The 3D printers we’re most familiar with use the fused deposition process, in which hot plastic is squirted out of a nozzle, to build up parts on a layer by layer basis. We’ve also seen stereolithography printers, such as the Form 2, which use a projector and a special resin to produce parts, again in a layer-by-layer method. However, a team from the University of North Carolina were inspired by CT scanners, and came up with a novel method for producing 3D printed parts.
The technique is known as Computed Axial Lithography. The team describe the system as working like a CT scan in reverse. The 3D model geometry is created, and then a series of 2D images are created by rotating the part about the vertical axis. These 2D images are then projected into a cylindrical container of photosensitive resin, which rotates during the process. Rather than building the part out of a series of layers in the Z-axis, instead the part is built from a series of axial slices as the cylinder rotates.
The parts produced have the benefit of a smooth surface finish and are remarkably transparent. The team printed a variety of test objects, including a replica of the famous Thinker sculpture, as well as a replica of a human jaw. Particularly interesting is the capability to make prints which enclose existing objects, demonstrated with a screwdriver handle enclosing the existing steel shank.
It’s a technique which could likely be reproduced by resourceful makers, assuming the correct resin isn’t too hard to come by. The resin market is hotting up, with Prusa announcing new products at a recent Makerfaire. We’re excited to see what comes next, particularly as the high cost of resin is reduced by economies of scale. Video after the break.
David Mills is as a research scientist at the cutting edge of medical imaging. His work doesn’t involve the scanners you might find yourself being thrust into in a hospital should you be unfortunate enough to injure yourself. He’s working with a higher grade of equipment, he pushes the boundaries of the art with much smaller, very high resolution CT scanners for research at a university dental school.
He’s also a friend of Hackaday and we were excited for his talk on interesting uses for CT scanners at EMF Camp this summer. David takes us into that world with history of these tools, a few examples of teeth and bone scans, and then delves into some of the more unusual applications to which his very specialist equipment has been applied. Join me after the break as we cover the lesser known ways to put x-ray technology to work.
A surprising use of 3D printing has been in creating life-like models of human body parts using MRI or CT scans. Surgeons and other medical professionals can use models to plan procedures or assist in research. However, there has been a problem. The body is a messy complex thing and there is a lot of data that comes out of a typical scan. Historically, someone had to manually identify structures on each slice — a very time-consuming process — or set a threshold value and hope for the best. A recent paper by a number of researchers around the globe shows how dithering scans can vastly improve results while also allowing for much faster processing times.
As an example, a traditional workflow to create a 3D printed foot model from scan data took over 30 hours to complete including a great deal of manual intervention. The new method produced a great model in less than an hour.
If you’ve ever experienced the heartbreak of finding a seed in your supposedly seedless navel orange, you’ll be glad to hear that with a little work, you can protect yourself with an optical computed tomography scanner to peer inside that slice before popping it into your mouth.
We have to admit to reading this one with a skeptical eye at first. It’s not that we doubt that a DIY CT scanner is possible; after all, we’ve seen examples at least a couple of times before. The prominent DSLR mounted to the scanning chamber betrays the use of visible light rather than X-rays in this scanner — but really, X-ray is just another wavelength of light. If you choose optically translucent test subjects, the principles are all the same. [Jbumstead]’s optical CT scanner is therefore limited to peeking inside things like slices of tomatoes or oranges to look at the internal structure, which it does with impressive resolution.
This scanner also has a decided advantage over X-ray CT scanners in that it can image the outside of an object in the visible spectrum, which makes it a handy 3D-scanner in addition to its use in diagnosing Gummi Bear diseases. In either transmissive or reflective mode, the DSLR is fitted with a telecentric lens and has its shutter synchronized to the stepper-driven specimen stage. Scan images are sent to Matlab for reconstruction of CT scans or to Photoscan for 3D scans.
The results are impressive, although it’s arguably more useful as a scanner. Looking to turn a 3D-scan into a 3D-print? Photogrammetry is where it’s at.
In a perfect futuristic world you have pre-emptive 3D scans of your specific anatomy. They’d be useful to compare changes in your body over time, and to have a pristine blueprint to aid in the event of a catastrophe. As with all futuristic worlds there are some problems with actually getting there. The risks may outweigh the rewards, and cost is an issue, but having 3D imaging of a sick body’s anatomy does have some real benefits. Take a journey with me down the rabbit hole of 3D technology and Gray’s Anatomy.
[the_digital_dentist] had a CT Scan done back in 2007 for treatment using orthodontics. Some how, he managed to get a copy of the CT Scan data from the lab, and has been playing around with it lately.
Since he has a 3D printer, the obvious end goal was to print his face using some of the data extracted from the CT Scan. This required a lot of manipulation to get it to the finished model you see above. He used an open source software called DeVIDE to process the data and export the STL. Not much information on this is given on his site, but in our research we managed to find another video documenting the process in DeVIDE on extracting the STL model from DICOM CT scan data.
Unfortunately, the STL is far from being ready to print after being extracted; there is a lot of extraneous data that needs to be cleaned up. He used mesh editing software to help blow away the unnecessary details. We don’t know for sure what software [the_digital_dentist] used, but MeshLab is a good one.
After that, it was just a matter of printing the STL file. But the really cool thing about using data from CT scans is the amount of detail it captures… Stick around after the break to see an animated GIF demonstrating this.
Anyone want to print a copy of their own skull? It’d look great with a plating of Adamantanium…