3D Printer Additive Technology Overview

3D printers have come a long ways since the 1980s when the working technology was first developed, there are two types of 3D physical manufacturing processes out there. The first one developed was subtractive, which involves removing material to make everything from engine blocks (that start as one solid piece) – this process is as old as mankind but the second, called additive manufacturing – the focus of this article – is the most recent and exciting in my opinion.

Why is it called additive manufacturing (printing)?

3D printers go layer by layer, adding a little material after each pass, depending on the technology, curing may occur in addition to other processes such as adding color (via an integrated inkjet printer) or switching between various materials at the same time using different %s of each for different rapid prototyping needs (one material that bends and is soft while the other is inflexible and hard). Here is a list of the additive technologies out there now (in alphabetical order).

• Chocolate Additive Layer Manufacturing (ChocALM)
• Direct metal laser sintering (DMLS)
• Electron beam free form fabrication (EBF3)
• Electron beam melting (EBM)
• Fused deposition modeling (FDM)
• Laminated object manufacturing (LOM)
• Plaster-based 3D printing (PP)
• Selective laser sintering (SLS)
• Stereolithography (SLA)
• (if you have another – add a comment below)

So, lets review them so you can understand the differences between them but first, what they generally have in common and technological advantages.

General 3D printing workflow

In my case, I use Autodesk 3DS Max to generate the 3D model but you can use Blender, SolidWorks or a host of other CAD type programs to do the same. That is the fun and most creative part in my opinion. After this is done, you export it as a STL format into proprietary software that may or may not come with your machine which then slices the model and orients it. Depending on the technology, require the addition of support material. Wait anything from a few minutes to a few days and it’s done!

General advantages of 3D printing

3D printing has been used for manufacturing over the past decades because it requires no tooling and parts can be built in hours (days) which otherwise would be impossible or too complex otherwise.

Chocolate Additive Layer Manufacturing (ChocALM)

Developed by Choc Edge (http://www.chocedge.com), ChocALM uses yummy chocolate, added layer by layer by a heated extruder to make your stomach happy!

Material

• chocolate… chocolate and more chocolate!

Advantages of ChocALM

• source material is both easy to find and edible
• instantly makes you the most popular person in town
• can make multiple treats in one shot

Disadvantages of ChocALM

• resolution isn’t that great
• can’t make moving parts
• can make multiple treats in one shot (leading to waist expansion)

Direct Metal Laser Sintering (DMLS)

Developed by EOS Electro Optical Systems (http://www.eos.info), DMLS machines use a 200 watt laser that fuses metal powder layed onto the build platform from the dispensing platform by transforming the powder into a solid by the process of melting.

Material

• any metal alloy powder (not cheap!)

Advantages of DMLS

• models are of high accuracy with great detail due to each layer being about 20 micrometers thick
• can have mechanical properties (meaning you can have moving parts)
• the metal used during the additive process is the same metal that can be used during the general manufacturing process
• prototypes are strong (model depending) and can be tested within their intended application

Disadvantages of DMLS

• models are small (build envelope is “only” 250 x 250 x 185 mm)
• surfaces need to be polished (depending on application, you may need a grinder!)
• removing metal support structures and thermal post-processing is time consuming (you can’t have the supports in a different material than the part)

Electron Beam Free Form Fabrication (EBF3)

Showcased by NASA (http://nasa.gov) about a year ago (it’s inventor with funding from DARPA and Lockheed Martin), Electron beam freeform fabrication (EBF3) uses an electron beam and wire to fabricate metallic structures. This allows you to basically build anything within a 3D environment as basically solid wire is fed and by using an electron beam, fused into place

Material

• wire

Advantages of EBF3

• can be done in a vacuum (which makes it great for welding in outer space)
• incredibly strong and smooth results
• works in a 3D environment, not a closed box like the other additive technologies in the list
• possible to change chemistry and incorporate sensors while the part is being built

Disadvantages of EBF3

• the most expensive of all the additive technologies
• requires a large capital investment for machines, material and qualified staff

Electron beam melting (EBM)

Developed by Arcam (http://www.arcam.com), EBM melts titanium alloy powder, layer by layer using an electron beam to bind them together within a vacuum.

Material

• Titanium alloys

Advantages of EBM

• titanium is safe to use in the body for implants and heavily used in high-end aerospace manufacturing
• requires no oxygen (done in a vacuum)
• ready to go right after it’s built as there is no filler to remove or support material
• can have moving parts
• layer thickness of 0.05mm and fast build rates of 80 cm³/h

Disadvantages of EBM

• requires a high operating temperature (700 and 1 000 °C)

Fused Deposition Modeling (FDM)

Invented in 1989 by Scott Crump who is also the co-founder of Stratasys Inc. (http://www.stratasys.com) along with his wife. FDM use a plastic filament or metal wire that is unwound from a coil which goes through a heated extrusion nozzle. Of all the additive technologies, this one is the simplest to build and operate though the resolution isn’t as high.

Material

• ABS
• ABSi
• polyphenylsulfone (PPSF)
• polycarbonate (PC)
• Ultem 9085
• (other types of thermoplastics)

Advantages of FDM

• cheap and easy to operate
• plastic filament easily sourced
• some plastics like Ulterm 9085 is fire retardant
• can use multiple extrusion heads to print support materials using a different material than the intended model
• can build multiple models at once

Disadvantages of FDM

• resolution is relatively low (compared to the other additive technologies)
• is widely used so profit margins are slim as are barriers to entry
• no post processing required (depending on model and intended use)
• material shrinkage, warping and increasing Z-layer error rate as model builds-up
• can’t really have moving parts (unless they are HUGE)
• one model at a time (unless your platform is large)

Laminated object manufacturing (LOM)

Originally invented by Helisys Inc. (now Cubic Technologies http://www.cubictechnologies.com), LOM is a relatively simple process of adding successive layers  of adhesive-coasted paper, plastic or metal laminate which is then cut with a knife or laser cutter (cross-hatches occur with area outside of build to facilitate removal).

Material

• sheets of paper, plastic, metal or other material laminates

Advantages of LOM

• cheap and abundant material
• characteristics of paper model is similar to wood
• can build HUGE models at a very affordable price
• can build multiple models at once

Disadvantages of LOM

• can’t have moving parts (unless they are HUGE)
• resolution limited by material used (layer wise with 0.2 mm (x, y); 0.3 mm (z) accuracy

Plaster-based 3D printing (PP)

Invented and developed by Z Corporation (acquired by 3D Systems Inc. http://www.3DSystems.com), PP involves a head moving over successive layers of powder (similar consistency to corn starch, flour or cocaine) with an ink-jet like head that deposits liquid binding material. This technology is amazing to see in person and is the technology I hope to use here on 3DMarvels.com to demonstrate and test products!

Material

• white powder

Advantages of PP

• capable of color printing each successive layer using normal HP inkjet cartridges
• prints about an inch per hour
• internal material recycling system (no waste!)
• no need for support materials
• can be used for casting fine jewelry
• very nice finish
• can build multiple models at once

Disadvantages of PP

• requires post-processing (basically spray-on a layer of crazy glue)
• finishing (air blasting) required once the model is picked-out of the machine
• you won’t get high snorting the powder

Selective Laser Sintering (SLS)

Patented by Dr. Carl Deckard at the University of Texas in the 80’s thanks to some DARPA funding though technologically similar to another patent held by R. F. Housholder in 1979. SLS is very similar to PP except instead of an inkjet nozzle squirting some liquid, it uses a laser similar to DMLS to fuse particles of plastic, metal (DMLS), ceramic or glass powder one layer at a time over a bead of powder. The powder is also heated so that the laser doesn’t have a long way to go for the melting point to be achieved, unlike DMLS.

Materials

• metal alloys (DMLS)
• ceramic
• composites
• glass
• polymers (nylon)
• polystyrene
• green sand

Advantages to SLS

• variety of materials can be used, each with their distinctive material traits
• multiple physical processes such as full melting, partial melting or liquid-phase sitering
• strong parts with 100% density (strong and resistant) can be built
• can build multiple models at once
• support materials not required
• large build area (machine dependent)

Disadvantages of SLS

•  cool down period required

Stereolithography (SLA)

SLA uses a liquid filled vat full of UV curable photopolymer (resin) that works in conjunction with a UV laser which builds the parts layer by layer by curing the resin on the surface. The layer thickness is between 0.05mm and 0.15mm.

Material

• Ultra-violet curable photopolymer (resin)

Advantages to SLA

• can build relatively large parts with a build envelope of 210×70×80 cm
• relative fast compared to other additive technologies
• strong enough for injection molding, blow molding, metal casting and thermoforming molding

Disadvantages to SLA

• parts need to be cleaned in a chemical bath and cured in a UV oven
• requires support materials
• resin costs between 80 to 210$US a liter with machines in excess of 100K$US