Finding Perfect Part Fits With The Goldilocks Approach (and OpenSCAD)

June 9, 2020 by Donald Papp 33 Comments

There is something to be said for brute force or trial-and-error approaches to problems, especially when finding a solution has an empirical element to it. [Tommy] perceived that to be the case when needing to design and 3D print servo horns that would fit factory servos as closely as possible, and used OpenSCAD to print a “Goldilocks array” from which it was possible to find a perfect match for his printer by making the trial and error process much more efficient. By printing one part, [Tommy] could test-fit dozens of options.

What made doing this necessary is the fact that every 3D printer has some variance in how accurately they will reproduce small features and dimensions. A 6.3 mm diameter hole in a CAD model, for example, will not come out as exactly 6.3 mm in a 3D-printed object. It will be off by some amount, but usually consistently so. Therefore, one way around this is to empirically determine which measurements result in a perfect fit, and use those for production on that specific 3D printer.

That’s exactly what [Tommy] did, using OpenSCAD to generate an array of slightly different sizes and shapes. The array gets printed out, servos are test-fitted to them, and whichever option fits best has its dimensions used for production. This concept can be implemented in any number of ways, and OpenSCAD makes a decent option due to its programmatic nature. Interested in OpenSCAD? It will run on nearly any hardware, and you can get up and running with the basics in probably less than ten minutes.

3D Printing Nuclear Reactors For Fun And Profit

June 8, 2020 by Maya Posch 18 Comments

Over the past decades, additive manufacturing (AM, also known as 3D printing) has become increasingly common in manufacturing processes. While immensely helpful in the prototyping of new products by allowing for rapid turn-around times between design and testing, these days additive manufacturing is used more and more often in the production of everything from small production runs of custom enclosures to hard to machine components for rocket engines.

The obvious advantage of additive manufacturing is that they use generic equipment and common materials as input, without requiring expensive molds as in the case of injection molding, or extensive, wasteful machining of raw materials on a lathe, mill, and similar equipment. All of the manufacturing gets reduced to a 3D model as input, one or more input materials, and the actual device that converts the 3D model into a physical component with very limited waste.

In the nuclear power industry, these benefits haven’t gone unnoticed, which has led to 3D printed parts being developed for everything from keeping existing plants running to streamlining spent fuel reprocessing and even the printing of entire nuclear reactors.

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3D Printering: Sticky Resin Prints And How To Fix Them

June 4, 2020 by Donald Papp 39 Comments

After going through all the trouble of printing a part in resin, discovering it feels sticky or tacky to the touch is pretty unwelcome. Giving the model some extra ultraviolet (UV) curing seems like it should fix the problem, but it probably does not. So, what can be done?

The best thing to do with a sticky print is to immediately re-wash it in clean isopropyl alcohol (IPA) before the UV present in ambient light cures stray resin. If the part remains sticky after it is dry, more aggressive steps can be taken.

We’ll get into those more extreme procedures shortly, but first let’s understand a bit more about how resin works, then look at how that applies to preventing and removing tacky surfaces on finished prints. Continue reading “3D Printering: Sticky Resin Prints And How To Fix Them” →

Cast Metal From Prints To Solidify Childhood Memories

June 1, 2020 by Kristina Panos 32 Comments

As far as the hacker’s toolbox goes, the 3D printer is way up there in terms of utility. Sure, it takes time to learn the ins and outs of designing, slicing, and extruding, but after that, the world is pretty much your additive oyster. Follow those design dreams, or use it to replace the things that break. The icing on the cake? You can chase those dreams into other materials, because 3D prints can be used to cast metal.

[RetroTech Journal] wanted to fry up some rosette cookies, a Scandinavian delight from his youth that look a lot like fancy, personal funnel cakes. They’re made with special aluminium irons that shape the dough while it fries, as opposed to the jumbled chaos that is funnel cake.

Rosette irons come in a few traditional shapes, but once you get tired of those, it’s up to you to cast them in aluminium. And how would you go about doing that? By creating a firmly-packed sand mold using a mounted 3D print.

In the endlessly entertaining video after the break, [RetroTech Journal] takes you through the entire process from CAD to cookies. It has everything you could possibly want: LEGO stop-motion, claymation, a little bit of cooking, and a whole lot of knowledge. We can’t wait to see what comes next.

We’ve seen quite a few sand casting projects over the years, but this lathe is among the most useful.

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Improving 3D Printed Supports With A Marker

May 27, 2020 by Tom Nardi 43 Comments

Anyone who’s spent some quality time with a desktop 3D printer is familiar with the concept of supports. If you’re working with a complex model that has overhanging features, printing a “scaffolding” of support material around it is often required. Unfortunately, supports can be a pain to remove and often leave marks on the finished print that need to be addressed.

Looking to improve the situation, [Tumblebeer] has come up with a very unique modification to the traditional approach that we think is certainly worthy of closer examination. It doesn’t remove the need for support material, but it does make it much easier to remove. The method is cheap, relatively simple to implement, and doesn’t require multiple extruders or filament switching as is the case with something like water-soluble supports.

The trick is to use a permanent marker as a release agent between the top of the support and the area of the print it’s actually touching. The coating of marker prevents the two surfaces from fusing, while still providing the physical support necessary to keep the model from sagging or collapsing.

To test this concept, [Tumblebeer] has outfitted a Prusa i3 MK3S with a solenoid actuated marker holder that hangs off the side of the extruder assembly. The coil is driven from the GPIO pins of a Raspberry Pi running OctoPrint, and is engaged by a custom command in the G-code file. It keeps the marker out of the way during normal printing, and lowers it when its time to lay down the interface coating.

[Tumblebeer] says there’s still a bit of hand-coding involved in this method, and that some automated G-code scripts or a custom slicer plugin could streamline the process considerably. We’re very interested in seeing further community development of this concept, as it seems to hold considerable promise. Having a marker strapped to the side of the extruder might seem complex, but it’s nothing compared to switching out filaments on the fly.

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Mimicking Exoplanet Exploration At Home

May 24, 2020 by Sven Gregori 3 Comments

Mankind will always wonder whether we’re alone in the universe. What is out there? Sure, these past weeks we’ve been increasingly wondering the same about our own, direct proximity, but that’s a different story. Up until two years ago, we had the Kepler space telescope aiding us in our quest for answers by exploring exoplanets within our galaxy. [poblocki1982], who’s been fascinated by space since childhood times, and has recently discovered 3D printing as his new thing, figured there is nothing better than finding a way to combine your hobbies, and built a simplified model version simulating the telescope’s main concept.

The general idea is to detect the slight variation of a star’s brightness when one of its planets passes by it, and use that variation to analyze each planet’s characteristics. He achieves this with an LDR connected to an Arduino, allowing both live reading and logging the data on an SD card. Unfortunately, rocket science isn’t on his list of hobbies yet, so [poblocki1982] has to bring outer space to his home. Using a DC motor to rotate two “planets” of different size, rotation speed, and distance around their “star”, he has the perfect model planetary system that can easily double as a decorative lamp.

Obviously, this isn’t meant to detect actual planets as the real Kepler space telescope did, but to demonstrate the general concept of it, and as such makes this a nice little science experiment. For a more pragmatic use of our own Solar System, [poblocki1982] has recently built this self-calibrating sundial. And if you like rotating models of planets, check out some previous projects on that.

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Conduit, Birdhouse, And Skateboard Become Giant Pen Plotter

May 23, 2020 by Elliot Williams 3 Comments

If you think you need fancy parts to build a giant robot drawing machine, think again! [Cory Collins] shows you how he built his Big-Ass Wall Plotter v.2 out of stuff around the house or the hardware store, including electrical conduit, gang boxes, scrap wood, and skateboard bearings, alongside the necessary stepper motors, drivers, and timing belt. (You should consider having this trio of parts on hand as well, in our opinion.) With a span of 48″ (1.2 m) on a side, you probably don’t have paper that’s this big.

And while the construction is definitely rough-and-ready, there are a ton of details that turn this pile of parts into a beautifully working machine in short order. For instance, making the rails out of electrical conduit has a few advantages. Of course it’s cheap and strong, but the availability of off-the-shelf flanges makes assembly and disassembly easy. It also hangs neatly on the wall courtesy of some rubber cuphooks.

Note also the use of zip-tie belt tensioners: a simple and effective solution that we heartily endorse. [Corey] makes good use of custom 3D printed parts where they matter, like the compliant pen holder and linear mechanism for the z-axis, but most of the mechanical accuracy is courtesy of wooden shims and metal strapping.

[Corey] uses the machine to make patterns for his paper sculptures that are worth a look in their own right, and you can see the machine in action, sped up significantly, in the video below. This is the perfect project if you have a DIY eggbot that’s out of commission post-Easter: it reuses all the same parts, just on a vastly different scale. Heck, [Corey] even uses the same Inkscape Gcodetools extension as we did in that project. Now you know what we’re up to this weekend.

Can’t get enough pen plotters? Check out this one that lets you write whatever you want!

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