Constant Velocity Joint Optimization

Now that we’ve gotten a few prototypes printed, we set off towards optimizing that design to create a more functional part.  Below are two of our initial prototype builds that have been highlighted in previous blog posts:

am-blog-postFig. 1: Prototype builds

In those initial builds, the parts either did not have enough clearance to allow for easy sliding, or had fused together during the build process. In order to help solve those issues, we added additional clearance between the parts. Below is the newest prototype build with improved clearances.


Fig. 2: Optimized Prototype

The new part had a significantly smoother sliding action, and prompted us to move forward with building the other parts of the design. One of the parts we had to build was the mounting platform that would contain the arms that hold the assembly. Below are a few examples of failures during the building of the platform.

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                                    (a)                                                                              (b)                                                                            (c)

Fig. 3: Three failures while building the mounting platform

The failures of the various mounting platforms occured due to various reasons. In the yellow mounting platform (Fig. 3a), warpage caused the large piece with a hole to not properly bond to the rest of the structure, and broke off. In the orange case (Fig. 3b), warpage caused the part to come off of the build platform. In the blue case (Fig. 3c), while printing the inner sparse matrix of the part the material stopped bonding to previous built layers. Our edits to these designs enabled future builds to be successful.

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                                          (a)                                                                                                (b)

Fig. 4: (a) Seperate components of successfully built mounting platform and (b) assembly of the mounting platform

The newly printed mounting platform parts also have a very nice sliding action between them, enabling smooth rotation. We also needed to print holding arms which would hold the actual joint. We printed these parts at the same time as those shown in Fig. 2, in a tall cylinder-like structure.


Fig. 5: Printed holding arms

Together, all of the parts fit together into a working prototype.


Fig. 6: Assembled Prototype

However, the assembly has the tendency to begin falling apart after a little time of spinning.

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                       (a)                                                 (b)                                                                          (c)

Fig. 6: (a) Assembled prototype falling apart while moving due to (b) poor tolerances between joint and holding arms and (c) holding arms and mounting platform

We believe that happens due to poor tolerances between the joint and the holding arms and between the holding arms and mounting platform. Our ongoing work is to tighten up those tolerances to create a part that can handle sustained rotation without any issues.

Check back next week to see how those new edits work out!