Throw FreeCAD Some Curves

August 12, 2023 by Al Williams 43 Comments

[Mango Jelly] got a question from someone trying to model a phone box with a complex curved roof. We have to admit that when we saw it, we knew it would be hard to model well. Naturally, there are several ways it could be one, but [Mango Jelly] used the curves workbench in FreeCAD to produce a wireframe of the shape, and you can see how that works in the video below.

The curve bench didn’t sound familiar to us, and that’s because it is an add-on workbench. He starts with a sketch of a curve, constrained to be symmetrical. Then the draft workbench allowed a rotation to convert the curve into a nice skeleton of the curved roof.

The curves workbench can create a Gordon surface over that skeleton. You can extrude that into a solid object. There are still some details to add, though, and you’ll see how each part of the roof takes shape.

Watching videos like this reminds us that we use a small fraction of what FreeCAD can do. You’ll probably pick up at least one tip from this video. If you need a quick basic tutorial, try the one from [NovaSpirit]. Or, try a longer one.

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Enhance Your Enclosures With A Shadow Line

August 7, 2023 by Donald Papp 15 Comments

Some design techniques and concepts from the injection molding world apply very nicely to 3D printing, despite them being fundamentally different processes. [Teaching Tech] demonstrates designing shadow lines into 3D printed parts whose surfaces are intended to mate up to one another.

This is a feature mainly seen in enclosures, and you’ve definitely seen it in all kinds of off-the-shelf products. Essentially, one half of the part has a slight “underbite” of a rim, and the other half has a slight “overbite”, with a bit of a standoff between the two. When placed together, the combination helps parts self-locate to one another, as well as providing a consistent appearance around the mating surfaces.

Why is this necessary? When a plastic part is made — such as an enclosure in two halves — the resulting surfaces are never truly flat. Without post-processing, the two not-quite-flat surfaces result in an inconsistent line with a varying gap between them.

By designing in a shadow line, the two parts will not only self-locate to each other for assembly, but will appear as a much more consistent fit. There will be a clear line between the two parts, but no actual visible gaps between them. Watch the whole thing explained in the video, embedded below.

This isn’t the only time design techniques from the world of injection molding have migrated to 3D printing. Crush ribs have been adapted to the world of 3D printed parts and are a tried-and-true solution to the problem of reliably obtaining a tight fit between plastic parts and hardware inserts.

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Splitting 3D Prints Into Parts Can Add Strength

July 28, 2023 by Donald Papp 5 Comments

One of the great things about 3D printers is their ability to make a single part all at once. Separating a part into multiple pieces is usually done to split up objects that are too big to fit on the 3D printer’s print bed. But [Peter] at Markforged (manufacturers of high-end 3D printers) has a video explaining another reason: multi-part prints can benefit from improved strength.

This part can be easily printed as a single piece, but it can be made nearly twice as strong when printed as two, and combined.

The idea is this: filament-based 3D printers generally create parts that are strongest along their X-Y axis (relative to their manufacture) and weakest in the Z direction. [Peter] proposes splitting a part into pieces with this in mind. Not because the part is inconveniently large or has tricky geometry, but so the individual pieces can be printed in orientations that provide the best mechanical strength.

This is demonstrated with the simple part shown here. The usual way to print this part would be flat on a print bed, but by splitting the parts into two and printing each in their optimal orientation, the combined part withstands nearly twice as much force before failing.

[Peter]’s examples use Markforged’s own filaments, but gives advice on more common polymers as well and the same principles apply. This idea is one worth keeping in mind the next time one is seeking to optimize strength. because of how simple it is.

We’ve seen a variety of methods to toughen up or ruggedize prints in the past, but they’re usually more complex (or at least messier.) Examples include embedding braided steel cable, embedding fiberglass mesh, applying electroplating to a printed structure, and plain old embedding some bolts and washers to buffer load-bearing areas.

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FreeCAD Is Simple, According To This Tutorial

July 5, 2023 by Al Williams 44 Comments

Remember learning to tie your shoes or ride a bike? Like many things, that’s easy once you know how to do it, but seems impossible before you learn. [NovaSpirit] asserts that Freecad is simple, and provides a simple walkthrough to create a part in the video below.

If this were riding a bike, this tutorial would be akin to watching someone ride a bike to pick up tips. You’d probably still want to have someone explain details to you before you attempt it yourself.

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You Can 3D Print A 12,500 RPM Brushless Motor

June 28, 2023 by Lewin Day 18 Comments

Typically, when most of us need a motor, we jump online to order one from a catalogue. [Levi Janssen] recently had to build his own for a college project, however, and learned a lot along the way.

[Levi] whipped up his brushless DC motor design in OnShape. The motor has six coils in the stator, with the rotor carrying eight neodymium magnets. It’s an axial flux design, with the rotor’s magnets sitting above the coils. This makes construction very easy using 3D printed components. Axial flux motors also have benefits when it comes to power density and cooling, though optimization is outside the scope of [Levi]’s work here.

[Levi]’s video covers both the development of the motor itself as well as the drive circuit, too. The latter is of key value if you’re interested in the vagaries of driving these motors, which is far more complex than running a simple brushed motor. He even gets his motor up to 12,500 rpm with his homebrewed drive circuit.

Making your own motors can help you solve some difficult engineering challenges, like building motorized rollerblades. Alternatively, if winding coils sounds too slow and too hard, you can just use off-the-shelf gear and hack it to make it work. Here, we support both methods.

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Using FreeCAD To Replace OEM Parts

June 10, 2023 by Bryan Cockfield 46 Comments

As much as we might all like it if manufacturers supported their products indefinitely with software updates or replacement parts, this just isn’t feasible. Companies fail or get traded, technologies evolve, and there’s also an economic argument against creating parts for things that are extremely old or weren’t popular in the first place. So, for something like restoring an old car, you might have to resort to fabricating replacement parts for your build on your own. [MangoJelly] shows us how to build our own replacement parts in FreeCAD in this series of videos.

The build does assume that the original drawings or specifications for the part are still available, but with those in hand FreeCAD is capable of importing them and then the model scaling to match the original specs shown. This video goes about recreating a hinge on an old truck, so with the drawings in hand the part is essentially traced out using the software, eventually expanding it into all three dimensions using all of the tools available in FreeCAD. One of the keys to FreeCAD is the various workbenches available that all have their own sets of tools, and being able to navigate between them is key to a build like this.

FreeCAD itself is an excellent tool for anyone repairing old vehicles like this or those making 3D prints, designing floorplans for houses, or really anything you might need to model in a computer before bringing the idea into reality. It does have a steep learning curve (not unlike other CAD software) so it helps to have a video series like this if you’re only just getting started or looking to further hone your design skills, but the fact that it’s free and open-source make it extremely attractive compared to its competitors.

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JITX Spits Out Handy USB Cable Tester

May 31, 2023 by Bryan Cockfield 12 Comments

When USB first came on the scene, one of the benefits was that essentially any four conductors could get you to the point where you could send information at 12 Mbps. Of course everything is faster these days, and reaching today’s speeds requires a little bit more fidelity in the cables. This simple tester makes sure that your modern cables are actually up to the task.

One of the design goals of this project is to automate away the task of testing cables or finding one that works, especially before thinking a problem with a device is somewhere in software, spending hours or days debugging, before realizing that it’s actually being caused by a hardware malfunction. The small PCB has two USB-C fittings to plug in both of the ends of a cable to, and between those connectors there is a number of LEDs. Each LED is paired to one the many conductors within the USB cable, and not only does it show continuity of these conductors but it can also show a high resistance connection via a dimly-lit or off-color display from an LED.

One of the other interesting facets of this build is the use of JITX, which is a software-defined electronics CAD tool which allows PCB design to be automated by writing out the requirements of the PCB into code, rather than drawing it manually. It’s worth a look, and a lot of the schematics of this particular project as well as some discussion on this software can be found on the project’s GitHub page. Incidentally, if this tester looks familiar, it’s probably because your’re thinking of the open source hardware USB tester created by [Álvaro Prieto].