If you think about it, STL files are like PDF files. You usually create them using some other program, export them, and then expect them to print. But you rarely do serious editing on a PDF or an STL. But what if you don’t have anything but the STL? [The Savvy Engineer] has a method to help you if you need to reverse engineer an STL file in FreeCAD. Check it out in the video below.

The problem is, of course, that STLs are made up of numerous little triangles. The trick is to switch workbenches and create a shape from mesh. That gets you part of the way.

Once you have a shape, you can convert it to a solid. At that point, you can create a refined copy. This gives you a proper CAD file that you can export to a STEP file. From there, you can use it in FreeCAD or nearly any other CAD package you like to use.

Once you have a proper object, you can easily use it like any other solid body in your CAD program. This is one of those things you won’t need every day, but when you do need it, it’ll come in handy.

Want to up your FreeCAD game? We can help. There are other ways to hack up STL files. You can even import them into TinkerCAD to do simple things, but they still aren’t proper objects.

Last time, we built a case for a PCB that handles 100 W of USB-C power, an old project that I’ve long been aiming to revive. It went well, and I’d like to believe you that the article will give you a much-needed easy-to-grasp FreeCAD introduction, Matrix knowledge upload style, having you designing stuff in no time.

Apart from my firm belief in the power of open-source software, I also do believe in social responsibilities, and I think I have a responsibility to teach you some decent FreeCAD design practices I’ve learned along the way. Some of them are going to protect your behind from mistakes, and some of them will do that while also making your project way easier to work with, for you and others.

You might not think the last part about “others” matters, but for a start, it matters in the ideal world that we’re collectively striving towards, and also, let’s be real, things like documentation are half intended for external contributors, half for you a year later. So, here’s the first FreeCAD tip that will unquestionably protect you while helping whoever else might work with the model later.

Okay, we’re all hackers, so I’ll start with zero-th FreeCAD tip – press Ctrl+S often. That’ll help a ton. Thankfully, FreeCAD’s autorecovery system has made big leaps, and it’s pretty great in case FreeCAD does crash, but the less you have to recover, the better. Now, onto the first tip.

Name Your Bodies, Always

The button is F2. That’s it. Click on your models in the tree view and give them a name. Do it for all extrudes, cuts, and even fillets/chamfers. You don’t have to do it for sketches, since those are always contained within an extrusion. If at all possible, do it immediately, make it a habit.

Why? Because names make it clear what the extrusion/cut/fillet is for, and you’ll be thankful for it multiple times over when modifying your model or even just looking at it the next morning. Also, it makes it way easier to avoid accidentally sending the wrong 3D model to your printer.

How to make naming easier? I’ve figured out an easy and apt naming scheme, that you’ve seen in action in the previous article. For Fusions, I do “primary object +addition” or “with addition”, mentioning just the last addition. So, “Bottom case +cutouts” is a cut that contains “Bottom case +logo” and “Cutouts”, “Bottom case +logo” is a cut that contains “Bottom case” and “Logo”, and “Bottom case” contains “Bottom floor” and “Bottom walls”.

It’s not a perfect scheme, but it avoids verbosity and you have to barely think of the names. Don’t shy away from using words like “pip” and “doohickey” if the word just doesn’t come to your mind at the moment – you’re choosing between a project that’s vaguely endearing and one that’s incomprehensible, so the choice is obvious. Naming your models lets you avoid them becoming arcane magic, which might sound fun at a glance until you realize there’s already an object of arcane magic in your house, it’s called a “3D printer”, and you’ve had enough arcane magic in your life.

Last but not least, to hack something is know learn its true name, and whatever your feature is, there’s no truth in “Cut034”. By the way, about FreeCAD and many CAD packages before it, they’ve been having a problem with true names, actually, it’s a whole thing called Topological Naming Problem.

Naming Is Hard, Topology Is Harder

How do you know where a feature really is? For instance, you take a cube, and you cut two slots into the same side. How does the CAD package ensure that the slots are on the same side? One of the most popular options for it is topological naming. So, a cube gets its faces named Face1 through Face6, and as you slowly turn that cube into, say, a Minecraft-style hand showing a middle finger, each sketch remembers the name of the side you wanted it attached to.

Now, imagine the middle finger hand requires a hole inside of it, and it has to be done at from very start, which means you might need to go back to the base cube and add that hole. All of a sudden, there will be four new faces to the internal cube that holds the finger sketches, and these new faces will need names, too. Best case, they’ll be named Face7 through Face10 – but that’s a best case and the CAD engine needs to ensure to always implement it properly, whereas real world models aren’t as welcoming. Worst case, the faces will be renumbered anew, the sketch-to-face mapping will change which faces get which names, and the model of the hand will turn into a spider. Spooky!

It’s not Halloween just yet, and most regretfully, people don’t tend to appreciate spiders in unexpected places. Even more sadly, this retrospective renaming typically just results in your sketches breaking in a “red exclamation mark” way, since it’s not just sketch-to-face mappings that get names, it’s also all the little bits of external geometry that you’ll definitely invoke if you want to avoid suffering. Every line in your sketch has an invisible name and a number, and external geometry lines will store – otherwise, they couldn’t get updated when you change the base model under their feet, as one inevitably does.

This used to be a big problem with FreeCAD, and it still kind of is, but it’s by no means exclusive to FreeCAD. Hell, I remember dealing with something similar back when my CAD (computer-aided despair) suite of choice was SolidWorks. It’s not an easy problem to solve, because of the innumerable ways you can create and then modify a 3D object; every time you think you’ll have figured out a solution to the horrors, your users will come up with new and more intricate horrors beyond your comprehension.

FreeCAD v1.0 has clamped down on a large amount of topological naming errors. They still exist; one simple way I can trigger it is to make a cutout in a cube, make a sketch that external-geometry-exports the cut-in-half outwards-facing line of the cube, and then go back and delete the cutout. It makes sense that it happens, but oh do I wish it didn’t, and it makes for unfun sketch fixing sessions.

How To Stay Well Away

Now, I’m no stranger to problems caused by name changes, and I’m eager to share some of what I’ve learned dealing with FreeCAD’s names in particular.

The first solution concerns cutouts, as they specifically might become the bane of your model. If you have a ton of features planned, just delay doing the cutouts up until you’ve done all the basics of the case that you might ever want to rely on. Cutouts might and often will change, and if your board changes connector or button positions, you want to be able to remake them without ever touching the rest of the sketch. So, build up most of your model, and closer to the end, do the case cutouts, so that external geometry can rely on walls and sides that will never change.

Next, minimize the number of models you’re dealing with, so that you have less places where external geometry has to be involved. If you need to make a block with a hole all the way through, do it in one sketch instead of doing two extrudes and a cut. You’ll thank yourself, both because you’ll have less opportunity for topo naming errors, but also because you have fewer model names to think up.

The third thing is what I call the cockroach rule. If you see a cockroach in your house, you back off slowly, set the house on fire, and then you get yourself a different house, making sure you don’t bring the cockroach into the new house while at it. Same can apply here – if you remove a feature in the base model and you see the entire tree view light up with red exclamation marks, click “Close” on the document, press “Discard changes”, open the document again, and do whatever you wanted to do but in a different way.

Why reload? Because Ctrl+Z does not always help with such problems, as much as it’s supposed to. This does require that you follow the 0th rule – press Ctrl+S often, and it also requires that you don’t press Ctrl+S right after making those changes, so, change-verify-enter. Thankfully, FreeCAD will unroll objects in the model tree when one of the inner object starts to, so just look over the model tree after doing changes deep inside the model, and you’ll be fine. This is also where keeping your models in a Git repo is super helpful – that way, you can always have known-good model states to go back to.

Good Habits Create Good Models

So, to recap. Save often, give your models names, understand topo naming, create cutouts last if at all possible, keep your models simple, and when all fails, nuke it from orbit and let your good habits cushion the fall. Simple enough.

I’ll be on the lookout for further tips for you all, as I’ve got a fair few complex models going on, and the more I work with them, the more I learn. Until then, I hope you can greatly benefit from these tips, and may your models behave well through your diligent treatment.

Over a year ago, we took a look at importing a .step file of a KiCad PCB into FreeCAD, then placing a sketch and extruding it. It was a small step, but I know it’s enough for most of you all, and that brings me joy. Today, we continue building a case for that PCB – the delay is because I stopped my USB-C work for a fair bit, and lost interest in the case accordingly, but I’m reviving it now.

Since then, FreeCAD has seen its v 1.0 release come to fruition, in particular getting a fair bit of work done to alleviate one of major problems for CAD packages, the “topological naming problem”; we will talk about it later on. The good news is, none of my tutorial appears to have been invalidated by version 1.0 changes. Another good news: since version 1.0, FreeCAD has definitely become a fair bit more stable, and that’s not even including some much-needed major features.

High time to pick the work back up, then! Let’s take a look at what’s in store for today: finishing the case in just a few more extrusions, explaining a few FreeCAD failure modes you might encounter, and giving some advice on how to make FreeCAD for you with minimum effort from your side.

As I explained in the last article, I do my FreeCAD work in the Part workbench, which is perfectly fine for this kind of model, and it doesn’t get in your way either. Today, the Part and Sketcher workbenches are all we will need to use, so you need not be overwhelmed by the dropdown with over a dozen entries – they’re there for a reason, but just two will suffice.

Last time, I drew a sketch and extruded it into a box. You’ll want your own starting layer to look different from that, of course, and so do I. In practice, I see two options here. Either you start by drawing some standoffs that the board rests on, or you start by offsetting your sketch then drawing a floor. The first option seems simpler to me, so let’s do that.

You can tie the mounting holes to external geometry from the STEP file, but personally, I prefer to work from measurements. I’d like to be easily able to substitute the board with a new version and not have to re-reference the base sketches, resulting in un-fun failure modes.

So, eyeballing the PCB, the first sketch will have a few blocks that the PCB will be resting on. Let’s just draw these in the first sketch – four blocks, with two of them holding mounting holes. For the blocks with holes, if your printer nozzle size is the usual 0.4 mm, my understanding is that you’ll want to have your thinnest structure be around 1.2 mm. So, setting the hole diameter (refer to the toolbar, or just click D to summon the diameter tool), and for distances between points, you can use the general distance tool (K,D, click K then click D). Then, exit the sketch.

To The Floor And Beyond

Perfect – remember, the first sketch is already extruded, so when we re-drew the sketch, it all re-extruded anew, and we have the block we actually want. Now, remember the part about how to start a sketch? Single click on a surface so it gets highlighted green, press “New sketch”, and click “ok” on the box that asks if you want to do it the “Plane X-Y” way. That’s it, that’s your new sketch.

Now, we need to draw the box’s “floor”. That’s simple too – just draw a big rectangle. You’ll want to get some dimensions going, of course. Here, you can use the general distance constraint (K,D, click K then click D), or constrain even quicker by clicking I (vertical dimension) and L (horizontal dimension). Now, for the fun part – filleting! Simply put, you want to round the box corners for sure, nobody wants a box with jagged sharp holes.

You might have seen the Fillet tool in the Part workbench. Well, most of the time, it isn’t even needed, and frankly, you don’t want to use it if a simpler option exists. Instead, here, just use a sketch fillet – above in the toolbar; sadly, no keybind here. Then, click on corners you want rounded, exit the tool, then set their radius with diameter tool (D), as default radii are way too large at our scale. The sketch fillet tool basically just creates arcs for you – you can always draw the arcs yourself too, but it’s way easier this way.

You got yourself a rounded corners rectangle, which, naturally, means that you’ll be getting a cease and desist from multiple smartphone makers shortly. You might notice that the rectangle is offset, and really, you’d want it aligned. Fortunately, we placed our STEP-imported board approximately in the center of the screen, which makes the job very easy, you just need the rectangle centered. Draw two construction lines (G,N) from opposite corners of the sketch. Then, click on one of the lines, click on the sketch center point, and make them coincident (C). Do the same with the second line, and you’ll have the sketch center point on the intersection of the two lines, which will make the whole sketch centered.

Extrude that to 1 mm, or your favourite multiple of your layer height when slicing the print, and that’s the base of your case, the part that will be catching the floor. Honestly, for pin insulation purposes, this already is more than enough. Feel free to give it ears so that it can be mounted with screws onto a surface, or maybe cat ears so it can bring you joy. If you’re not intimidated by both the technical complexity and the depravity of it, you can even give it human ears, making your PCB case a fitting hacking desk accessory for a world where surveillance has become ubiquitous. In case you unironically want to do this, importing a 3D model should be sufficient.

Build Up This Wall!

Make a sketch at the top of the floor, on the side that you’ll want the walls to “grow out of”. For the walls, you’ll naturally want them to align with the sides of the floor. This is where you can easily use external geometry references. Use the “Create external geometry” tool (G, X) and click on all the 8 edges (4 lines and 4 arcs) of the floor. Now, simply draw over these external geometry with line and arc tool, making sure that your line start and end points snap to points of external geometry.

Make an inset copy of the edges, extrude the sketch, and you’re good to go. Now, did you happen to end up with walls that are eerily hollowed out? There’s two reasons for that. The first reason is, your extruded block got set to “solid: false” in its settings. Toggle that back, of course, but mistaken be not, it’s no accident, it happens when you extrude a sketch and some of the sketch lines endpoints are not as coincident as you intended them to be. Simply put, there are gaps in the sketch — the same kind of gaps you get if you don’t properly snap the Edge.Cuts lines in KiCad.

To fix that, you can go box-select the intersection points with your mouse, and click C for a coincident constraint. Sometimes the sketch will fail. To the best of my knowledge, it’s a weird bug in KiCad, and it tends to happen specifically where external geometry to other solids is involved. Oh well, you can generally make it work by approaching it a few times. If everything fails, you can set distance (K,D) to 0, and if that fails, set vertical distance (I) and then horizontal distance (L) to zero, that should be more than good enough.

And with that, the wall is done. But it still needs USB-C socket holes. Cutting holes in FreeCAD is quite easy, even for a newcomer. You make a solid block that goes “into” your model exactly in the way you want the cut to be made. Then, in Part workbench, click the base model that you want cut in the tree view, click the solid block model, and use the “Cut” tool. Important note – when using the “Cut” tool, you have to first click on the base object, and then the tool. If you do it in reverse, you cut out the pieces you actually want to save, which is vaguely equivalent to peeling potatoes and then trashing the potatoes instead of the peels.

Want a souvenir? In Part toolbox, click Chamfer, click on the USB-C opening edges, set chamfer distance to something lower than your wall thickness, say, 0.6 mm (important!), and press Ok. Now your case has USB-C openings with chamfers that as if direct the plug into the receptacle – it’s the nicer and more professional way to do USB-C openings, after all.

Stepping Up

Once you get past “Hello World”, and want to speed your FreeCAD work tremendously, you will want to learn the keybinds. Once again, the key to designing quickly and comfortably is having one hand on keyboard and another hand on mouse, doesn’t matter if you’re doing PCBs or 3D models. And the keybinds are very mnemonic: “d” is dimension, “c” is coincident.

Another tip is saving your project often. Yet another one is keeping your FreeCAD models in Git, and even publishing them on GitHub/GitLab – sure, they’re binary files, but revision control is worth it even if you can’t easily diff the files. We could always use more public 3D models with FreeCAD sources. People not publishing their source files has long been a silent killer of ideas in the world of 3D printing, as opposed to whatever theories about patents might be floating around the web. If you want something designed to your needs, the quickest thing tends to be taking someone else’s project and modifying it, which is why we need for sharing culture so that we can all finally stop reinventing all the wheels our projects may require.

This is more than enough to ready you up for basic designs, if you ask me. Go get that case done, throw it on GitHub, and revel in knowing your board is that much less likely to accidentally short-circuit. It’s a very nice addition for a board intended to handle 100 W worth of power, and now it can also serve as a design example for your own needs. Next time, let’s talk about a number of good practices worth attending to if you want your FreeCAD models to last.

Open source software can be fantastic. I run almost exclusively open software, and have for longer than I care to admit. And although I’m not a serious coder by an stretch, I fill out bug reports when I find them, and poke at edge cases to help the people who do the real work.

For 3D modeling, I’ve been bouncing back and forth between OpenSCAD and FreeCAD. OpenSCAD is basic, extensible, and extremely powerful in the way that a programming language is, and consequently it’s reliably bug-free. But it also isn’t exactly user friendly, unless you’re a user who likes to code, in which case it’s marvelous. FreeCAD is much more of a software tool than a programming language, and is a lot more ambitious than OpenSCAD. FreeCAD is also a program in a different stage of development, and given its very broad scope, it has got a lot of bugs.

I kept running into some really serious bugs in a particular function – thickness for what it’s worth – which is known to be glitchy in the FreeCAD community. Indeed, the last time I kicked the tires on thickness, it was almost entirely useless, and there’s been real progress in the past couple years. It works at least sometimes now, on super-simple geometries, and this promise lead me to find out where it still doesn’t work. So I went through the forums to see what I could do to help, and it struck me that some people, mostly those who come to FreeCAD from commercial programs that were essentially finished a decade ago, have different expectations about the state of the software than I do, and are a lot grumpier.

Open source software is working out its bugs in public. Most open source is software in development. It’s growing, and changing, and you can help it grow or just hang on for the ride. Some open-source userland projects are mature enough that they’re pretty much finished, but the vast majority of open-source projects are coding in public and software in progress.

It seems to me that people who expect software to be done already are frustrated by this, and that when we promote super-star open projects like Inkscape or Blender, which are essentially finished, we are doing a disservice to the vast majority of useful, but still in progress applications out there that can get the job done anyway, but might require some workarounds. It’s exactly these projects that need our help and our bug-hunting, but if you go into them with the “finished” mentality, you’re setting yourself up for frustration.

If you’ve ever wanted to merge the worlds of holiday cheer and clever geometry, [Kris Wilk]’s gingerbread house hack is your ultimate inspiration. Shared in a mesmerising video, [Wilk] showcases his 2024 entry for his neighborhood’s gingerbread house contest. Designed in FreeCAD and baked to perfection, this is no ordinary holiday treat. His pièce de résistance was a brilliant trompe l’oeil effect, visible only from one carefully calculated angle. Skip to the last twenty seconds of the video to wrap your head around how it actually looks.

[Wilk] used FreeCAD’s hidden true perspective projection function—a rarity in CAD software. This feature allowed him to calculate the perfect forced perspective, essential for crafting the optical illusion. The supporting structures were printed on a Prusa MK4, while the gingerbread itself was baked at home. Precision photography captured the final reveal, adding a professional touch to this homemade masterpiece. [Wilk]’s meticulous process highlights how accessible tools and a sprinkle of curiosity can push creative boundaries.

For those itching to experiment with optical illusions, this bakery battle is only the beginning. Why not build a similar one inside out? Or construct a gingerbread man in the same way? Fire up the oven, bend your mind, and challenge your CAD skills!

After 22 years of development, FreeCAD has at long last reached the milestone of version 1.0. On this momentous occasion, it’s good to remember what a version 1.0 is supposed to mean, as also highlighted in the release blog post: FreeCAD is now considered stable and ready for ‘real work’. One of the most important changes here is that the topological naming problem (TNP) that has plagued FreeCAD since its inception has now finally been addressed using Realthunders’ mitigation algorithm, which puts it closer to parity here with other CAD packages. The other major change is that assemblies are now supported with the assembly workbench, which uses the Ondsel solver.

Other changes include an updated user interface and other features that should make using FreeCAD easier and closer in line with industry standards. In the run-up to the 1.0 release we already addressed the nightmare that is chamfering in FreeCAD, and the many overlapping-yet-uniquely-incomplete workbenches, much of which should be far less of a confabulated nightmare in this bright new 1.0 future.

Naturally, the big zero behind the major version number also means that there will still be plenty of issues to fix and bugs to hunt down, but it’s a promising point of progress in the development of this OSS CAD package.

Within the world of CAD there are the well-known and more niche big commercial players and there are projects like FreeCAD that seek to bring a OSS solution to the CAD world. As with other OSS projects like the GIMP, these OSS takes on commercial software do not always follow established user interactions (UX), which is where Ondsel sought to bridge the gap by giving commercial CAD users a more accessible FreeCAD experience. This effort is now however at an end, with a blog post by Ondsel core team member [Brad Collette] providing the details.

The idea of commercializing OSS is by no means novel, as this is what Red Hat and many others have done for decades now. In our article on FOSS development bounties we touched upon the different funding models for FOSS projects, with the Linux kernel enjoying strong commercial support. The trick is of course to attract such commercial support and associated funding, which is where the development on the UI/UX and feature set of the core FreeCAD code base was key. Unfortunately the business case was not strong enough to attract such commercial partners and Ondsel has been shutdown.

As also discussed on the FreeCAD forum, the Ondsel codebase will likely be at least partially merged into the FreeCAD code, ending for now the prospect of FreeCAD playing in the big leagues with the likes of AutoCAD.

Thanks to [Brian Harrington] for the tip.