Sep 22, 2016 | By Alec
In the right hands, 3D printers are fantastically versatile and can construct virtually anything that fits on the build plate. Anything, that is, made from materials that are 3D printable. And that highlights the main limitation of 3D printing, as other manufacturing techniques have access to a far greater range of building materials. But as hacker and veteran maker Adam kumpf of Makefast has reminded us, even this 3D printable material limitation can be overcome. Through a series of clever hacks, he has actually encapsulated liquids, sand and metal components into 3D printed objects, combining their attractive properties with the accessibility of 3D printing.
The benefits of these kinds of hybrid 3D prints are obvious: they can provide greater strength or even embed functions into hitherto mundane objects. It’s also something many makers rely on without even knowing it; even making room for a hex nut pocket relies on a hybrid principle. But veteran engineer Adam takes it even further, relying on his extensive making background. Before showcasing his abilities at Makefast, he studied at MIT and received three degrees in Electrical Engineering & Computer Science and Media Arts & Sciences, and designed instruments and objects at Fiddlewax, The Chaos Collective and Teague.
As he explains, enabling the complete encapsulation of external and loose materials relies on the ability to pause prints mid-way – something which many maker-style 3D printers are capable of. “There are hot elements, electronics, and rapidly moving parts, so BE CAREFUL. That said, [the 3D printers’] open designs mean you can pause a print mid-way and hack not only the printer itself, but also the final outcome of the printed part,” he says.
Hack #1 – 3D printing with liquids
The opportunities this creates are showcased by three separate projects, of which the first is the most mind-boggling of all: a 3D printed can chiller. A can chiller relies on a cooling material that doesn’t freeze, so Adam designed a can holder that can store concentrated salt water. Thanks to its high salt content of 23 grams of salt mixed with 77 grams water, it won’t freeze (and thus expand and possibly tear the print) until reaching -21 degrees Celcius – making it compatible with most freezers.
The 3D print designed for this hack is fairly basic, essentially consisting of a beer cozy with an hollow area that can hold the salty liquid. Stopped halfway through 3D printing, the liquid is poured in. If properly programmed to prevent marks upon resumption, the water should be perfectly encapsulated within once 3D printing is completed. The model itself can be found on Thingiverse here.
But working with water is fairly dangerous – as any spills can immediately fry your 3D printer. That means keeping plenty of paper towels nearby and being constantly vigilant. “You can also build a dam around your part with modeling clay before filling it just in case the print has a hole and things get wet in a hurry,” Adam advises. It also means being very careful when pouring in the liquid, preferably with a tool that gives you plenty of control. Even when being careful, however, sloshing can run everything and we’ve all seen how quickly prints can move from one place to another. That means leaving ample room near the top of your print to catch any spills. Also keep an eye on your bed temperature to prevent boiling or combustion, depending on the liquid material you use.
Adam experienced another problem as well, one that scares off many industrial manufacturers: microscopic leakage. While 3D prints obviously appear to be rock solid, minor variations in temperature, humidity and material can cause gaps thinner than a hair’s width. Adam himself found three or four of these pinhole leaks, and eventually patched them with hot glue. Nonetheless, it adds an additional layer of stress to working with liquids.
Hack #2 – 3D printing with sand
Fortunately, the second hack suffers from fewer pitfalls, while bringing significant time-saving opportunities to the table. Taking the same hollow 3D printing approach, Adam instead filled the gaps with sand this time. Perfect for cutting down on material expenses and production times, while also adding plenty of much sought-after weight to any object.
But it also makes sound when shaken, and this is perfectly illustrated by this cool 3D printed maraca. “As with the liquid filled can chiller, the process was pretty straightforward: just print up to a certain height, pause the printer, add sand, then resume,” Adam said of the project. “Overall the results are pretty much as expected, except for a prominent line between the layers where the print was paused/resumed.” The STL files for this cool toy can be found on Thingiverse here.
But the maraca wasn’t without its challenges either. Pausing any print can let layers cool down too much, creating adhesion issues and poor aesthetic results when resuming the print. This can best be overcome by pre-heating the sand (on the printbed, for instance) and by filling as quickly as possible. “The difference between using room temperature sand and pre-heated sand is pretty significant in terms of shrinkage due to cooling. The second maraca we made (right) is much more structurally sound due to pre-heating and minimizing fill time,” Adam says of the experience.
Hack #3 – 3D printing with metal
The third and final hack is much closer to home already, as it essentially builds on the concept of providing room for hex nut pockets. But Adam takes it even further to the field of ball bearings, which paves the way for a very wide range of actually movable parts. Of course ball bearings and 3D printing have been brought together in the past, mostly in the form of 3D printed balls. While cool and illustrative for the power of industrial 3D printers, creating spherical balls that roll as smoothly as necessary is another matter.
Adam therefore elected to design bearings that can be paused mid-print for the insertion of little mass-produced metal balls – creating embedded ball bearings that can be used for a variety of subsequent projects. Most importantly, it ensures that the balls glide very smoothly. Achieving that obviously requires very tight design tolerances that leave very very little wiggle room. “That means a lot of trial and error, creating offsets in the dimensions for the CAD model so that when the part prints it will ultimately be the intended size,” he says. Ultimately, they used colorFabb’s nGen filament for the parts visible here, while the ball bearing files can be found on Thingiverse.
Again layer adhesion is a clear issue and seems to be the overarching problem for these hacks. Adhesion can be problematic on any regular print, but even more so when starting/stopping prints to insert the balls or any other material. In this particular case, Adam found it possible to therefore simply slow down feed rate to 10 or 20 percent of the normal speed, and add the balls during printing. Nerve racking and dangerous (avoid that hot plastic!) – but prevents the need for stopping. “On the upside, the slow-down technique produces some incredible looking parts where the insertion layer looks like all the others with the expected bonding properties,” he says.
While all three hacks therefore require quite a bit of ingenuity, they certainly pave the way for a whole new spectrum of functional and practical 3D prints. So much is possible once the pausing obstacle can be consistently overcome, and Adam’s achievements inspire more experimentation.
Posted in 3D Printing Technology
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