Octopodes and useless plastic baubles begone. It’s time yet again for another installment of learning how to make a thing with 3D design tools. This week, we’re making something with AutoCAD. It’s an amazing piece of software that costs $4000 per seat. Hilariously expensive for any home tinkerer, but if you go to a university with an engineering program, there’s a computer lab with machines running AutoCAD somewhere on campus.
Last week we took a look at making something with OpenSCAD. AutoCAD is much, much different. Where OpenSCAD is sorta, kinda like programming, AutoCAD is just a digital version of t-squares, triangles, straight edges, and people getting uppity when you don’t call their drawing device a ‘lead holder’.
I’ve broken this tutorial down into two parts: right now you’re reading the tutorial on drawing 2D objects in AutoCAD. This weekend I’ll publish the transformation of 2D objects into a 3D printable part. Read on for how to create a 2D object in AutoCAD.
Because demonstrating different way to create a 3D printable object without using the same object each time, we’re going with this drawing again. That drawing is nearly 100 years old, but it’s still a great introduction to drawing and turning a picture into a 3D printable object.
Let’s just dig right in.
We’re going to start by drawing the top perspective of our part.
Start by drawing two circles. From the ‘Home’ tab, click on the Circle drop down menu and select ‘Center, Diameter’. This will allow you to draw a circle by picking a point for the center and entering a number for the diameter. From our nearly 100-year-old drawing of our thing, we simply need to draw a 1 inch diameter circle and a 2 3/8 inch diameter circle with the same center point.
I’ll preface this next part by saying this isn’t the right way to do AutoCAD, or any drafting app. The professional way to do this next step is to create another type of line – preferably a different color, and one that extends to infinity. This is called a construction line, and it’s the proper way to do this sort of thing. Nevertheless, I’m an idiot and this is the simple way to do things.
The next step is to create those little bits sticking off the end of the circles on our thing. We’ll start with the one with the weird radii on them.
Draw a line 1 ¼ inch long starting from the center of the circles. Then, draw a line on either side of the bottom of the line 1 3/8 inch long. You’ll end up with something that looks like the pic to the right. Now, just delete that first line coming from the center of the circles, add that 5/16 inch long part on the side, and then draw another line going intersecting with the big circle.
Those corners look a little rough compared to the hundred year old drawing, so let’s round them off. From the Home tab, select ‘Fillet’. AutoCAD then prompts us to select an object and shows the words [Undo Polyline Radius Trim Multiple] in the command bar. Type in Radius, specify 0.125, and click on one line of the hard corner, then the next line. After you click the second time, that 90 degree corner will be replaced with a nice rounded edge. Do the same with the two other radii connecting the flange to the big circle and you’ll start to see the 100-year-old part take shape.
In terms of projecting this part into a 2D drawing, there’s an extra line right now we need to get rid of. It’s between the last two fillets we just drew. You can get rid of that line by clicking on the Trim button in the Home tab. It will ask you to select objects, so click on the last two fillets we just created. Once they’ve both turned into dotted lines, hit enter, click the line you’d like to get rid of, and it’ll disappear.
Finishing off the ‘top’ part of our part, as projected onto a 2D drawing is left as an exercise to the reader.
Now, there’s only one bit missing from our part, and it’s also a great way to demonstrate another tool in AutoCAD. Start by drawing a line – it doesn’t matter how long – from the center of our circles. Using the Rotate command, select this line, specify the center of the circles as a base point, hit enter, and specify a rotation angle of 45 degrees. Now all we have to do is cut a 3/8 inch slot and trim everything up. Type ‘Offset’ into AutoCAD (There’s a button on the Home tab. It looks like an upside-down letter T written in bubble letters), specify the offset distance – in this case a half of 3/8ths, or 0.1875 in decimal, hit enter, and click on the line we just rotated. Click on one side of our rotated line, then on the other side. Delete the center line, trim everything up, and there’s your part. Who would have thought you could actually convey information with an animated .gif?
There’s our top projection
Since we have a drawing of our ‘thing’ when seen from above, all we have to do now is bring everything into a third dimension. This post is already pushing 1000 words, though, and the previous OpenSCAD tutorial got a few comments appreciating how short it was.
This weekend I’ll finish off turning this drawing into a 3D printable object. It’s not especially hard, but explaining it will probably take a 1000 words yet again.