Stealing 3D Prints By Sound

In the open hardware world, we like to share 3D design files so that our friends and (global) neighbors can use and improve them. But we’ve all printed things from time to time that we’d like to keep secret. At least this is the premise behind this article in Science which proposes a novel method of 3D-printer-based industrial espionage: by recording the sound of the stepper motors and re-creating the toolpath.

Unfortunately, the article is behind a paywall so we’re short on the details, but everyone who’s played the Imperial March on their steppers has probably got the basic outline in their mind. Detecting the audio peak corresponding to a step pulse should be fairly easy. Disentangling the motions of two axes would be a bit harder, but presumably can be done based on different room-acoustic filtering of the two motors. Direction is the biggest question mark for us, but a stepper probably has a slightly audible glitch when reversing. Keeping track of these reversals could do the trick.

What do you think? Anyone know how they did it? Does someone with access to the full article want to write us up a summary in the comments?

[Thanks LVfire via Ars Technica]

[Edit: We were sent a copy of the full article (thanks [PersonUnknown]!) and it doesn’t explain any technical details at all. Save yourself the effort, and have fun speculating, because reading the article won’t help.]

Error Correction of 3D Printers

From the very first RepRaps to the newest and latest printers off the Makerbot assembly line, nearly every consumer 3D printer has one significant shortcoming: it cannot recover from missed steps, slipped belts, or overheating stepper drivers. Although these are fairly rare problems, it does happen and is purely a product of the closed open-loop control system used in 3D printer firmware.

[Chris Barr] has come up with a rather clever solution to this problem. He’s designed a system that will detect and correct problems with the mechanics of 3D printers. It’s technically not a closed-loop control system, but it does allow him to get the absolute position of a nozzle on the build plate, detects error states, and can automatically calculate the number of motor steps per millimeter. It’s also much simpler than other closed loop control systems we’ve seen in the past, requiring only a few bits and bobs attached to the axes and to the printer controller board.

[Chris]’ system uses a magnetic encoding strip, a single chip, and a little bit of support circuitry. It’s actually not that much different from the moving axis on a desktop inkjet printer. It’s not closed loop, though; the firmware hack is only a ‘basic error correction’ that moves the nozzle back to where it should be. Although this is somewhat of a kludge, it is much simpler than refactoring the entire printer firmware.

In the video below, [Chris] demonstrates his solution for error correcting the printer by jerking his axis around during a print. The nozzle miraculously returns to where it should be, producing a usable part.

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MRRF: Launching an Adorable Printer For Fun

Patrick and Matt hold a running Kitten Printer. The frame is stiff enough that the printer can be held or turned upside down and it can keep printing.
Patrick and Matt hold a running Kitten Printer. The frame is stiff enough that the printer can be held or turned upside down and it can keep printing without visible defects in the print.

[Patrick] and [Matt] have been coming to the Midwest RepRap Festival from Minneapolis for the past few years and bringing their trusty Tantillus printers with them. However, sometime between this year and the last [Patrick] decided that it would be really fun to make his own 3D printer, and liking the size and accuracy of the Tantillus, started there.

The adorably sized printer is adorably named too: Kitten 3D printer. The printer is certainly an enthusiast’s choice. It’s expensive at 1200 and small, but very well made. Its one big advantage?  It prints really accurate parts.

The Tantillus also printed well, but the extruder left a lot to be desired, and the low stretch fishing line movement was very difficult to get tensioned just right. The secret behind the Tantillus and Kitten’s great print quality, aside from good design, is the small xy movement and low weight of the extruder set-ups. By having a movement over a very small range, cumulative errors in construction never get to add up. Also vibrations are less likely to show and smaller moments on the joints mean less flex at the extremes of the movements.

Really stunning print quality almost entirely free of ringing and z-wobble.
Really stunning print quality almost entirely free of ringing and z-wobble. 100mm x 100mm tray. These are very small parts.

[Patrick] is a mechanical engineer for his day job, and since this was a just for fun printer, he cut no corners. The frame is made with Misumi extrusions and linear movements. The build plate sits on a machined aluminum plate. It’s not flexing or going anywhere.

Part of what really stood out to me about the printer are a lot of neat little features which show careful thought. For example, the extruder movement sits neatly under one of the motors. All the parts except for one can be printed inside its build envelope without support. It uses around 200g of plastic. Every axis is constrained just enough, rather than the common tendency to over constrain that plagues 3D printer design. The spec sheet reads like my printer part wishlist: Bondtech extruder, Rambo board, E3d nozzle, heated bed, flat borosilicate build plate, name brand linear movements, and a well designed Z.

cleverdetails
The entire extruder assembly tucks under one of the XY motors at the corner of its movement. Compare its size to the size of a NEMA14 stepper motor.

Another interesting aspect of the design is the extremely light extruder assembly. The lighter an extruder can get, the less ringing will show in your parts at speed. This is one of the most compact designs I’ve witnessed. It consists of two fans, an E3d v6 lite nozzle, and two small linear bearings. The cold end is handled by a bowden set-up and a Bondtech extruder at the back of the printer. The only way to get it lighter would be a different nozzle, such as the upcoming insanely light 13g Pico from B3 unveiled at the festival. I was also interested to see that the bearings on the supporting rails were printed bushings to keep the weight even lower. [nop head] has tested these extensively, they should be fine as long as the rods have a good finish.

I’ve mentioned the size before, but it’s hard to grasp just how adorable this printer is without seeing it. The build envelope is 100mm x 100mm x 100mm, the printer itself is 200mm x 200mm x 240mm. That’s only 50mm wider than the build footprint. It’s a really fun design just to look at and see how they fit it all in there. There are lots of neat little tricks with belt routing and part design to get it all right.

For the enthusiast this would make a good small parts printer and travel printer. However, for me, it was neat to see people still setting out to try designing their own printer. In some ways the 3d printer movement has become crowded with Chinese knock-offs, and I was excited to see something new at the festival. It wasn’t the only new printer design there, but it stood out to me the most. I like the uncompromising nature of it, many people try to design for the lowest BOM and not the nicer print. There are still lots of low-hanging fruit in the 3d printer world and many of them are just getting the mechanics right.

[Patrick] and [Matt] came to the festival with their printer to see if people would like it. They didn’t have grand dreams of selling tons of printers and making millions. They were quite aware that their price point and the small size made it not for everyone. However, their table always had a small crowd. They just really like 3D printers, and that honesty resonated. They didn’t even have a website up at the start of the convention, but by the end they had gotten so many requests they had to oblige. They expect to have 3 kit options available by the end of April. If you’re interested there’s a mailing list sign up on their website. Let’s hope we see them at MRRF again next year with another cool design to look over.

Hackaday Links: March 28, 2016

[Tom] sent this in to be filed under the ‘not a hack’ category, but it’s actually very interesting. It’s the User’s Guide for the Falcon 9 rocket. It includes all the data necessary to put your payload on a Falcon 9 and send it into space. It’s a freakin’ datasheet for a rocket.

A year ago in Japan (and last week worldwide), Nintendo released Pokkén Tournament, a Pokemon fighting game. This game has a new controller, the Pokkén Tournament Pro Pad. There were a few cost-cutting measures in the production of this game pad, and it looks like this controller was supposed to have force feedback and LEDs. If any Pokemon fans want to take this controller apart and install some LEDs and motors just to see what happens, there’s a Hackaday write up in it for you.

There are a lot of options for slicing 3D objects for filament-based 3D printers. Cura, Slic3r, and MatterControl are easily capable of handing all the slicing needs you’ll ever have for a filament 3D printer. For sterolithography (resin) printers, the options for slicing are limited. [skarab] just put together a new slicer for SLA that runs entirely in JavaScript. If anyone wants to turn a Raspi or BeagleBone into a network controller for a resin printer, here’s your starting point. [skarab] will be working on smoothieboard integration soon.

The STM32F4 is an extremely capable ARM microcontroller. It can do VGA at relatively high resolutions, emulate a Game Boy cartridge, and can serve as the engine control unit in a 1996 Ford Aspire. There’s a lot of computing power here, but only one true litmus test: the STM32F4 can run Doom. [floppes] built this implementation of Doom on the STM32F429 Discovery board to run off of an external USB memory stick. The frame rate is at least as good as what it was back in 1993.

The Oculus Rift has just come to pass, but one lucky consumer got his early. The first person to preorder the Rift, [Ross Martin] of Anchorage, Alaska, got his facehugger directly from [Palmer Luckey] in a PR stunt on Saturday afternoon. Guess what [Ross] is doing with his Rift?

rift

Extremely Thorough Formlabs Form 2 Teardown by Bunnie

[Bunnie Huang] recently had the opportunity to do a thorough teardown of the new Formlabs Form 2 printer. It’s a long read, so just head over there and immerse yourself in every detail. If you want the cliff notes, though, read this but still go look at all the pretty pictures.

First, it’s a major upgrade with pretty much every component. The CPU is a huge step up, the interface went from monochrome to full color touch screen, the connectivity has been upgraded with WiFi and Ethernet, the optics are much better and safer, the power supply is integrated, there are lots of little improvements that handle things like bed leveling, calibration, resin stirring, pausing jobs, and resin refilling during a print. Bunnie practically gushes at all the features and impressive engineering that went into the Form 2.

You can compare the teardown of the Form 2 to [Bunnie’s] teardown of the Form 1 printer back in 2013.

MRRF: 3D Printed 2D Paintings

3D printing is obviously best used in printing three-dimensional objects. Laser cutters, jig saws, and CNC routers are obviously well-equipped to machine flat panels with intricate shapes out of plastic sheets, plywood, or metal, but these devices have one drawback: they’re subtractive manufacturing, and 3D printers add material. What good is this? [Jason Preuss] demonstrated a very interesting 3D printing technique at this year’s Midwest RepRap Festival. He’s producing 2D paintings with a 3D printer, with results that look like something between very intricate inlay work and a paint by numbers kit.

[Jason Preuss]' multicolor 2D print. Notice the toolpaths in the reflection. Click to embiggen.
[Jason Preuss]’ multicolor 2D print. Notice the toolpaths in the reflection of the upper left hand corner. Click to embiggen.
[Jason] is using a 3D printer, a series of very specialized techniques, and a software stack that includes a half-dozen programs to print multicolor 2D scenes. This isn’t pigment, paint, dye, or ink; the artwork becomes a single piece of plastic with individual colors laid down one at a time.

The best example of [Jason]’s work is a copy of a paint by numbers scene. Here, [Jason] makes an outline of all the shapes, separates onto different layers by color, and prints each color, one layer at a time. It’s an incredibly labor-intensive process to even get models into a slicer. Actually printing the model is even more difficult. [Jason]’s paint by numbers scene uses about twelve different colors.

[Jason]'s 3D printed paint by numbers scene. About a dozen different colors were used for this print.
[Jason]’s 3D printed paint by numbers scene. About a dozen different colors were used for this print.
We’ve seen [Jason]’s work at MRRF before, including last year’s exhibition of a fantastic chocolate clock that was a 3D printed version of an old scroll saw pattern. Taking what is normally a 2D design and translating that into something that can be built with a 3D printer seems to be [Jason]’s forte, and the results are remarkable. If you don’t know what you were looking at, you would just think these art pieces are a strange industrial fabrication process. Once you look closer, you have an immediate respect for the artistry and craftsmanship that went into a sheet of plastic only a few millimeters thick and no bigger than a piece of paper.

[Jason] hasn’t documented his build process for these 2D pictures on a 3D printer quite yet. There’s a reason for that: it’s supposedly very complicated, and it’s going to take a while to get all the documentation together. Eventually, the process will be documented and a tutorial will pop up on [Jason]’s website. He’s also on Thingiverse, with a few semi-related designs available for download.

From what we’ve seen at MRRF, in the next few years, a dual extrusion printer will be a necessity. While dual extrusion won’t be able to recreate such colorful pictures, it will make the creation of these 2D plastic panels much easier, and they will surely be popular. We can’t wait to see what [Jason] comes up with next.

Tiny Open Source Robot

We watched the video introduction for this little open source robot, and while we’re not 100% sure we want tiny glowing eyes watching us while we sleep, it does seem to be a nice little platform for hacking. The robot is a side project of [Matthew], who’s studying for a degree in Information Science.

The robot has little actuated grippy arms for holding a cell phone in the front. When it’t not holding a cellphone it can use its two little ultrasonic senors to run around without bumping into things. We like the passive balancing used on the robot. Rather than having a complicated self-balancing set-up, the robot just uses little ball casters to provide the other righting points of contact.

The head of the robot has plenty of space for whatever flavor of Arduino you prefer. A few hours of 3D printing and some vitamins is all you need to have a little robot shadow lurking in your room. Video after the break.

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