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How to cut a complex tunnel out of an extruded surface?

Question asked by Michael Grabis on Jan 8, 2016
Latest reply on Jan 8, 2016 by Michael Grabis

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Hello I have not been able to figure this one out after hours of pondering the issue.

I am creating an undertray which includes a tunnel from front to end and the diffuser at the end of the undertray. In order to have the file run through a cfd program, I need to be able to hollow out the tunnel. The attach image shows where the cut will start (first solid blue square) and then follow the purple guide line and end at the dotted blue line. The thickness of the material will be 3/16 of an inch. How do I make this cut? Lofted cut seems not to be working. I can attach the file if need be.

Thanks in advance for the help, this is very frustrating.

Jody Byram Jan 8, 2016 8:18 PM

Correct Answer

It shelled as easy as pie for me (using SW2004). I selected the bottom surface, and the two ends as surfaces to remove:

The tunnels were extruded up to the red surface below, before the shell command.

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Casey Bergman Jan 8, 2016 3:50 PM

Just curious, can you shell the body you are trying to hollow out?

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Michael Grabis @ Casey Bergman on Jan 8, 2016 4:06 PM

The only issue is that I need the ends to be open on both sides, think of it as tunnels for air passing through. Another issue I am facing is that the inlet eventually gets flat with the bottom of the under tray, then around a foot later the diffuser tunnel starts up again so I think I will have to cut the 2 sections separately.

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Casey Bergman @ Michael Grabis on Jan 8, 2016 4:09 PM

No problem, just wanted to see if you had thought about it that way. I agree with Chris on how to do it then.

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Chris Michalski Jan 8, 2016 4:00 PM

Have you tried using 4 guide curves, one along each corner? Or creating a solid body of the material to be removed and then subtracting that instead of cutting. This could define if the problem is in the lofting portion or the cutting portion of the loft-cut feature.

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Michael Grabis @ Chris Michalski on Jan 8, 2016 4:06 PM

Oh this is a great idea. I will try that now and will see if it works for me. Didn't even think about doing it this way.

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Jesse Robbers Jan 8, 2016 5:24 PM

The tunnel look simple, the outer side may be planar while the inner side is a radius curve or only a few segments, the top surface of the tunnel is curved, but it's a 2D profile. What about sketching a closed profile which extrude cuts in this direction from left to right? You may be able to off-set from the exterior planar surface by your targeted wall thickness. You may need to extrude a vertical surface off-set from the inner curved surface which is your wall thickness, and use this extruded surface as up to surface condition.

The Shell suggestion sounds the best, maybe after splitting the part into bodies and combining after the shell is performed.

Keep it simple if possible with 2D type items, don't use lofts or boundary surfaces or things like that in conditions like this if not necessary and your previous geometry isn't made from lofts and things of that nature.

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Jody Byram Jan 8, 2016 8:18 PM

It shelled as easy as pie for me (using SW2004). I selected the bottom surface, and the two ends as surfaces to remove:

The tunnels were extruded up to the red surface below, before the shell command.

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Jody Byram @ Jody Byram on Jan 8, 2016 8:23 PM

Also worked if each end was selected, but not the bottom.

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Michael Grabis Jan 9, 2016 7:57 AM

Thanks a lot for this. I don't know why the shell method was not working for me earlier but I did exactly this and I got a clean cut. This is the perfect and efficient way to do this!

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9 Replies

Casey Bergman Jan 8, 2016 3:50 PM
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Correct Answer
Just curious, can you shell the body you are trying to hollow out?
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- Michael Grabis @ Casey Bergman on Jan 8, 2016 4:06 PM
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  Correct Answer
  The only issue is that I need the ends to be open on both sides, think of it as tunnels for air passing through. Another issue I am facing is that the inlet eventually gets flat with the bottom of the under tray, then around a foot later the diffuser tunnel starts up again so I think I will have to cut the 2 sections separately.
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  - Casey Bergman @ Michael Grabis on Jan 8, 2016 4:09 PM
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    No problem, just wanted to see if you had thought about it that way. I agree with Chris on how to do it then.
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Chris Michalski Jan 8, 2016 4:00 PM
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Correct Answer
Have you tried using 4 guide curves, one along each corner? Or creating a solid body of the material to be removed and then subtracting that instead of cutting. This could define if the problem is in the lofting portion or the cutting portion of the loft-cut feature.
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- Michael Grabis @ Chris Michalski on Jan 8, 2016 4:06 PM
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  Oh this is a great idea. I will try that now and will see if it works for me. Didn't even think about doing it this way.
  Like • Show 0 Likes0
  Actions
Jesse Robbers Jan 8, 2016 5:24 PM
Mark Correct
Correct Answer
The tunnel look simple, the outer side may be planar while the inner side is a radius curve or only a few segments, the top surface of the tunnel is curved, but it's a 2D profile. What about sketching a closed profile which extrude cuts in this direction from left to right? You may be able to off-set from the exterior planar surface by your targeted wall thickness. You may need to extrude a vertical surface off-set from the inner curved surface which is your wall thickness, and use this extruded surface as up to surface condition.

The Shell suggestion sounds the best, maybe after splitting the part into bodies and combining after the shell is performed.

Keep it simple if possible with 2D type items, don't use lofts or boundary surfaces or things like that in conditions like this if not necessary and your previous geometry isn't made from lofts and things of that nature.
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Jody Byram Jan 8, 2016 8:18 PM
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Correct Answer
It shelled as easy as pie for me (using SW2004). I selected the bottom surface, and the two ends as surfaces to remove:
The tunnels were extruded up to the red surface below, before the shell command.
Like • Show 0 Likes0
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- Jody Byram @ Jody Byram on Jan 8, 2016 8:23 PM
  Mark Correct
  Correct Answer
  Also worked if each end was selected, but not the bottom.
  Like • Show 0 Likes0
  Actions
Michael Grabis Jan 9, 2016 7:57 AM
Mark Correct
Correct Answer
Thanks a lot for this. I don't know why the shell method was not working for me earlier but I did exactly this and I got a clean cut. This is the perfect and efficient way to do this!
Like • Show 0 Likes0
Actions

How to cut a complex tunnel out of an extruded surface?

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