Designing the Belt Drive for our Cocktail Machine

Designing the Belt Drive for our Cocktail Machine

One obvious design need for our cocktail machine was movement.  SirMixABot needs to either bring a drink to the glass, a glass to the drink, or a combination of the two.  Additionally, it should do so using durable, affordable components that are easy to work with.  Following that criteria led us to stepper motors, liquor bottle dispensers, linear rails, and other parts documented in the “how to” section of SirMixABot’s blog.  The decision was made to use a stepper motor, belt driven setup to control the horizontal movement.  This satisfied the durability and affordability requirements, while simultaneously providing a very cool process to watch.  After all, it should be just as fun watching a drink being made as it is drinking it!

Powering the Belt Drive

cocktail machine stepper motor belt drive

SirMixABot’s drink platform moves across a horizontal axis, and needs to stop precisely under different ingredient holders.  The power source needed to be affordable and reliable, but ideally compact as well.  A stepper motor proved to be the perfect component for both the horizontal movement, as well as powering the drive rod on the drink platform.  The easiest way to translate the circular motion of the stepper motor is to fix it in place, and use a belt between it an the platform.  With a simple 3D printed mounting enclosure the belt driven assembly also gives the cocktail machine a great look.  We love to “see how it works”, and exposing these components lets the user do just that.

Tensioning the Belt Drive

cocktail machine belt tension

Now that the power source and connection method are determined, it’s time to figure out how to keep that belt taught.  Anticipating small differences in installation, as well as wear over time, led to the use of an adjustable tensioner.  The robotic bartender uses a flex coupling on the vertical drive rod, but it would need a different type of spring for this solution.  Fortunately this one is not as complicated, and a simple spring was sourced.  Two 3D printed pieces are designed to interlock, and move horizontally.  The larger is fixed to the base of the automated bar, while the smaller one is slid into a channel.  The spring prevents it from full compression, while the outer wall prevents release from the channel.  A wheel is fixed to the spring loaded piece, and the belt is attached to provide full tension.  It’s another simple, durable, and aesthetically pleasing solution.

The Final Belt Driven Cocktail Machine

When the belt, stepper motor, and drink platform are linked together it’s time to visit the SirMixABot cocktail app and order a drink!  The system  utilizes limit switches and magnets for position sensors.  Seeing the robotic bar dispense your first drink is an amazing experience.  It’s easy to want to gulp it down and place your glass to see it all happen again.  Just like a good drink though, you shouldn’t rush!  SirMixABot is designed for the long run, and there will be plenty of time for future concoctions.

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