Embedded Files
Microgreens Harvesting Device
Microgreens Harvesting Device
Winter 2018 MAE 156B Sponsored Project
University of California, San Diego
Department of Mechanical and Aerospace Engineering
Background:
Background:
Trimmer
Trimmer
The Trimmer was made using a Ryobi hedge trimmer retrofitted to use custom machined 304 stainless steel blades. The blades were made to have 1.57 teeth per centimeter which was ideal for cutting the greens and used a carving blade profile which was the most economical option. One blade was put into the trimmer and powered by the motor while the other was welded onto the trimmer. the bottom blade reciprocates across the stationary top blade and slides across low friction delrin spacers. A camshaft mechanism was used to balance the forces of the reciprocating blade and reduce vibration for a cleaner cut.
Nozzle
Nozzle
The nozzle was designed to collect microgreens across a 25.4 cm (10 in) wide tray with enough suction power to hold up the greens for cutting and a wide enough opening to prevent jamming. This part was modeled in Solidworks and printed with ABS plastic, which is durable enough to meet the needs of a prototype nozzle. A mount attachment was added to the nozzle to allow the adjustable mount to interact with the nozzle.
Objective:
The sponsor wanted the team to design a harvesting device that could:
· Cleanly cut the greens without harming them
· Collect the greens without bruising them
· Be handheld and portable
· Be affordable to construct
Final Design:
Final Design:
The team’s solution to these criteria was a Ryobi trimmer modified with a custom cut 25.4 cm reciprocating blade to cut the greens. A 3-D printed, 25.4 cm nozzle collected the greens. The nozzle was connected to the Ryobi trimmer by a mount that allowed for nozzle height and angular adjustment. The greens were sucked through the nozzle into a Thein Baffle powered by a standard 4.5 Kw Shop-vac and then dropped into a collection bin.
To understand this project, one must first understand microgreens. Microgreens are young vegetable greens that are usually harvested in the first few weeks of their growth. They have become common as a visual and flavor component in fine dining. Since microgreens are so sought after in the restaurant industry, they have a very high price per pound, which is very attractive to potential growers. The problem lies in their harvesting. Because they’re so young, microgreens are easily damaged by conventional harvesting methods.
Adjustable Mount
Adjustable Mount
The Nozzle mount was designed in Solidworks and 3-D printed for a perfect fit with the nozzle. The mount connects the nozzle to the Ryobi trimmer and allows the nozzle's height and angle above the greens to be adjustable. The height is adjusted using a track with a tooth and lock mechanism for different height settings and a compression spring to keep the nozzle in the desired setting. The angle is adjusted using a rotary gear with settings ever 15 degrees. The mount enables the nozzle to have the perfect position to collect greens immediately after they are cut.
Summary of Performance Results:
Summary of Performance Results:
The first round of testing involved using the Ryobi trimmer to cut a tray of small microgreens,vacuum the greens using the nozzle, run the greens through the Thein Baffle, and collect the green in the collection container. This first round of testing was very successful. The tray of greens was cut within a minute with very little damage to the greens as determined by our sponsor.
To reduce the damage of the greens even further, a mesh screen was added on the inside of the thine baffle. The screen provided a softer wall to hit than the acrylic wall that the greens were colliding with before. After testing the prototype again with the addition of the screen, no greens were found to be damaged.
The second round of testing had a few small problems. This round used larger microgreens with more leaves. These larger microgreens had a tendency to clump up which sometimes impeded the flow of the nozzle. This was accounted for by increasing the height of the nozzle opening by 0.635 cm and adding a plug that could be put in the entrance of the nozzle to reduce area, but increase flow rate. These two changes improved the performance of the prototype, but greens were still getting stuck in the nozzle albeit less often. This issue only pertained to the larger greens while the smaller greens were unaffected.
A recommendation to resolve the nozzle problem is changing the shape of the nozzle opening to be half as wide (12.7 cm) but twice as high (6.35cm) . This would allow more room for the larger greens to be collected while maintaining the same flow rate into the nozzle. This would also involve cutting the length of the blade in half (6.35 cm) to prevent excess cutting. This would still fall within the sponsors parameters of cutting the tray in two passes.
Thein Baffle/Collection Container
Thein Baffle/Collection Container
The Thein Baffle separates the cyclone created by the vacuum from the collection container where the fragile greens rest. When greens enter the Thein Baffle, they are directed into a small slot that connects the collection container and the Baffle. A curtain made of a soft weed guard mesh was hung where the greens impact the side of the Thein Baffle to reduce damage.
Page updated
Report abuse