Visual 3D Print Finishing Guide

With 3D printers now dropping to record low prices, more and more people are getting on the additive manufacturing bandwagon. As a long time believer in consumer-level desktop 3D printing, this is a very exciting time for me; the creativity coming out of places like Thingiverse or the 3D printing communities on Reddit is absolutely incredible. But the realist in me knows that despite what slick promotional material from the manufacturers may lead you to believe, these aren’t Star Trek-level replicators. What comes out of these machines is often riddled with imperfections (from small to soul crushing), and can require considerable cleanup work before they start to look like finished pieces.

If all you hope to get out of your 3D printer are some decent toy boats and some low-poly Pokemon, then have no fear. Even the most finicky of cheap printers can pump those out all day. But if you’re looking to build display pieces, cosplay props, or even prototypes that are worth showing to investors, you’ve got some work cut out for you.

With time, patience, and a few commercial products, you can accomplish the ultimate goal: turning a 3D printed object into something that doesn’t look like it was 3D printed. For the purposes of this demonstration I’ll be creating a replica of the mobile emitter used by the “Emergency Medical Hologram” in Star Trek: Voyager. I can neither confirm nor deny I selected this example due to the fact that I’m currently re-watching Voyager on Netflix. Let’s make it look good.

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Less Than Production, More than One-Offs

We build things we think are cool. Sometimes, other people agree with us and they want a copy of what we’ve built. If you’re lucky enough to have an enviable product but you’re not ready for full-scale manufacturing, you may be looking at a low-volume production run. [Eric Strebel] walks us through one such instance where he makes some custom color swatches for a show. Video after the break.

[Eric Strebel] is an industrial designer so he plays to his strengths by designing the swatch shape, jig, tool, and hangers. He hires out the painting, laser cutting, and CNC machining. This may seem like a simple statement but some of us have a hard time paying other people for things we’re capable of learning. In some cases, we just have to pay the professionals to do it correctly and keep our focus.

The mentality of small runs in this video is perfect for people who sell on Tindie or want to make more than a handful of consistently nice parts. Our own [Lewin Day] recently talked about his experience with a run of 200 mixers called gMix.

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Lathe Turns the Corner, Makes a Cube

[Tim] was tired of using his lathe to turn round things. He decided to make a gaming die—something that’s iconically square—out of cylindrical scrap. As it turns out, this is possible to do on a lathe with a three jaw chuck. [Tim] discovered that the bevel on the jaws will hold a cylindrical puck of scrap sideways while he squares off the round sides into faces.

Turning a cube on a lathe looks pretty fiddly, so we applaud [Tim]’s lovely handiwork even more. As you’ll see in the video down below, things were going gangbusters until he went to make the last facing cut. Maybe the tool wasn’t lined up just so, or something was off in the chucking, but the first pass made a bit of a gouge in the stock. Looks like it was easy enough to fix, though. After four 90° turns and facing cuts, he had a nice looking rough cube to work with.

This is a regulation-sized die, so the next step was to trim it down to 16mm³. Then it was time to sand, polish, and add the dots. To lay them out, [Tim] sprayed the cube with layout fluid and scribed unique line patterns on each face. Then he drilled the indentations and filled them in with aluminium black.

Most of the dice we see are electronic, like this extremely random pair and these PIC-driven LED dice. We’d like to see [Tim] make a second D6 so he has a pair. And then make a D20. Please?

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Stop Motion with the Time Glove

What do you get when you put an ultra-bright LED in the palm of a glove, and strobe it controlled by an accelerometer? A Time Control Glove! In creator [MadGyver]’s own words, it’s “just a stroboscope with frequency adjustment” but the effect is where all the fun is.

The Time Control Glove uses the stroboscopic effect, which many of us have seen used in timeless water drop fountains where the strobe rate makes drops appear to change speed, freeze in place, and even change direction. [MadGyver] made the entire assembly portable by putting it into a glove. An on-board accelerometer toggles the strobe in response to a shake, and the frequency is changed by twisting the glove left or right. The immediate visual feedback to the physical motions is great. The whole effect is really striking on the video, which is embedded below.

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Laser Levitation With Scrap Parts

After a year away from YouTube, the ever-energetic [Styropyro] has returned with whiteboard in hand to remind us just how little we actually know about lasers. In the last month he’s really hit the ground running with plenty of new content, but one video of his particularly stands out: a practical demonstration of laser levitation. Even better, unlike most of his projects, it looks like we can replicate this one without killing ourselves or burning our house down!

For those unaware, laser levitation is probably as close as we’ll get to Star Trek-style tractor beams in our lifetimes. In fact, the NASA Innovative Advanced Concepts program has been examining using the technology for capturing small particles in space, since it would allow sample collection without the risk of physical contamination. While the demonstration [Styropyro] performs lacks the “tractor” part of the equation (in other word’s, there’s no way to move the particle along the length of the beam) it does make us hopeful that this type of technology is not completely outside the reach of our home labs.

The trick seems to be with the focus of the laser beam itself. Your average laser pointer just doesn’t have the appropriate beam for this kind of work, but with a diode pulled from a DVD burner and a driver circuit made from parts out of the junk bin, the effect can be demonstrated very easily as long as you can keep the air in the room extremely still. Of course, what you’re trying to pick up is also very important, [Styropyro] has found that synthetic diamond powder works exceptionally well for this experiment. At about $1.60 a gram, it won’t break the bank either.

So how does it work? With a few trips to the aforementioned white board, Professor Pyro explains that the effect we’re seeing is actually electromagnetic. If the particle you want to levitate is small enough it will become polarized by the light, which is in itself an electromagnetic wave. Once you’ve got your mind wrapped around that, it logically follows that the levitating particle will experience the Lorentz force. Long story short, the particle is suspended in the air for the same reason that a projectile is ejected from a rail gun: if you’ve got enough power and the mass of the object is low enough, there will be an observable force.

We’ve been covering the work of [Styropyro] for years now, and are glad to see him back on YouTube creating new content and terrifying a new generation of viewers. Between this and the return of [Jeri Ellsworth], it’s like we’re experiencing a YouTube hacker Renaissance.

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Go From Resin Caster to Resin Master

When it comes to resin casting, time is of the essence. It helps to gather everything you’ll need and have it within reach before starting. But if you don’t know what you don’t know, it can be difficult to anticipate needs. Luckily, [Botzen Design] has a few tricks up his sleeve that will save time, materials, and sanity for novices and old hands alike.

It may seem somewhat obvious to mix up resin in a disposable or reusable plastic cup. But not all cups are created equal. Polypropylene cups won’t outgas into your resin, but polystyrene will. If you use a silicone cup or any polypropylene food container marked #5/PP, cured resin will peel cleanly off of the cup walls.

For some reason, the giant jugs of resin [Botzen Design] uses don’t come with pumps. How do they expect someone to meter out exact amounts of resin and hardener while pouring them out of gallon jugs? Stadium-style condiment pumps at a restaurant supply store make things much simpler while avoiding costly spillage.

Our favorite tip (and seemingly [Botzen Design]’s as well) is the drip hammer. When air bubbles mature into craters, they can be filled easily and precisely with a drop or two of wet resin. A pipette would probably just get clogged, but an icicle of cured resin hanging from a stick makes the perfect drip applicator.

Want to get into resin casting but don’t know where to start? Hackaday’s own [Gerrit] has you more than covered.

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Mendocino Motor Drives Cubicle Conversations

Mendocino motors are solar-powered electric motors that rely on pseudo-levitation.  The levitation comes from magnets mounted on either end of the shaft, which repel same-field magnets fixed below them into the base.  When light shines on the solar panels, current flows through connected magnet wire windings, creating an electromagnetic field that interacts with a large stationary magnet mounted underneath. These constantly repelling forces spin the shaft, and the gaps between the solar panels provide the on-off cycle needed to make it spin 360°.

As [Konstantin] discovered, building this simple motor and getting it to spin depends on a lot of factors. The number of windings, the weight of each solar panel, and the magnet sizes all figure in. [Konstantin]’s struggles are your gain, however. His Instructable takes the guesswork out of the tolerances and he designed a nice, open-source 3D-printed structure to boot.

You’re right, these motors can’t do much work. But it would definitely look cool on your desk and might even start a conversation or two. If not, whip up this little electromagnetic train.

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