Installing Cover Plate
The rotational mechanism employs a separate platform that attaches to the enclosure cover. These parts are separated to avoid printing overhanging geometry. The parts are secured together with three M3 x 6mm machine screws.
Place the plate over the enclosure cover and orient the parts so the mounting holes line up properly. While holding the two together, insert and fasten the M3 x 6mm machine screws into them mounting holes. I found it easier to preinstall the screws into the plate first. Drive the screws until fully tightened.
With the cover plate assembled, we can work on securing the DC motor to the cover. We'll need two M3 x 25mm long machine screws.
Trim Motor Parts
This particular motor features some elements that prevent it from fitting inside the case along side all of the various components. So we'll need to cut them off to remove them. This TT motor has two shafts, one on either side of the motor. In this project, we only need one so we can remove the other by clipping it with shears or cutting with a blade. The mounting tab on the top of the motor will also need to be removed – flush diagonal cutters does the job nicely.
Motor Mounting Screws
The machine screws for the securing motor are inserted and fastened through the top of the enclosure cover. Drive the two until the shank of the screw comes through the other side. These mounting holes have built-in standoffs to lengthen the hold on the screw threading.
The motor features two mounting holes. These are have a slightly larger diameter than 3mm so it can be pressed into screws. The length of the screw provides a mechanical hold on the body of the motor. Make sure to orient the motor so the shaft can stick out through the hole in the cover. Line up the mounting holes with the screws and fit the motor over them. Press the motor down until it's flush with the standoffs in the cover.
The shaft of the motor should be slightly protruding through the hole in the cover and plate. With the motor secured to the cover we can start assembling the reset of the build.
The cover is ready to be installed. The motor is positioned in between the DC jack and potentiometer switch. There's very little clearance between these components. With the USB cable, DC plug and jumper wires, the spacing gets a little tight. The wiring really needs to be positioned in a way where the motor can be fitted and the cover fitted over the case. I suggest taking time and effort to properly lay out the wiring.
When the wiring has been optimized for the placement of the motor, the case should be able to easily shut closed. If it bulges out or won't quite close all the way, try readjusting the wires so they're away from the motor. I found trimming the third terminal from the DC jack and re-orienting the USB cable helped free up some space for the motor.
Snap Fit Case
The lip on the cover features indentations that allow tabs on the edge of the enclosure to snap fit and lock into place. These parts will "click" when press fitted together.
In order to get the platform rotating, we need to install a drive hub onto the shaft of the motor. This drive hub is press fitted over the shaft and should have a tight tolerance. The drive hub is keyed to the motor shaft and should rotate with the shaft of the motor.
The rotating platform secures an 8oz container. It's comprised of three pieces, the tray, bearing mount plate and container holder. We'll use three M3 x 8mm flat head machine screws and hex nuts to secure these parts together.
Start by stacking the parts together. The container holder goes over the tray while the bearing mount plate goes underneath. Orient the parts so the three mounting holes line up with each other. While holding the parts together, insert and fasten the machine screws into the holes. I'm using flat header screws here because they'll be flush with the surface when fully fastened. Drive the screws until they have fully tightened the parts together. Then insert and fasten hex nuts until fully tightened.
Install Ball Bearing
The ball bearings are press fitted into the round tubes on the bottom of the bearing mount plate. They should have a tight tolerance and hold in place.
The two remaining ball bearings are press fitted onto pegs on the cover plate. These should have a right tolerance. Two pivoting caps are pressed fitted over the ball bearings. These caps should spin freely and have a tight hold on the ball bearings.
With the bearing installed we're ready wrap up the platform assembly. The pegs on the bearing caps are designed to be press fitted into the inner diameter of the ball bearings.
Orient the pegs so they're all facing the same direction – This will make alignment and installation easier. The shape of the plate and position of the pegs are set in way where they can only be install in one direction. Start by press fitting the peg from the motor hub into one of the bearings. Then proceed to press fit bearings onto the remaining pegs making sure alignment is correct. The bearings should be mostly seated in the caps (they'll be slightly exposed). The platform should rotate freely.
The tolerances in the parts holding the bearings ought to be fairly secure. If they're too loose, the platform could fly off the cover when in operation. Under heavy loads, the platform can wobble and become unbalanced if the bearings are fully seated. Quick solution to loose parts is to use a mounting tack around the pegs to tighten the hole – I'd avoid glues and adhesives as that could prevent the bearings from spinning freely. If the pegs are too tight, a few minutes of filing should be enough to loosen it up.
One of the last things I did to the build was install a nicely machined knob to the potentiometer. I got this one from sparkfun, it's machined out of aluminum is has nice knurling. It press fits over the spline on the potentiometer. Just orient the knob so the marker is oriented to the desired position. It's totally optional but makes adjusting the dial more comfortable.