Pour Over Coffee Bot: Gimbal

With the Dispenser design wrapped up, it’s time to move on to the not-so-sexy, but oh-so-necessary part of the build – the gimbal chassis (plural variety). I know chassis has strong engineering connotations not typically associated with desktop coffee makers, but I don’t know what else to call the plastic components that hold all our motors and bearings together.

When tackling the design of this 2-axis gimbal, it seems to be easiest to work from the inside, out. I’ll start by working out the chassis for the inner sub-assembly (Y-Axis rotation), and then repeat these steps for the larger outer sub-assembly (X-Axis rotation).

Inner Sub-Assembly

Screen Shot 2017-10-24 at 10.23.31 AM

To start things off, I positioned the components in Fusion 360 where I’d like them to ultimately be. From the image above, you can see that the dispenser will need to be pressed into the bearing from left to right, so our servo mounting features need to be on the right side as well.

Screen Shot 2017-10-24 at 10.28.29 AM

Here you can see the mounting posts for the Micro Servo, as well as a feature to secure the 8 mm bearing. I designed in some clearance for the rotation of the dispenser, as we need to ensure it won’t collide with the chassis. Let’s look at how we can verify this.

JointLimitRotationCheck2.gif

Within Fusion 360, I setup Joint Limits for the rotation of the dispenser to be 45 degrees in either direction, which seems greater than I’ll ever need to rotate. By animating this joint, we can then see that we have the necessary clearance.

Outer Sub-Assembly

Similar to the inner sub-assembly, I first positioned the outer Servo and Bearing. It’s important to note that the two axes of rotation are co-planar. This results in a more compact design, as well as significantly easier calculations down the road when programming the motion control. With the components in place, I’m was able to add the necessary features to the inner chassis to mount the outer Servo and Bearing.

Screen Shot 2017-10-24 at 10.48.51 AM.png
Handy M8 captive nut for securing the inner sub-assembly to the rotating portion of our Bearing

Just like before, I modeled the basic form of the chassis to hold the outer sub-assembly components in place and check for clearance. For consistency I set the Joint Limits to 45 degrees in either direction.

OuterJointLimit
clearance is clearance, right?

With the gimbal complete, all that’s left is to build a structure that raises this assembly off the table-top, and fits around a coffee mug and pour-over cone.

Next Step: Complete design of overall structure.

 

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