Creating tube miter correctly

[jamami]

I have been struggling with this issue for weeks using Acad2012, Win 7.

To draw the cope end I subtract one tube from the other, this creates a taper from wall thickness t at the intersection of the inner tube face to zero at the intersection of the outer wall face. This loss of wall thickness is not ideal. To get rid of this less than full thickness material I create a slicing plane through intersection of non-cut tube 1 and the inner wall of the tube to be cut, I establish this point by drawing a 2D cross section.

I realise this a bit of a hack and it never works out spot on as the slicing plan never seems to match exactly the intersection point of the 3D tube inner wall.

I have tried to get a work around. ie:

- drawing a tube inner radius only subtracting from that then shelling-this only re creates the taper.

-offsetting the intersection edge of the inner wall and trying to project onto outer at 90deg-this does not offset correctly due to the complex geometry.


Capture.jpg

I was hoping the COPE file from SEANT post in the Customisation forum may answer my problems but I cannot get to work and would like to find out if this can be acheived using in built functions or methods?

If anyone can provide me some help with the following I would be really grateful:



1. How to create a mitre maintaining full wall thickness. 90 degree intersections.

2. How to create a mitre maintaining full wall thickness. Non 90 degree intersections.

3. How to create a mitre maintaining full wall thickness. Tubes angled in 2 planes ie: for triangular space truss.

4. How to create a mitre maintaining full wall thickness. Tubes angled in 2 planes centres lines not coincident ie internal members offset to enable 2/3 to meet at same node.
5. How to deal with the above when using non round tubes.

[ReMark]

I can appreciate your attention to detail but I have to ask why is this really necessary? Who is going to see this level of detail when the drawing is printed? Don't you have to trust the people who are doing the fabrication to know what they are doing when coping a tube shape?

[jamami]

I need to get manufacturing drawings produced to issue to suppliers. Im trying to achieve single stage manufacture process ie laser cut. Trust would be good but unfortunately when dealing with some overseas suppliers I have found that things need to be buttoned up tight.

[ReMark]

I think this would be better handled by Inventor or another piece of software (tube design?) given the level of precision you are looking to achieve.

Just out of curiosity, what are you constructing?

[SEANT]

. . . .
I was hoping the COPE file from SEANT post in the Customisation forum may answer my problems . . . .

That “Cope” routine is to develop a template allowing the cope to be cut by hand (i.e., jigsaw or band saw). Probably not what you intend to do.

Laser cutting removes the need for a template, but still presents its own set of problems. If we just consider a perpendicular layout, would the attached describe what you need as an end result?

[nestly]

For mitered joints you'd have to thicken the inside surface toward the outside, as described above by SEANT, but then also thicken the outside surface inward. The "interference" would be the end product.

[SEANT]

For mitered joints you'd have to thicken the inside surface toward the outside, as described above by SEANT, but then also thicken the outside surface inward. The "interference" would be the end product.

Well stated.



The basic square butted layout in my example is probably the only orientation that does not specifically require the secondary intersect operation.

[jamami]

In this case space frame trusses. Aluminium 6082T6, modular lengths from 2m to 8m.

[jamami]

I think this would be better handled by Inventor or another piece of software (tube design?) given the level of precision you are looking to achieve.

Just out of curiosity, what are you constructing?

ReMark
I think you are right, I have seen exactly what I am trying to achieve produced on Inventor. Problem is I do not own Inventor or know how to use it.

[jamami]

SEANT many thanks for this example, this looks spot on for 90 deg mitre. Please excuse my lack of experience with surfaces, I have always used solids. In my mind surfaces were only needed for terrain modelling or highly complex irregular forms, or just to visualise things. Now I am enlightended.
I have tried to create a 60 deg mitre along these lines, see attached. The leading(obtuse) edge appears OK but the trailing(acute) end does not appear correct. Is this because I have only thickened in one direction?

Cope_60.dwg