Converting Ortho with 45 degree plane to isometric. Help me please

[Anonymous]

I have an assignment to design a jig or fixture to hold a flange and drill a 45 degree hole in a specific part of it. I designed my object and drew it on Autocad in orthographic. But I am having some problems with converting it to isometric because of the non iso plane.

[Anonymous]

https://drive.google.com/file/d/0B3PbDRh7deywUkd5eG1QYmo5TzA/view?usp=drivesdk

[Anonymous]

If anyone could see if they could do something in the model space I would be grateful

[akaterr55]

kyle,

if you are wanting to stay in the 2D realm, try these nifty little programs:

-Mark

[Anonymous]

Going to try it inna sec

[Anonymous]

Im nit understanding how to use those files

[Anonymous]

*not

[Kent1Cooper]

I think the discussion here may be relevant.  I concluded in it somewhere that the projection of an Ellipse on the "virtual" face of a cube in isometric is not an Ellipse.  I'm not sure without working through some similar steps whether the projection of a Circle in isometric on a plane that's not parallel to a virtual cube surface can be represented accurately by an Ellipse, but maybe it can.  I'll ponder it, but in the meantime, look at that other thread, and see whether it sheds any light.

[SEANT61]

All projection methods, including perspective, convert ellipse to (though modified) ellipse. This can be tested with the Flatshot command - for isometric and other parallel projections. It should work with perspective as well but Flatshot just uses a segmented polyline.

[Anonymous]

Thanks for the support guys but I'm pretty new to Autocad, so I not 100% sure I know how to execute most of those commands. Did you guys look at my drawing?

[SEANT61]

I'm a bit confused by the dimensions.  One of them leads me to believe that the circular flange holder is diameter 100, and another view is showing 113.0721.

[SEANT61]

And another view has it at 112.3528.

[Anonymous]

Oh my, I was unsure how to get the circle on side and plan view so I projected the endpoints and center lines and used the ellipse function to line up with the lines. There is a clamp on my drawing I forgot to mention that above, so you would pull the handle back to release the flange and then the spring would send the clamp back to its initial position. I can't believe there is something up with the orthographic drawing

[leeminardi · Accepted solution]

First, it is important to note the difference between an isometric drawing and an isometric projection.  An isometric drawing is created by measuring true distances in a principal isometric direction (+ or - 30°, or vertical).  To create an isometric drawing of a 120” cube you would measure off a 120" distance at a 30° slope, then vertical 120” etc.  With an isometric projection, you would rotate a cube with dimensions of 120” so that it is viewed from an isometric orientation (i.e., looking down any of the diagonals of the cube).  An isometric projection will be about 82% the size of an isometric drawing.

Orienting a 2D drawing to an isometric orientation in 3D space can be done via two rotations about principal axes or one rotation about a skewed axis.  For example, to place a square constructed on the XY plane at an isometric projection orientation do the following in AutoCAD:

Give the rotate3d command (not 3drotate)  and rotate the square about the Y axis by 45° then use rotate3d again to rotate the object by 35.2644° about the X axis. Looking from the top view you should see an isometric projection of a square.

To rotate a circle representing the outer edge of the cylinder in your drawing try the following.

1. Create a circle of radius 60 on the XY plane.
2. Rotate3d about the X axis by -45° (this will tilt the circle back to be on a plane parallel to the plane of the cylinder in your drawing).
3. Rotate3d about Y axis by -45°
4. Rotate3d about x axis by -35.2644°
5. This will place the circle in the correct orientation but because it is an isometric projection rather than a drawing you are looking at you need to scale it up by 1/0.82 = 1.22.  Scale the circle by  1.22. 
6. Use the flatten command (from the top view) to project the circle to the XY plane yielding the desired ellipse!  It’s the yellow ellipse in the attached drawing.

Note, the 35.2644° angle is the angle of a cube's diagonal with the base = atan(1/sqrt(2))

~Lee 

[SEANT61]

Nice tutorial Lee. It looks like the OP is off and running. The original drawing still has me a bit confused, but at the end of the day, it's the technique that matters.

[Anonymous]

Thanks Lee. I will try to do that. Are the orthographic views alright though?

[Anonymous]

Would be very grateful if someone could take a crack at completing the iso

[leeminardi]

Kent,

"... I concluded in it somewhere that the projection of an Ellipse on the "virtual" face of a cube in isometric is not an Ellipse. .."

There are several papers posted on the web that the projection of an ellipse onto a plane does yield an ellipse. Here is one source.

I can't say I understand much of the discussion so I tried it out graphically in AutoCAD.

The geometry in white in the back row shows a cylindrical cylinder that is sliced with a plane.  After a couple of explodes, you can isolate the intersection and AutoCAD shows it to be an ellipse. The process is repeated but with an ellipse that is extruded and then sliced (green geometry).  Again, the result is an ellipse.  Not necessarily a proof bu it looks like you can say the projection of an ellipse onto a plane is in fact an ellipse.

The isocircle option for an ellipse (which only appears if you have Isometric snap for grids set) allows you to create an ellipse using the conjugate axes but this is only for regular isometric parallelograms.  It would be nice if it worked for any set of conjugate axes. 

~Lee

[Anonymous]

Yeah I wish the same

[leeminardi · Accepted solution]

There are several discrepancies with your orthographic views.  I have created a solid model the best I could considering the missing details.

Here is your original drawing.

The drawing below was taken from the solid model I created.  It is not clear from your orthographic views how to interpret the details of the unit that overhangs at the top. I assume this is made from more than one piece as I don't think the could be fabricated except via 3D printing.

I hope this helps.

~Lee