was evaluated for CTD Risk Index (see Figure 8, Appendix), which was 1.569. From such analyses, we decided that the current job should be moved to Mexico, because redesigning the tools or increasing the frequency for productivity cannot completely resolve the CTD risk.


From Figure 4, the CTD Risk Index of the original process was found to be 1.47, almost times the limit of 1. Hence, it can be concluded that the CTDs injuries of ClipCo workers were due to the design of the workstation and tools being used. Indeed, the frequency, force and posture factors are the main contributors to the CTD risk index. Due to the need to keep productivity constant, only the force and posture factors can be adjusted and redesigned for improvements. To find rooms to lower these two factors, we evaluated the 2 tools and workstation. Particularly, we found that the wire cutter had short handle length and wide grip span, which required users to put a lot of forces from the wrist to cut wires and was difficult to hold as well. For the screwdriver, we noticed that its handle was made of plastic, and the shape was not optimal. An optimal design for screwdriver handle is made of non-slipped materials (rubber is the most common) and designed so that the three long fingers can grasp the handle without overlapping any part of the fingers.

New designs of the tools (wire cutter and the handle of screwdriver) and workstation were proposed, as said in the Results section. For the wire cutter, we double the length of the handle and reduce the grip span to resolve the difficulty and excessive amount of forces needed. For the screwdriver, from Figure 9 (Appendix), we suggest replacing the present screwdriver with the one labeled D. Finally, the workstation was redesigned and had its objected replaced and rearranged. Particularly, we replaced all the holders on the table with inclined gravity bins and arranged them in a circle, so that the workers can get access to the wire and materials without little hand deviation and shoulder flexion. Note that these new holders are open top to eliminate the bending or any ulnar deviation. On the table, we created a rectangular slot into the table to not only lower the wooden assemble box but also hold the tools (wire cutter and screwdriver, for example). This is based on the observation that the worker in the video clip kept turning her body from left to right and reaching out to get the wire cutter and screwdriver. If not doing so, she would bend her hand to get the screwdriver under the wooden assemble box. This change also helps move the assemble box closer to her eyes for detailed assembling and precision when using wire cutter. Furthermore, a new incline was added next to the wooden assemble box, with the slope away from her to hang the hammer and better position the glue guns. This improvement will help resolve partially the need to flex and abduct her arms to above the blue container to get the hammer and reduce the ulnar deviation when she reaches for the glue gun (note that the glue gun was projected away and downwards if left standing on its own). Finally, we added a hole on the table, with the recycle bin right beneath it to allow workers to dump trash without shoulder abduction and trunk twisting, compared to turning leftwards to do so.

A re-evaluation of the new process showed the new CTD Risk Index to be 1.11, still more than 1, even with that much change. To arrive at that number, we expect that the new design will lower the force factor by half (2 to 1) and the posture factor by 0.2 (see Figure 7). As we said, with that many changes, the risk for cumulative trauma disorder is still higher than the acceptable value. Hence it can be concluded that redesigning the present task to reduce CTD risk and increase the productivity is not a very profitable and sustainable approach.

Also, increasing the frequency by 20% to improve the productivity (without the design changes), as expected, imposes an even higher CTD risk compared to the original process. Just by a quick estimation, a case of carpal release surgery generally costs $1,200 out-of-pocket pay (1), not to mention the profit loss due to worker compensation and loss of workday for workers recovery. In addition, any possible increase in profit from increased frequency can be easily outweighed by the loss of workplace reputation due to the frequent of CTD injuries. From these analyses, it can be concluded that ClipCo should move this assembly job to Mexico, but still apply the preventive approach in the redesign to avoid harming the Mexican workforce and losing its reputation abroad. These protections also allow the manufacturing engineers to adhere to their engineering ethics because in the end, these Mexican workers are also the prospective customers. On the side of Wilkes Barre city, there will be a substantial tax base loss as well as a great increase in the local unemployment rate, but this decision is in the nature of business: the profit is more worthy of consideration because it will make or break the existence of the firm.


With all the findings in this paper it appears that the production that is currently taking place in the Wilkes Barre plant must be moved to Mexico. From our analysis and redesign efforts, it can be concluded that CTD risk index cannot be brought below 1, not to mention to increase productivity. While ClipCo must deal with the unfortunate situation of closing their plant in Pennsylvania, they will be more likely to regain what they have lost through previous worker compensation for CTD injuries and even improve revenue.


What is the cost of carpal tunnel surgery? (2017, December 12). Retrieved February 23, 2021, from https://www.mycarpaltunnel.com/carpal-tunnel-surgery/cost/



1. Abdulelah Bawazir: CTD analysis – Present & with a 20% increase in productivity

2. Ahmad Alshafi: Discussion and interperation of results

3. Wail Alshehari: Redesign of process, tools, and workplace. CTD analysis (after redesign).





Tool Evaluation Checklist of the Original Screwdriver


Tool Evaluation Checklist of the Original Wire Cutter


Workstation Evaluation Checklist of the Original Workstation


CTD Risk Assessment Form for the Current Process


Redesigned Wire Cutters


Redesigned Workstation Featuring a Wrist rest and New Tool Holders


CTD Risk Assessment for the Redesigned Process


CTD Risk Index for Present Job With 20% Increase in Frequency


Various Screwdriver alternatives for This Job

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