Weekly Challenge Group

I usually do this by assembling surfaces, but this time I used planes, two planer sketches, a 3d-Sketch, blocks, two surface cuts, a circular pattern and a delete face. Fun & Games :-)

J'adore cet objet...

Fait sur AutoCAD

https://grabcad.com/tutorials/construction-of-a-dodecahedron

Simply as an exercise in "thinking of alternative ways" to achieve the same objective, I share this idea applicable to "any starting object":

1) Make a cut in the frontal plane

2) Make the same cut, mirrored vertically, on an inclined plane

3) Make a circular array

Sometimes it is convenient to mould and other times to sculpt...

Each one of these is always interesting.

Inventor. 4 Features.

Can you please enlighten us, as to how you created the initial irregular hexagon(!) that you used for your cuts, without constructing the dodecahedron first ;-)

Nice challenge, 4 features

Hi Steen,

I made some observations about the final object:

1) Recognize the lengths of the sides of that irregular polygon. There are four long segments (in red) and two short segments (in green) whose lengths are related to each other in a regular pentagon:

2) Draw an irregular polygon with four long and two short segments, knowing that:

a) Each pair of segments are parallel to each other.

b) The long segments are tangent to a circle that passes through the center of each pentagon.

Note 1: the two short segments are automatically positioned based on the four long ones that are located according to a) and b).

Note 2: the radius of the circle inscribed in the long segments (which is that of a sphere that touches four pentagonal faces) arises automatically from lines perpendicular to the waypoints marked on said segments.

Had a dream about this over the weekend. Figured out how to do it by just extruding two simple pentagons. The key was letting the CAD system calculate the extrusion taper angle. The geometry is quite similar to what Marcelo did.

Inventor. 2 features

I really like when these ideas arise thanks to "putting in crisis and rethinking" the things that we already assumed as resolved.

I always remember a phrase by Dr. Edward De Bono (inventor of "lateral thinking"): "When new solutions are not sought because they believe that the one obtained is ideal"... from which he develops the idea that we have "a side blind" to things that we believe are already well resolved and we cannot innovate with them.

Congratulations Bob!

I'm not sure if it's the same as what Bob thought. But it is possible to extrude a pentagon with an angle, up to a specific height:

and then draw another pentagon on the top face and make an extrusion with cut, also at an angle, and voila!

Learning to design is learning to think!

That’s it! Although instead of a cut it’s easier to just use the intersection of the two extrusions.

It's true! Only (in Solidworks) you would have to do an extra operation to intersect the extruded solids. That's why I opted for the cut. Perhaps Steen knows if it is possible to do it by intersection in two operations.

These puzzles and similar exercises are possible for me because of a college class in Descriptive Geometry. Not sure if they even teach it anymore because it harkens to the days of working these things out manually on a drawing board instead of CAD. While CAD does many of these geometric constructions for you, it still pays off to know how to lay them out.

In theory, descriptive geometry hasn't stopped being taught... However, in reality, CADD-born students don't practice it or try to reason with it at all (they just go after the end result that the software automatically provides them with). If something is understood and practiced regularly, then it is learned and deepened. But if it is understood and not practiced... it is simply lost!

Hello gents,

As far as I know, there are only the two options in Solidworks: 1) Extrude to correct height and cut-extrude with 'Flip side to cut' = two features, or 2) two extrusions and a boolean combine 'common' = three features.