Glenn Sakamoto Graham Funk Makiko Mito Mathieu Bouscasse Sponsor: Les Bohna (Apple Barn) Supervisor: Paul Winkleman Abstract: The grading of produce takes place at large scale sorting plants. For a smaller scale farm, the grading cost can be a significant amount of their gross profit. In order to optimize their overall profit, a mobile grading machine was desired where grading can be completed at a lower cost while the cucumbers are being picked. The grading machine must measure and sort cucumbers according to their length. Prior to building the prototype, tests were performed by sliding, dropping, and grading cucumbers. The tests indicated that cucumbers have a high coefficient of friction and they are easily damaged when dropped on their noses. Based on the test results, a mobile grading machine was designed where a cucumber slides on an inclined conveyor system. While sliding down, the cucumber gets measured and sorted based on its measurement. It is recommended to revisit the design to improve jamming and sensitivity of measuring by implementing device such as torque sensor and fibre optic light beam sensors. The design can also be improved by replacing parts with more durable and food safe material. Introduction: The grading for retail produce in British Columbia is performed at specialized packing plants. These plants house expensive machinery designed to process large batches. Private greenhouse growers, with limited production, require more flexible and affordable alternatives. A grading device was designed to be utilized at one of Apple Barn’s greenhouses. The grading device accepts and sorts mini-­‐cucumbers based on their length measurements. The grading machine also provides a smaller size and lower initial investment while maintaining grading quality to meet product standards. Design Overview: The mobile grading machine consists of four main functions: in-­‐feed, grading, sorting, and storage. In-­‐
feed consists of two parts: the hopper and the scooper. Cucumbers are fed into the hopper and they are transferred onto conveyor system by the scooper. The sensors measure a cucumber’s length while the cucumber slides down on a conveyor. If a cucumber is determined to be longer or shorter than the standard length, a solenoid is actuated to redirect cucumber to a nonstandard sized tote. Technical Analysis and Testing: Mini-­‐cucumber sliding test: The coefficient of friction was determined experimentally and used to find the angle required for a cucumber to slide at the required speed. The cucumbers were found to slide at an angle of 14 degrees with an estimated velocity of 1 ft/s Mini-­‐cucumber drop test: The cucumbers were dropped from various heights and orientations to determine the maximum height a cucumber can be dropped from without any damage. The most significant damage occurred when a cucumber is dropped on its nose (vertical orientation). Grading system test: The photo sensor’s range between sensors was also tested. With a waterproofing cap on, it was found that 52 cm was the maximum range the photo sensors can detect. Discussion and Conclusion: The mini-­‐cucumber grading machine is able to sort the cucumbers into two categories: standard and nonstandard. However, cucumbers are easily jammed at the scooper section due to the sticky surface of the cucumbers. The main requirements of the grading machine were achieved while speed requirement was not firmly met. The sticky surface of cucumber became problematic in our design process. It would have impacted our design significantly if the problem was discovered at the early stage of the design process. Recommendations: 1. Insert a torque sensor to the input shaft of the hopper to prevent damaging the scooper when jamming occurs. 2. Replace all 1/2" plywood pieces of the hopper with 1/2" UHMW food safe plastic sheeting 3. Use a more secure waterproof sensor mount setup for the photo sensors 4. Use Fibre Optic Light Beam sensors for length measurements for better accuracy and precision. 5. Use a bigger rechargeable battery (12V Lead Acid Battery) for longer lasting operation 6. Use a set of racking and steel decking so the overall frame is more rigid. 7. Use all brass shafting for plastic rollers for better friction 8. Extend the length of current conveyor system such that a cucumber travels a shorter distance after exiting the conveyor. Cucumbers will also have less impact when landing on a tote. 9. Incorporate a roller system onto the hopper. This will prevent jamming at the in-­‐feed system. 10. Add some padding to the end of the sorting mechanism to prevent damage of cucumbers.