Rapid prototyping, a blanket term for any process in which a scale model or physical representation of a part to be used in the development and fabrication of the final part, is the digital construction of physical 3D objects without the need for part specific tooling. This technology is widely used in product development and manufacturing processes. For the process to be truly considered a rapid prototyping process, it must require significantly less time for the production of the physical part in comparison to traditional methods of fabrication.
Why do I need Rapid Prototyping?
Rapid prototyping has endless applications and possibilities but some of the most common are:
- Form, fit, and function verification
- Display models
- Creative form development
- Scale models
- Casting cores
- Low quantity production runs
- Many, many more.
3D Printing and the relation to rapid prototyping:
3D printing is a process in which a new part, or revision of an existing part, is designed using CAD software and then created physically by ‘printing’ the part on a 3D printer. There are several different printing processes which 3d printers utilize to create the part. Each has its advantages and disadvantages, which are described in further detail below.
Additive Manufacturing is the process of creating a three dimensional part or solid object from a digital model achieved from the additive process where successive layers of material are built up from nothing. As opposed to the traditional machining techniques which rely on the subtractive processes such as milling or drilling from a solid blank.
Currently, there are four mainstream processes; Polyjet Matrix (Polyjet), Fused Deposition (FDM), Selective Laser Sintering (SLS) and finally Stereolithography (SLA). Click on the method title to see a picture.
Polyjet matrix printing builds very thin layers of acrylic based photopolymers, down to 16 microns, of model material one on top of another, curing each layer as it is laid down with UV light, to create parts. Having a layer thickness of only 16 microns creates a high resolution representation of your part that requires a minimal amount of finishing. A large advantage of the Polyjet process is its ability to print multiple materials simultaneously. This allows parts to be created with a wide range of material characteristics, such as flexibility or transparency, all within an individual part creating a nearly identical representation of the CAD model. The ability to print multiple materials simultaneously give the Polyjet process the ability to print parts that have overhanging or hollow features by supporting them during printing with a special “support material” which is then easily removed using a waterjet process after the part is printed. Since the polymers used in the Polyjet process are non-toxic and require only water for clean up, it makes the system ideal for office environments.
Much like the Polyjet process, the fused deposition process (FDM) lays down layers of material one on top of each other. However, unlike the Polyjet process the material is a thermoplastic which is in a solid state before printing and is then melted and deposited onto the print surface. Most FDM machines also utilize a “support material” and therefore can print part with overhanging or hollow features. The FDM process does not allow for multiple materials to be printed simultaneously like it’s Polyjet counterpart, but multiple materials can be printed.
Unlike the FDM or Polyjet processes, selective laser sintering (SLS) does not deposit material layer by layer. Instead it uses a high powered laser fired at a layer of powdered or granular model material to fuse (sinter) the particles together creating the part. Much like the FDM process, SLS does not allow for multiple materials to be printed simultaneously but does allow for a wide range of materials from plastics to metals and their alloys, to be printed.
Stereolithography (SLA) utilized a process similar to that of SLS, with the exception that instead of using a layer of powdered model material and a laser, a UV light is fired on the surface a vat of liquid resin. The UV light cures the resin bonding it with the layer below, at which point the part will descend into the vat for another layer of resin to be applied. A chemical bath is needed to clean the part after printing since the part was fully submerged in model material. The need for potentially hazardous chemicals makes the SLA process less ideal for office type environments.