How to fill 3D gaps and make a new solid

[Drewpan]

Hi All,

I am making a Geodesic Sphere and I am designing the connector plates.

The plates are simple hexagons and pentagons made of equilateral and isosceles triangles.

The 2D version is easy to draw but the 3d version is a bit harder.

The two critical measurements are the angle of the holes for the struts and the distance from

the centre. I have calculated these so now I have to draw it.

I have created a primitive shape of a triangular wedge with the required angles and holes of

the correct length. I have extruded various shapes I can use the SUBTRACT command on after

I have built the 3D shape. I have rotated the primitive to the correct angle. I have used an

ARRAYCLASSIC command to create the Hexagon as a polar array. So now I have a hexagonal

shape of 6 wedges at an angle with some parts I can subtract from the final shape.

The problem is that when I rotate the wedges along the outside edge of the hexagon, instead

of them fitting nicely together they split apart. I knew this would happen, what I don't know is

how to fill the gaps with solid material so that I can then UNION the wedges together, then

SUBTRACT the parts to make the holes.

The nearest I can see to do this is to use meshes somehow but I don't know much about them.

I cannot even work out how get the mesh menu on the top ribbon. I can bring up mesh commands

by typing them into command line but I don't know what they all are or do.

Ultimately what I need is the completed hexagon and pentagon shapes, with the correct distance

from centre and correct angle holes, in a single solid shape, that I can save as an .STL file to then

generate CNC code for fabrication.

For those who might have seen my posts before - yes this my homework for my Engineering Course.

The actual subject is "Manage Self in the Engineering Environment". So in case you are wondering

it is basically "if I was a real engineer and ran into this problem - what would I do?" The answer is

ASK SOMEONE! so here I am asking.

I have attached two files below. One is the 2D version of what I need and the other is where I am at

with this problem in 3D. The two critical values are the 24mm from the centre line to the end of the

15.88mm hole, and the 11.992 and 10.135 degree angles. The reason for this accuracy is that in theory,

the same connector plates could be used for a fabricated structure anywhere between 1m and 50m

in diameter - it is fully scaleable, the Strut sizes are an exact ratio of lengths to get the different sizes.

Also in case you are wondering, I have adjusted the precision of some numbers because they are not

critical, so when something says 5mm it may actually be 5.075 because it doesn't matter.

Thanks in advance for your help all.

Cheers

Andrew

[parkr4st]

Study the attached to see if it a result you want.

XLINE added the blue lines for guidelines as to where the solid is.  Snapped to points and used M2P to locate xlines centered in gaps.

Top and bottom closed 3dpolylines and lofted

Subtracted the center post.

You can subtract a solid for the other hole and array the result, union for one solid if that is what is needed.

[dbroad · Accepted solution]

It looks like you are a student, so I will limit my answer to items that won't do the work for you.

• The orthographic views have problems. Depending on how much you rely on them, any solution you create may be in error. For example, The hexagonal plan view is a simplified diagram of the situation, where the cylindrical holes are modeled as slices along their midline.  The outside edges have many overlapping lines.  Section AA has errors in projection up to .4mm as should be evident on close inspection.  Lines that should be vertical aren't.  Lines that should meet don't.  One bottom side is higher than the other.  This means that before modeling in 3D you need to get the original views corrected. 
• Creating wedges from the plan view and rotating them won't get what you need.  It has gotten to the point where you are.  In addition, due to mis-alignments, any attempt to extend the geometry of each wedge and create interference solids that could be used to fill in the gaps reveals errors in that alignment. Sometimes fixing a poorly thought out 3d model is much more difficult than doing it right.
• I suggest, creating the plan from the dimensions using basic geometry and object snaps.  using a correctly drawn section AA, create the alignments necessary for lofting the profiles to create the hexagonal plate.  Draw the cylinders to be subtracted, align them to one of the top surface and rotate them.  UCS manipulation is required.  Polar array the holes, explode and subtract.  Careful manipulation of the holes for correct position and length is critical before using array.  The end result for the hexagonal figure should look like this, which includes some of the 2d geometry necessary to create the shapes.
• 

[Drewpan]

Hi All,

It was a bit of a Saga, but after a software upgrade to AutoCAD Mechanical 2022, I started from

scratch and completely re-drew both components. Even that was a problem as I then had to

export them to 3D printable (.stl files) and CNC readable (.stp files). For those interested, the final

products are below.

Thanks again Community for your help.

Drewpan