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Sunday, April 4, 2010

3D Printing; General-Types-Type-Comparison-Materials

3D printing is a complex subject, and so we've compiled information on the topic from various sources. 

Often referred to as 3D printing, these processes are also referred to by other names such as rapid prototyping, direct digital manufacturing, or any of the process names. All 3D printing works on the concept of building up layers of material on top of each other to produce a finished part. During the process, any part of the model that overhangs must be supported - each process handles this differently which can have implications for the final product. Some processes allow for multiple parts to be nested together / built at once with only a slight increase in build time – this is better for higher volume orders.

Every process has its strengths and weaknesses - to best utilize the technology, you'll need to understand how each can be used to its full advantage

FDM – Fused Deposition Modeling

This is currently the most widespread form of 3D printing. All new machines are built by Stratasys under the trade names Dimension or Fortus. It builds each layer by extruding a thin filament of nearly-melted thermoplastic onto a build surface. It builds in a criss-cross fashion, so that each layer's “grain” is perpendicular – which makes the part stronger. It's support material comes in break-away and soluble forms – the latter allows for much more complicated geometries by allowing water to wash away support.

Strengths:

  • plastics used are very durable
  • a wide variety of materials are available
  • soluble support technology allows for intricate geometry, including simple moving parts
  • materials are cheap

 

Weaknesses:

  • Untreated surfaces have a rough finish
  • Strength along the Z-axis direction is far less than in X or Y (because of layer adhesion)
  • Slower build-times with multiple parts

 

SLA – Stereolithography Apparatus

This was the original form of 3D printing. Currently, all systems are built by 3D Systems. The process forms each layer by scanning a UV laser over a build surface covered in a special resin that cures when exposed to UV light. The plate lowers into a vat to re-coat the surface for each layer. Support material is the resin itself.

Strengths:

  • Accuracy
  • Good surface quality
  • Wide variety of materials

 

Weaknesses:

  • Resins
  • Long post-processing times (due to removing support material)
  • Resins are toxic & unsafe for an office environment

 

PolyJet / ProJet

PolyJet is produced by Objet Geometries, and ProJet is produced by 3D Systems. This form of 3D printing lives up to the name “printing”. These machines work similarly to inkjet printers, but instead of using ink they use resin. The resin is jetted onto the surface and then cured by a passing light – similarly to the SLA curing. The support material isn't quite soluble, but is washed away by a jet of water.

Objet's Connex systems can print in multiple materials at the same time. This allows models to have transparent features with opaque internal parts. Also, using their “Digital Materials” technology, you can even intermix the materials with a variable ratio to allow parts with multiple materials properties in one build.

Strengths

  • Great Accuracy
  • High Resolution / Feature Detail
  • High complexity parts
  • Moving parts are possible
  • Ability to print in multiple-materials

 

Weaknesses

  • Expensive
  • Support can be difficult to remove in some circumstances – limiting some geometries

 

Z-Corp

Another form of 3D printing using inkjet technology is known by the company's name: Z Corp. These machines create each layer by using an inkjet head to deposit a binder onto a bed of compacted powder. Powder is layered and cured in succession until a part is formed. After each build, the loose powder is removed leaving only the part remaining. The fresh part is then coated in elastomer which gives the parts added rigidity. Some machines have the ability to print parts in full color.

Strengths

  • Fast part production
  • The only full color parts process

 

Weaknesses

  • Fragile parts – even when coated
  • Lowest surface quality than other “jet” processes

ThermoJet / Solidscape

These machines print in wax in a similar method to the ProJet / PolyJet processes. They build up layers of wax by printing each layer on top of the last. Solidscape machines are used to print in wax that is later used as a lost-wax pattern in metal casting – used by jewelers to create rings. ThermoJets are generally used to produce purely aesthetic parts.

Strengths

  • Accurate
  • High detail
  • Great surface quality
  • Cheap

 

Weaknesses

  • Very fragile wax parts
  • Limited Materials

 

SLS/SLM/DMLS – Selective Laser Sintering/Melting & Direct Metal Laser Sintering

In this process, a laser is scanned across the top of a compacted powder surface. The laser is strong enough that it sinters / melts the materials together.

Strengths

  • Wide range of materials
  • Durable parts
  • Accurate
  • Good at bulk jobs (because each layer can be sintered quickly)

 

Weaknesses

  • Expensive (machine purchase cost)
  • Mediocre surface quality
  • Large flat parts tend to warp

 

ProMetal - Direct Metal Printing

This technique is named after the trade name of the company that builds it: ProMetal. The process is similar to Z Corp where an inkjet head deposits binder onto a powder surface. The difference is that the powder is stainless steel and must be sintered in an oven. Later, the part is “infiltrated” to full density by heating the part in the furnace over bronze. This produces a hybrid SS / bronze material – gold is also possible.

Strengths

  • Cheapest metal printing
  • Bulk part printing
  • Ability to print very large parts

Weaknesses

  • Lower accuracy
  • Limited
  • Casting quality surface finish

ProMetal RCT – Rapid Casting Technology

This is similar to the other ProMetal method, however instead this one produces sand molds for metal casting. The end result after casting is a part of identical quality as traditional green sand casting, without the need to produce patterns – this cuts time and enables novel geometries.

Strengths

  • Fastest metal castings
  • No limited on material to be cast

 

Weaknesses

  • Expensive (machines & prints)

 

DLP (EnvisionTec)

This technique is exclusive to EnvisionTec and is similar to SLA in that it uses a vat of light-curable resin. Instead of using a laser, it uses a DLP chip and a UV light source to cure each layer in one step (no XY scanning). This makes it five times faster than SLA.

Strengths

  • Accurate
  • High Resolution / Feature Detail
  • Fast
  • Casting friendly materials

 

Weaknesses

  • Expensive (machine purchase cost)
  • Accuracy fall-off (more accurate in the center than edges)

 

LOM – Layered Object Manufacturing

This process uses layered sheets of material (usually paper or plastic) that are cut out by laser or blade and adhered together. The latest version of this process is the Mcor Matrix which uses A4 printer paper and PVA glue to make prototypes.

Strengths

  • Very cheap & available materials (paper & glue)
  • Thin layer thickness
  • Greenest 3D printing technology

 

Weaknesses

  • Limited material selection
  • Lower part strength

 

Other processes:

V-Flash

This system was released by 3D Systems to reach the low-cost / desktop market. Each layer is applied using a resin coated plastic sheet which applies materials.

Strengths

  • Inexpensive
  • Good accuracy
  • Good resolution

 

Weaknesses

  • Supports made of build material – high post-processing time
  • Limited part size

 

Huntsman Digitalis

This system is currently only in prototype form and was debuted at the 2009 RAPID Show. It uses a novel Micro Light Switch technology to expose a vat of resin to a UV curing light.

Strengths

  • Fast
  • Accurate
  • High Resolution
  • Large build area

 

Weaknesses

  • Limited Materials
  • Probably will be expensive

Posted via web from SolidWild's posterous

6 comments:

  1. Mr SolidWild,

    Thank you very much for posting the information on 3d printing processes. Your blog points out some great info. DMLS is what we specialize in and you are correct about the strengths and weaknesses. We always say that if it can be machined and not too complex than go that route. The parts can be finished to a mirror finish which I think you had left out. It seems as if all weaknesses for each process is "expensive". It is a prototype lol for the prototype arena, it is a normal cost! Thanks again.

    GPI PROTOTYPE AND MANUFACTURING
    Specializing in:
    * DMLS – Direct Metal Laser Sintering
    * 3D Printing - Objet
    * RTV Casting and Urethane Molds
    * SLA, SLS, FDM, CNC
    * Laser 3D Scanning
    * Short Run 1-1000 Prototypes
    * Manufacturing

    Tim Ruffner

    ReplyDelete
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