3D Internal Structure For Better 3D Printed Objects

Makerbot is in the gutter, 3D Systems and Stratasys stock is only a shadow of their 2014 glory, but this is the best year 3D printing has ever had. Machines are now good and cheap, there’s a variety of various thermoplastic filaments, and printing useful objects – instead of just plastic trinkets – is becoming commonplace.

Gradient-Grid
The standard rectilinear infill from Slic3r

There’s one area of 3D printing that hasn’t seen as much progress, and it’s the software stack. Slicing, the process of turning a 3D object into a Gcode file for a printer has been basically the same for the last few years. Dual extrusion is still a mess, and automated bed leveling is still in its infancy.

One aspect of slicing that has been severely overlooked is infill. Obviously, you don’t want to print plastic trinkets completely solid – only the outside surface matters, and a part with 100% infill is just a waste of plastic. Different slicers have come up with different ways of filling the inside of a print, usually with a grid of squares, triangles, or hexagons.

While the most popular methods of filling in a 3D printed objects do the job of adding a little bit of strength to a print and supporting the top layers of a print, it’s not an ideal solution. The desired strength of the finished part is never taken into account, print artifacts are sometimes visible through the side of a print, and the spacing of the infill grid is completely arbitrary. You can only set a percentage of infill, and telling a slicer to make an internal support grid with 10mm spacing is impossible.

Type A Machines just changed all of this. With the release of their public beta of Cura Type A, the infill for a 3D printed part is also 3D. The dimensions of the infill are predictable, opening the door to stronger and better looking parts.

From the Type A press literature and white paper, this new type of ‘infill’ isn’t; it’s more properly referred to as ‘internal structure’, with proper dimensions between infill features. Instead of a grid of squares or triangles stacked one layer on top of each other, it’s a true structure, with the infill following the perimeter of the 3D printed object.

Generating 3D Infill

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Infill generated from Type A Machine’s Cura beta. Note the 3D structure of the infill.

Right now, infill is generated in a slicer by specifying a percentage. Zero percent infill means a hollow object, and 100% infill is a completely solid part. These two edge cases are easy, but anything else means the slicer must fill the part with filament in a grid of tessellating shapes, either rectangles, triangles, or hexagons. With current slicers, the dimensions of this internal structure are, for all practical purposes, random. Printing an object with 20% infill might mean a grid of squares with 5mm or 2mm spacing. Telling the slicer to infill a part with a grid of squares spaced 10mm apart is impossible.

Type A Machine’s latest Cura release changes all of this, allowing a designer to set a precise distance between rows and columns of infill. By defining infill in absolute dimensions, this allows for stronger parts using less infill.

Absolute dimensioning is only one feature of the Type A Machine’s latest release of Cura. Even more exciting is the development of 3D internal structure. Instead of stacking layers of squares, triangles, or hexagons on top of each other, Type A Machine’s Cura uses an infill of cubes turned on their side. While each individual layer of infill looks like a series of triangles and irregular hexagons, when assembled into a printed 3D object, this infill forms a true 3D structure.

The closest comparison to this sort of structure is the difference between graphite and diamond. Both of these materials are made out of the same element, carbon. The physical structure of graphite is just, 1-atom-thick layers of graphene, producing a relatively weak material. Diamond, on the other hand, has a true 3D structure and is one of the hardest materials known to man. While adding 3D structure to the infill of 3D printed objects won’t make the objects any stronger, it will drastically reduce delamination, and be much more resistant to stresses in all three dimensions.

While Type A Machines has done some great work here, it does mean there’s yet another version of Cura to deal with. Type A Machine’s Cura, in addition to the LulzBot edition and the original are now the defacto standard for turning 3D objects into printed parts. Having an open source solution is great, but forking the development this much surely can’t be ideal.

The Hacker is The Future of the Prosthetic: Hackers Helping Those In Need

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Even the city’s welcome sign is held high by two prosthetic arms.

In the show Full Metal Alchemist, there’s a city called Rush Valley whose main and only business are the high performance prostheses called Automail. Engineers roam the street in Rush Valley; the best have their own shop like that of the high-end clothiers in Saville Row. Of course; it’s all fantasy set in a slightly ridiculous Japanese cartoon, but while walking through this year’s Maker Faire I began to wonder if is a future that may come to be.

The problem with prosthetics is the sheer variety of injuries, body types, and solutions needed. If an injury is an inch higher or an inch lower it can have a big effect on how a prosthetic will interact with the limb. If the skin is damaged or the nerves no longer function a different type of prosthesis will be needed. Some prostheses are to replace a lost limb, others are to assist an ailing body in order to return it to normal function. More than a few are simply temporary aides to help the body along in its healing efforts. Unfortunately, this means that it’s often the case that larger companies only sell the prostheses people are most likely to need; the rarer cases are often left without a solution.

The e-Nable project doesn't mess around.
The e-Nable project doesn’t mess around.

However, we see hackers stepping up and not just working on the problems, but solving them. One of our semifinalists last year, openbionics, inspired one of the projects we’ll be talking about later. There are robotic legs. We met a guy at MRRF who has been 3D printing hands for his son from the E-nable project.

Along these lines, we saw two really cool projects at Maker Faire this year: The first is the Motor-Assistive Glove, or MAG. MAG is designed to help people with Peripheral Neropathy regain some use of their hands while they go through the lengthy road to recovery. Perhipheral Neuropathy is a disease, usually resulting from diabetes, toxin exposure, or infection, where the nerves are damaged in such a way that typically the hands and feet are no longer mobile or feel sensation in a useful way. Once the disease is in full swing, a previously able person will find themselves unable to do simple things like hold a can of soda or grasp a doorknob firmly enough to open it.

The Motor Assistive Glove
The Motor Assistive Glove

We had a chance to interview one of the members of the MAG team, [Victor Ardulov], which you can see in the following video. [Victor] and his group started a research project at the University of Santa Cruz to develop the Motor-Assistive Glove. The concept behind it is simple. People with Peripheral Neuropathy typically have some movement in their hands, but no strength. The MAG has some pressure sensors at the tips of the fingers. When the user puts pressure on the pad; the glove closes that finger. When the pressure is off; the glove opens. The concept is simple, but the path to something usable is a long one.

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Hexapod Tank from Ghost in the Shell Brought to Life

Every now and then someone gets seriously inspired, and that urge just doesn’t go away until something gets created. For [Paulius Liekis], it led to creating a roughly 1:20 scale version of the T08A2 Hexapod “Spider” Tank from the movie Ghost in the Shell. As the he puts it, “[T]his was something that I wanted to build for a long time and I just had to get it out of my system.” It uses two Raspberry Pi computers, 28 servo motors, and required over 250 hours of 3D printing for all the meticulously modeled pieces – and even more than that for polishing, filing, painting, and other finishing work on the pieces after they were printed. The paint job is spectacular, with great-looking wear and tear. It’s even better seeing it in motion — see the video embedded below.

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Feeding The Cat, Reinventing the Wheel

There are few projects that we see as many iterations of as the pet feeder or the plant waterer. (What is it with you people? Are you all as forgetful as we are?) Still, the fun is in the details of the implementation. Or at least that’s the case with [Emmaanuel]’s cat feeder.

The writeup is split into three parts: the worm-drive, the electronics, and the housing (here in English: worm, electronics, housing). And of course, there’s a video inlined below.

The auger and motor housing make great use of PVC pipe and 3D printing, and the dispenser unit looks quite professional. There’s not all that much to say about the electronics — an Arduino clone, an LCD, and a cheap gear motor do just about what you’d expect.

The CNC’ed case with spring-fit tabs steals the show, however. It’s made out of MDF, which doesn’t take well to screwing or glueing. With carefully routed pins and tabs that have a little spring in them, [Emmaanuel] was able to take the pieces off the mill table and just snap them together. Awesome.

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Sweet 3D Printer

Dylan’s Candy Bar is an upscale sweet shop in Manhattan. In a stunning proof that 3D printing has become buzzword-worthy, they’ve announced a deal with Katjes Magic Candy Factory to bring four 3D gummy printers to the US (specifically, to New York, Chicago, Los Angeles, and Miami).

The device looks a bit like a classic 3D printer, but it extrudes eight different gummis in a variety of flavors. The store offers twenty designs but you can also print text or your own drawings (including, apparently, your face).

Each creation costs about $20. Time will tell if this is just a stunt, or if we are going to see food printers cropping up at a mall near you. You can see a video they posted to Twitter below along with a video from the product roll out of the printer in question.

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Super Strong 3D Component Carbon Fiber Parts

[prubeš] shows that parts printed with carbon fiber filament are as strong, or at least as stiff, as you’d expect. He then shows that his method for producing carbon fiber parts with a mixture of traditional lay-up and 3D printing is even stronger and lighter.

[prubeš] appears to be into the OpenR/C project and quadcopters. These things require light and strong parts for maximum performance. He managed to get strength with carbon fiber fill filament, but the parts weren’t light enough. Then he saw [RichMac]’s work on Thingiverse. [RichMac] designed parts with pre-planned grooves in which he ran regular carbon fiber tow with epoxy. This produced some incredibly strong parts. There’s a section in his example video, viewable after the break, where he tests a T joint. Even though the plastic starts to fail underneath the carbon fiber, the joint is still strong enough that the aluminum tube inside of it fails first.

[prubeš] innovation on [RichMac]’s method is to remove as much of the plastic from the method as possible. He designs only the connection points of the part, and then designs a 3D printable frame to hold them in place. After he has those in hand, he winds the tow around the parts in a sometimes predetermined path. The epoxy cures onto the 3D print creating a strong mounting location and the woven carbon fiber provides the strength.

His final parts are stronger than 100% infill carbon fill prints, but weighs 8g instead of 12g.  For a quadcopter this kind of saving can add up fast.

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Hacklet 107 – 3D Printing Projects

3D printers have forever changed the hardware hacker movement. From the original RepRap project on up through current commercial offerings, 3D printers have become an indispensable tool for hackers, makers, and engineers. While printers may not have started a desktop manufacturing revolution, they are a desktop prototyping evolution. It’s rare for a day to go by on Hackaday without a project that uses a 3D printed part in some way shape or form. These printers also continue to evolve, with new projects pushing the technology ever forward. This week’s Hacklet is all about some of the best 3D printer projects on Hackaday.io!

reprapWe start with [TTN] and Icepick Delta. [TTN’s] passion is creating 3D printers as cheaply as possible. The Icepick definitely succeeds at this. Icepick’s frame is made of wood. The motors are commodity steppers. Control is via the long proven Ramps 1.4 board, which can be picked up with drivers and an Arduino Mega clone for under $35 these days. A few ball bearings and metal parts fill out the vitamins of this design. Just about everything else is 3D printed in true RepRap style. The printer is currently running Marlin firmware, but [TTN] plans to move to Repetier in the future.

Even with these humble origins, Icepick manages to print at a very respectable 50 mm/s before frame flex becomes a problem.  Prints at 0.1mm layer height look great, on par with any current commercial printer.

strataNext up is  [Machinist] with 3D printer brain retrofit. Commercial 3D printers have been available for decades now. This means some of the older models are getting a bit long in the tooth. [Machinist] has a very tired 15 year old Stratasys Dimension 768. The mechanics of the Dimension are still in good shape, but the electronics have seen better days. [Machinist] is ditching all the old electronic hardware (and the DRM which goes with it) and setting this machine up with a Smoothieboard 5X. So far the Dimension has been gutted, and [Machinist] has gotten the monster stepper motors playing sweet music with his new control board. I can’t wait to see how this project progresses.

coffeeNext we have [jcchurch’s] Coffee Maker Delta 3D Printer. [jcchurch] has managed to convert an old Norelco coffee maker into a mini sized 3D printer. The warmer plate has even become a heated bed for ABS prints. Unlike Icepick up top, the aim of this design is to use as few 3D printed parts as possible. The idea is that this would be the first printer to build when you don’t have another printer handy. Think of it as a caffeinated RepStrap. According to [jcchurch], this printer has been running strong at Tropical Labs for over a year. You can even pull the delta assembly off and make a pot of coffee! The coffee maker printer is still somewhat of a teaser project. If you see [jcchurch] online, tell him to head over and give us more details!

linearFinally, we have [DeepSOIC] with linear stepper motor 3d printer. 3D printers all use good old fashioned rotary stepper motors. [DeepSOIC] is trying to eliminate all that rotary motion, along with the belts and pulleys required to convert to linear motion. Linear stepper motors can be thought of as regular stepper motors, just unrolled. They tend to be very expensive though, so [DeepSOIC] is building DIY versions. His first attempt was to print motor parts using BlackMagic3D’s ferromagnetic filament. This lead to a whole separate project to measure the permeability of the filament. Unfortunately, the filament isn’t permeable enough to act as a motor for a printer. [DeepSOIC] hasn’t given up though. This is the type of project we love – one that might not work out, but really gets people thinking. Check out the comment thread on the project to see Hackaday.io collaboration at work!

If you want to see more 3D printer projects, check out our updated 3D printer list! If I didn’t wake up early enough to catch your project, don’t be shy, just drop me a message on Hackaday.io. That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!