Hi Anthony - the difficulty of relative tolerancing with the sweep is that your case needs to be relative not to the bounding box around the entire curve being used (as was the case with Trim) but instead around the smallest sub-segment within the shape.

That has some potential to possibly make an excessively tight tolerance in the case where someone inadvertently has some tiny micro segment within a profile that they did not really even know about.

I'll take a look at it, but it's a somewhat more complex case with more potential side effects than what I did for Trim.

- Michael

Here's props file back as a solid with .0001 meter G2 fillets at the hub connection and the blade tips... I also changed the hubs cone bottom to be a conic surface with an RHO value of .9999 (Since he likes the little numbers)

I have another file where I made the hub front a G2 blend also, and cut the blade section out to rotate seperatly to try and animate for fun..

I couldnt mesh it. Anything comming even relatively close was an issue for my system.

cool video, how did you make that?

Thats just a turntable capture in 3d-coat... I hadnt cut the blade section from the body yet so you can see the G2 nose cone turning too.. Right now, I'm doing some renders in Carrara trying to get some blur correct for the blade spinning, but it's proving more time consuming than I wanted, because i meshed the blade section very dense and it's dragging things down... I may have to go to sleep and remesh the blades tommorow to allow the render testing to get it to look right.. :o

Hi,

For anyone interested here is an updated model. I was working with the fillets trying to find something both manufacturable and that meets the requirements. This is a close first pass. It leaves room for a blend between the hub and the airfoil. The airfoil isn't ground out as this brings up the tolerance issues talked about. But its a good start and that's all I really was looking for at this point. In this model I increased the size of the forging, changed the hub geometry and put in some decent sized fillets. Everything in MoI works so long as you don't try to mess with the airfoil.

Anthony

Edit; File has been removed to save server space.

Hi Arthur, so I've been looking more deeply into why your original sweep example (The A400M Propeller Example.3dm file that you attached previously) doesn't work right, and I've found a couple of problem areas. The good news is that there is a way to work around them.

The first problem is that the sweep goes through a routine in the geometry library that decides that any edge smaller than 0.001 units is degenerate and that edge just gets left out of the trimming boundary.

So to avoid that, increase the size of your object until the smallest segment in it is at least 0.001 units or larger in length, probably best to have a bit of cushion on that so maybe target something like 0.01 units. This part can be done easily to your example file by just switching your unit system from meters to millimeters (as long as you have not turned off the option to scale objects when the unit system changes which is enabled by default).

So that's the first step - switch to units = millimeters.

Then the next thing that goes wrong is related to having not just one tiny segment but actually having 2 tiny segments right next to each other like this:



Instead of having little arc segments one after the other like that, you've got to delete those 2 little pieces and instead put in 1 single arc piece in there instead (something that Burr tried earlier also), like this:



Having 2 little tiny segments adjacent to one another causes a problem with the joining stage - sweep basically builds one surface for each segment of the profile being swept and then does a joining process to glue those surfaces together into a connected piece. But with those 2 little segments side by side, they end up actually being within the join tolerance of each other and the joiner goes ahead and glues them to each other making a mess in this case. When you have only one little edge in there that won't happen. So getting just one arc piece instead of 2 arc pieces like in one of Burr's previous tries is another key thing.

To replace the arcs, use Edit > Separate to break the curves apart into their segments, delete the 2 little arcs, and use Draw curve > Arc > 3 pts to put in a new larger arc there, then join all those segments together into a closed curve.


I've attached an updated version of your file which should now sweep file - so again the steps to alter your file are - switch units to millimeters, and replace the 2 little side-by-side arc segments at the top and bottom with just 1 arc in each of those spots.


So Burr you were definitely on the right track! :)


- Michael

Thanks Michael,

I understand I think, I'll give it a shot. I updated the previous post. I watched all your tutorials and read the manual some more. So this update has better surfaces in it, based on what I learned. I updated the hub some and the size of the fillets. I'm going to keep this model, as I like having a model of the forging. I'll make another one where I try to have the finished blade.

I was watching the videos and I saw when you update the rails the sweep will update. But when I tried it nothing updated. But I haven't read the manual fully so it's probably something I'm not doing right.

Anthony

Hi Anthony,

> I was watching the videos and I say when you update the
> rails the sweep will update. But when I tried it nothing updated.

Are you trying it after you've done other operations to the result of the sweep like booleaned them?

If so then, that's the difference - some kinds of operations can break the "history chain" that connects curves to their generated descendents.

If you do the editing immediately after doing the sweep before you do other operations to it, that's when you should be able to see the update happen.

In the future I do want to make the history function deeper and persist through more kinds of operations, that is a complex area to handle well though.

- Michael

Hi Michael,

Yeah, you hit it on the head. I was wondering if that was the cause. A persistent memory could be useful. The idea would be after I did the fea and saw how much the blade was moving and in what direction, I could come back in and move the rail points. Then keep iterating until its close. But I was planning on regenerating the rails with my code and start the model all over. So its not that big of a deal, but it could make it a bit simpler.

I tried your suggestions about modelling the blade and you are right. It works perfectly. I switch to mm then do the sweep. Also make sure the ler and ter are one arc. I had been doing that though after you guys brought it up. I think the missing link was switching to mm. Also to make it display shaded right on my laptop I have been setting the mesh angle to 1 degree with no apparent side effects.

Thanks so much, I am really really happy with MoI. No need for Rhino, PowerShape, or Autodesk 123D.

Anthony

Wow,

It took me no time at all to do the final machined blade with all the fillets, transitions etc... This program rocks. Once done, I changed the units back to meters and it re-scaled it to the proper dimensions. I did see it was best to keep the mesh angle to 10 degrees with this model. Otherwise it was real slow to do everything. The critical transition of ter to hub came out pretty well considering this was my first pass at it and I've never used this program before. You may be able to smooth it out a bit more. But it looks pretty good. If you examine this area you will see what I was saying about needing to model it for stress purposes. Hopefully, I've answered all the questions. I really appreciate everyone's help. I never thought I'd get the model this far. I'm blown away by the ease of use and power of the program.

Sincerely,

Anthony Falzone

http://propdesign.weebly.com/

I improved the transition from airfoil to hub and made the hub more detailed. It's not exact but pretty close. I don't know what the exact shape would be. It's basically a concept. Line replaceable fixed pitch blades. Two bolts would hold each blade in place. The configuration is a pusher the cone in the back is the exit. It would be mounted on the other end to the aircraft. That's why the round part isn't there anymore.

Just for the sake of consistency, here are the files I now include in PROP_DESIGN. I updated my documentation to recommend MoI, I removed any reference to Rhino as well. I just have the one example now. Its so easy to create, I had no need for the rough machined model. It takes up space in the upload/download process as well. I don't know if my model is good enough for your gallery. But if you want to use it there, feel free. Thanks again for all the help.

Edit; Files have been removed to save server space.

Hi Anthony, that's awesome that it's all worked out so well!


> I don't know if my model is good enough for your gallery.

Sure, it would be great to have your model in the gallery - the gallery actually does not contain 3DM files though, only images.

If you'd like to upload it there, that would be great - just the screenshot that you posted here would be fine. You can put a couple of notes in there about how it was created and a link to your prop_design SourceForge site as well so anyone interested could find your stuff.

Thanks,
- Michael

Cool,

I uploaded it to the gallery with a description. Thanks again. I didn't have enough room to mention I only used your program for two days. A testament to how easy it is to use. Not to mention I normally hate CAD work with a passion and veer from it as much as possible. With MoI, I love doing it now. Your website, support, and pricing are unbelievable as well. This is the easiest recommendation ever.

Thanks very much Anthony!

- Michael

I spent the day experimenting with the blend between the blade and hub. Trying to get a more fluid shape that would resemble what is actually ground by hand. Before it was a little too rigid. This seems better, but probably a little off. I think its the best it can be, in software, though. Real life is a bit different. This would give me a good approx. for FEA. I have experience a few graphics glitches. I posted a few here. I noticed that for thin parts, even a plate, the edge curves will show through. Also, on my super small ter it can display weird. But it seems like its just an issue of being zoomed in and rotated in a way that brings the model a lot closer than you could get in parallel or just zoomed in to the max. Moreover if you pick a spot on the middle of the blade on the ter and zoom in to the max, there is no issue. But if you then rotate the model another spot on the blade will come into view making it even closer than the zoom allows, then the issue shows up.

Whoops,

Hit post by accident, here are the attachments.

Edit; Attachments have been removed to save server space.

Hi Anthony,

> I have experience a few graphics glitches. I posted a few
> here. I noticed that for thin parts, even a plate, the edge
> curves will show through.

Yeah, the display has to work within several limits - like it has to work within the framework of what common video cards can do, and it needs to try and update the display quickly. So because of that there are various kinds of shortcuts it takes which can result in an imperfect display inside of your working viewport. That's normal and it's just something to ignore.

Please see these previous posts for some more detailed explanation on this particular display issue:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4123.62
http://moi3d.com/forum/index.php?webtag=MOI&msg=4061.6

I do have some ideas for things to try in the future to improve it though.

- Michael

Wow you are fast and with references too, lol. Makes sense, the display is awesome and fast. Just wanted to make sure you new there were a few bugs, but you already new, so cool.

Mabe I have missed it, but is there limitation to the ImportPointFile script such as number of points etc.? I downloded a sample .xyz file, but I am un able to open it with script. It does not error out, but simply does nothing.

Any clues?

Michael T.