The last week or so has been all about gettin distracted! I have been continuing to run test parts in my tumble polisher, and while I waited, I decided to get started on sketching out a plan for my coupler testing.
But diving into that led me to a whole rabbit hole of fun playing around with some diaphragm flexure design concepts.
Below is a bit of my meandering through all of that. I’m quite curious if anyone is interested in these ‘rough sketch’ and brainstorming aspects of my design journey. So I’d love any feedback ya’ve got for me!
Coupler Tester
My current thinking is a 3 module design.
As I’m currently envisioning it, this will not allow for dynamic measurements, but I think I’m ok with just some static testing…at least to start.
By separating them into individual modules, I can use adjustments at the interfaces between them to vary the alignment and axial preload between tests.
Here is my first rough sketch of the ‘rotating’ portion of the system. One change I already know I’ll need is the addition of a second radial roller for each sensor module. With the single one each I’ve included in the sketch, they will not be properly constrained in rotation about X and Y. On the load cell side, I’m going to need to figure something out to not have the roller bearing interface influence load measurements.
I’m thinking I’ll make custom sensors for both the load cell and the torque sensor (although for the former I could just use some of the cheapo load cells I have on the shelf). My biggest hesitation is that if I use plastic-printed flexures for these, they will have horrible drift behavior and require regular recalibration. But arguably unnecessary custom sensors is exactly the sort of scope creep I find irresistible, so I’m at least going to take a stab at some design concepts.
For the Load Module, I am not going to include any axial support, like thrust bearings. My assumption is that the axial force will be balanced between the two coupler interfaces and no net axial force needs to be supported by the Load Module’s housing. So for the below, simplified free body diagram, I’m assuming F1=F2 and therefore FR=0. In fact, it occurs to me as I’m writing this, if FR does not equal 0 it will directly impact my axial load measurements. So I will need to take a more detailed look at this in the design.
…then I started thinking about the Axial Load Sensor, and it’s making me want to revisit an old project I have been eager to take another stab at….and now you see why it takes me months for each video.
Diaphragm Flexure-based Sensor
The project was the displacement sensor whose model is shown below.