How to Draw a Tetrahedron in Autocad

In the continuing battle against 3D printers used exclusively for fabricating plastic octopodes and useless trinkets, here's yet another installment of a Making A Thing tutorial. If you've ever wanted to make one single object in multiple 3D design softwares, this is for you.

Previously, we've built a 'thing' in a few different 3D modeling programs, including:

• OpenSCAD
• AutoCAD Part I
• AutoCAD Part II
• Blender Part I
• Blender Part II
• SketchUp

See that 'Read more…' link below? You might want to click that.

Our Thing

Like all of these Making A Thing tutorials, we're using this switch base, torn from the pages of an 85-year-old textbook on Engineering Drawing.

Thanks to me being an idiot, we're not making anexact copy of this switch base. In the graphic to the right, there's a slight taper to the vertical flange on this switch base. I'm not one to change these tutorials in mid-stream though, and the finished product will be close enough.

Starting Up, or, Holy Crap, What's With All These 123D Products?

If you head on over to the Autodesk 123D page, you'll see a ton of related products in Autodesk's line of freeware modeling and design softwares. The Make app is basically a slicer that turns 3D objects into something akin to those die-cut plywood dinosaur models you built as a kid. Catch turns a camera into a 3D scanner. Sculpt is an iDevice app that's probably far less useful than it is cool. Design is what we're after. It's a full-featured piece of 3D design software that allows you to create objects for your 3D printer.

123D Design is available as a web app, an iDevice app, or as a free download for Mac and PC. I'm using the PC version, so if you're following along, go here and download your copy. Install it, and you'll end up with the screen below:

First things first. Since our 'thing' was designed in fractional inches, we'll need to change 123D's units to inches. Do that by clicking on the Units button in the bottom right hand corner.

If you've used AutoCAD before, you'll find the UI for 123D Design is extremely similar. On the right side of the screen, there are buttons for pan, orbit, zoom, and fit, just like in AutoCAD. Also, in the top right hand corner is the 'view cube', allowing you to rotate the window around and fix it to a top, bottom, front, back, left, or right view. Double click on the top of the cube and 123D will orient the window so we can make our thing in two dimensions first, then extrude them into the Z dimension.

Making A Thing

At the top toolbar, you'll see the Sketch tool. From there, select Circle and draw a 1-inch circle. Then, draw a 2 3/8″ circle on the same center. Just as in AutoCAD, you can simply type a number on your keypad and 123D will make the circle that size. Unlike AutoCAD – and just about every other drafting program ever – the number you type in 123D will be thediameter, not the radius. I find this a little more user friendly than typing in a radius, and if anyone has some insight into that UX decision, I'd love to hear it.

Now for another tool. From the Sketch menu, select Polyline. Draw two lines starting from the centers of the circle, both 1.25″ long, one at 0 degrees, and another at 135 degrees. From the bottom of the 0 degree line, sketch a rectangle 1 3/8″ by 5/16″. Using the mirror tool, mirror this rectangle along the 0 degree line.

The fillet and trim lines work just like they do in AutoCAD. Put a 1/8″ radius fillet on the outer corners of the rectangles we just laid down.

Now For The Slot

We already have a line going through the center of where the slot on our thing should go. Under the Sketch menu, there's an Offset tool. Select the Offset tool, click the slots center line, and offset it 3/16″. Just like in AutoCAD, we can use the Trim command to clean everything up.  Adding the other flange, you should have something that looks like the pic to the right.

Under the Modify tab on the top toolbar, select Extrude. Pull the main part of our switch base up 7/16″, and the other weird flange part up 21/16″. Once you're in 3D-land, you can use the Fillet command under the Modify tab to put our inside fillets in. Just select the inside corner between the 'washer' and 'wide flange' parts, and set a fillet radius of 0.125″ By now, your part should look something like this:

Putting A Top On It

After clicking on the 'Front' of the 'view cube', put a series of concentric circles on the top of the flange. After that, play with the view cube until you're in some sort of comfortable isometric or orthographic view and extrude those circles until you have something resembling our 'thing.

Note the Extrude tool has pseudo-Boolean operations for it in a drop-down menu to the right of where you input your dimensions. 123D is a little weird in how it decides to extrude parts into other parts; my advice is just to play around with this option until you get something approximately right.

When you're done, you'll have this, our thing, ready to be exported to an .STL file and sent to a 3D printer:

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That's it for Autodesk 123D. If you have a suggestion on what software to cover next in this tutorial series, I'm all ears.

I'd also like to thank [tarasbot] for taking it upon himself to suggest the 123D tutorial, and for doing a write-up which this tutorial was heavily based on. Also, he made this thing! With the right taper!

freemanandii1971.blogspot.com

Source: https://hackaday.com/2014/01/22/3d-printering-making-a-thing-in-autodesk-123d/

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