project:centrifugal_laser_sintering:start
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project:centrifugal_laser_sintering [2015/01/09 02:13] – [Start by attemping capacitive powder dispensing without doing any sintering] timthelion | project:centrifugal_laser_sintering:start [2016/11/25 09:35] – ruza | ||
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+ | ====== Centrifugal laser sintering ====== | ||
+ | {{template>: | ||
+ | name=Centrifugal laser sintering| | ||
+ | image=sinterer.png| | ||
+ | sw=GPL3| | ||
+ | hw=GPL3| | ||
+ | founder=[[user: | ||
+ | interested=| | ||
+ | status=active | ||
+ | }} | ||
+ | |||
+ | I believe that centrifugal laser sintering might be the future of rapid prototyping and short run productions. Centrifugal laser sintering is a laser sintering process involving a rotating bed with a slight vibration or tremor into which powder is poured, a laser mounted on a single axis to sinter that powder, and a rotating pick and place machine for small parts. | ||
+ | |||
+ | This type of laser sintering has a large number of advantages over flat bed laser sintering: | ||
+ | |||
+ | - You can do an automated, rough cleaning of the parts right in the machine simply by opening some holes and spinning the powder off. | ||
+ | - Since powder is leveled by centrifugal force rather than by a leveling blade, you can do pick and place of small parts directly onto the powder. | ||
+ | |||
+ | ===== Basic approach ===== | ||
+ | |||
+ | |||
+ | Each machine can handle a practically unlimited set of powder types. However, for normal operation it is necessary that the powders be separable in order to allow for their re-use: | ||
+ | |||
+ | - Build material which is heavier than water(metal). | ||
+ | - Support material which is soluble in water(salt). | ||
+ | - Build material which is lighter than water(plastic). | ||
+ | - Ferrous build material which can be separated magnetically. | ||
+ | - Any number of centrifugally and chemically separable materials. | ||
+ | |||
+ | The materials are poured into the centrifuge while it is spinning. The laser has the ability to preciscely measure the height of the material. When the material is the right height, we stop pouring the material, and start sintering one layer. | ||
+ | |||
+ | We repeat, until we get to a layer in which we would like to place a small pick and place component. | ||
+ | |||
+ | Once we are done sintering, we open up a series of vents in the centrifuge(or we move an inner, mesh type container, horizontally away from a solid one) then we pour salt into the centrifuge to replace the build material. | ||
+ | |||
+ | Once the centrifuge has be stopped, we take this torus, salt filled container, and carefully submerge it in water. | ||
+ | |||
+ | Waste powder is separated, by dissolution in water/ | ||
+ | |||
+ | ===== Variants ===== | ||
+ | |||
+ | It would also be possible to have the pick and place components rotate along with the rest of the centrifuge. | ||
+ | |||
+ | ==== Leveling methods ==== | ||
+ | |||
+ | Leveling methods are going to be a very important topic for centrifugal SLS. While the original idea was to use vibrational leveling, there are several problems with it. It is hard to produce, causes unwanted sinking of pick and placed components etc. The key point here, however, is that we cannot use a leveling blade if we want to pick and place components onto the powder or do multi-material sintering. | ||
+ | |||
+ | * Wind based leveling: Blow air at the dust in the centrifuge to make the particles move to their lowest positions. | ||
+ | * Electrostatic leveling: Charge particles before dispensing them into the centrifuge, this will make it so that they push away from each other into a very even spray. (This could also be used to lift powder from the dispenser onto the centrifuge, which would simplify the process of opening/ | ||
+ | * Capacitive leveling: Create a charge differential between a static plate which is suspended inside the centrifuge, and the centrifuges chamber. This will lift particles up slightly and maybe they would come to rest leveler than before. | ||
+ | * Careful powder dispensing: Don't level at all, just be careful to dispense powder very evenly. | ||
+ | ===== Building the thing ===== | ||
+ | |||
+ | Centrifugal laser sinterers have many risks associated with them: | ||
+ | |||
+ | - Dust can/will get into the air, causing health concerns. | ||
+ | - Need for high voltage. | ||
+ | - Lasers | ||
+ | |||
+ | However, if we start very simple than it may be possible. | ||
+ | |||
+ | ==== Start by attemping capacitive powder dispensing without doing any sintering ==== | ||
+ | |||
+ | I would start out not trying to build a centrifugal laser sinterer at all. Rather, I would create a vacuum tight box, with our centrifuge in it, and a tray with powder in it. I would pump out all the air with a cheep vacuum pump(seems they go for 20-$50 on ebay). I would charge the powder tray to +20 000 volts or so, and the centrifuge to -20 000 volts and see if the powder doesn' | ||
+ | |||
+ | If our capacitive powder dispensing trick works at all, we would move on to trying to turn the dispenser on and off. Can we dispense some powder into the centrifuge and then take away the static charge and have the flow stop in some reasonably controlled fashion? | ||
+ | |||
+ | If not, we try some simpler dispensing method, like gravity, for instance. | ||
+ | |||
+ | If the capacitive powder dispensing trick does work, then GREAT! We've invented a way of dispensing powder with esentially no moving parts :D. | ||
+ | |||
+ | ==== Once we get powder dispensing down, THEN we can think about lasers and sintering ==== | ||
+ | |||
+ | It seems to me that the best bet is to get an 900nm infrared diode laser with a fiber optic cable pre-attached to it. CO2 is more powerful, cheeper, and works better, but has a semi-limited life-span and requires high voltages(which, | ||
+ | |||
+ | Once we get a laser installed in our centrifuge, we will do a bunch of tests just burning black lines in paper to test the laser. | ||
+ | ===== Known problems with this approach ===== | ||
+ | |||
+ | Dust dust dust dust dusty dusty dust dust. Powder, better known as dust, is bad for small electronic components. | ||
+ | |||
+ | Centrifugal forces on powders, especially during the end stage where we remove the excess powder from the container, cause powder to fly through the air, creating heath concerns. | ||
+ | |||
+ | Centrifuges are often used for separating materials with varying densities. | ||
+ | |||
+ | Similarly, when we pick and place components, it will be necessary that they are always placed atop of already sintered surfaces. If they are placed atop powder, they will sink into the powder. | ||
+ | |||
+ | Multiple powder types pose a problem when the powders melt at radically different temperatures. | ||
+ | |||
+ | Vibrations will cause ball bearings to wear out quickly and might create precision issues. (Perhaps one could use air flow rather than vibration for leveling). | ||
+ | |||
+ | ===== Crazy Sci-Fi wet dreams ===== | ||
+ | |||
+ | The year is 2025 and the MaaS(Manufacturing as a Service) revolution is in full screen. | ||
+ | |||
+ | In a long white walled factory outside of Kladno, a 4 meter tall centrifuge begins to spin up. This is a state of the art machine featuring: | ||
+ | |||
+ | * Multiple lasers to ensure fast build times. | ||
+ | * Dozens of powder types. | ||
+ | * A multitape pick and place system with automatic tape transfer, allowing you to choose from any of the thousands of electronic components in stock. | ||
+ | * Fabric, thread and wire laying mechanisms allowing you to produce strong, light, composite materials. | ||
+ | * Reprap like FDM extruders with multiple material types, making it so that you can produce items with hollow, air tight, cavities. | ||
+ | |||
+ | The outer compartment of the centrifuge is on a rail. Once the build is finished, it slides out of the build area. Dust sprays out of the tiny holes in its sides, and is replaced by salt dust. Then the compartment slides further along its rail, into an outer torus envelop. This envelop is then rotated, so that the centrifuge is horizontal rather than vertical, and is lowed into a water basin. The salt is dissolved, and the torus is opened. A robotic arm lifts your assembly out onto a drying line. | ||
+ | |||
+ | 24 hours after the print command is issued a UAV is at your door with the finished assembly. This is the first time your assembly comes in contact with a human being. Due to high competition in the area, and low overall costs, the price of the item is less than if you had bought it in a store. | ||
+ | |||
+ | |||
+ | ===== Crazy Pol-Sci wet dreams ===== | ||
+ | |||
+ | The samething as the Sci-Fi but the machine is at home, can self replicate, everyone has several and it uses infinitely recyclable materials which can be recycled at home so that there is no need to even buy powder. |
project/centrifugal_laser_sintering/start.txt · Last modified: 2016/11/28 00:50 by ruza