Inventor General

## Inventor General

Valued Contributor
Posts: 50
Registered: ‎10-01-2003
Message 1 of 23 (123 Views)

# Complex Lofting Question

123 Views, 22 Replies
12-05-2002 04:13 AM
I have a need to form what is known as a Francis vane impeller (double curvature). Lucky me, huh? Anyway, I understand the loft method for generating a shape from multiple planar sketches, but how on earth can you generate a 3D sketch on a non-planar surface??? As far as I can tell, 3D sketch is only for sweeps. A couple of good similar examples of what I'm trying to do would be either a propeller for a airplane or a boat if you were trying to do the lofting outward, STARTING (I repeat - STARTING) from the hub surface which for both of these objects are curves....Thanks in advance.

Troy Zellers
Member
Posts: 3
Registered: ‎12-05-2002
Message 2 of 23 (123 Views)

# Re: Complex Lofting Question

Though probably not identical to your design, the Autodesk Inventor 5 Essentials Courseware has an example of creating a fan blade using the loft feature. See Chapter 7 (7-5 through 7-9
*Caldwell, Larry
Message 3 of 23 (123 Views)

# Re: Complex Lofting Question

Centrifugal pump. eh? You have a profile of the
shape or a way to determine it? If you want to email me the profile, I'll give
it a shot.

Larry

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
I
have a need to form what is known as a Francis vane impeller (double
curvature). Lucky me, huh? Anyway, I understand the loft method for generating
a shape from multiple planar sketches, but how on earth can you generate a 3D
sketch on a non-planar surface??? As far as I can tell, 3D sketch is only for
sweeps. A couple of good similar examples of what I'm trying to do would be
either a propeller for a airplane or a boat if you were trying to do the
lofting outward, STARTING (I repeat - STARTING) from the hub surface which for
both of these objects are curves....Thanks in advance.

Troy Zellers

Valued Contributor
Posts: 50
Registered: ‎10-01-2003
Message 4 of 23 (123 Views)

# Re:

Yeah. It is easy to be impressed with the simple lofts and extrusions, etc when they demonstrate the software. I was. But I have yet to see the complex shapes of pumps, turbines, etc easily demonstrated.

As it stands right now, I only have the profile of the bottom edge of the vane,not the top. I was trying to see if I could project the 2D profile onto the curved impeller shroud first. If I could do that, then I could do the same on the other shroud and have two non-planar (or 3D) "sketches" to serve as the beginning and terminating loft points.

I'm having to scan the original hand-drawn drawing, convert to vector, import into AutoCAD and re-trace via polylines and then import the AutoCAD profile into Inventor. I'm sure there is an easier way, but I haven't found one yet.
*Costan, Tom
Message 5 of 23 (123 Views)

# Re: Complex Lofting Question

Search customer files for this example.  An
excellent treatment on lofting.

size=2>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Sent: Thursday, October 24, 2002 7:06 PM

Subject: Propeller R6 update

Here's that prop Kent. I updated (re-drew) it in
R6.

~Larry

size=2><<<<<<<<<<<<<<<<<<<<<<<<<<<

-tom

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
I
have a need to form what is known as a Francis vane impeller (double
curvature). Lucky me, huh? Anyway, I understand the loft method for generating
a shape from multiple planar sketches, but how on earth can you generate a 3D
sketch on a non-planar surface??? As far as I can tell, 3D sketch is only for
sweeps. A couple of good similar examples of what I'm trying to do would be
either a propeller for a airplane or a boat if you were trying to do the
lofting outward, STARTING (I repeat - STARTING) from the hub surface which for
both of these objects are curves....Thanks in advance.

Troy Zellers

Valued Contributor
Posts: 50
Registered: ‎10-01-2003
Message 6 of 23 (123 Views)

# Re:

Pardon the dumb question, but is there a way to get to the customer files in www mode? I used to do all newsgroup, but had problems with the laptop had to reformat a few times. So I've procrastinated in setting it back up. Besides, I haven't figured out newsgroups from behind a firewall at work so I have to do them after hours via dial-up (yuk).
Valued Contributor
Posts: 50
Registered: ‎10-01-2003
Message 7 of 23 (123 Views)

# Re:

Duhhhhh. Nevermind, I found it. sorry.
Valued Contributor
Posts: 50
Registered: ‎10-01-2003
Message 8 of 23 (123 Views)

# Re:

Ok. I found the file and downloaded it. I agree it is a excellent treatment of lofting, however, all of the sketches are planar. This is easy. I'm talking about establishing a sketch ON A CURVED surface and using it as loft ...er plane..

Any ideas?
*Costan, Tom
Message 9 of 23 (123 Views)

# Re:

All sketches in IV are going to be planar. (at
least in my experience)  I'm not sure about the new
surface capabilities of IV6; maybe something to look at there.  I
suggested the propblade because it seemed to have some unique lofting.
More food for thought than an exact example.  I could  have
been more specific.

I have allways used planar profiles on our fan
blades and  I'am constanly repeating to my self, "it's only a
fan".

As a possibility - MDTs surfacing and stitching if
you have the patience.

-Tom

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
Ok.
I found the file and downloaded it. I agree it is a excellent treatment of
lofting, however, all of the sketches are planar. This is easy. I'm talking
about establishing a sketch ON A CURVED surface and using it as loft ...er
plane..

Any ideas?

Valued Contributor
Posts: 50
Registered: ‎10-01-2003
Message 10 of 23 (123 Views)

# Re:

Thanks Tom.

Frankly, this is one of my fears (that Inventor isn't set-up - yet - to do this type of feature). I just couldn't face learning P/E. Besides, at another pump manufacturer, the P/E guys didn't tackle this issue either - they "faked" it for visual purposes, not actual dimensions.

I would try MDT.....something else to learn.
Troy Zellers

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