Inventor Sheet Metal Failing Miserably on Loft

[Vincent.Solarman]

Hi, I'm trying to recreate the attached / depicted surfaces as a sheet metal part. Unfortunately, no matter how I approach the cake, Inventor comes up with a "doesn't work, because doesn't work" every friggin time. As you might have guessed correctly, I'm 'a little' frustrated by now.

Since Inventor seems to be incapable of either creating / flattening mini-lofts (the flaps on top) from arcs, or creating parametric polyline divisions (that are usable as lofting curves)  I have decided to import the sketches from Rhino/Grasshopper. This leaves me with lofting between a straight line and a polyline. On each segment of the polyline I want to create one of the little flanges that you see on top.

BUT:

- In Inventor, a sheet metal loft seems to be incapable of having flanges on the (side) rail edges

- also, if the outer lines in both loft sketches are straight lines, no flanging possible

- If I create surfaces and thicken them, the single surfaces cannot be joined as a sheet metal, "because". Thickness was set to Thickness and all extrusion directions were tried

- creating single surfaces with gaps (2-3x Thickness) does not help either. Inventor fails to create bends on a edges that belong to a lofted surface

I really hope there is a "oh you have to do it like this when working with sheet metal and lofts" in Inventor.

Never thought I'd ditch Inventor for Grasshopper when working with sheet metal, but it seems so much more straight forward and stable in this case, albeit more work setting everything up. 

Helpful hints are GREATLY appreciated. 

THANKS for your wise input!

Vincent 

[cadman777]

Just an FYI:

The 'fingers' on top are double-rolled in 3d space, so they won't flatten in Inventor, and they also won't accurately, not in Rhino without an add-in. You can get close in Rhino with UV flattening, but you have to play with it, as I'm sure you know.

In past times when I had projects like yours, this is how I would make it:

1. You're going from a straight line to a arc, so that's like a partial transition

2. So you could I'd make a press-brake formed sheetmetal transition from those 2 sketch features

3. Then I'd make fingers at each flat on top

4. But I'd have to make a concession on how to make those 'V's' for the fingers, considering the radius of the press-brake formation that marks their beginning and end

5. I do not know how to make a partially press-brake formed part, but if that's possible, then I'd do it like that.

6. Or maybe you can make your loft and then add to the top a transition of press-brake formed feature and then add your fingers.

That should flatten, even with side flanges.

When I get time I'm gonna try it to see if I can make it.

Incidentally, I have IV2010, so can't view your ipt file.

[cadman777 · Accepted solution]

Find attached a part that resembles yours.

I didn't know what the dimensions were.

It was a bit tricky, but maybe this gives you an idea of one way to go about making it.

[Vincent.Solarman]

Hi Cadman, yes the way you did it is the way to go. I worked on the problem during my "nigh shift" (couldn't sleep) and just created the same geometry that you made (but in Grasshopper).

It also seems that the problem poses one of these corner cases where you need bends and space for bending curves when in reality you could crease the top of the part to create the polygon, but let most of the rest of the sheet metal  just follow the light bend...  This leads to the rather unpleasant and maybe not entirely necessary corners on the bottom of the part (in CAD)

Anyhow, thanks guys for straightening me out 😉 

[Vincent.Solarman]

/rant on/

Well, one more thing: I managed to recreate the part in Inventor now - halfways. Mirroring does not work for me, probably because Inventor does not recognize that a certain bendline is (supposed to be) perpendicular to the mirror surface. This can be fixed by manually and tediously repeating all the steps that got the file working on the one side on the other side. 

I really have to say, once you are leaving the rectangular box territory in inventor, forget about parametric work. The amount of error messages I get, manual hacks to avoid them and "not possible because I dunno" is plain ridiculous. What if, in my case from above, I want to / have to change the  number of flanges from 12 to 15? As far as I can see, I would have to go through the tedious work of rebuilding and fixing everything again. 

Revit has Dynamo, Rhino has Grasshopper, MatLab has Simulink (probably many more examples out there) but in Inventor we have to mouse-select features like we're still in the 90s. E.g. we can't even select more than one flange at a time, if we dare to put an offset on the starting curve...  

In my view, Autodesk really needs to fix this stone-age non-parametric behaviour. 

Please do. Thanks

/rant off/

[cadman777]

I am compelled to agree with you on all counts. After years of waiting and watching Autodesk 'rearrange the furniture' in AutoCAD (release 10 through 2010!), I learned my lesson. No more hopes and dreams, only harsh reality. Then came SUBSCRIPTION SLAVERY! Like the Amish say, 'once burnt twice shy'.

So that's why I refused to upgrade since Inventor 2010 (I started on Inventor 7). I wasn't going to repeat being the foolish patsy for Autodesk Investors. So I made the decision to sit in my chair using IV2010 year after year and WATCH for the Investors, Directors and Executives at Autodesk to IMPROVE Inventor. But since no SUBSTANTIAL improvements were forthcoming, I just kept using IV2010 AND Rhino/Grasshopper, AND other software relevant to my work. The world doesn't stop for Autodesk.

When you have limited tools available, you learn to make the best of what you got. The only thing I HATED was having to use Rhino and scan processing software in conjunction with Inventor. I wanted every process to be seamelessly integrated into Inventor PARAMETRICS. Some very important projects in the past needed that PARAMETRIC INTEGRATION. Fusion is not the answer, which is why I never began using it. Anyway...

Find attached an updated part. This time I used the circular array for the 'fingers'. It didn't work during the initial process of making the part, but once the geometry got cleaned up and stabilized, it worked. I didn't spend the time on the i.s. corner details, that is, doing the math in the Parameters to drive the features used to create those minute additions. If you use MathCAD, I'm sure you can figure it out (it's 3d trig). That way, you can have a totally parametric model, or nearly so.

[cadman777]

Incidentally, I made a compromise on the flange corner miter ('meh...'). It would've been too much fiddling around to get it right, so I just cheated and made it the easy way. But I'm sure you can figure it out by looking at the tools I used to get it like that.

Can you share your Rhino and GH files w/me?

I want to see how you did it in GH.

[Vincent.Solarman]

Hey, sorry, can't do that. My boss won't like me posting internals here. All I can say is, that in the end it took me less time than building the manual version in Inventor. This plus https://www.food4rhino.com/en/resource/sheet-metal-bends-2 and some of the available unrollers that some people translated from Rhino to GH should be enough for my project to work with. There are still quite a few useful features in Inventor that I'm missing out on this way, but for this part at least it's not worth the pain... 

Best regards

[cadman777]

No Worries.

Rhino has come a long way since I first bought it back in Version 2!

I just began using Grasshopper a couple years ago.

Amazing visual programming language that SHOULD BE in Inventor.

VP has been around since the early 80's!