July 29, 2015 | By Alec
3D printing is known as a futuristic manufacturing technology, but we rarely come across 3D printed creations that are as futuristic themselves as this cool device visible above. It’s the Anti-Gravitator, a 3D printed device developed by German chemist Stefan Kneip, which uses a magnetic field to create a stable magnetic levitation situation capable of holding small metal objects. It doesn’t get much more science fiction-esque than this.
While it looks like something straight out of Star Trek, the Anti-Gravitator has actually been designed by German chemist Stefan Kneip as a small hobby project. ‘I am interested in technical things, complex machines especially kinetic machines, mechatronics and of course electronics. Fortunately and thanks to my wife I am able to do all these things I like,’ he tells 3ders.org.
So what exactly is the Anti-Gravitator? Well, as Stefan is quick to emphasize, the Anti-Gravitator is just a cool name, but not something capable of disabling gravitational forces. ‘The principle of the Anti-Gravitator is to compensate the gravity though a magnetic field generated in a copper coil. I use a strong Nd-magnet as object and an ferromagnetic antipole (in form of a M6 x 40 mm screw) on top of the system. If the coil is switched off and you would bring the magnetic sphere nearby the ferromagnetic coil core the two poles would move towards each other due to the magnetic force of attraction,’ he explains.
As Stefan tells us, it wouldn’t be possible to create such a stable magnetic levitation with permanent magnets, so electricity is required. ‘Either both magnets bang together or the movable one drops down. What I do now is the following: I overlay an electromagnetic field to this permanent attraction by means of an copper coil. The current through this coil (and so the magnetic force generated by it either) is controlled by a magnetic field sensor (Hall sensor) just underneath the coil. If the floating magnet lifts up and approaches the hall sensor he gives the signal to the OPAMP to reduce the current through the coil,’ Stefan explains. ‘This leads to a lower magnetic force and the sphere moves downwards. This movement reduces the hall response instantly again and the current in the electromagnet will be increased, resulting in a liftup again. This permanent sweep process leads at the end to a stable levitation’
Stefan began building this cool device at the end of 2014, after seeing a similar device in the German edition of MakeMagazine. ‘I wanted to try out the levitation machine described there. But it does not work as described in my case. So I took some parts onto my breadboard and made a model experiment. After some modifications my version worked fine,’ he explains. The next step was to build a more stylish casing with his 3D printer to ensure the exterior looks the part. ‘I searched the internet for some ideas and found a similar project at this site. The user of this site, Andreas Titze, build up his levitron of aluminum parts and used a slightly different electronic circuitry. He gave me the permission to use his design of the "case".’
The complete CAD design for this cool levitation device was designed in FreeCAD 0.15. ‘My profession is chemistry, I have a PHD in inorganic chemistry, so my knowledge in engineering is somewhat limited. But using FreeCAD for this purpose was a good idea. The program is easy to use after a short period of learning and it has a very engaged community to help if you have problems. I love this kind of open source projects!’ he tells us. The electronic circuitry and the board were subsequently designed using CadSoft’s EAGLE-PCB design software and built in Stefan’s own little laboratory.
The 3D printed parts were all made using a customized Hadron Pro 3D printer, equipped with a BulldogXL extruder and E3Dv6 hotend. ‘All the parts for the Anti-Gravitator are printed of PLA. I used gold and silver PLA of 1.75 mm thickness from fabbmatic.com. It took me overall one day to print all the parts, including some modifications in the CAD files which where necessary,’ Stefan tells us. The only parts that haven’t been 3D printed are the metal components and the electronic circuit.
If you’re interested in building one of these futuristic devices yourself, you can find all necessary downloadable files on Thingiverse here. You will also need quite a lot of other components to create the magnetic field, including a power supply, a hall sensor, an electronic board and enough copper wire. The full list of parts is included in Stefan’s building instructions on Thingiverse.
While 3D printing itself is fairly straightforward – without support structures and with 20% infill – the assembly is fairly complicated due to all the metal parts involved. However, carefully following Stefan’s instructions in regards to assembling the copper wiring and mounting all electronic parts will make this project much easier. Afterwards, it’s a matter of systematic calibration to get your hands on a stable levitation setup. ‘Take in account that the power supply pulls a current of about 400 mA if the hall sensor does not detect a magnetic field (eg. because the floating sphere is falling down). This current leads to a slowly heatup of the coil. So don´t leave the instrument unattendet and turn off the power if no sphere is inside. During a stable levitation the current is much lower (< 100 mA),’ Stefan advises.
The Neodymium magnets are also very powerful and will break each other into pieces when colliding, so careful use is very much advised. However, the results are incredibly cool and well worth giving a try. You can check out the Anti-Gravitator in action below.
Posted in 3D Printer Applications
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this one need no electricity https://www.youtube.com/watch?v=dTXshrNsD-8
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