3D Printering: When an STL File is Not Quite Right

STL files are everywhere. When there’s something to 3D print, it’s probably going to be an STL. Which, as long as the model is good just as it is, is no trouble at all. But sooner or later there will be a model that isn’t quite right in some way and suddenly project progress hits a snag.

When models interface with other physical things, those other components may not always be exactly as the designer expected. Being mindful about such potential inconsistencies during the design phase can help prevent problems, but it’s not always avoidable. The reason it’s a problem is because an STL file represents a solid model as a finished unit; it is not really intended to be rolled back into CAD programs for additional design changes.

STL files can be edited, but just like re-modeling a component from scratch, it can be a tricky process for those who don’t live and breathe this stuff. I’ll describe a few common issues related to STLs that can hold up getting that new project together, along with ways to deal with them. Thanks to 3D printing becoming much more commonplace, basic tools are within reach of even the least CAD-aware among us.

Continue reading “3D Printering: When an STL File is Not Quite Right”

3D-Printing Saves Collectible Lures from a Fishy Ending

Give a man a fishing lure, and he catches fish until he loses the lure. Give a fisherman a 3D-printer, and he can print all the fishing lures he wants, especially replicas of those that are too valuable to actually use.

It may seem strange that some people collect fishing lures rather than use them, but when you look at [Hunter]’s collection, it’s easy to see why. Lures can be very artistic, and the Heddon River Runts in his collection are things of beauty and highly prized. They’re also highly effective at convincing fish to commit suicide, so rather than risk the originals, he and his dad 3D-printed replicas.

After modeling the body of the lure in Blender, they modified it with air pockets for buoyancy and located holes for attaching the treble hooks and lip spoon, which was fabricated from a scrap of brass from a rifle casing. The finished lure lacks the painted details and some of the charm of the original River Runt, but it has something Mr. Heddon couldn’t dream of in 1933 when he introduced it — it glows in the dark, thanks to the phosphorescent PLA filament used. That seems to be irresistible to the bass, who hit the lure so often that they got sick of taking pictures. See it in action in the video below.

[Hunter] and his dad have been busy exploring what 3D printing can do, replicating all sorts of Heddon lures. They’ve even got plans to design and print their own lures. But maybe archery is more your sportsman thing than fishing, in which case this PVC pipe compound bow or a recurve bow from skis would be something to check out.

Continue reading “3D-Printing Saves Collectible Lures from a Fishy Ending”

Make 3D-Modeling Child’s Play with a Can of Play-Doh

You need to replicate a small part on a 3-D printer, so you start getting your tools together. Calipers, rulers, and a sketch pad at a minimum, and if you’re extra fancy, maybe you pull out a 3D-scanner to make the job really easy. But would you raid your kid’s stash of Play-Doh too?

You might, if you want to follow [Vladimir Mariano]’s lead and use Play-Doh for accurately modeling surface features in the part to be replicated. Play-Doh is a modeling compound that kids and obsolete kids alike love to play with, especially a nice fresh can before it gets all dried out or mixed in with other colors or gets dog hair stuck in it.

For [Vladimir], the soft, smooth stuff was the perfect solution to the problem of measuring the spacing of small divots in the surface of a cylinder that he was asked to replicate. Rather than measuring the features directly on the curved surface, he simply rolled it across a flattened wad of Play-Doh. The goop picked up the impressions on the divots, which were then easy to measure and transfer to Fusion 360. The video below shows the Play-Doh trick up front, but stay tuned through the whole thing to get some great tips on using the sheet metal tool to wrap and unwrap cylinders, as well as learning how to import images and recalibrate them in Fusion 360.

Run into a modeling problem that Play-Doh can’t solve? Relax, we’ve got a rundown on the basics for you.

Continue reading “Make 3D-Modeling Child’s Play with a Can of Play-Doh”

OpenSCAD: Tieing It Together With Hull()

What’s your favorite OpenSCAD command? Perhaps it’s intersection() or difference()? Or are you a polygon() and extrude() modeler? For me, the most useful, and maybe most often overlooked, function is hull(). Hull() does just what it says on the can — creates a convex hull around the objects that are passed to it as children — but that turns out to be invaluable.

Hull() solves a number of newbie problems: making things round and connecting things together. And with a little ingenuity, hull() can provide a nearly complete modelling strategy all on its own. If you use OpenSCAD and your creations end up with hard edges, or you spend too much time figuring out angles, or if you just want to experience another way to get the job done, read on!

Continue reading “OpenSCAD: Tieing It Together With Hull()”

Roller Coaster Tycoon IRL

Additive manufacturing has come a long way, but surely we’re not at the point where we can 3D-print a roller coaster, right? It turns out that you can, as long as 1/25th scale is good enough for you.

Some people build model railroads, but [Matt Schmotzer] has always had a thing for roller coasters. Not content with RollerCoaster Tycoon, [Matt] decided to build an accurate and working model of Invertigo, a boomerang coaster at King’s Park, the coaster nirvana in Cincinnati, Ohio. Covering a sheet of plywood and standing about 3′ tall, [Matt]’s model recreates the original in painstaking detail, from the supporting towers and bracing to the track sections themselves. It appears that he printed everything in sections just like the original was manufactured, with sections bolted together. Even though all the parts were sanded and vapor smoothed, the tracks themselves were too rough to use, so those were replaced with plastic tubing. But everything else is printed, and everything works. An Arduino Mega controls the lift motors, opens and closes the safety bars on the cars, and operates the passenger gates and drop floor in the station. The video below shows it in action.

Fancy a coaster of your own, but want something a little bigger? We understand completely.

Continue reading “Roller Coaster Tycoon IRL”

OpenEMS Makes Electromagnetic Field Solving… Merely Difficult

To ordinary people electronics is electronics. However, we know that the guy you want wiring your industrial furnace isn’t the guy you want designing a CPU. Neither of those guys are likely to be the ones you want building an instrumentation amplifier. However, one of the darkest arts of the electronic sects is dealing with electromagnetic fields. Not only is it a rare specialty, but it requires a lot of high-powered math. Enter OpenEMS, a free and open electromagnetic field solver.

We would like to tell you that OpenEMS makes doing things like antenna analysis easy. But that’s like saying Microsoft Word makes it easy to write a novel. In one sense, yes, but you still need to know what you are doing. In fairness, though, the project does provide a good set of tutorials, ranging from a simple wave guide to a sophisticated phased array of patch antennas. Our advice? Start with the waveguide and work your way up from there.

The software uses Octave or MATLAB for scripting, plotting, and support. You can download it for Windows or Linux.

If you want to start with something more intuitive for electromagnetic field visualization, this might help. If you prefer your models more concrete and less abstract, perhaps you should work at Lincoln Lab.

Circuit Design? Spread the Joy

Accountants and MBAs use spreadsheets to play “what if” scenarios with business and financial data. Can you do the same thing with electronic circuits? The answer–perhaps not surprisingly–is yes.

Consider this simple common emitter amplifier (I modeled it in PartSim, if you’d like to open it):

In this particular case, there are several key design parameters. The beta of the transistor (current gain) is 220. The amplifier has an overall voltage gain of about 3 (30/10). I say about, because unless the transistor is ideal, it won’t be quite that. The supply voltage (Vcc) is 12 volts and I wanted the collector voltage (VC) to idle at 6V to allow the maximum possible positive and negative swing. I wanted the collector current (IC) to be 200mA.

Continue reading “Circuit Design? Spread the Joy”