Hot Date Kitchen: Automatic Date Orientation Assmebly
Background
Hot Date Kitchen is a small start-up outside of Boston that creates and sells sunflower-butter filled dates covered in chocolate. This delicious snack was initially produced completely by hand, from cutting the fruit, to filling it, to coating it.
​
However, Hot Date Kitchen was looking to increase manufacturability to meet demand, so they approached Generate for an industrial machine to automatically orient and cut dates. I worked with a team of mechanical and electrical engineers to accomplish this task, and while I supported all mechanical assemblies, my focus was on the development of an automatic orienting mechanism.
​
Objectives, Constraints, & Skills Applied
Objectives
-
Design a mechanism to automatically sort and orient dates for the cutting process
Constraints
-
The mechanism must fit seamlessly within the entire cutting machine as a whole
-
The machine must not require the need for an operator
-
Dates must be able to be "dumped" into machine without need for hand-placing them
-
The orienting mechanism must be placed before the cutting mechanism
-
The mechanism must not interfere with any other machine parts
Skills Applied
-
Fusion360 3D Modeling
-
Standard Shop Tools
-
OTS Part Sourcing
-
Subassembly Part Ownership
Complete Mechanical Assembly
Before isolating the sorting and orientation subassembly, it is important to understand how the entire machine works as a whole.
Functionality & Assembly Overview
This machine works by placing dates on the entrance slide, where they either naturally fall into place into vertical compartments on the rotary plates or do so with the help of the brush roller assembly. When in place, the wheels spin the dates across a steel wire (located between both plates) and the freshly cut dates fall down the exit slide. When running, the machine has 2 moving components: the rotary plates and the brush roller assembly. The entire mechanism is enclosed within an 80/20 frame, running on a power supply located in the electronics box. The design emphasizes modularity, as different mechanism are bound by their quadrants, with an available quadrant 4 for future functionality.
Rotary Plates & Drivetrain
The rotary plates are connected to the system through a hex shaft that is powered by a CIM motor. The drivetrain begins with that motor, and uses bevel gears and spur gears to achieve the desired output torque magnitude and location. The wheels have compartments in which the dates fall into, and the rotary design maximizes space and cost constraints by having the process begin and end in the same location.
​
Entrance & Exit Slides
Slides are used to efficiently move the dates in and out of the system without a constant need for an operator. They are both placed in quadrant 1, as seen in the aerial view of the mechanism in the figure above, with the entrance slide located above the exit.
​
Brush Roller Assembly
The brush roller assembly - the mechanism in which I focused on throughout this project - is responsible for automatically orienting the dates vertically within the plate. This occurs in between quadrants 2 and 3, and the brush roller rotates opposite to the direction of the wheel so that dates get pushed back until they fall into place. This creates a feedback loop that prevents dates from reaching the next step until it can travel underneath the roller in their compartments.
​
Wire Placement & Tensioning Fixture
Dates finally are cut once they pass the brush roller to the steel wire, fixtured in between quadrants 3 and 4. The wire runs from one end of the 80/20 to another, and is placed in a thin opening between the 2 plates. The spacing and plate sizing was determined so that the resulting cut dates would, on average, be equal in size. With sustained use, the wire becomes less and less taut, so a screw is used to be able to tighten the slack whenever necessary. Once dates pass through the wire, they travel back to quadrant 1, where they fall out of the exit slide.
Brush Roller Assembly
This assembly consists of a Mini CIM motor that directly powers the brush roller through a custom shaft coupler.
Concept Design Process
When originally tasked with developing an automatic orientation system, 2 concepts were explored before reaching the final brush roller model: a funnel system and a hopper system.
-
A funnel system would store dates in columns above the rotary plate, and would release dates periodically to fill the plate without overflowing it. However, this breaks a main constraint of having to sort the dates by hand and would also require more parts in order to achieve automatic dispensing.
-
A hopper system would consist of a constantly vibrating or shaking assembly that would feed into the rotary plate once dates are oriented correctly. However, for ideal functionality, this mechanism would break cost and space constraints and was determined to be unfeasible.
​
The brush roller assembly was adopted when inspecting larger scale food processing systems that utilized constantly rotating brushes to automatically orient small fruits and vegetables on conveyer belts. This idea was scaled down to fit a smaller machine with a rotary plate.
Brush Selection
An original constraint for this project was making the entire machine food-safe, but doing so would be way over budget, so this model used cheaper parts to display functionality, and the company would recreate it with food-safe parts. The chosen brush is mainly used for laboratory or cleaning purposes but is sufficient for the functionality of this prototype.
Coupler Design
A custom coupler was necessary to transfer torque from the motor to the brush because it needed to account for the metric sizing from the motor shaft (8 mm) to imperial sizing for the brush shaft (1/4"). The coupler also needed a key slot, so rather than sourcing a part with these requirements, creating a 3D printed part was determined to be more efficient. The first design, shown on the right, included 2 parts that were connected with M2 nuts and bolts.
​
The final design, shown in the assembly above, addressed 2 main issues: a relatively large amount of material and components for use . The new design introduced a press fit coupler (on both ends) with heat set inserts and set screws for extra tightening. When comparing the 2, the press fit coupler was easier to use and had less torque loss from the motor shaft to brush shaft.
​
Results
Final Design Functionality
The final prototype incorporated all the subassemblies was able to function as intended. As seen in the video, the brush roller assembly achieved the desired goal of automatically orienting the dates without the need for an operator. When measured, the machine was able to exceed the minimum desired number of dates sorted and cut from 12 per minute to 30 per minute.
Future Design Considerations
Possible future designs can include:
-
Addition of a mechanism that automatically pits the dates. As mentioned previously, the current design allows for a seamless addition to one of the quadrants, so a future design could pit the dates before cutting them, saving the company from either manually pitting dates or paying a premium on buying pitted dates.
-
Features that reduce either the need to clean or difficultly of cleaning. After continuous testing, there was high date residue buildup on the bottom plate (where the dates stand) and the wire (where they get cut). With a larger budget, the team would have access to greater material selection and coatings that can be applied to reduce this buildup.