haiti breadfruit shredder - edgeedge.rit.edu/content/p15482/public/publications and...

Multidisciplinary Senior Design Conference

Kate Gleason College of Engineering Rochester Institute of Technology

Rochester, New York 14623

Copyright © 2015 Rochester Institute of Technology

Project Number: P15482

HAITI BREADFRUIT SHREDDER

Brittany Griffin Industrial Engineering

Samantha Huselstein Mechanical Engineering

Andrew Beckmann Mechanical Engineering

Patrick Connolly Mechanical Engineering

Alan Kryszak Mechanical Engineering

ABSTRACT

Farmers in Haiti have a surplus of the fruit, breadfruit. Due to its short shelf life and the short breadfruit season, most of the fruit spoils before it can be used. In order to optimize its use in such a needy area, processing the breadfruit into flour will allow for many uses and drastically increase shelf life. Prior to the flour process, the breadfruit must be peeled and cored. It is then shredded, dried out, and then ground into flour. The main constraints addressed for use in Haiti were low maintenance cost and low/no electric energy input. The best design to meet all of our requirements was shredding blades made of high grade, hardened steel. This gives the device a long life, requiring little maintenance. The final design was selected through Pugh and feasibility analysis of promising solutions. Results from various tests were collected and analyzed to provide the final conclusions and recommendations for the project.

INTRODUCTION Haitian Farmers in the peasant organization KGPB have identified breadfruit as one of the most wasted

agricultural products in the area because it is hard to transport, store, and preserve. They hope to increase food supply and make a profit by turning breadfruit into flour. The flour process can be outlined in three processes, shredding, drying and grinding.

The goals of this project are to create a low cost, low energy input breadfruit processor/process that will result in consistent flour quality. This group focused on the shredding part of the process. The final deliverables were a working prototype with maintenance and operation instructions, a technical paper, and test plans with results.

PROCESS/METHODOLOGY Key stakeholders in the project include: Farmers of KGPB, Haitian economy, 3rd world farmers, Haitian

consumers, project sponsor, Sarah Brownell, investors, and our project team. The low energy food dryer team addresses the second step in the flour producing process, which makes them another key stakeholder for our team.

After conducting a customer interview, the team created a list of customer needs (or requirements) to capture what the Haitian farmers were really looking for in the project. Table 1 is a list of our most important customer requirements (CRs). Note: Fufu is a Haitian dish that is made by boiling and mashing breadfruit, similar to mashed potatoes. The goal is to be able to make a similar dish using the breadfruit flour and boiling water.

Proceedings of the Multidisciplinary Senior Design Conference

Project P15482

Benchmarking was done for both the shredding and grinding portion of the flour processing. Since one of the most important and limiting constraints was to use no electrical or fuel based energy, only solar, bike, and hand crank power were considered. These were evaluated based on force input requirements, time to run the machine without a break, and cost. As for the material selection, hardened steel and Delrin plastic were evaluated due to their food grade status. The main requirements focused on for this decision were using available resources and having a low maintenance cost.

Table 1: Customer Requirements of Highest Importance Category Requirement Feasibility Uses available resources Feasibility Minimizes water usage Cost No energy cost Cost Low maintenance cost Ease of Use Could be used by adult breadfruit farmer Safety Provides barrier to hazardous parts Safety Does not contaminate food Profit Provides flour that can be used for fufu

From the CRs, the team decided on how best to measure whether our product reached these criteria. These

became our Engineering Requirements (ERs) and are shown in Table 2 (Located in results section of this paper).

Figure 1: Functional Decomposition. Shows how the shredder fits into the overall system architecture of the project. Note that "Obtain Breadfruit" and "Prepare Breadfruit" will be done by the farmers.

After brainstorming, the team put together complete concepts through consensus voting (all team members

had to approve a concept before moving forward). We then selected 10 concepts to analyze in a Pugh Diagram. This selection method allowed us to compare each concept based on specific criteria: Doesn’t use electricity, Available in Haiti, Easy to maintain/sharpen cutter, Effort required to operate, Easy to understand, Within budget, Peels and cores (bonus). The bonus was not counted against design but gave some an extra point towards their final score. The team moved forward with two designs, a bladed shredder concept and roller grinder as the first choice and an apple peeler shredder concept with a roller grinder. The latter was previously prototyped by a Mechanical Engineering Technology design team at RIT and could be iterated on and improved. The apple peeler was chosen as a back-up design due to its slow processing rate, but it was a concept that had already been proven. The bladed design evolved through more benchmarking which led us to our final concept. We chose if for its ease of use and high capacity for shredding breadfruit.

Proceedings of the Multi-Disciplinary Senior Design Conference


Example of Apple Peeler Design Example of Shredding Roller early concept (http://tclauset.org/16_StGuides/ch13/picts/applepeeler.jpg) (http://www.lenzing-technik.com/fileadmin/_processed_/csm_grobhomogenisator_01_fc818f2f51.gif)

After choosing our final concept, we conducted several feasibility tests to make sure the end prototype would function. The first thing we did was a prototype for the blades. We used scrap aluminum to make a mini version of the shredding components. Using squash, because breadfruit is unavailable in the winter, we determined the 3-blade design would give a consistent, usable shred. We also used old horizontal mill tooling to test the impact of adding more teeth to the blades. We discovered that it was more difficult to turn because of number of teeth engaged and “mashed” the squash instead of shredding it.

3-Blade Prototype Horizontal mill tool Prototype

Once we decided on geometry for the blades, we tested whether or not it would be feasible to use plastic

(cheaper and lighter) instead of food grade, hardened stainless steel. We uploaded the geometry to finite analysis software to apply a load to the part. This analysis showed it may be feasible, however, it would be a huge risk. We were not confident with the assumptions we were making and were concerned that the plastic blades would deform and interfere with each other. Because of this, we opted to go with the stainless steel blades.

Screenshot of Plastic Blade Analysis

Next we attempted to determine the life of our shredder by doing a fatigue analysis for the shafts. After

reviewing with a subject matter expert, we determined the shafts will support the system with infinite fatigue life. We also were able to calculate the maximum deflection in the shafts (approximately 0.014in), which helped with bearing selection.


Project P15482

After discussing the shaft analysis results, we realized we needed a fail-safe incase the user tried to apply too much torque to the shafts (for example, a rock fell into the blades with the breadfruit). To prevent this, we built a “shear pin” into the handle and performed calculations to appropriately size the pin to allow enough torque to shred breadfruit but not enough to cause damage to the shaft keys or blades. We will discuss later how we tested to make sure our calculations were correct.

Due to the custom design for the chosen bladed shredder, the team machined a majority of the parts, which totaled to over 100 starting from raw materials. Although it was quite time consuming to make the parts, this design and assembly is very robust and will be very durable for use in Haiti.

In order to ensure our final prototype met all our ERs, 5 unique tests were planned for when the build was complete. The first is the Shear Pin Test. A shear pin, 5/16in diameter nylon pin, was used in the handle of the shredder as a fail-safe if something that could damage the blades is put into the device. This experiment allowed us to ensure the shear pin will fail when expected. This allowed for easy maintenance since the key ways and blades will be protected. Testing standard ASTM B769 was used to complete the test.

The next is an Interference Test. There is no specific standard for our team to follow, so the team checked each part after manufacturing to make sure it was within the required specification and designated tolerance. For the shaft assembly, we measured each individual blade and created a customer spacer to hold our 0.0035in tolerance between blades. This test allowed us to ensure quality parts that are within specification and make the assembly process easier. The final, most important, part of this test was to make sure there is clearance once completely assembled to ensure there was no interference in our final prototype. If there is not proper clearance between blades, they will wear quickly and have a potential of binding and making the product unusable.

Another test that was performed is the Operating Metrics Test. Again there is no standard for this test. This test is to check that our product meets multiple Engineering Requirements (ER2, 9, 10, 11, 13). This was done by timing team members and non-team members in a variety of tests including: time it takes to train new users, how long it can be used without a break, how long it takes to process breadfruit (based on amount in weight, i.e. g/hr), and time it takes to clean.

The Assembly Timing Test is used to determine how feasible it would be for a Haitian farmer to make the initial set up of the product (and tear it down to move it if necessary). A user is given the shredder and necessary tools for the test. The timer starts once the user first begins to remove the hopper and ends when the last tool/piece is put down.

Finally, the shredder yield test shows the team how effective the product is in shredding breadfruit. This makes it possible to determine the amount dropped, the amount shredded, and ultimately determine how feasible our machine is. The amount of breadfruit was weighed before entering the hopper and after it was collected. If any pieces fell, they would be collected and measured to find the percent dropped (this did not happen during testing).

RESULTS Final Prototype: Figure 2: CAD Model Design Figure 3: Final Prototype



The final prototype, Figures 2 and 3, feature many different parts, all contributing to the meeting of all our requirements. The height of the handle was based on the average height in Haiti. The stand was constructed so that a 5-gallon bucket could be used to catch the shreds as they are processed. The base was lengthened to allow for more stability and to make it easier to anchor it down with cinder blocks, which are readily available in Haiti. The shredder box itself is very heavy due to the amount of steel used to make it. The food-grade, stainless steel shredder blades are offset on each of the shafts to ensure effective shredding when in motion. There are delrin plastic “fingers” in between each blade to guide the breadfruit to the blades and to avoid pieces of fruit getting stuck in the sides of the box. There are guards on either end of the box to protect the gears and the shafts and also to prevent food from getting stuck anywhere. The hopper, made of polycarbonate and steel angle iron reinforcements, was constructed to make it difficult for a user to get their hands in the blades. There is also a hinged lid for easy loading.

Figure 4 is the handle connection to the shredder box. The shear pin is secured with a nut and will break if something harder than breadfruit is input to the machine. When the prototype is sent to Haiti, a bag of extra shear pins will be included. This prevents the blades and keys from being damaged and is a cheap fix.

Figure 4: Shear Pin Below you can find the engineering requirements and the actual values that were obtained after testing: Table 2: Engineering Requirements Actual Values ER#

Description Metric Direction Target Marginal

Actual S1 Percent of total cost to import parts Percent of cost Decrease <50% <25% 95.4% S2 Time it takes to clean Time (minutes) Decrease <10 <30 24.58 S4 Amount of water used for cleaning bucket/day Decrease <1 <2 <1/2

S5 Materials in contact with food that are food grade Percent Increase >95% >75%

100%

S6 Percent of power provided by manual labor Percent Increase >95% >75%

100%

S7 Cost of materials USD Decrease <800 <1000 891.46

S8 Cost to maintain (including cutting surfaces costs) USD Decrease <25 <110

0

S9

Increase in time for new user vs. experienced user (simple instructions) % increase Decrease <200% <400%

6% S10 Training time minutes Decrease <15 <20 0

S11 Time operator can run operation without a break hours Increase >1 >0.5

Not tested*

S12 Percent of materials that are corrosion resistant

Percent by number of components Increase >95% >75%

98% S13 Shredder processing rate breadfruit/hr Increase >24 >12 71.2

S15 Time to disassemble and reassemble for transportation hours Decrease <0.5 <1.5

0.166 0.287

S16 Initial set up time hours Decrease <1 <3 0.287 S17 Total weight pounds Decrease <75 <150 70

S18

Machine Capacity (the maximum amount the hopper and machine can hold)

breadfruit at a time Increase >6 1

5-6

S19 Protection around hazardous components (max gap size) inches Decrease 0.25 0.375

0.23

S21 Shortest Lived part (excluding cutting surface)

Analysis (years) Increase >3 >1

Not tested*

S22 Percent of breadfruit dropped % of breadfruit/hr Decrease <5% <20%

0%

S23 Amount of finished product collected % collected Increase >95% >80% 98%*

S24 Percent of breadfruit input to machine that is shredded Percent Increase >90% >80%

100%


Project P15482

The percent of the total cost to import parts ended up being 95.4% because the design was created to be very robust and to not need repair for a significant amount of time. The 4.6% accounts for only the angle iron stand, which is available in Haiti. Our decision was justified because we expect the shredder to be durable and to last in Haiti for years without a need for repairs. This is crucial because of the rural location of the KGPB farmers. They will not have access to machinery to make new parts. The time it takes to clean the device was slightly high, but still met the marginal value. This was due to the fact of how intricate the blade design is. It’s necessary to clean each blade and spacer with a small brush, which adds a lot of extra time. It’s also necessary to take part of the device apart in order to reach all of the parts that need to be cleaned (this is outlined in the devices cleaning manual). The amount of water used for cleaning is something that was concerning due to the lack of availability of clean water in Haiti. Using a water/bleach mixture to clean the blades solved this issue. This way, everything will be sterile and only a small amount of clean water is necessary for a final rinse. Less than half a bucket was used in total which was well under our target value. All of the materials that are in contact with food are food grade, which is above our target value of >95%. The blades are hardened steel, as are the spacers, shafts, and shredder box. The black, plastic fingers that are in between the blades are made of Delrin plastic, which is a food grade material. The gears are covered with a steel plate so that food does not come into contact with them. This ensures that only food grade material will come in contact with the breadfruit. Since the power input that was chosen was a hand crank, all of the power is provided by manual labor. This is important due to the lack of electricity and motor power in Haiti. It was discovered later in the design process that the area in which the device will be going has access to a small generator, so going forward with this project in the future it could be useful to allow the device to be used with a hand crank but also with a generator. This way if the generator breaks down, which happens fairly often, the device can still be used. The cost of the machine overall was more than was first thought at the beginning of the project. The original budget was just $400. It was increased to $1000 because of the need to use food grade materials, which adds a lot of cost to the overall device. We were able to stay below this new budget and the cost to maintain at zero because of the robustness of the design. The only part that should need replacing is the shear pin, extras of which will be sent down to Haiti with the device. As mentioned before, the shear pin is designed to fail during misuse of the machine to prevent damage of more important parts (i.e. shaft keys and blades). Engineering requirements S9 and S10 were to ensure that the machine was simple and easy to understand. There isn’t a difference between the time it takes a new user to use and the time it takes an experienced user to use. It can be said with confidence that the design is easily understood and takes little to no training time. Time a user can run the device without a break is one of the engineering requirements that was not measured. This was due in part to the fact that we did not have enough breadfruit to run a test that long. It was also justified by the fact that the dryer, the next step in the process, will be the bottleneck operation so it would be unnecessary to shred breadfruit for very long each day. In the future, if the dryer operation is further optimized, the issue of how long a user can run without a break could be reanalyzed. The shredder’s processing rate was well above our target at a rate of approximately 71 breadfruits per hour. Also, the time to disassemble and time to reassemble was well under our target. Reassembly took slightly longer due to the fact that it is slightly more difficult to reassemble with just one person. Having two people working on reassembly could easily reduce this time. Regardless, our target was met and both took less than a half hour. The initial set up time was also found to be the same as the reassembly time because it involves the same steps. The shortest-lived part engineering requirement was not tested because the shortest lived part will be the shear pin, which will break at an unquantifiable time. This will be when something is put in the machine that shouldn’t be. It was estimated that this would be most likely in less than a year but there is no way to measure it. Although the machine shreds 100% of the breadfruit that is inputted, it was measured that only 98% of the finished product was collected. This can be explained by pieces of breadfruit that have been shredded that get stuck on the underside of the device or on the plastic fingers. All of the input is shredded but not all of it makes it out of the shredder box. This isn’t of major concern because if the handle is run backwards for a few turns and then run forward again, it usually knocks out most of the stuck fruit. This will also be cleaned out when the device is cleaned, which will be each day that it is used.



Table 3: Shear Pin Test Results

Specimen Diameter Peak Load Peak Stress Strain At Break No. in lbf psi in/in 1 0.25 539.401 10988.6 0.078 2 0.25 515.229 10496.1 0.058 3 0.25 507.271 10334 0.062 4 0.25 544.512 11092.7 ****

We ran a simulation to determine when the pin should shear before the small shaft key. It was found that the pin

had to shear at values between 1,191.14 and 11,697 psi in order to prevent damage to the key. The result of the shear pin test above shows that all pins sheared at values less than the upper limit value of 11,697 psi. Therefore the shredder will not need to be taken apart but rather; one can simply replace the shear pin to continue operation. Major maintenance will not be needed on the shredder and the unit can stay together as shipped to the customer.

CONCLUSIONS AND RECOMMENDATIONS Overall, our project was successful. We delivered a working prototype that is being shipped to Haiti in the

summer of 2015 to be implemented. We learned a lot during the building process and encountered a few problems and learned new insights about our project. The trade-offs we made by designing for infinite life instead of maintainability makes our machine difficult to reproduce. The material cannot be found in Haiti and is difficult to machine (mostly stainless steel). By designing for infinite life, the weight of our shredder was affected. The weight metric is barely met, and most of it is contained in the shredder unit itself. The heavy weight was also a weight vs cost trade-off. We could have used lighter materials in the housing of the shredder, however, this would have significantly driven up the cost. Being too heavy makes it difficult to ship to Haiti and move around once it’s there. Another effect of the weight is difficult handling. Once painted, the shredder housing is smooth and cannot be picked up by the handle (may damage/cause misalignment of the gears). This makes it difficult to pick up and easy to squish fingers when setting it down. There are multiple things we would have done differently in hindsight. One is to add a handle to aid in moving the shredder (as discussed above). This would prevent users from picking up the shredder by the handle, mitigate the risk of it being dropped, and overall improve user experience. Another thing we would change is the timing of when everything got painted. The paint needs 48 hours to cure and we painted 24 hours before it needed to be reassembled. This caused multiple scratches in the paint and chipping. It also caused some of the parts to be stuck together. This is not an issue for parts we do not want the farmers to take apart, however, caused problems on parts we wanted to take apart. Other design changes would include changing the finger bolts to be countersunk for better locating (and preventing interference with blades). Also, it would have helped to turn the shaft nuts from scratch to fit our custom build. Other things we would have done as a team include: using GroupMe (a messaging app) for communication starting at the beginning of the project, checking the drawings more closely, having more than one engineer work on CAD, and use our Work Breakdown Structure more frequently. Some drawings that were changed and not reviewed had mistakes that could have been avoided, and design changes that would have been update quicker/been reviewed with more than one engineer doing CAD work. More frequent use of the Work Breakdown Structure would have saved a few headaches by identifying parts that were falling behind sooner and decrease confusion by clean documentation of who is currently working on what part. As of right now, our project does not need a second iteration of senior design. The prototype will work to show whether or not it will be productive for the KGPB farmers. We recommend teaching about the function of the shear pin to the local farmers (we will send instructions, but verbal explanation may be better) as well as teaching about the safety functions of the hopper. These are critical to ensure the durability of the machine and safety of the users.


Project P15482

We also recommend collecting feedback from the farmers after a season of using it. Some questions we feel are useful include:

• What do you like about the Shredder? • What do you not like? • How often do you use the Shredder? • Does your family use breadfruit flour? • Are the women selling the flour in the market? • Is there part of the flour process that could be better?

One reason this project will be reiterated in MSD would be if the demand for this product in Haiti

increases. This may happen if the farmers make a huge profit from the flour and want to expand their operations. If this happens, there may need to be even more focus on food safety and FDA regulations if the market wants to be expanded globally. Below is a list of recommendations the next MSD team should focus on:

• Design a shredder that is easier to manufacture o Multiple could be made if flour operation continues to expand

• Use cheaper, lighter materials o Do a more thorough analysis of food grade plastics

• Operable through manual or motor power o KGPB currently uses a diesel motor to run their coffee grinder o Can use manual power when motor is broken

Our final recommendation would be to implement any feedback given by the KGPB farmers after using the

initial prototype. Feedback is key when designing for a customer, and will hopefully result in a more useful product with happier customers.

ACKNOWLEDGMENTS Special thanks to our faculty guide Sarah Brownell for helping us understand our constraints when designing for

customers in Haiti. We would also like to thank machining specialists Rob Kraynik and Jan Maneti for their continuous support throughout the design and build of our project. Thank you to Rochester Steel Treating Works for heat-treating our blades for greater durability and to Wegmans for helping supply fresh breadfruit for our testing.

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