Laser sintering works by laying down a thin layer of metal powder and then hitting it with a strong enough laser to sinter the particles together. (Sintering sticks the grains together without getting the metal hot enough to melt it.) The rapid local heating and cooling required to build up 3D objects expands and cools the metal, and can result in stresses inside the resulting object.
The Northwestern team still lays down layers of powder, but glues the layers together with a quick-drying polymer instead of fusing them with a laser. Once the full model is printed, they then sinter it in one piece in an oven.
The advantages of adding this extra step are higher printing speed — squirting the liquid out of syringe heads can be faster than fusing metal particles with a laser — and increased structural integrity because the whole model is heated and cooled at one time. A fringe benefit is that the model is still a bit flexible before firing, opening up possibilities for printing a flat model and then bending it into shape before sintering.
And if that weren’t enough, the team figured that they’d add a third step to the procedure to allow it to be used with rust (iron oxide) as the starting powder. They print the rust and polymer model, then un-rust the iron using hydrogen, and then fire it as before. Why rust? Do you know anything cheaper to use as a raw material?
What do you think? The basic idea may even be DIYable — glue metal particles together and heat them up enough to stick. Not in my microwave oven, though. We’d love to see a more energy-efficient 3D metal printer.
Almost exactly two years ago, news of a great revolution in 3D printing carried itself through blogs and tech columns. Patents were expiring, and soon the ‘squirting filament’ printers would be overtaken by a vastly better method: selective laser sintering. In the last two years, the market has been markedly silent on the possibilities of SLS technology, until now, at least. Today, Sinterit is launching their first printer. It’s an SLS printer that builds objects by fusing nylon powder with a laser, producing things with much better quality than filament-based printers.
The Sinterit Lisa is a true laser sintering printer, able to create objects by blasting nylon powder with a 5W laser diode. Inside this box that’s about the same size as a laser printer is a CoreXY mechanism to move the laser diode around, heated pistons, cylinders, feed bed and print bed for keeping the print volume at the right temperature and the top layer perfectly flat. The layer thickness of the printer goes down to 0.06 mm, and the maximum print size is 13 x 17 x 13 cm. Material choice is, for now, limited to black PA12 nylon but other materials are being tested.
Filament printers are here to stay, and in the past year there have been a number of SLA and DLP resin printers that can create objects at mind-boggling high resolutions. Both of these technologies have their place, but printing really complex objects without also printing supports is out of the question.
[Brandon] has been working to create an open source printer using a different technology, selective laser sintering. That’s a laser melting tiny particles of stuff to create an object. This printer can work with any material that can be turned into a powder and melted by a laser, and also has the neat bonus of printing without any supports.
[Brandon]’s printer, Ester, uses small meltable polyester dust as both a print material and support structure. The object to be printed is created by shining a laser over a bed filled with polyester, drawing one layer, and putting another small layer of material over the previous layer.
The machine is using a diode laser, with a few experiments with a 1 Watt diode providing some very nice parts. The mechanics of the machine were built at [Brandon]’s local TechShop, and already he has an IndieGoGo for future development and a $3000 development kit. That’s a bit expensive as far as project printers go, but SLS is an expensive technology to get right; ‘pro’ SLS printers are in the hundreds of thousands of dollars.
Unlike just about every other inexpensive 3D printer, [Andreas]’ design doesn’t rely on either squirting plastic onto a bed or curing liquid resin with UV light. Instead, a fine layer of powder is spread over a build platform and melted with a laser. The melted layer drops down, another layer of powder is applied, and the cycle repeats until the part is finished. It’s a challenge to build one of these machines, but [Andreas] had the great idea of retrofitting an off-the-shelf laser cutter, allowing him to focus on the difficult task of designing the powder and piston system.
It’s an extremely interesting project, and most of the custom parts are made from laser cut acrylic: easily cut to size on whatever laser cutter you’re retrofitting with 3D printing capability. There’s a lot of info over on the Wiki, and a few videos showing the sintering process and powder distribution below.
Oh. One last note. [Andreas] developed this while at [Jordan Miller]’s amazing lab at Rice University. There’s a lot of interesting things happening at this Advanced Manufacturing Research Institute, including bioprinting, DLP resin printers, and using inkjets for cell cultures. Check out this post for a great talk at the Midwest RepRap Festival.
We’re not sure how we missed this one, but it definitely deserves a look. Professor of Mechtronics [Olaf Diegel’s] 3D printer must go to 12, because he’s printed these incredible electric guitar bodies. You probably won’t be making your own on your filament printer, however, because [Diegel] uses SLS (Selective Laser Sintering) to create the body out of nylon, then he dyes the resulting piece in a two-step process. You can read more about the construction specifics on his website.
And, they’re more than just eye-candy: the guitars sound brilliantly metallic. There are more than enough pictures and videos to keep you occupied on the site, where you can sift through all eight designs to your heart’s content. You’ll want to keep reading for a couple of videos embedded after the break, which feature some demonstrations of the guitar and comparisons to traditional electric guitars, as well as a brief history of its construction and build process.
Meet pwdr, the open source 3D printer that is a complete departure from the RepRaps and Makerbots we’ve come to love.
Instead of squirting plastic onto a build surface, pwdr operates just like the very, very expensive powder printers used in industrial settings. Pwdr uses gypsum, ceramics, and concrete for its raw stock and binds these powder granules together with water deposited from an inkjet cartridge.
Inside pwdr there are two bins, one for storing the raw material and another for building the part. The part to be printed is built one layer at a time, just like your regular desktop printer. After each layer is finished, a counter-rotating drum scrapes the raw material over the build area and another layer is printed.
There are a lot of advantages to pwdr versus the melted plastic method of printing used in the Makerbot; because each build is self-supporting, it’s possible to print objects that just couldn’t be made with an extruder-based printer. Pwdr also supports laser sintering, meaning it’s possible for pwdr to make objects out of ABS, Nylon, and even metal.
Right now, pwdr is still in the very early stages of development, but you can build your own powder printer from the files up on Thingiverse. Check out the video of pwdr printing after the break.
We covet laser cutters and this diy model with a 1 Watt IR diode may be well within our price range. Most commercially available laser cutters, and some homemade ones, work in the 20-100 Watt ranges, using a CO2 laser. They have more than enough power to cut right through a lot of materials so how can a 1W diode compare? It seems that the weaker laser is still quite powerful right at its focal length, so moving that point along the Z axis will let you burn away a larger depth of material. The test rig seen above uses optical drive components for the three axes and managed to cut a rectangular piece out of the black plastic from a CD case.