It seems you were able to totally over complicate this. Although you may have your reasons,,
See my explanation above (Post #3) & try it.
It's cool how you use the spread sheet to drive your model, but unless you're doing multiple variations of this, I don't understand why you would do this.
I also don't understand why you created the vanes as these fancy swept surface features (Or whatever you call them in your CAD...), they can be created as I mentioned above, & use a revolved cut to trim to the shape desired.
In my example as I explained above, there are no fancy sweeps, surfacing, or using trajectories to define all these crazy "Guide curves" as you mention. Just straight up solid modeling.
Am I missing something???
John
Hi John,
Thanks for the comment. A couple of responses:
On the spreadsheet, you have put your finger on the reason - this was a matter of testing different designs and trying out different parameters. I "only" printed the case twice and the impeller three times, but there were several intermediate stages where I tweaked the design and looked to see how the parts would interact. Over time, I have found it worthwhile to generate a table of parameters for anything more than a very simple one-off. At this point, this project as a whole is likely to be a one-off, but it was not simple, so it was very helpful to have the parameters organized and available. I should add that I have had the experience of designing a one-off that later turned out to be the perfect foundation for a new variant. Whenever that has happened in the past, it sure is annoying if I have to go back into each and every sketch to update a parameter, and conversely it is so nice when I have all the parameters broken out like this and can change everything at once.
On the complexity factor vs. a more simple approach - absolutely I could have taken the simpler approach, and in fact, I did just that for the first impeller I modeled and printed. A simple sweep along a 2d curve gave me the vanes at full height; then a simple revolve cut them into the desired shape ... sort of. Note that with the simple approach, the "ogee" curve of the impellers comes out skewed with respect to the cross section of the blade. Does this matter? Probably not; given that this is being 3d printed on a so-so FDM printer, I'm guessing the variations from one print to another would have as much effect on efficiency as the difference between one approach or the other.
But I wanted to challenge myself to produce a blade that followed a smooth, continuous sweep, in part as a way to learn more about how to make more complex shapes. There are situations where one needs, say, a pipe to follow a curve that cannot be defined only in a single plane - e.g., a fancy exhaust header. Another factor was wanting to fillet the edges of the blade, and as Krypto notes, FreeCAD doesn't always succeed with fillets, especially for shapes that have undergone several steps like this. This is, of course, a limitation of the tool ... but all tools have limits, and I like to discover ways to achieve results in spite of the limits.
Bottom line: I wouldn't say that you are missing anything; I just made different choices based on what I wanted for the final outcome and how I wanted to be able to make changes to the model. I make ZERO claims that I have done this the right way, none at all. I only wanted to share my "work in progress" in learning how to model things in FreeCAD, knowing that 1) there are other tools that other users will prefer, 2) there are other approaches that others will prefer, 3) there are other people who could have done all of this much better whether in FreeCAD or in any other software!
