Loft around an axis

nathaniel_zaharia

Hey all!

So I am trying to get a feature that is sort of like an auger, but while the part of the auger along the center axis follows a helix down the shaft, I want the outer edge of the auger to remain flat.  



When I select the outer guides, this comes close to working, but not quite.  It almost looks like the loft is trying to come into the second face from the wrong side.


When I select either of the inner guides (helices) the loft fails.

The outer guides have coincident constraints on the loft faces and the helices have pierce constraints on the loft faces.

Any ideas?

mbattistello

I was able to make this work by creating a new plane and sketch thats build from the end of your helixs and your existing outside guide planes. Then I lofted from your start/end rectangles and used all 4 guides. 

Here is the public version of the model - https://cad.onshape.com/documents/57a4cabbe4b0989f5bc70a67/w/8f1cedb02bf045fd2a51f47d/e/b7100244fda8ae6afa21e537

mbattistello

I built a plane using the two ends of the helix and then a third point from the outside guides. Then I "use" the two end points of the helixs and the two end points of your outside guide to build a rectangle. The rectangle I drew is probably not perfect, 90 degs on each corner, but not sure how critical it is. Its purpose was to give the proper guides for the loft to complete. Once I did this I did the loft. Finally I trimmed the loft back to the plan you wanted it to end at originally.

I suspect one of your profiles was not coincident with your guides. I think the fact that the helix guides extended past your end profile might have been main issue. I played with changing the length of your helix but Im not sure I could get both helix to end exactly at the same place due to rounding so instead I just used them as is to build the plane.

owen_sparks

Can you give us a public copy to have a look at?

nathaniel_zaharia

I remade the thing in a public file.  I hope this helps.

It's not 100% identical.  I wondered if I made the two end faces of the loft offset by 10 degrees instead of being parallel that might help.  It did not...

https://cad.onshape.com/documents/d455e826d3972a0385629e26/w/d5ee86c60023716dd64e037c/e/d3b33bc790d4018b73c0e10a

mbattistello

I was able to make this work by creating a new plane and sketch thats build from the end of your helixs and your existing outside guide planes. Then I lofted from your start/end rectangles and used all 4 guides. 

Here is the public version of the model - https://cad.onshape.com/documents/57a4cabbe4b0989f5bc70a67/w/8f1cedb02bf045fd2a51f47d/e/b7100244fda8ae6afa21e537

nathaniel_zaharia

mbattistello said:

I was able to make this work by creating a new plane and sketch thats build from the end of your helixs and your existing outside guide planes. Then I lofted from your start/end rectangles and used all 4 guides. 

Here is the public version of the model - https://cad.onshape.com/documents/57a4cabbe4b0989f5bc70a67/w/8f1cedb02bf045fd2a51f47d/e/b7100244fda8ae6afa21e537

Holy smokes!  Thanks so much @mbattistello! 

Can I ask, did you use a pierce constraint for all 4 vertices?  

mbattistello

I built a plane using the two ends of the helix and then a third point from the outside guides. Then I "use" the two end points of the helixs and the two end points of your outside guide to build a rectangle. The rectangle I drew is probably not perfect, 90 degs on each corner, but not sure how critical it is. Its purpose was to give the proper guides for the loft to complete. Once I did this I did the loft. Finally I trimmed the loft back to the plan you wanted it to end at originally.

I suspect one of your profiles was not coincident with your guides. I think the fact that the helix guides extended past your end profile might have been main issue. I played with changing the length of your helix but Im not sure I could get both helix to end exactly at the same place due to rounding so instead I just used them as is to build the plane.

nathaniel_zaharia

That's it.  Making the plane with the 3 points and making the rectangle like you said.

That works!  Thanks so much, dude!