Hot Date Kitchen
Hot Date Kitchen is an established startup in the food production industry that produces and sells chocolate-covered dates that are filled with spiced sunflower butter. To date, the client has worked with a partner machinery manufacturer to automate all functions aside from the process of pitting and slicing dates. Hot Date Kitchen requested a piece of machinery to automate this process to increase the capabilities of production volume and lower production costs.
I worked as a hardware engineer at Generate Product Development Studio to design a custom industrial date-cutting machine to automate the production of a sustainable snack with a team of 6 engineers.
During the initial phase of brainstorming and research, we looked into existing date pitting machines - and on a broader scale - food processing machines as a whole. Information was collected from there: what features were successful and why, what types of fruit or other food products were they applicable to, and how were existing products addressing the challenges of working with dried fruit - size variability, sticky and sugary outer coatings, etc. Ultimately, there was no marketable machine that was doing what Hot Date Kitchen had asked the engineering team to do - sort, pit, and slice dates all at once.
After determining functionality requirements and essential characteristics through decision matrices, we then identified core deliverables: inclusion of a slicing and output mechanism, and to have automation compatibility in the final assembly.
Assembly Overview
Rotary Design
The rotary design allows for the loading and unloading of dates at the same speed as the moving plate. With this design, the dates only pass over the wire once. With this rotary design, we were able to include a brush roller and backboard sub-assembly, which prevents any dates from falling out before being cut.
The rotary design also allows for modularity in the future. The moving plates are divided into 4 quadrants. Rotating counterclockwise, the first quadrant features an entrance slide, where dates are dumped into a shoot and enter the machine. The second quadrant is where dates are loaded and fall into slots in the moving plates. The third quadrant has a brush system that agitates the remaining dates and pushes them into the date vessels. Between the third and fourth quadrants, the dates are cut by the stationary wire. The fourth quadrant is open for potential functionality. The dates then return to the first quadrant, where they fall out of the machine via an exit slide.
Rotary Plate and Drive Integration
A rotary plate system was used to facilitate date cutting and precision indexing. This subsystem entailed custom machined plates and hubs with unique geometry for effective transfer of power and modular mechanisms for easy cleaning. The double disk system integrates statistically driven dimensioning with a densely populated plate area for efficiency and accuracy.
The purpose of this drive train is to output a sufficient speed and torque on the output hex shaft to spin the rotary plates to cut dates against the stationary wire.
The drive train starts with the CIM motor. The CIM motor runs at a free speed of 5,330 rpm and has a stall torque of 2.41 Nm. From testing we performed using dates, a wire fixture, and artistic wire, we found an average torque of 13.3 Nm for an 18” diameter wheel. This figure acts as our continuous rated torque, which by conservative estimates is ~1/5 of the stall torque. Our output stall torque must reach 66.5 Nm, meaning our overall gear ratio must be 28:1 or larger.
The CIM motor is mounted to a bar of 80/20, and the output shaft from the motor spins the right-angle gearbox, which has 1:1 bevel gears. The right-angle gearbox saves vertical space in the machine by utilizing the horizontal space at the bottom. Attached to the top of the right angle gearbox is a gearbox, made of 4:1 and 7:1 stages, making a 28:1 gear ratio. A 1.4” diameter spur gear sits on the output shaft of the gearbox and spins a 2.8” diameter spur gear attached to the output hex shaft that spins the moving plates. The overall gear ratio becomes 56:1 with a stall torque of 134.96 Nm and a free speed of 95.2 rpm.
The resin-printed plates were iterated from a laser-cut two-dimensional geometry to include inset hubs and fileted guiding holes. The half-inch hex shaft hubs were designed with multiple points of contact with the plates to ensure stability with high torque loads. These custom hubs were also SLA printed to ensure durability without needing to be industrially machined.
The plate system created a rotary motion mechanism to pass the dates efficiently through a stainless steel wire to be cut horizontally. The rotational dynamics of the mechanism enabled a high torque drive system to be easily integrated and mounted. At the top of the machine crates of dates are poured in via the acrylic slides and agitated via the brush roller. Ultimately dates fall into holes seen in the plate, which operate as individual vessels for each date. Each vessel has a gap between the top and bottom plate, this way as the plates move in a circular motion dates can be pushed through a wire, effectively cutting them in half
Wire Tensioning Fixture
The design of this subassembly primarily focused on fixing and tensioning the stationary wire with minimal deformation. By using two opposing 3D printed fixtures with a thin slit slightly larger than the wire’s diameter, the wire is secured to each frame piece. In order to apply the tension to the wire, a secondary tensioning fixture is placed below one of the mounting fixtures, where a thumb screw is tightened, pushing itself away from the fixed block (Illustrated going from the configuration in the middle image to the configuration in the left image). Relative to the entire assembly, the two beams where the blocks are secured are opposite each other and attached to the rest of the frame; the wire is intended to sit in between the two rotating wheels and should not be in contact with anything else other than the dates being cut.
Frame and Assembly Integration
Aluminum 80/20 was selected for its blend of sturdiness, relative cheapness, and ease of interfacing fabricated and OTS parts onto the frame. The entire frame consists of approximately 24 inches of 1”x1” 80/20.
