So a while back I talked about using OpenSCAD to tack on support struts to tough builds, giving them a better shot at printing properly.  My printer’s still not fully calibrated yet, but as you can see, despite huge overhangs, this steggy printed out just fine with some support struts.

But the process of dragging the pegs around in OpenSCAD was a bit tedious, so I worked up a quicker way to place them: Blender!  By creating a separate object with all the posts placed and aligned, OpenSCAD only needs to do a single union operation to merge the posts to the model, and an intersection to flatten the feet to the right height.  Here’s an example of what I mean– I colored the posts blue so they’d be visible:

The model could probably use a fifth post in the center to hold everything up, but the important thing with posts seems to be that they are wide enough to print solidly, and close together enough that the plastic “bridges” from post to post easily.  On my machine and in my climate this is a little under a centimeter– you might try building a bridging test object to see what works best for you!

I had some questions in comments on my peg placement, so here’s a snapshot of the model with the pegs in.  When it printed, they snapped off easily and the head turned out pretty well considering how small I printed it!

I didn’t try supports for the belly and tail, and the underside of both came out a little scraggly as a result, but at this scale (less than 8cm long) those details ended up being less important than keeping the head from falling over during printing.

On more complex models I’ve found you can get away with surprisingly little support, but the cost of going too far with this can be anything from a ponytail that twists off before it reaches the connection point up top to total build failure.  Like with all home 3D printing, you get a “sense” for what will work and what won’t over time…

Enter the support peg.

The idea is to basically extend a vertical support peg through your model, allowing the fairly common practice of bending or breaking the “45 degree rule” to stretch a little farther than it usually does.  For my example I’m going to use this adorable but tough-to-print stegosaurus model:

The body could use a little support, but the big trouble will be the head and tail, which on a 3D printer without support material will have undersides coated with strands, and may cause some “pull-up hazard”, meaning that the strands might get caught on the print head and yank the model off the build area.  So let’s get this file into OpenSCAD, which I’ve found is a great tool for putting posts into models because of its solid geometry tools.

I recommend you put the file in your OpenSCAD installation directory for now, although some people like to have a separate directory for the files.  Either way, make sure you have the whole path to the file for the next step, starting your OpenSCAD file.  (If you’re still new to OpenSCAD you might want to check out my getting started tutorial or even try the big list of them.)

import_stl("/home/allan/Downloads/dinosaur.STL");

(I found that for some reason I had to open this file in Blender and re-save the STL to get OpenSCAD to like it.  This might be due to some non-uniformity with how STL is implemented and is an example of why it’s good to know at least the basics of a few tools. I also rotated and translated it so it was sitting upright on the origin.)

Now you’ve got it in OpenSCAD you should get a picture like this:

With that done I started in with the pegs.  Each peg is a “cube” object stretched into a thin post and unioned onto the dinosaur:

union()
{
import_stl("/home/allan/Downloads/dinosaur.STL");
translate([-45,0,-37])cube([3,3,100],center=true);
translate([-35,0,-35])cube([3,3,100],center=true);
translate([-55,0,-35])cube([3,3,100],center=true);
translate([-25,0,-35])cube([3,3,100],center=true);
}

Now the dinosaur has long posts coming down out of its neck.  At 3x3mm, they should snap off fairly easily, but they extend a long way down past the feet.  This is intentional, because I’d rather use my next trick to get them exactly the same height as the feet, and simultaneously make the feet a little flatter.  Intersection!

The bit of code I’m adding uses the intersection operator to cut off the bottoms of all the pegs– and just a little bit off the dinosaur’s feet!  I basically did this by typing in numbers, hitting F5, and then doing it again until I had the height *just right*:


intersection(){
union(){
import_stl("/home/allan/Downloads/dinosaur.STL");
translate([-45,0,-37])cube([3,3,100],center=true);
translate([-35,0,-35])cube([3,3,100],center=true);
translate([-55,0,-35])cube([3,3,100],center=true); translate([-25,0,-35])cube([3,3,100],center=true);
}
translate([0,0,23])cube([290,60,60],center=true);
}
The new version of the STL should print much more smoothly!

(There are, by the way, a lot of handy video tutorials on BlenderCookie.)

Blender 2.5 was a ground-up recode, but not only are all the features (except for a few really obscure ones that the forum dwellers are still arguing about) are back, and the interface is actually a lot better.  The mirror modifier is available from the dropdown that pops up when you switch to the modifier tab in the “buttons panel” as the above control is called:

In addition to the mirror modifier, there are a whole LOT of other options, which I highly recommend playing with.  Below I’ve highlighted the ones you’re most likely to find useful:

(The others might really be handy in a few niche cases, but these ones are probably the must-try ones.)

Combining them can get you a LOT of detail from almost no actual geometry:

OnShoulders is officially my new favorite makervlog. Devastating production values, amazing tutorials on stuff I didn’t even know I could do. In this episode, OpenSCAD and an equation editor tool called MathCast combine to form a sort of kinematics workbench for computing leg linkage angles from Cartesian coordinates. Amazing!

A really neat round-off tutorial!

Making shapes with smooth edges and corners isn’t as easy in OpenSCAD as it is in SolidWorks, but it’s still definitely possible, and this walk-through shows you step-by-step how to make a carving “blank” and digitally “scrape down” the edges in your project!

Looking forward to more of this series!

So then, here’s Blender’s new interface as of the 2.5 recode:

The middle panel is your 3D view, and it’s most of what matters here. Here are the basic navigation controls for simply looking at what is in the 3D view. (We’ll get to actually making things in a second.)

On your number pad:
7, 1, and 3 are top, left and front views, respectively.
5 toggles perspective in the view.  (Things further away will look smaller in perspective mode, not always what you want for mechanical design.)

A mouse with a scroll wheel is highly recommended for Blender, as it gives you the following features:  Middle-click and drag to rotate the view.  There’s an invisible point in the center of the screen around which your view of the scene rotates. This point is not marked by anything (That little red-and-white ring is actually the 3D Cursor, about which we’ll learn more later), so it’s a good idea to occasionally twist the view a bit with middle-drag, which you’ll usually do a fair bit when modeling.  You can also use the scroll wheel to zoom the view, so if you roll the wheel back, you’ll zoom out, rolling forward, in.

One odd property of Blender: right click to select.  This is a bit odd, and you can change it, but it’ll make other tutorials wrong so I tend to recommend getting used to it.  Highlighting defaults to an orange outline, so it should be obvious when you select anything in the scene.  Another tremendously useful feature is the period key on your number pad to center the view.  When you are rotating the view with middle-drag, you will rotate around the last place you selected with the period key.

The 3D view has six modes. If you click on the mode icon on the lower left of the view, you’ll see this list:

However, if you’re only going to be doing design for 3D printing, you won’t need all of them, and at first you’ll only need the Object Mode and Edit Mode, and the Blender developers have made the tab key the shortcut for jumping between them.

Once in Edit Mode, you’ll have the ability to select the individual vertices of the mesh.  All the above tips still work, which is why the six modes above are all part of the same 3D View framework: this way, your basic navigation tools will always be the same.  (This is a recurring theme in Blender: if something works as a way to do something somewhere, chances are good that it will do the same thing or something similar in other views.)

You can now select and shift-select to select multiple vertices.  There are shortcuts for moving, scaling, and rotating vertices or groups of vertices:

g key to “grab” or drag vertices
s key to scale vertices
r key to rotate

While you are doing any of the above, you can either left click to accept or hit the escape key to abort your changes.  You also may hit additional keys to refine these motions: x, y, and z to restrict to an axis, or hold ctrl to move in discrete steps.

Blender is a complex tool to do a complex job, and the subset of Blender associated with solid modeling is still pretty large.  Hopefully though, this guide of the 3D view is enough to get a sense of the key weirdnesses to Blender’s interface design so that you can get on with modeling.

Other Blender guides:
BlenderCookie Getting Started Guides
Blender: Noob to Pro Wikibook

These days of course, no animator worth two shakes of a Griffin’s tail would touch them, since they generate fairly awful topology when meshed, but for 3D printing, they might make sense at least as a fun and comparatively intuitive tool for sketching out shapes.  Naturally, like so many things you thought had vanished from the Earth, Blender has them.  Just shift-A add Meta Ball:

(Yes there are a fair number of suboptions here too.)

Once you’ve got one, to figure out what it is you’re doing with this not-terribly-well-rendered sphere, hit shift-d to duplicate and move this new one around.

If this is your first experience with MetaBalls, about now you’re probably thinking, CUTE.  Metaballs attract and “blob” into each other, and were once a primary method for simulating the look of fluids.  (In those days actually simulating the physics of fluids would have been prohibitive, to put it gently.)  Scaling them works, so you can drag them around, add new ones, and generally sculpt-by-adding these blobs together.  They eventually get kind of messy in the selection department pretty quickly, but in terms of ease of adding geometry, they’re pretty sound.

One thing that’s nice about these though is that they’re pretty much always going to be manifold, since they’re a form of Constructive Solid Geometry.  Once you have a shape you’d like to print, just go to the Object menu and select Convert -> Mesh from Curve/Meta/Surf/Text

(By the way, Blender has a “Generate Text” set of commands which you can then convert into mesh data.)  Blender converts the metaballs into a fairly ugly (at least, to an animator’s eyes) but printable mesh from here:

This can be exported to STL and from there to the printers.

If you’re like me, then using an Arduino is a wonderful, downright life-affirming experience because it works right away and has a ton of capabilities.  But you also find yourself looking wistfully at those standalone AVR chips, which cost between 1/6 and 1/11 the price of an Arduino and take up an equally shrunken amount of space.  Now, you might need to solder to properly make use of that space reduction, but if you’re using a breadboard, you can still save a bit of cash going with a standalone AVR, plus the breadboard has plenty of remaining space for prototyping.

Plus, you’re programming the very chip itself rather than an API, which saves memory space, enhances performance, and makes you feel way cooler.  I tried using an Arduino to program AVRs a couple years back and it was rough.  I had to hack the Arduino, hack the sketch, hack AVRDude’s config files, and Windows never could do it, I had to go with linux…  Rough.

But that’s all changed recently!  Following SparkFun’s excellent tutorial on the subject, I got up and running in an hour or so, and using Code::Blocks‘ built-in options for using avr-gcc, (new project -> AVR, I kid you not) I got the entire process of compiling and uploading to the board down to one click!

You don’t get all the features of the Arduino environment by a long shot, and without a crystal (coding the fuse bits to use them can be a bit fraught and many a fine AVR has been bricked this way) you won’t get a terribly precise internal sense of timing, but I have definitely been impressed with how much I can get done with a sub-$2 ATTiny13.

One thing we don’t see much of these days on Thingiverse is schematics.  They’re certainly out there, but not quite the cornucopia of awesome that is mainstream 3D printing Thingiverse…

Blender 2.5 finally has .stl support!

First, you’ll need a recent build (lately these have been more or less bug-free for me at least) from GraphicAll.org.

To enable exporting (and all the other goodies!) go to file -> user preferences and click the add-ons tab.  One of them is stl io, and once that’s enabled, you’re ready to export STL from the increasingly stable and awesome Blender 2.5!

(I recommend you start Blender then immediately change these settings, then select “Save As Default” at the bottom of the settings, which will make sure you always have these tools handy.  This saves everything about your workspace, so if you have changes you usually make such as splitting the screen, they’ll be saved too!)

One quirk I’ve noticed is that if you scale things in object mode, those transformations don’t “count” towards the stl file.  If you notice you’re not getting the size you wanted, you can hit Object -> Apply -> Scale from the 3D View menu to fix that.