Ergonomic Design Intervention and Evaluation of the Rubber Tapping Knife
Natural rubber production is one of the main source of income in most parts of Kerala and Karnataka. I am from the southern part of Kerala were rubber tapping is still a primary source of income. As a result, I have been involved with the entire process of production from a very young age. So when it came to deciding on a project to work on, I was sure I had to do something related to the rubber production. As rubber tapping is one of the main process during the production, I decided to work on the rubber tapping knife. The aim of the project is to identify the problems faced by the rubber tappers and the design a solution relavent to their needs and then evalluate the feasibility of the solution.
Rubber Tapping Process
Rubber tapping is the process by which latex is collected from a rubber tree. The latex is harvested by slicing a groove into the bark of the tree at a depth of one-quarter inch (6.4 mm) with a hooked knife and peeling back the bark. Trees must be approximately six years old and six inches (150 mm) in diameter in order to be tapped for latex.Rubber tapping is a very labor intensive process. Usually there are multiple tappers working simultaneously, especially in the case of large plantation. They start their work very early in the morning, usually at 2 am, because they have to finish tapping before too much sun rays hit the tree. Otherwise the yield of latex will be considerably less.
Every night, a rubber tapper diligently removes a thin layer of bark in a downward half spiral along the tree trunk. With precision and expertise, this tapping process enables the extraction of latex for up to five hours from the designated panel. Subsequently, the tapper proceeds to tap the opposite side, allowing the previously tapped area to heal and recover. This spiral pattern facilitates the smooth flow of latex, guiding it downward into a collecting cup. To optimize the latex extraction, this laborious task is performed during the night or early morning hours, before the temperature rises significantly, ensuring a prolonged dripping period before the latex coagulates and seals the incision.
Problem Identification
After conducting extensive research and reading various papers, came to the conclusion that focusing on the traditional tapping knife would be the most appropriate choice for the project. Despite the tapping knife having its flaws, the project presents ample opportunities for improvement and innovation in this area.
Research
To gain a comprehensive understanding of the tapping knife and the challenges encountered by tappers, extensive primary and secondary research was undertaken. As part of the primary research, a diverse range of techniques were employed, including those outlined below.
1. Contextual Inquiry
As a part of the contextual inquiry, a Nordic questionnaire was prepared along with a series of questions about the profession and the tapping knife.
Nordic Questionnaire
Age : 75
Height : 5’7
Weight : 64kg
Experience : 64 years
Hours of work a day : 6 hrs
Questions Asked
How many trees do you tap in a day - Almost 800
How many days do you work in a month - Around 28-30
How long to tap a tree - 30 sec
Working Hours- 2 am - 8 am
What kind of tools do you use - Ordinary tapping knife and Jabong knife
Which is the latest tool in your inventory - Ordinary tapping knife
Which is the oldest tool in your inventory - Jabong knife
How did you learn this job - Observation and practice
How many days did you take to learn - 30 days
How do you maintain the tool - Takes it to the blacksmith
Do you spend money to repair your tool - Yes
Age : 75
Height : 5’7
Weight : 64kg
Experience : 64 years
Hours of work a day : 6 hrs
Questions Asked
How many trees do you tap in a day - Almost 800
How many days do you work in a month - Around 28-30
How long to tap a tree - 30 sec
Working Hours- 2 am - 8 am
What kind of tools do you use - Ordinary tapping knife and Jabong knife
Which is the latest tool in your inventory - Ordinary tapping knife
Which is the oldest tool in your inventory - Jabong knife
How did you learn this job - Observation and practice
How many days did you take to learn - 30 days
How do you maintain the tool - Takes it to the blacksmith
Do you spend money to repair your tool - Yes
2. Tool Analysis
The traditional tapping tool, also now as the Michie Golledge has a blade made out of cast iron and a handle which is usually made of wood. The blade of the knife is almost 6 inches when new, but the length will reduce during the course of its lifetime.
Ordinary Tapping Knife/ Michie Golledge
Price: ₹1200
Metal Blade
Wooden Handle
Good Knife lasts up to 8 years
Have to sharpen after 1-2 months
Weight: ~0.35kg
Price: ₹1200
Metal Blade
Wooden Handle
Good Knife lasts up to 8 years
Have to sharpen after 1-2 months
Weight: ~0.35kg
Tapping Kinfe Dimensions
Issues with the current knife
The traditional knife has to be taken to the blacksmith frequently because the edges will start folding inside after almost 2 months of tapping. Also this has to done by an expert blacksmith otherwise it won’t be optimal for tapping.
Ergonomic Checklist for the Evaluation of Hand tools
An evaluation was done based on the ergonomic checklist for the evaluation of hand tools to get a better understanding about the usability of the tapping knife. The final score for the traditional tapping knife came out to be 68/100, which was below average. This will aslo be useful for comparing the traditional knife with the redesigned knife.
3. Market Study
The Jabong knife
The Jabong knife is becoming more popular in India. It can tap slightly faster than the traditional knife but will scrap more bark in doing so.
Rubber tapping machine
In some part of Kerala, people have started using the rubber tapping machine, which is electronical operated. It is easier to tap using the machine but it doesn’t make the process easier. And it is also quiet expensive.
4. Nordic Body Mapping
1. Severe pain in the upper and lower neck area
2. Severe knee pain after tapping
3. As the tapping cut lowers the pain in the lower back also increases
4. Hand highly likely to get bruised
2. Severe knee pain after tapping
3. As the tapping cut lowers the pain in the lower back also increases
4. Hand highly likely to get bruised
5. Time Motion Study
After the time-motion study, it was evident that the tapping of a single tree would take around 20 sec. Also the process of tapping took the most amount of time, almost 50 per of the total process.
6. RULA- Posture Analysis
Final RULA Score : 7
The final RULA score came out to be 7, which was the maximum score. And it meant that the knife need investigation and immediate implementation of changes.
Design Brief
To redesign and evaluate the traditional tapping knife, ensuring increased safety for the user and enhanced usability for unskilled individuals.
Objective
1. To make the tapping knife safer
2. To improve the ergonomics of the handle and improve the efficiency of tapping
2. To improve the ergonomics of the handle and improve the efficiency of tapping
Ideation
During the course of ideation, the main focus was to redesign the knife so that it is safer and ensured better comfort to the user and has better handle design.
Initial Concept
The initial concept incorporated a central hump, aiding users in identifying the starting point of the sharp edge. Moreover, it featured interchangeable handles, allowing users to select the most suitable handle for their needs. Furthermore, the presence of a hole in the middle of the blade was intended to enhance visibility.
Initial Mockup
Initial Concept review
After presenting the initial concept to both users and a blacksmith, a significant issue arose. The groove, meant to guide users and enhance the design, proved less effective over time as the tip's length extended beyond the grove position. Moreover, the presence of the groove contributed to a fragility problem, making the entire blade vulnerable. Similarly, the hole intended to improve visibility became less useful as the edge's length extended beyond it.
Further Ideation
Final Concept
The final concept incorporates a handle design reminiscent of those found in various hand tools, such as cutting saws. This ergonomic handle promotes a relaxed wrist position, significantly reducing stress on the joints during use. Additionally, a removable component serves the dual purpose of replacing the grove from the initial concept and providing a comfortable resting spot for the fingers, enhancing overall user experience.
Final Concept Dimension
Final Mockup
Evaluation
To replicate the finger rest of the final design, a small piece of thermocole was added to the actual tapping knife and given to the user for testing.
1. The user tapped a few trees with the modified knife and expressed great satisfaction.
2. The added extension provided excellent cushioning and significantly reduced pain in their right index finger during tapping.
1. The user tapped a few trees with the modified knife and expressed great satisfaction.
2. The added extension provided excellent cushioning and significantly reduced pain in their right index finger during tapping.
The user was also provided with the thermocole mock-up of the new handle design.
1. After holding it and trying to replicate the tapping action, they were genuinely impressed with the innovation.
2. The new design offered a much more relaxed wrist position and influenced how the knife was gripped.
3. The user conveyed immense satisfaction, emphasizing that the new handle felt just right.
4. They firmly believed that the design would be successful if manufactured.
Ergonomic Checklist for the Evaluation of Hand tools
The evaluation of hand tools was conducted again for the redesigned tapping knife and the final score came out to be 98/100, which was really good and was a considerable improvement from the traditional model’s score.
Final Verdict
Following the evaluation and user testing, the redesigned tapping knife demonstrated clear superiority over the traditional knife, offering enhanced safety and comfort to the user. It received significantly higher scores in the checklist, validating its improvements. The user's positive impression of the new design further reinforced its potential.
Future Steps
The next crucial step involves creating a fully functional prototype and distributing it to a diverse range of users. Gathering their feedback will be essential to make any necessary adjustments and refinements. Once the product reaches a state of near-perfection through this iterative process, the aim will be to commence mass production, ensuring that the well-designed and user-friendly tapping knife becomes widely available to meet the needs of users everywhere.
Thank you!
Ergonomic Design Intervention and Evaluation of the Rubber Tapping Knife
by Arjun Abhilash
