Having problem making unions and subracting solids

[JMJ]

I have some elliptical solids that were created using the 'loft' command. there are several that form a 'draft tube'. Basically, it is an upside down funnel that bends.

 

Anyways, I cannot get the sections of the draft tube to union. Also, Autocad will not subtract most of the draft tube solids from the building solid.

 

Any assistance would be greatly appreciated.

 

Thanks.

 

JJDRAFT-TUBE-test.dwg

[nestly]

Those are some very strange solids. There are 11 solids that make up the funnel/duct, but when I select them all, I get only 19 grips, and I can't even snap to anything other than those grips, and really strange behavior when moving a face. What was the original geometry used to create the solids? Do you have a copy of the drawing before you lofted them?

 

http://screencast.com/t/KQGJpsuU

[Jack_O'neill]

I made the different segments different colors so I could see what was going on. Part of the problem is that in that third band from the top, you got 2 solids occupying the same space at the same time. In real life that causes a nuclear explosion, according to Mr. Spock!

 

[SEANT]

It may also make sense to create these as ruled lofts. Solids based on ruled surfaces would probably behave better in AutoCAD, and provide more useful geometry to assist subsequent fabrication (if destined for tinsmith).

RuledLofts.dwg

[JMJ]

How do you do ruled lofts?

 

JJ

[JD Mather]

How do you do ruled lofts?

 

JJ

Personally I wouldn't fool with ruled lofts, but perhaps you need to fill us in on your design intent - how will this model be used? In-house, externally fabrication. More information is needed on DFM.

[ReMark]

LOFTNORMALS system variable. The default is for Smooth Fit which would be a setting of "1". Make the setting "0" instead for Ruled.

[JMJ]

The structural engineer wants a product that can be sent to a Metal fabrication shop for a steel sleeve to be inserted in the draft tube. Also, he want the capability to have any made and measure with a degree of accuracy.

 

JJ

[ReMark]

The LOFTNORMALS system variable is explained in your Help file.

[SEANT]

If we are talking standard sheet metal fabrication then Loft with the Ruled option in the Loft Settings dialog (or, as Remark mentioned, via LOFTNORMALS system variable) is the best geometry for the job.

 

 

 

While there is no guarantee that AutoCAD will always produce a Developable Surface with Loft-Ruled, you will stand the best chance.

[JMJ]

Thanks all!