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| Designation additive-manufacturing process | Process description | Technologies | Materials | Medical use | Pros | Cons |
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| Vat photo-polymerisation | Vat polymerisation uses a vat of liquid photopolymer resin, out of which the model is constructed layer by layer | Stereolithography (SLA)
Digital light processing (DLP) | (i) Photopolymer resin | Bone, dental models [13], dental implant guides [14], hearing aids [15] | (i) High resolution and accuracy
(ii) Complex parts
(iii) Decent surface finish: smoother finish
(iv) Flexible printing setup | (i) Lacking in strength and durability
(ii) Still affected by UV light after print
(iii) Not for heavy use |
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| Material jetting | Material jetting creates objects in a similar method to a two-dimensional ink jet printer. Material is jetted onto a build platform using either a continuous or drop on demand (DOD) approach | Multijet modelling (MJM) | (i) Plastics
(ii) Polymers: polypropylene, HDPE, PS, PMMA, PC, ABS, HIPS, EDP | Medical models [16], dental casts, dental implant guides [17] | (i) High accuracy
(ii) Low waste of material
(iii) Multiple material parts and colours in one process | (i) Required support material
(ii) Limited materials: only polymers and waxes are supported |
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| Binder jetting | The binder-jetting process uses two materials; a powder-based material and a binder. The binder is usually in liquid form and the build material in powder form. A print head moves horizontally along the x and y axes of the machine and deposits alternating layers of the build material and the binding material | Powder bed and inkjet head 3D printing (PDIH)
Plaster-based 3D printing (PP) | (i) Stainless steel
(ii) Polymers: ABS, PA, PC
(iii) Ceramics: glass | Colour models especially colour coding of anatomy [18] | (i) Range of colours
(ii) Multiple materials supported
(iii) Faster
(iv) Different binder-powder combination for various mechanical properties | (i) Not always suitable for structural parts
(ii) The cleaning of the 3D-printing result needs time and increases the time of the procedure |
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| Material extrusion | Fuse deposition modelling (FDM) is a common material extrusion process and is trademarked by the company Stratasys. Material is drawn through a nozzle, where it is heated and is then deposited layer by layer. The nozzle can move horizontally, and a platform moves up and down vertically after each new layer is deposited | Fused deposition modelling (FDM)
Fused filament fabrication (FFF) | (i) Plastics;
(ii) Polymers: ABS, nylon, PC, AB | Medical instruments and devices [19], rapid prototyping exoskeleton [20] | (i) Inexpensive process
(ii) Widespread
(iii) ABS plastic supported: good structural properties and easily accessible | (i) Dependence of quality on the noozle radius: bigger nozzle leads to less quality
(ii) Low accuracy and dependence on the nozzle thickness
(iii) Low speed
(iv) Contact pressure needed to increase quality |
| Powder bed fusion | The powder bed fusion process includes the following commonly used printing techniques: direct metal laser sintering (DMLS), electron beam melting (EBM), selective heat sintering (SHS), selective laser melting (SLM) and selective laser sintering (SLS) | Selective laser sintering (SLS)
Direct metal laser sintering (DMLS)
Selective heat sintering (SHS)
Selective laser melting (SLM)
Electron beam melting (EBM) | Powder-based materials. Common metals and polymers used are
(i) SHS: nylon
(ii) DMLS, SLS, SLM: stainless steel, titanium, aluminium, cobalt chrome, steel
(iii) EBM: titanium, cobalt chrome, stainless steel material, aluminium and copper | Models that require a lattice, medical devices such as implants and fixations [21] | (i) Inexpensive
(ii) Small technology: office size machine
(iii) Large range of material options | (i) Low speed; lack of structural properties in materials
(ii) Limited sizes
(iii) Dependence on powder grain size |
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| Sheet lamination | Sheet lamination processes include ultrasonic additive manufacturing (UAM) and laminated object manufacturing (LOM). The ultrasonic additive manufacturing process uses sheets or ribbons of metal, which are bound together using ultrasonic welding | Laminated object manufacturing (LOM)
Ultrasonic consolidation (UC) | Paper, plastic and sheet metals | Orthopaedic modelling of bone surfaces [22] | (i) Speed
(ii) Inexpensive
(iii) Ease of materials handling | (i) Dependence on paper or plastic material
(ii) Need of postprocessing
(iii) Limited material range |
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| Direct energy deposition | Directed energy deposition (DED) covers a range of terminology: “Laser engineered net shaping, directed light fabrication, direct metal deposition, 3D laser cladding” it is a more complex printing process commonly used to repair or add additional material to existing components | Laser metal deposition (LMD) | Metals: cobalt chrome, titanium | Limited. Commonly used to repair existing parts and build very large parts | (i) High control of grain structure
(ii) High-quality-dependent on speed
(iii) High-accuracy-dependent on accuracy
(iv) Fast built with rapid material deposition
(v) Fully dense parts; no need for supports
(vi) Best process for part repair | (i) Limited range of materials;
(ii) Poor surface quality;
(iii) Wire process is less accurate |
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