In the latest versions of Blender you can go to file -> User Preferences to select a whole bunch of things, including a new mouse zoom mode that’s a lot more like what you’ve come to expect from other CAD tools, such as SolidWorks.  These options are under the Interface tab of the User Preferences dialog.

Checking the Zoom to Mouse Position and Rotate Around Selection boxes will cause the zoom function (scroll the mouse wheel) to be centered on the mouse position, and rotating the view (click the middle mouse button or alt-left click) will move around whatever you have selected.  (For alt-left clicking in new versions you’ll also have to enable Emulate 3-button Mouse in the Input tab.)

Okay so you’ve got Blender and you’re trying to model something with lots of drill holes and Blender’s solid boolean operations are driving you up the wall.  Meshes hash into mounds of needle-like triangles quickly, and needle-like triangles break the boolean engine.  Nature of the beast, I’m afraid, Blender is a mesher.  And meshers aren’t anything like SolidWorks or OpenSCAD, which can handle hundreds of boolean operations without batting an eyelash.

But let’s say you’re not in love with coding object positions by hand and SolidWorks isn’t in the budget.  Now what?

Subsurface Modifier to the rescue.

» Continue reading “The Subsurface Modifier For Mechanical Designs”

A lot of entries to Thingiverse are missing things like descriptions, working previews, or separated STL files.  This is more of a checklist than a tutorial, but it seems a fitting topic for the last day of printability week.

First, the model files themselves.  Make sure you have done your manifold checks, check your scaling, and make sure you have your STLs arranged appropriately in their files.  If they are meant to be printed in a specific orientation, make sure they have that orientation.  If your model contains a really large number of STLs, consider including a zip file for ease of downloading.

Second, make sure you get a title and basic description in there.  The tab for adding titles and descriptions is over on the left after you upload, don’t forget to visit there before hitting that publish button!  And while you’re there, don’t forget the Licensing dropdown!  For those of you who are new users, Thingiverse doesn’t default to an open-source license, so make sure you make a choice that you’re comfortable with.

Third, go through the tagging fields and click some.  It’s unlikely anyone will complain if you don’t, but doing so will make your model easier to find when someone’s looking for it later!

Finally, if you’ve got extras, add them!  If you have sketches from early in the design process, or documentation for use, or the original files for your modeler of choice, these all add to the treasure trove of stuff available on Thingiverse, and make it a more inspiring place to be!

There are a LOT of 3D packages people are using to create models for Thingiverse.  From the ultra-professional (and ultra-expensive) CSG package SolidWorks to free, lightweight modelers like AOI, the diversity is huge.  And it all funnels into one format in the end: STL.  Without an STL, a lot of printer operators will dismiss an object without so much as a glance at the format it’s in, because hey, if you haven’t exported to the standard format, what else might you be forgetting?

Fortunately, many of the tools have STL as an export option, so it’s mostly more of a checklist thing than a real technical challenge.  Also, Blender can export to STL, and import from a really crazy number of formats.  Also, if you remember having a horrible time getting Sketchup files to STL, you should check out the latest version, as it’s much easier now: the most recent free Sketchup version exports to .dae, which Blender supports!

(Note Blender’s fairly massive list of supported files, although so far only in 2.49)

Tomorrow, we’ll take a quick overview of the total checklist when uploading to Thingiverse for maximum printability!

One of the common questions I get when I describe 3D printing to members of the geek community who aren’t 3DP enthusiasts (yet) is framed like this: “What’s the voxel size?”  The first time I got this question I stared back blankly and tried to think how I was going to explain this one.

Now of course, I rattle off the following without hesitation:

3D Printing with extruded thermoplastic is not like printing with an inkjet.  It’s more like using a pen plotter.  When the printer is running, a thin noodle of plastic is being squeezed into place along a set path.  So rather than “voxels” what you really have is a minimum layer and line thickness.  And that line can be placed to a precision much higher than the thickness of the line, so what you can and can’t do is kind of a weird question.

Another question I get is, “how long does it take to cool?” and again, the answer isn’t as easy as the question makes it sound.  In this case, the answer is that the bottom is cool long before the model is done usually, and when the print finishes the top is still a bit molten.  Both of these little stories are key to understanding how your model looks to an experienced printer operator.

Minimum wall thickness is a specification you’ll read about in a lot of the 3D printer ads.  Models with very thin protrusions can be really difficult for a 3D printer to create, and those protrusions will be more susceptible to all manner of glitches and hiccups.  Take this rose I designed for example:

The petals are tall, thin structures near the minimum wall thickness.  This is problematic for several reasons, but let’s look at wall thickness.  As the print head draws the outer perimeter of each petal, it’s laying down very little plastic, which won’t have long to cool before the print head moves on.  As a result, any problems with the print head lifting plastic as it moves from place to place will be magnified.  This rose doesn’t break the 45-degree rule, and it’s manifold, but it’s going to be one tough print to get right.  Keep in mind that small details near the wall thickness limit will make your model harder to print properly, even if it’s still technically possible.

Another problem with this model (I had a real field day pointing out the flaws in my design once the first 3rd party print of this showed up) has to do with the many tall petals.  Each petal is going to be molten on the top as it prints.  When considering how easy something is going to be to print, imagine your model partly build and all the plastic near the top is gooey and soft, and a hard, hot nozzle is swooping around scant microns above.  If you winced doing that for the rose model, you’re thinking about it right.  As the nozzle jumps from petal to petal, it’ll be liable to pull up plastic or bend the petals and mangle this delicate flower.

There are Skeinforge settings to fix things like this.  (In particular, COOL, and Oozebane.)  I’m very sure that there is a way to get a halfway decent rose out of a MakerBot.  But with those thin protrusions it isn’t an easy print, and it’s also a good illustration of some things to think about if you’re trying to make a model that is not only printable, but easy to print well.

The MakerBot and RepRap machines don’t have support plastics like the expensive 3D printing machines from Dimension, and while Skeinforge does have a “support gridding” option, at the moment you’re much better off altering your model so you don’t need it.  Today we’ll discuss making shapes more print-friendly with a minimum of impact to the shape of the final object.  The basic design rule is: no overhangs greater than 45 degrees.  If you always obey this, odds are you will never have a problem with dangling plastic noodles.

This, however, is a rule that can be bent, and occasionally even broken, if you think ahead and in terms of 3D printing technology.  One key: overhang is size dependent.  A 2mm circular hole will print just fine with no teardropping, but a 2 centimeter hole will start to get droopy loops:

Droop is also a function of how long the overhang goes on for.  If an edge of a layer is resting almost on thin air, but the noodle marking this perimeter only dodges briefly out over the abyss, it’ll likely hold firm, whereas a long trek can cause the whole thing to sag in the finished print.  You can even get away with short horizontal jogs out into nothingness if they’re brief, especially if they have someplace to go.  Note the test part with a square(!) horizontal cavity here:

The truth is that both holes will probably be usable, although you’ll have to file off a bunch of ugly hanging plastic on the cavity to the left.  Horizontal overhangs shorter than a centimeter will often hold up just fine!  Thingiverse has a few examples of print jobs that bend the rules but still come out okay.

And this is all well and good for mechanical designs– you’re going for function, not form.  But what about your character designs?  How are you supposed to effectively design a figurine or a fantasy structure if you’re worrying about the mechanical limits of the plastic deposition?  The answer generally is: cheat!  If your character has arms that hang by its sides, put them up on posts.  If you have a dome, support it with pillars you can snap off after printing, like this:

If you’re really pressed, break your model up into pieces that can be glued together:

It’s best to think ahead from as early as possible when preparing these tactics of course– it can be a real nightmare to pick apart a model and add support structures or cut it apart.

If you’re using a Solid Constructive Geometry product like OpenSCad or SolidWorks, manifold geometry is automatic– you’re combining solid shapes to make other solid shapes.  SCG is a powerful technique with tremendous range, but a lot of more organic shapes are quite difficult to pull off with SCG, and more sophisticated mesh modelers are open source than SCG, so if you’re designing sans budget, mesh modeling might be your best option.  Also, a lot of artists use meshers, and to an experienced mesh modeler SCG can be pretty daunting.

But in mesh modelers, manifoldness is anything but automatic.  The natural flow of a design might not result in a solid mesh.  And a mesh that looks solid could have a tiny hole in it somewhere, have self-intersections, or have many faces with incorrect normal vector orientation.  This post is about making choices early in a design that will help you keep your geometry healthy!

» Continue reading “Design for Manifoldness: Inside and Out”

The tons upon tons upon TONS of excellent-looking entries to the Thingiverse contest have me thinking it might be a good time for a blanket design guide post.  Thingiverse is all about printable, sharable objects, which means a good entry should be as well-arranged for printing, cutting, or other fab technology as possible!  In this series of posts, we’ll be giving you pointers for getting your models from “pretty but it’ll never print” to “all the cool kids are printing it”.

The focus will be on designing for 3D printing technology, the system that runs MakerBot and RepRap.  We’ll make sure that if you don’t have a 3D printer, these posts will help you know what the operators are looking for in models to print.

Cathal Garvey, the man who brought you the makerbottable dremelfuge and micro-lathe needs a mousetrap and he’s willing to pay $25 for someone to design it.

I have a problem. There lives in my house a tiny mouse, and as I am friend to all animals I wish him no harm.

The live mousetrap I tried didn’t work: crafty mouse escaped it repeatedly. I also invented a few wacky methods involving pitfalls, narrow bottles full of bloating foods and even tried to suck him out onto a vacuum cleaner head covered with cheesecloth. No avail!

I am offering a bounty for something:
$25 to the first design that catches the mouse. It must:
- Not harm the mouse
- Be printable on a Makerbot
- Work

Mouse get!

Whichever design Cathal chooses, we’re going to sweeten the deal and send them a MakerBot t-shirt if they will upload the design to Thingiverse under an open license.

Can you build a better (MakerBottable) mousetrap?

Like yesterday’s post, this one is from the BitsFromBytes Skeinforge Wiki.

Here’s an option I ignored because I didn’t know what it was for, but which could have saved me a TON of frustration if I’d known about it.  Clip is one of those little nudge-items that can make the difference between a trouble-free build and a trouble-fought build.  When the print head makes a loop on the build surface, Skeinforge can tell the head to stop short of completing the loop– this matters because if the head makes the complete loop, plastic will get extruded onto the same point twice, resulting in a blob, which can cool into something for the head to pick across in later traversals or mar the surface.

The Clip option is phrased: Clip Over Extrusion Width (ratio).  A value of 0.5 is a jump of half the extrusion width, 2 is twice that, and so on.  The default value is 0.15, but given my experiences with blobs at this setting, 0.5 or more is probably a better choice.