Needing help drawing fan blades using loft tool with rails

[mgianzero]

I'm a newbie to mechanical CAD work, never mind Fusion 360.  I'm attempting to make a fan with complicated blades - they are twisted in many directions with a distinct profile on each edge.  I've gotten the general blade bend I wish, but now I'm struggling to trim the leading and trailing edges of the blades using a specific profile I want.  

Ideally, I was hoping to using the loft tool to not only define the basic shape of my blades, but to also define my leading and trailing blade edges with no success. I attempted to do the trailing edge using a revolving cut and leading edge with a fillet.  Not exactly what I want, not to mention, seems more complicated than it needs to be.   How would I do this?

I've attached a pic of my fan as well as the Fusion 360 file to show my problem.

Any help is very much appreciated.  Thanks everyone!

Marc

[laughingcreek · Accepted solution]

Didn't mean to bag on your workflow.  we all have a different way of approaching things.  doesn't mean it's wrong, just can be hard to follow someone else's train of thought.  (I was primarily referring to the blade creation approach.)

Here's a screen cast of the basic approach I would take to making such a thing. (easy when our free of the constraints of actually making it look like anything in particular 😉  I just started the screen cast and let it run, didn't really have a plan, so there are a few miss-steps.

Notes:

-For this example, I just extruded a basic cylinder for the hub.  For your hub, the approach you took of revolving a cross section is better.

-started with the hub and blade as separate components. blade can then be positioned somewhat more easily. also easier to do edits to later.  if it needs to be positioned exactly, that can be done with joints or align.  (usually joints, but since the body in the blade component ultimately ends up with the hub component, align would work)

-when I draw splines for things like foils, I have a workflow of placing control points at mins and max (peaks and valleys) and then constraining the tangent handles to be horizontal/vertical.  unless I know I want to rotate, then I make them parallel to lines that form a right angle.  you can see me fiddling with that some in the cast.

-for free form splines like the rails, I leave the tangent handles alone and shape them from orthographic views (top, side, etc.) by moving the control points.  Gives the same result as using intersection curves, but a little easier to get things snapped to the right point.

-here I over built the length of the blade, and trimmed it back to size, both at the hub and shroud end.   which is what I would do if this were a personal project.  if this were to be mass produced, I would stop it well short of the hub, and create a nicely lofted transition in to the hub, but that's getting into another level of lofting.

-after making the fillet, I sliced the blade back off the hub to use in a "pattern body".  probably bad practice from a performance standpoint, but saves having to put a fillet on each fan blade separately later.  If fusion started to take a performance hit, this is one of the things I would look for and change. 

So, not really very different approaches, just a few small tweaks. 

take a look, happy to go over questions you may have.

[laughingcreek]

meant to attach the file the resulted from the screen cast for reference.

[mgianzero]

Alex, Thanks again for this video. This was incredible! Once again I learned a lot. I really liked the way you drew your 3D rails after the profiles were made simply by joining using a 2-point spline which you could then edit by adding additional points and moving them around to suit the profile you wanted. Really, really simplified my lofting technique! I also really liked the concept of making the hub and blades as separate components so that you can edit individually as well as have better control over positioning each in relation to each other. But I had to play around with Fusion 360 a bit until I found the preferences option to turn off Active component visibility under General - Design. This makes it easier to see the blade and hub separation using just color cycling. However, I thought another reason to make separate components was also to assemble these parts using some sort of joint. I'm assuming it would be rigid using the blade and hub. Why did you not do this? Does this eliminate the ability to duplicate blades using the circular pattern? I'm merely asking so as to know all my options here. So I noticed that you combined the blade and hub into one body at one point, but then separated them again using split body. My understanding was you wanted to make a fillet to joint these bodies together smoothly but then split it in order to use circular pattern. Correct? Also F-360 seems to randomly pick a color for each component. Where's the option to choose your exact color for this? I know -- now I'm being picky! Marc

[laughingcreek · Accepted solution]

Glad it helps.

There isn't a strongly compelling reason to start with the fan blade as a separate component.   It's going to end up a physical part of the hub, so a joint isn't really necessary.  I did it for organizational reasons.

-It's easier to JUST work on the blade.

-After the part is done, you end up with all the tools you used (sketches etc) in one place.

-You can look in the time line and quickly tell what features are associated with making the blade by component color.

-When you move a component, all those things move with the component, (vs. moving just a body). And you don't have "move" features in the time line.

You are correct on the fillet.  the first join was needed so I could create the fillet.  I did want to create the fillet before the pattern, to avoid having to apply it to each individual blade after. (not to big a deal with 3 blades.  a bigger deal with 10)

In theory, You can pattern "faces" selecting all the faces on the blade and all the fillets, with out splitting the body off.  Used to be one of my go to methods.  (Doesn't always work, depending on circumstance).  I've found out recently that patterning faces is a resource hog compared to pattering bodies, and tends to slow things down.  So I've gotten in the habit of patterning bodies when possible.  (The order of best performance to worst for patterning is Body/Feature/Faces.  Don't know yet how pattering a component factors in, but I suspect it's between bodies and features)

No luck on selecting our own colors for component color cycling.  I believe it's an idea in the idea station.  Pretty sure I voted for it.  (user configurability is generally lacking in fusion - can't configure custom shortcut keys, colors for different line types, colors for component cycling...  I hope it's because AD hasn't gotten around to it yet, and not because of a general mindset at AD)

[mgianzero]

Alex, Yes, so now I understand more of your process with your explanation. I did seem to notice a BIG performance gain when patterning bodies as opposed to faces. I did that in an earlier model if you remember and it really slowed things down. Thanks for that tip! There is one thing to be said for using separate components for the blades vs the hub and joining them later, and that is ... in future models, we "may" want to design a few different blade airfoils and simply tack them on to the same hub. But, according to what we did in this F 360 file, we cut the blade ends using the hub. So I'm not sure how to keep this separate and neat here. But I'm probably getting way ahead of myself here. Probably too complex to implement right now. Another slight problem I seem to be encountering is, although I cleaned up my airfoil by using your technique which made it MUCH simpler to edit blade profiles, I still can't seem to get the right blade shape I want. I think the reason stems from the fact that my blade tip is draw on a plane that is parallel to the blade base plane and, instead, should probably be turned to be tangent to the outside blade shape. I know my explanation is really bad, but here's a pic to illustrate where my blade tip plane is and where I think it should be. My biggest problem is that when I cut the outside blades round, it really cuts off most of my outside profile. You can see in my pic the red line which is more of what I would like the outer profile of blade to look like from above. Marc

[mgianzero]

Okay, I'm making some progress. After I rotated my blade tip airfoil profile about 15 degrees, my blades seem to have more of that "hook" effect at the ends that I'm looking for! See my diagram below. I guess I was looking for a more automated way of determining this angle, but at least I get more of the result I am looking for by manually rotating my airfoil. I'm not exactly sure the amount that I had rotated this profile since the Move / Copy command never saves the previous movements that you make. (Is anybody concerned about this feature? If someone goes back months later to a project, you may never know the exact movements you made since they are not stored anywhere.) This brings me to another problem. Since I cut my blade ends using a circular shroud (using split body) the ends are rather sharp. Is there any way to fillet an odd curve like this to round the edges? And my last question ... what happened to my formatting for posting on this forum? I type things in paragraph form, but everything seems to come out as one continuous paragraph. It doesn't seem to matter if I type it using Rich Text or HTML. Marc

[mgianzero]

Attached is the latest F 360 file that I talked about above for those who want to see. Marc

[davebYYPCU]

Gooday Marc, 

Looks like you have it nailed, well done.

[mgianzero]

Dave, Thank you for the vote of confidence. It's taken quite a bit of work to get this far. However, my saga continues. Alex's suggestions for setting up the blade and hub as separate components and later combining does seem to make the drawing a bit simpler. However, I've discovered a few more difficulties now doing it this way. That is ... As I mentioned before, I find if I rotate the plane that the blade tip is drawn on, I get much more expected results for my lofted wing. Unfortunately, the way I did this was to use the Move / Copy command and rotate the whole blade tip profile sketch about 15 degrees CCW so as to make the sketch more tangential to the hub. The reason for this is that the blade tip is positioned quite a bit aways (maybe about 20mm down my Y-axis) which brings the sketch quite a ways out of alignment with the blade end-cut (see my previous pics for that). However, with the rotated airfoil blade tip sketch, you can no longer individually drag the airfoil points as easily as you must use the Move / Copy command for each individual point (I guess F360 only encourages 2D plane movement and not in true 3D space - a limitation that's been mentioned in other threads that developers are aware of). But even when you edit a single point in this new 3D airfoil profile, it no longer recognizes the spline as a closed sketch and breaks the loft. So I don't know how to fix this. So how does one get around this limitation? I'm guessing it's always best to draw your 2D sketches in a true plan (origin XYX or a constructed one). So, if my logic is correct, I'll have to find a nice way to create a newly tangential plane (like the one I artificially rotated) to edit my airfoil profiles. Ideally, it would be nice to create a tangential plane to draw my airfoil at the blade tip and rotate that plane at any time as I edit the sketch. If I'm not making myself clear, please refer to my F360 file that I uploaded earlier to see what I mean. And lastly, why does all my text that I post upload as one paragraph, when I neatly wrote it on my end? I've tried it using both Rich Text and HTML. Marc

[laughingcreek · Accepted solution]

The first type of move in the move dialog forgets it's previous value, apparently by design.  The next 2 DO keep their values, so you can go back and edit them in the time line and previous values are  still there.  Make sure your moving the body, as I don't believe component moves are ever parametric. (again, by design.)

A second way is to use joints.  roll time line back to before you did any modifications to the basic blade form (cuts positioning etc). place a sketch with something like a circle in the hub component on the origin plane that is perpendicular to the tangent direction of the blade to act as an anchor point for a joint.  then use joints to attach/position.  The joint can be edited for displacement and rotating at any time that way. (let me know if yo need a screen cast of that.

Just a FYI on moving sketches: moving sketches with move is never parametric, and doesn't even put a feature in the time line.

[laughingcreek · Accepted solution]

Also, if you place your wing tip on a "Plane at an angle,"  you can adjust the angle of the plane, instead of moving the profile into a 3d situation.  Which I agree would make future edits rather annoying.  

Here is a screen cast of me moving the sketch in my example file.

You'll note that I fight with 2 bugs in this cast, but left them in b/c it's one of those things you have to deal with.

The first bug is that in certain situations (situations I don't know how to predict)  the first edit of a plane sometimes changes it's orientation (in turn changing the orientation of any sketch on it).  The effect is that the sketch gets rotated around the origin.  This is a known bug and is hopefully getting worked on.  after the first adjustment, it won't change again.

The second bug is that when using the "Move" tool in an active sketch, even entities on in-active sketches are effected.  The solution is to make sure you only select what you want.

[mgianzero]

Alex,

I found an even better solution to making my edits easier for my blade tips by using the "Tangent Plane" instead of using "Plane at an Angle" technique as you suggested.  What I did was to make a shroud (same profile that I used to round the blade tips) and I recreated my blade tip profile on this plane.  Now I can literally twist the blade ends however I like and really tweak the blade shape with ease!  Works nicely.  (See my attached model.)

I also see your points about when moving in space using the "Move / Copy" option that some actions are parametric and others are not by design.  It would be nice if F360 somehow made that distinction clear to you before you choose your option (not sure how you would implement that).  Furthermore, I'm speculating that if I wanted to model my impeller with a different set of blades (same hub) that I would then make the the blade and hub as separate components (which I "mostly" did) and then use joints to make the finished model.  I'll have to play around with that as I've only used joints a few times in my other models.  

I'm still learning when it's practical to make parts of my design components and when to make them separate files to import and assemble them using "joints" option.  I think that's what you suggested.  Problem here is that we combined the two components so that we could fillet them and then used split bodies to copy them so that gets a little messy.  But in my attempt to organize my model, I tried to label things in detail so I can follow what I did months from now.  I also utilized the "Groups" feature to try to categorize my design areas.  It becomes a little more obvious the distinction when using the "Component Color Cycling" option. 

Marc

[laughingcreek]

nice work.

I was suggesting possibly using a joint as a way to achieve a somewhat parametric way of positioning the blade.  just another approach to using the move command.

[mgianzero]

Thanks Alex. I think I'll stick to my current method as I think making joints for blades for this application is complicating my design more than necessary. So, I was just about to wrap things up with the project as it has been quite a learning experience, when I noticed these funny lines on my fillets from blade to hub. Any ideas where they came from. My blade appears very smooth by zebra analysis (no real crinkles) and the joint line between blade and hub appear to be smooth. Why this line in this picture? I've attached my latest file for review of this strange fillet glitch. Once I figure this out, I think I'll be done with my drawing my project. And hopefully on to print. Please feel free to review my whole project and make any last minute comments before I close out this thread. Marc

[mgianzero]

Sorry, I forgot my picture showing these funny fillet lines. And why do all my posts from my home computer show as one paragraph, but looks as I type it on my laptop? Both are rich text. Marc

[davebYYPCU · Accepted solution]

Gooday Marc,

That fillet edge is normal behaviour - you will see lots of them inside the cooling holes, too.

Change your Display settings ( first icon, of the 2nd group at the bottom of the screen but above the timeline.

Display Setting > Visual Style > to Shaded, and it and all other edges, will be removed 

Some prefer it with edges,

[mgianzero]

Thank you Dave. That was the issue. I'm not sure how to close out this thread, but I imagine it is best to always submit a solution to help close out the conversation. Since I had a slew of questions that everyone so graciously answered with detailed explanations and even quite a few screencasts, I guess I would have to make all of those posts as part of my solution - should I do that? Any ways, thank you again Dave and Alex for ALL of your time and help with my project. Marc

[davebYYPCU]

Gooday Marc,

Would you circle back here with a pic of the real world part when made, if that's your intention....

that would be the ideal close out for the thread., 

The thread as taught me a few things, the reason we are here, forever learning

[mgianzero]

Absolutely Dave.  Not exactly the direction I plan to go from here.  But will let you know how I make out.

I'm thinking I want to 3D print part for form and fitment which I am sure will be a challenge.  If I understand correctly, F360 now supports 3D printing.  If not, will have to consider CNC milling.

May also do some simulation studies as it is my understanding that F360 also has some capabilities in this department.  I'm figuring  stress analysis, modal vibration studies would be revealing.  But I know little in the way of how to do this.  Anyone, please feel free to point me in the right direction on this one.

Marc

[davebYYPCU]

The 3d printing will be a not so tuff learning curve, 

The model will need to be one body, select it from the browser, Save as STL.  Then take it into your favourite Sliceing Software.

Can assist with the printing, dependant on the slicer

Can't help with Simulations,

I would suggest new thread for both subjects if needed, but please tag me when you do.