3D: Liquid-Based AM System

Photopolymers

• usually curable in the UV range

• formulated from photo-initiators and reactive liquid monomers

Photopolymerisation

• the process through which photopolymers are cured

  • the liking of small molecules (monomers( into chain-like larger molecules (polymers)

Free radical polymerization

• elementary steps include…

  • initiation

  • propagation

  • chain transfer

  • termination

• an initiator is broken (through heat) and becomes a free radical, those free radicals attach to a monomer, and a chain begins.

Cationic photopolymerization

• relies on cationic initiators to start polymerization

• better physical and mechanical properties

• requires more power and more time

Stereolithography Apparatus (SLA)

• photo-curable liquid resin fills the vat

• laser beam is directed onto each cross section

• a wiper moves across the surface to recoat the resin

• laser moves down a layer

• process repeats

• quality depends on..

  • properities of resin

  • speed, power, and type of laser

  • post-curing process

SLA advantages and disadvantages

advantages:

• doesn’t need supervision

• can build various volumes

• high accuracy

• good finish

• wide range of materials

disadvantages:

• needs support structures

• requires post-processing

• requires post-curing

SLA applications

• models

• prototypes

• investment casting (Quickcast)

• tools

Envisiontec’s DLP (digital light processing)

• product: perfactory

  • small and compact

• STL cross section file converted from 3D model is made into a bitmap file

  • white → material / black → void

• builds model top down

• done through DMD (digital micromirror device)

  • where each mirror represents one pixel in a projected image

  • through the positioning of 2 pairs of electrodes

DLP Advantages & Disadvantages

advantages

• fast

• small machine

• less use of material

• no wiper

• no shrinkage

disadvantages

• limited volume

• must peel model off build platform once completes

• requires post-processing

CLIP (Continuous Liquid Interface Production)

• similar to DLP except…

  • contains a dead zone

    • composed of a transparent oxygen permeable window

Stratasys’ Polyjet (Polyjet)

• awarded more than 40 patents!

• jetting heads move along x/y axis and drop a thin layer of material

  • material is immediately cured by the UV light

  • thickness of 16μm

  • process is repeated

• support material is removed by the water jet

Stratasys’ Polyjet Advantages & Disadvantages

advantages

• high quality and accuracy

• fast

• smooth surface finish

• wide range of materials

• individual nozzles can be replaced

disadvantages

• post-processing (water jet)

• waste of materials

application

• medical imaging/biomodel

Two-Photon Polymerisation (2PP)

• doesn’t undergo layer-by-layer process

• achieved through free radical polymerization

• resin solidifies around the focal spot

• laser is moved in the x, y, or z direction

• hardness and amount of shrinkage can be controlled

2PP Advantages & Disadvantages

advantages

• can cure anywhere within the resin

• uses infrared light (perfect for bioprinting)

• high resolution and quality

disadvantages

• lack of scalability

• high resolution causes negative effects

applications:

• bioprinting, photonics, microneedles

RegenHU’s 3D Bioprinting

• main products: 3DDiscovery, BioFactory

• building material: BioInk (semi-synthetic hydrogen used for cell growth)

• converted in G-Code format

• produced the tissue and cells layer by layer

RegenHU’s 3D Bioprinting Advantages & Disadvantages

advantages

• unique technology

• cost effective

disadvantages

• small building volume

• required sterile environment

applications:

• skin model

• drug discovery

Optomec’s Aerosol Jet Systems

• uses nanomaterials

• key components:

1. mist generation- atomizing liquid raw materials

2. in flight processing- focusing the aerosol and depositing the droplets

• process

  • a mist from an atomized source material is carried out from a head

Optomec’s Aerosol Jet Systems Advantages & Disadvantages

Advantages:

• able to print planar and non-planar

• can print thin layers

• wide range of materials

• no need for heat

disadvantages:

• particle size limitation

• limited resolution

applications:

• when printing needs to be done on a shape

3D Ceram

• thickness: 25 to 100 microns thick

• ceramic paste is spread over a plan in layers

• each layer is cured by a UV laser and the process repeats

• final part is heat treated (debinding, then sintering)

3D Ceram Advantages & Disadvantages

Advantages

• high resolution

• high speed and variety with shapes

• efficient

Disadvantages

• long post-processing time

• large shrinkage

• no multi-color or material capabilities

Applications

• biomedical (bone implants)

• luxury, industrial

Volumetric Printing

• layer-less

• printed by rotating the vat and propagating the resin from a different angle

• only technique that can print around an object

Volumetric Printing

Advantages:

• fast

• doesn’t require supports

• smooth surface

• complex geometries

• can print over an existing structure

Disadvantages:

• lacks stability

• lacks accuracy

• no scalability