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.

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Digikey Tips Its Hat To Kicad With Its Own Library

Digikey might wow us with their expansive stock, but now they’re wowing us with a personal gesture. The US-based electronics vendor is nodding its head in approval to KiCad users with its very own parts library. What’s more, [Chris Gammell] walks us through the main features and thought process behind its inception.

With all the work that’s going into this library, it’s nice to see features showing that Digikey took a thorough look at KiCad and how it fits into the current state of open-source PCBA design. First off, this library follows a slightly different design pattern from most other KiCad libraries in that it’s an atomic parts library. What that means is that every symbol is linked to a specific manufacturer part number and, hence, gets linked to a specific footprint. While this style mirrors EagleCad’s; KiCad libraries usually separate symbols from footprints so that symbols can be reused and parts can be more easily swapped in BOMs. There’s no “best” practice here, so the folks at Digikey thought they’d expose the second option.

Next off, the library is already almost 1000 parts strong and set to grow. These aren’t just the complete line of Yageo’s resistor inventory though. They actually started cultivating their library from the parts in Seeed Studio’s open parts library. These are components that hobbyists might actually use since some assembly services have a workflow that moves faster with designs that use these parts. Lastly, since all parts have specific vendor part numbers, BOM upload to an online cart is more convenient, making it slightly easier for Digikey to cha-ching us for parts.

Yes, naysayers might still cry “profit” or “capitalism” at the root of this new library, but from the effort that’s gone into this project, it’s a warm gesture from Digikey that hits plenty of positive personal notes for hobbyists. Finally, we can still benefit from plenty of the work that’s gone into this project — even if we don’t use it as intended. The permissive license lets us snag the symbols and reuse them however we like. (In fact, for the sharp-eyed legal specialists, they actually explicitly nullified the clause stating that derivative projects need not be licensed with a creative-commons license.)

With maturing community support from big vendors like Digikey, we’re even hungrier to get our hands on KiCad V.

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When Detecting Lines Is Harder Than Expected

[Conor Patrick] is no stranger to hardware development, and he’s had an interesting project for the past few months. He’s attempting to create a tool to convert images of technical drawings (such as footprints for electronic components) into digital formats that can be imported into other tools. This could automate turning a typical footprint drawing like the one shown into an actual part definition in a CAD program, which could really speed up the creation of custom parts.

Key to the entire concept is the detection of lines in a black-and-white technical drawing. To some people this won’t sound like a particularly challenging problem; choose one or another baked-in line detection function, maybe with a bit of pre or post-processing, and that should be that. It turns out that detecting lines can be harder than expected, and as usual the devil is in the detail.

When [Conor] tried some existing methods for detecting lines, the results appeared good at first but came up short in frustrating ways. Software did not appreciate that in a technical drawing, a line is a single unbroken unit from point A to point B. Without that assumption, what should be a single line sometimes had sections missing, or single lines were detected as multiple segments instead of a unit. Lines that crossed other lines complicated things. Unwanted lines like a “1” or the lower half of a “Y” were being detected. There had to be a better way.

In the end, a custom solution that took proper advantage of the nature of the source images and made the correct assumptions is what made all the difference. With some intelligent threshold setting combined with looking at vertical and horizontal line instances separately, it was possible to locate lines and their lengths far more accurately than any other method he had tried. The system doesn’t handle sloped lines yet, but it might be possible to simply iterate through rotations of the image while applying the same method. If you have a better solution, [Conor] wants to hear from you.

Of course, garbage in means garbage out and sadly not all technical drawings measure up.

How To Reverse Engineer Mechanical Designs for 3D Modeling

If you’re interested in 3D printing or CNC milling — or really any kind of fabrication — then duplicating or interfacing with an existing part is probably on your to-do list. The ability to print replacement parts when something breaks is often one of the top selling points of 3D printing. Want some proof? Just take a look at what people made for our Repairs You Can Print contest.

Of course, to do that you need to be able to make an accurate 3D model of the replacement part. That’s fairly straightforward if the part has simple geometry made up of a primitive solid or two. But, what about the more complicated parts you’re likely to come across?

In this article, I’m going to teach you how to reverse engineer and model those parts. Years ago, I worked for a medical device company where the business model was to duplicate out-of-patent medical products. That meant that my entire job was reverse engineering complex precision-made devices as accurately as possible. The goal was to reproduce products that were indistinguishable from the original, and because they were used for things like trauma reconstruction, it was critical that I got it right.

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Gamecube Dock For Switch Mods Nintendo with More Nintendo

[Dorison Hugo] let us know about a project he just completed that not only mods Nintendo with more Nintendo, but highlights some of the challenges that come from having to work with and around existing hardware. The project is a Gamecube Dock for the Nintendo Switch, complete with working Gamecube controller ports. It looks like a Gamecube with a big slice out of it, into which the Nintendo Switch docks seamlessly. Not only that, but thanks to an embedded adapter, original Gamecube controllers can plug into the ports and work with the Switch. The original orange LED on the top of the Gamecube even lights up when the Switch is docked. It was made mostly with parts left over from other mods.

The interesting parts of this project are not just the attention to detail in the whole build, but the process [Dorison] used to get everything just right. Integrating existing hardware means accepting design constraints that are out of one’s control, such as the size and shape of circuit boards, length of wires, and often inconvenient locations of plugs and connectors. On top of it all, [Dorison] wanted this mod to be non-destructive and reversible with regards to the Nintendo Switch dock itself.

To accomplish that, the dock was modeled in CAD and 3D printed. The rest of the mods were all done using the 3D printed dock as a stand-in for the real unit. Since the finished unit won’t be painted or post-processed in any way, any scratches on both the expensive dock and the Gamecube case must be avoided. There’s a lot of under-cutting and patient sanding to get the cuts right as a result. The video (embedded below) steps through every part of the process. The final screws holding everything together had to go in at an odd angle, but in the end everything fit.

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3D Printed Desk Harnesses the Power of Fusion 360 and McMaster-Carr

Black pipe furniture is all the rage now, and for good reason — it has a nice industrial aesthetic, it’s sturdy, and the threaded fittings make it a snap to put together. But if you’ve priced out the fittings lately, you know that it’s far from cheap, so being able to 3D-print your own black pipe fittings can make desks and tables a lot more affordable.

Cheapness comes at a price, of course, and [Vladimir Mariano] takes pains to point out that his desk is a light-duty piece that would likely not stand up to heavy use. But since the flange fittings used to connect the plywood top to the legs and as feet would cost about $64 all by themselves from the local home center, printing them made sense. Together with custom pieces to mount stretchers between the legs, the 3D-printed parts made for a decently sturdy base.

But the end product isn’t the main point of the video below. Thanks to the ability to browse the McMaster-Carr catalog from within Fusion 360, [Mariano] was able to seamlessly import the CAD model of a suitable iron flange and quickly modify it to his needs. The power of this feature is hard to overstate; you can literally browse through a catalog of engineered parts and print usable replicas instantly. Sure, it’s not made of metal, but it’s a huge boon to designers to be able to see how the final product would look, especially in the prototyping phase of a project.

Not familiar with McMaster-Carr? It’s an engineer’s online playground, and we covered the ins and outs of doing business with McMaster a while back.

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LEGO Prototyping with Tinkercad’s Brick Mode

[Andrew Sink] made a brief video demonstrating how he imported an STL of the well-known 3D Benchy tugboat model, and instead of sending it to a 3D printer used the Brick Mode feature to make a physical copy out of LEGO bricks in an eye-aching kaleidoscope of colors.

For those of you who haven’t used Tinkercad lately, Brick Mode allows you to represent a model as LEGO bricks at various scales. You model something as usual (or import a model) and by pushing a single button, render it in LEGO as accurately as can be done with standard bricks.

In addition, [Andrew] shows how the “Layers” feature can be used as a makeshift assembly guide for the model, albeit with a couple of quirks that he explains in the video embedded below.

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