While 3D-printing might sound like a modern or newer technology, the concept of additive manufacturing from the 1980 & an inverse of subtractive manufacturing, for example with machining where a solid block of metal shaved away inside a CNC by high speed cutting tools that chip or cut away metals very precisely, in a process that is time consuming & expensive, such that custom CNC parts are costly.
One of the main reasons that a limb amputation replacement robotic limb so expensive, precision machining of the parts, low volume production, custom fitting & similar slow processes executed by educated intellectuals who command high pay. Thus, many factors influence the cost of a robotic limb, especially the high precision machining. 3D printing can produce these parts for lower costs than machining alone, though often SLS metal 3D printed parts have to undergo final machining to make the gaps & interfaces meet the level of precision needed for the application. Thus a rough 3D printed part in metal can be refined by traditional CNC machining.
The history of 3D printing can be traced to 1981 in Japan, where Hideo Kodama was contriving a way to rapidly prototype parts. His idea was to cure photo-resins with precision guided UV light, known today as resin printing, there are several emerging technologies in photo-resins, largely developed as precision mask layer chemicals for integrated circuit manufacturing by IBM, Intel, Texas Instruments & other chip makers. Known as photo-resist in the chip sector, these same UV curing polymers were later adopted into 3D laser galvanometer scanner printing with oxygen diffusion through a semipermeable membrane in the more recent optimized versions.
Even personal hobby scale resin printers are available now, though the use a LCD to control the emission from a panel array of UV LED's, such that the image on the LCD determines where the resin will be cured. The build platform in resin printing hangs upside down, such that as the photo-polymer layers are cured, a precision screw guide mechanism lifts the build platform to lift the cure layer up, so that the next layer of photo resin can be cured & bonded to the previous layer. Layer by layer, the photo resin hardens into very precise polymer parts, on professional machines these are used by dentists & doctors in their offices to make medical appliances, dental fixtures & other parts custom designed to match the patients needs.
Resin printing technology known as SLA, like the Form 3+ for around $4000 < click link to see it at the manufacturers website / be cautioned that resin printing at home requires its own vented room & as much special equipment as at least the cost of the printer + more, for the workflow setup kit. The resin for 3D printing a lot more expensive than common filaments for FDM like 1KG spools of PLA or PETG that are popular with home 3D printer enthusiasts or hobbyists. I just 3D PLA printed an exact scale model of 9mm bullet via a file from https://www.thingiverse.com/thing:56142/files on my 2018 Prius Mini ^^ setup, in "White PLA" in 0.1mm DETAIL & 0% infill, which has a mass of just over 1g & takes about 40 minutes to print. I am at the end of a spool & was looking for a low mass fun print to use up the ~65g of remaining filament :)
IPA or isopropyl alcohol, by the gallon, in a SLA parts rinsing station, removes any uncured resin reside on your parts. Then the part must be loaded in a UV curing station to enhance the mechanical properties by completing the photo-curing stage in post. You can go to the above Form Labs website to learn about the workflow for the Form 3+, their current major product offering.
Gloves, IPA wipes, paper towels, resin resistant surfaces, masks, q-tips, replacement films for the resin bath, bottles of expensive photo-resins, resin recovery funnels, complex toxic waste handling, there are a lot of disposable or consumables in SLA workflow that make it an impractical or very expensive hobby, something you would have to really dedicate your time & resources to doing at home in a specially vented room dedicated to SLA with special air handling, activated carbon air filtering at the minimum. Again more consumables that increase the workflow costs of operation, well above the cost of a high quality SLA printer.
Fumes from resin printing are not good for your health & must be remediated chemically or vented to the atmosphere for your safety. Never do SLA in your bedroom or anywhere that you spend a lot of time. Never SLA resin print in your kitchen, the fumes can become part of foods, stick to pots & pans & other glassware, plates, utensils. SLA something that should be done in a dedicated shed or a structure physically isolated from your home, for fume safety reasons. Similar if your are FDM printing ABS, do it in the garage or other "outside space" as the fumes from ABS printing are toxic to brain neurons. You have to wear clothing dedicated to resin printing, eye protection, a face shield, & disposable gloves when handling resins or the resin bath. The workflow is messy, all the supports for your parts also have to be tossed, making complicated polymer waste streams.
Leftover resin will spoil from ambient UV present in sunlight and emitted by common lightbulbs, screens & other lamps & artificial light sources like HID, LED, CLF, FL, Tungsten, Halogen, Short-ARC, Xenon, Krypton, Mercury Vapor, CCFL, Sodium Vapor, Metal Halide & other bulb lamp technologies. This is why the resin bottles, containers & cartridges are made of dark light proof plastics, which also have to be thrown away as toxic trash because they are contaminated with photosensitive resin, which is a skin irritant, eye irritation & lung irritant. For the reasons mention, SLA not really a hobby 3D printing tech, you & you children will be much happier with an FDM printer & PLA filament, which is cheap & non-toxic. In FDM many parts can be printed without supports too! 3D FDM printers are cool way to teach your children about 3D design software by bringing some of the designs to life, as toys or other parts. I have printed a huge variety of different decorative & functional parts on my Prusa Mini, a very high quality $400 FDM printer than I highly recommend! https://www.prusa3d.com
When Charles Hull, a frustrated furniture manufacturer filed his patent in 1986, he came up with the idea to make small custom parts needed in furniture making. His system was designed to use a laser scanner to draw curing patterns on each layer of photosensitive resin, which he was determined to make when he founded 3D Systems Corporation, the group responsible for the first commercial SLA printer known as the SLA-1 released in 1988.
Thankfully selective laser sintering or SLS was being developed by Carl Deckard at the University of Texas in 1988. In this configuration a bed of metal powder, fine, of uniform particle size, scanned by a powerful laser able to melt the metal particles together. The laser scanner draws an image layer melting the particles into that image, then the part is lowered & brush scraping mechanism casts a new layer of metal particles over the part, the laser scanner then melts the next laser image layer into the previous layer, layer by layer building up metal parts. SLS today utilized to make rocket engines with far fewer parts, which improves reliability & enables higher specific impulse or longer burn-time, usually measure in hundred of seconds, that energize rockets for rocket launching stuff & people into outer space, usually satellites in lower or medium Earth Orbits, so much, by the tens of thousands that space trash is now a problem.
Fused metal powders also enable the use of exotic alloys, that can be made into metal dust but much harder to cast or mould into larger parts. The precision variable thermal regime of the metal crystallization in SLS also enables dissimilar metal layers to be bonded, enable complex multi-alloy parts creation that would be impossible by any other means. Actually SLS can bond metal, ceramic & plastic by changing the powder in each layer, creating multiple materials parts, with nested materials of different kinds, also impossible to make any other way. The first commercially available SLS printer released in 2006, enabling the rapid nearly-instant production of industrial parts for iterative design improvements. Functional metal parts made with SLS can be used directly in applications, including high performance aerospace, automotive & commercial applications.
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