A Beaker is useful for determining volume

A few days ago I started designing a new case for my new Polargraph drawing robot brain.   ((Joe Penniston via Compfight))  My goal was to design a simple to design, simple to assemble, and sturdy box-like case.  ((One of the reasons I am interested in a box-like case is to make sure it is easy to mount on a wall or inside a larger project box.))  However, I was stumped when it came to figuring out whether my new design conserved plastic better than the other Polargraph case design from Sandy Noble on Thingiverse.  After experimenting a little, these are the two easiest ways I found to figure out the volume within an STL file.  ((While particularly simple, I suppose if you had a really large beaker and a certain volume of water, you could print your STL file, submerge it, and compare the results.  However, this seems impractical for a lot of reasons.))

1. AdMesh
   1. Tony Buser was kind enough to suggest an application I had never heard of before – AdMesh.  AdMesh is a free command-line tool created by AMartin¹ which can provide all kinds of information about an STL file.  After fiddling around with the program a little bit, I found this command gave me the best results:
      • admesh –normal-directions –tolerance=0.01 –exact %1 >> stl-stats.txt
   2. While AdMesh worked pretty well overall, it had problems with some STL files and was unable to provide statistics.
2. NetFabb
   1. Alternatively, NetFabb also provides some ways to find out the volume inside an STL file.
      

      The little button circled in red

      1. NetFabb’s cloud-based STL repair service provides information about the repaired file including surface area, triangles, and volume.  Just submit your STL file for repair (even if it doesn’t really need it) and get back a link to your fixed file along with the relevant statistics.
      2. NetFabb’s “NetFabb Studio Basic” is a free downloadwhich also provides detailed statistics about STL files and basic mesh fixing tools.  Here’s how you do it:
         1. After you open NetFabb, “Control-O” will give you the option of selecting an STL file.
         2. Keep adding as many STL files as you would like.  It won’t matter that they are all overlapped.
         3. Click the third icon from the left, a little cube frame with a circled ”i” on it.
         4. A window will pop up providing information, including volume, for each of the STL’s you have imported.
      3. I found the Studio Basic version of NetFabb’s offerings to be more useful.  The statistics seemed to be more consistent than the values from the cloud service and Studio Basic also allows you to import numerous files at once so you can compare the numbers “side by side.”

Do you have a suggestion on how better to figure out the volume in an STL?  If so, let us know in the comments!

1. Sorry!  I couldn’t find your full name! [↩]

Here is a lovely morning treat for you: The Engineer vs. Designer-MakerBot challenge has ended and the winners have been named! Find out here!

The contest called for a upload an “ironic, backward, cynical, or comically self-defeating 3D designs in watertight stl format,” and indeed brought out some of the most creative Things on Thingiverse of any competition we’ve been a part of.

At stake were a Makerbot Replicator, a one-year Cadjunkie Pro Membership, and an EvD Tshirt!

The gents at EvD have a special edition podcast up today that you must listen to! The very enjoyable 26 minutes features Al Dean of Develop3D Magazine who said the competition saw submissions that he “not only want[s] but need[s] and lust[s] after.”

After reviewing all the 183 (one hundred eighty three!) submissions that cadjunkie’s Adam O’Hern said primarily sought to “insult, denigrate, damage and destroy” iPhones, SolidSmack.com’s Josh Mings says he was overjoyed with the members of Thingiverse for having “more wit and sarcasm than any community I know.”

Without any further ado, please direct your ears to Episode 33 of ENGINEERvs.DESIGNER, where you will hear all the hilarious highlights of the contest and an interview with the winner!

UPDATE! The judges announced in the podcast that the winner of this contest was Thingiverse user aubenc, for his perfectly-executed design iFlail! The description says it’s a perfect accessory, if you’re into medieval war. Plus, as aubenc notes, “you will most probably have no pockets in your armor.” Genius.

Are you cooking up a wild and wacky new iPhone accessory in your brain skillet? Serve it up for a chance to win your very own Replicator!

Together with our friends Adam and Josh over at  Engineer vs. Designer, we’re kicking off the Absurd iPhone Accessory Design Contest! Slap on that thinking cap and upload your oddest, awesomest iPhone accessory design to Thingiverse and tag it ‘EvD’ to enter. Submit your design by March 19, 2012 and see it (and you!) featured on the Engineer vs. Designer blog.

Details after the jump!
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SketchUp to STL Plugin with No Dialogs by br3ttb

Google Sketchup is a free surface modeling program with a gentle learning curve.  While it does not export to STL’s for 3D printing, users have created some plugins that give it this functionality.  Thingiverse user br3ttb has made this process even simpler.  After installing his hacked version of an existing plugin, an STL of your work is just a few clicks away!

As a bonus, I’ve been collecting some of my favorite Sketchup plugins.  You might find some interesting ones in that list.

I sometimes have trouble getting a watertight STL out of Sketchup.  What software do you use to fix meshes?

Thanks for the tip Chris!

Simple Hinge by PieterNr1

Apparently, when you properly arrange objects in an STL for printing at once, you can do so in such a way as to eliminate the need for support structures!  Not only is this a clever use of limited build space, but it also conserves plastic while allowing printing of ever more intricate designs.

PieterNr1′s Simple Hinge above is the first object I’ve seen to use this technique.  It appears from the photograph that there is some slight drooping underneath the top two ledges – but I’m guessing this isn’t enough to interfere with proper operation.  Looking at his implementation of this technique, I have to wonder whether it could be used to print some of the various tracks and treads under development on Thingiverse.

Untitled by PieterBos

This thing brought to you by

Heart Gears by emmett (Opened in Wings3D)

While MakerBot Operators are more than happy to print the thousands of incredible objects posted to Thingiverse, eventually many catch the design bug and reach out for guidance for how to get started designing models.

Your mission: to create a solid, manifold (“watertight”) STL-formatted file for importing into ReplicatorG. STL, created as the format for stereolithographic CAD files, is a ubiquitous format, so the design application options are vast. ReplicatorG also offers experimental OBJ and Collada file import capability — though the files are then converted into STL files. (You can open dozens of file formats in MeshLab, netfabb Studio Basic or similar 3D swiss army knife tools — and then export as binary or ASCII STL files, opening up even more models to ReplicatorG.)

Choosing Your Hammer

8-bit Heart by schmarty (3DTin.com image)

For design software, there are many powerful free and open source design tools for us to introduce to Operators. Favorites include 3dtin.com, Sketchup, OpenSCAD, Wings3D, and Blender. We have heard about but not experimented much with POV-ray (excellent tutorials here), FreeCAD, HeeksCAD, and Art of Illusion — apps that have serious fans in the 3D printing world.

Plastruder MK5 Solidworks 2011 Model by kai

For commercial solid CAD apps: Rhino (Mac users — jump on the free beta), Autodesk Autocad, Inventor, Creo, and SolidWorks are probably the biggest players in the field. But perhaps you don’t have upwards of $1k to spend on design software? Try the highly-capable $99 Alibre Personal Edition, Cheetah3D (mac only), or bonzai3d.

Below the fold is a handy five step exercise for brand new designers to get their feet wet with 3D modeling.

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Analog eggs are so fragile

Because they’re difficult to put back together again. ¹  Taking a digital object and converting into an STL will essentially shatter it into a bunch of triangles.  This is great if you’re a 3D printer.  It’s not so great if you want to open, edit, modify, scale, create a derivative, or do anything with that digital file other than just print it.

Not infrequently people will upload their designs to Thingiverse just as an STL file.  This is great for printing, but not so great for creating derivatives.  Other times, people will upload their design files, but not an STL.  This is great for creating derivatives, but deprives users of being able to preview a thing and hampers them if they don’t have a program that supports the file format.

I’m a big fan of Google’s Sketchup.  I know it’s not open source – but it is free and super easy to use.  There are several STL import plugins for Sketchup that all work with varying degrees of success.  They tend to miss the finer details on objects.  The only reliable way I’ve found to edit an STL file without a loss of data is to import it into Blender, save as a 3DS file, and import it into Sketchup.

One problem with editing an STL file even after it has been converted into a more fungible format is that what was once a simple structure is now a spider web of triangles.  Editing a mess of small triangles in Sketchup could get unwieldy pretty quickly.  In order to simplify the entire model and potentially reduce the number of triangles involved, consider using the decimate function in Blender or the Polyreduce plugin for Google Sketchup.  Either method will provide you with a much simpler digital model for editing and modification.

1. Photo courtesy of WaveCult [↩]