What is the difference between Procedural DMLs and Declarative DMLs.?

How do 3-D printers work?

There are many Rapid Prototyping technologies available today. With over 40 technologies that have been developed over the years, it can be overwhelming! There's stereolithography, laser sintering, 3d printing, fused deposition modeling, and polyjet just to name a few. Then there are acronyms like SLA, SLS, 3DP, FDM, LOM, MJM, and DMLS. In addition names like Z Corp, Stratasys, 3d Systems, Objet, and EOS are added to the confusion. To make matters worse, there are different materials and different machines and machine settings to choose from. Often 3D printing (aka additive manufacturing) can be looked in the same way we look at car purchases. There are many types of cars and they all perform differently, the same is true for RP materials. They are created by different manufacturers and each type brings something different to the table. There are different models and with each model comes different benefits. For the sake of clarity I will attempt to summarize some of the key features of each Technology and the available options. Okay so there have been over 40 technologies developed right? Right, but there are really only a hand full of key players. One the largest factors is the success an RP technology is marketing and financial backing. With marketing, follows sales and with sales comes additional R&D which in turn leads to continued presence in the market place. Financial backing allows the the technology to grow and provides potential buyers with peace of mind knowing that if they buy a $50k-$500k piece of equipment there is going be a company there to provide training and materials for years to come. Only a few have managed to offer both. So which of the top 5 is best for you? I'll let you decide. 3D Systems is a publicly traded company that invented the stereolithography (SLA). They also offer a polyjet technology, but SLA is their bread and butter. Machines average somewhere between $250k-$750k. They operate using a vat of uv curable resin that is cured layer by layer at approx .0035". Some build chambers are up to 59" x 30" x 22", but with larger envelopes comes larger build times. Filling a machine up sometimes takes up to 4 days to completely print...not so great in the world of RAPID prototyping. Nonetheless, they create great looking plastic prototypes. Post processing requires the removal of lattice shaped support structures from all undercuts. This material is thrown out. Additional costs include expensive laser replacements up to $40k. The majority of owners are large powerhouse Fortune 500 companies with large r&D depts. These companies usually accommodate the SLAs long print time with additional RP technologies or service bureaus. Z Corp creates 3D printers that use a plaster composite that has been engineered to work with ordinary inkjet printer cartridges. The technology was developed by MIT and has since grown to not only be the world's faster 3d printer but also the only one with the ability to print in 24bit color. The largest downside to Z Corps printers is that the material is a plaster, not a plastic. So the material is rigid and contains properties similar to a ceramic. There is however an elastomeric material offered, although is is not its most popular material. Pros include much more affordable turn key compared to SLA, no use of support structures, 24 bit color, layers at a .0035", much faster than any other technology, semi automatic post processing, ability to stack parts, and no sharp tools required for post processing. For those reasons, many large AND small companies integrate Z Corp 3d printers into their r & D programs so they can get something in their hands quickly, affordable, and move on with the next design change. Their low operating costs also makes them a favorite amongst schools. Stratasys offers a line of fused deposition modeling (FDM) machines. They use 2 cartridges ( 1 model and 1 support) and extrude plastic through a heated nozzle. The nozzles range from .007-.012" which about 2-3x thicker than SLA, Z Corp, or SLS (we'll get to in a moment). This thickness often creates what is called "stair stepping", a noticeably raged surface which is sometime melted with acetone to improve its appearance but alter its accuracy. Also because of the small nozzle, parts have the longest build times in the industry when compared to other similar sized machines. In addition they also required removal of supports similar to SLA. The key benefit to FDM is the material which is ABS like. Polycarbonate is also available if you own a top of the line machine. They are most popular amongst schools who do not have aesthetic requirements or deadlines. Selective Laser Sintering (SLS) is manufactured by 2 large contenders, 3d Systems and EOS. Both operated the same way, using a laser to sinter, or melt the powder layer by layer. Materials includes different polymides (nylons) that offer incredible strength. Similar to Z Corps 3d printer, SLS uses powder which eliminates the need for support structures. However because of the nature of sintering, some of the surrounding powder gets partially cured and must be discarded. Layer thicknesses are comparable to Z Corp and SLA with machine price tags similar to SLA. Objet is 1 of 2 large manufacturers of polyjet type machines. Essentially a UV curable material is dispensed layer by layer in addition to a gel-like support. Depending on machine, layers can be printed at .0006" or .0012" in either an acrylic like plastic or rubber like elastomer. That is unless, the Connex500 is being utilized, in which case 2 different materials can be used simultaneously to simulate overmolding. It's incredible detail is also it's Achilles' heel. With .0006" layers (about 6 for every 1 Z Corp) comes a very long print time. For that reason, it is only practical to print small parts. Another downfall is the materials sensitivity to heat. And the final pitfall is the inability to print its support structure in a lattice like pattern to save material (something SLA and FDM can do). Now a perfect 3d printer would be the fastest, most affordable, and create the best parts, but in reality you really need to make a choice as to what's important to you. Speed, cost, functionality, color, accuracy? If you're still struggling, I am currently the prototype services manger for EMS, Inc. and would be happy to email any literature your request. P.S. There are additional additive manufacturing methods including cutting sheets of laminate layer by layer, paper layer by layer, sintering metals (DMLS), printing wax, even ways of using sugar and chocolate! However, the top 5 are...well the top 5. I invite anyone reading this to add additional technologies that I simply forgot to mention or did not have time to go into further detail.