At this point, all mechanical design work for the CookMate has been completed, and enough of the ordered parts have arrived to begin building. The first build session for the CookMate took place on February 18th, 2021.
Frame Assembly
The frame of the CookMate needs to be quite robust in order to support all of the loads caused by the components that will eventually be housed within the frame. Additionally, the frame must be easy to assemble, given the lack of access to a machine shop or certain large power tools. Thus, the frame was designed to be assembled from 1" x 1" aluminum extrusions, right angle brackets, screws and drop-in-T-nuts. The aluminum extrusions and the fasteners were sourced from CPI Automation, while the right angled brackets could easily be sourced from any home hardware store. The results of the frame assembly can be seen in the image below.
Flat Bearing Supports
As per the original CAD design, the cooking vessel in the CookMate must rotate about its axis in order to stir its contents. In order to facilitate this rotational motion and keep the cooking vessel secured, two sets of bearings were used. The first pair of bearings would be placed underneath the pot to support its rotation, which will be discussed further in the next section. The second pair of bearings are flat-cage needle roller bearings which will support the top of the cooking vessel at two points in order to keep it stable.
In order to secure the two flat-cage needle roller bearings to the aluminum frame of the CookMate, two bearing holders were designed and 3D-printed. The CAD design of these two bearing holders involved quite a bit of trigonometry, as the flat roller bearings needed to be at a 45 degree tangent to the pot which was already inclined at 30 degrees from the vertical axis. The two holders are mirrored versions of each other as one will hold the roller bearing to the right of the pot, and the other to the left. Below is an image showing one of the flat-cage roller bearings in its 3D-printed holder.
As can be seen in the image above, the 3D-printed holder keeps the bearing at a specific angle, and has mounting holes such that the holder can be fixed to the aluminum frame of the CookMate. Below is an image of the two bearings and holders mounted to the frame.
As a quick side note, the two flat-cage roller bearings are rated for temperatures well above 300 Fahrenheit, as thus should be suitable to be in contact with the pot at cooking temperatures.
Pot Rotation Mechanism
As discussed in a previous post on the mechanical design of the CookMate, the pot rotation mechanism will use a motor driving a gear system to rotate a stepped shaft. This stepped shaft will be supported by two deep-groove ball bearings and serve as the axis upon which the cooking vessel will rotate. To secure the two ball bearings to the frame of the CookMate, a system of supports were designed. As these supports along with the bearings would be bearing the entire weight of the cooking vessel and its contents, simply 3D printing these supports would not be sufficient in terms of strength. Therefore, these supports were designed to be machined from square aluminum stock. Additionally, as the stepped shaft would need to be machined from round aluminum stock. The machined parts for the pot rotation mechanism can be seen in the image below.
From the image above, the two aluminum blocks resting upon the extrusion have been tapped with 1/4"-20 UNC threads from below, to allow them to be firmly fastened to the aluminum extrusion. Also, please note that in the above photograph, the second ball bearing had not yet been placed onto the stepped shaft. The reason for this is because at the time, the stepped shaft needed to be sanded to refine the fit of the bearing on the shaft.
Next Steps
The pair of gears for the motor and the stepped shaft have yet to be ordered. The gears require very specific bore diameters to fit on the motor's shaft and the stepped shaft. additionally, the gears must have setscrews to allow them to be firmly affixed without slippage. Additionally, the machined aluminum supports must be secured to the frame of the CookMate, which would require drilling holes through the extrusions. Finally, a mount for the DC motor must be designed and fabricated to position the motor in an orientation to allow the gears to mesh.