3D printing - Additive manufacturing: An introduction

Excerpt: Due to sophisticated computer software (3D parametric modelers), Rapid Prototyping, through Additive Manufacturing, has emerged as the preferred process for many plastics application.

3D printing or additive manufacturing (AM) is any of various processes for making a three-dimensional object of almost any shape from a 3D model or other electronic data source primarily through additive processes in which successive layers of material are laid down under computer control. A 3D printer is a type of industrial robot.

Early AM equipment and materials were developed in the 1980s. In 1984, Chuck Hull of 3D Systems Corp invented a process known as stereolithography employing UV lasers to cure photopolymers. Hull also developed the STL file format widely accepted by 3D printing software, as well as the digital slicing and infill strategies common to many processes today. Also during the 1980s, the metal-sintering forms of AM were being developed (such as selective laser sintering and direct metal laser sintering), although they were not yet called 3D printing or AM at the time. In 1990, the plastic extrusion technology most widely associated with the term "3D printing" was commercialized by Stratasys under the name fused deposition modeling (FDM). In 1995, Z Corporation commercialized an MIT- developed additive process under the trademark 3D printing (3DP), referring at that time to a proprietary process inkjet deposition of liquid binder on powder.

Additive Manufacturing Technologies can be classified by the physical type of material used like sSolid, liquid, powder and by the specific means to use that material like

  • Fused Deposition Modeling

  • Stereolithography

  • Laser Sintering

  • Laminated Object Modeling

AM technologies found applications starting in the 1980s in product development, data visualization, rapid prototyping,and specialized manufacturing. Their expansion into production (job production, mass production,and distributed manufacturing) has been under development in the decades since. According to Wohlers Associates, a consultancy, the market for 3D printers and services was worth $2.2 billion worldwide in 2012, up 29% from 2011. Applications are many, including architecture, construction (AEC), industrial design, automotive, aerospace, military, engineering, dental and medical industries, biotech (human tissue replacement), fashion, footwear, jewelry, eyewear, education, geographic information systems, food, and many other fields.

Given below are some of the technologies in vogue which are marketed by Stratasys.

Fused deposition modelling technology

Fused deposition modelling (FDM) was developed by S. Scott Crump in the late 1980s and was commercialised in 1990 by Stratasys. FDM Technology is a powerful Stratasys-patented additive manufacturing method.

FDM builds concept models, functional prototypes and end-use parts in standard, engineering-grade and high- performance thermoplastics. It's the only professional 3D printing technology that uses production-grade thermoplastics, so parts are unrivaled in mechanical, thermal and chemical strength.

The invention of FDM Technology

Stratasys founder Scott Crump invented FDM Technology more than 20 years ago, and Stratasys has continued to lead the 3D printing revolution ever since, developing a range of systems that appeal to large manufacturers, designers, engineers, educators and other professionals.

How FDM works

3D printers that run on FDM Technology build parts layer-by-layer from the bottom up by heating and extruding thermoplastic filament. The process is simple:

  1. Pre-processing: Build-preparation software slices and positions a 3D CAD file and calculates a path to extrude thermoplastic and any necessary support material.
  2. Production: The 3D printer heats the thermoplastic to a semi-liquid state and deposits it in ultra-fine beads along the extrusion path. Where support or buffering is needed, the 3D printer deposits a removable material that acts as scaffolding.
  3. Post-processing: The user breaks away support material away or dissolves it in detergent and water, and the part is ready to use.
FDM benefits
  • The technology is clean, simple-to-use and office-friendly

  • Supported engineering-grade thermoplastics are mechanically and environmentally stable

  • Complex geometries and cavities that would otherwise be problematic become practical with FDM technology

FDM thermoplastics

FDM technology uses the same tried and tested thermoplastics as traditional manufacturing processes.For applications that demand tight tolerances, toughness and environmental stability – or specialized properties like electrostatic dissipation,translucence , biocompatibility, VO flammability and FST ratings–there's an FDM thermoplastic that can deliver.

PolyJet Technology
3D print precision prototypes in a wide range of materials

PolyJet 3D printing technology is a powerful additive manufacturing method patented by Stratasys.


Colourful bike seats, all three can print in one job with cyan, magenta and yellow.

3D printers powered by PolyJet technology feature 16-micron layers with accuracy as high as 0.1 mm for smooth surfaces, thin walls and complex geometries. It is the only technology that supports a range of materials with properties from rubber to rigid and transparent to opaque. And with Objet Connex technology, multiple materials can even be printed simultaneously in the same part.


Digital ABS with Overmolding

How PolyJet 3D printing works

PolyJet 3D printing is similar to inkjet printing, but instead of jetting drops of ink onto paper, the PolyJet 3D Printers jet layers of curable liquid photopolymer onto a build tray. The process is simple:

  1. Pre-processing: Build-preparation software automatically calculates the placement of photopolymers and support material from a 3D CAD file.
  2. Production: The 3D printer jets and instantly UV-cures tiny droplets of liquid photopolymer. Fine layers accumulate on the build tray to create a precise 3D model or prototype. Where overhangs or complex shapes require support, the 3D printer jets a removable gel-like support material.
  3. Support removal: The user easily removes the support materials by hand or with water. Models are ready to handle and use right out of the 3D printer, with no post-curing needed.

PolyJet 3D printing benefits

PolyJet 3D Printing technology offers many rapid-prototyping advantages, including astonishingly fine detail, smooth surfaces, speed and precision.

  • Create precise prototypes with exceptional final-product realism Produce complex shapes, intricate details and smooth surfaces.

  • Incorporate color and diverse material properties into one model with the greatest material versatility available.

Color and multi-material 3D printing

The most advanced PolyJet systems, Objet Connex 3D Printers, combine diverse 3D printing materials in one model by jetting multiple materials simultaneously. This means you can selectively position multiple materials in one printed prototype and even combine two or three materials to create composite digital materials with distinct, predictable properties. Combine rigid and rubberlike materials to simulate a range of Shore A values; mix cyan, magenta and yellow for a range of blended hues; even combine rubberlike materials with color to create vibrant, flexible prototypes that look and feel more like your future products.

With hundreds of digital material combinations and colors to choose from, PolyJet technology gives you better finalproduct realism than any other 3D printing method.

PolyJet 3D printers and materials

PolyJet 3D Printers work with a vast array of materials, including Rigid Opaque and Rubberlike materials in hundreds of vibrant colors, clear and tinted translucent shades, Simulated Polypropylene,and specialized photopolymers for 3D printing in the dental and medical industries. Hundreds of composite materials add to the possibilities.

Conclusion

Due to sophisticated computer software (3D parametric modelers), Rapid Prototyping, through Additive Manufacturing, has emerged as the preferred process for many plastics application.