There are different methods of having a prototype made. However, all 3D prints require a 3D CAD model to be made. These 3D CAD models can be created by a CAD Service such as Restoric Design Ltd.
This article focuses on the rapid prototyping process also known as 3D printing.
Very few prototyping companies offer all technologies, but some have a selection. The following are the main technologies used for 3D printing:
- Selective Laser Sintering (SLS)
- Stereolithography (SL)
- 3 Dimensional Printing (3DP)
Selective Laser Sintering (SLS)
Selective Laser Sintering (SLS) is a well-developed additive manufacturing process that can be successfully used for both prototyping and manufacturing applications. The process works in a similar way to the stereolithography (SL) process in that an Argon laser is used to create a 3D part, layer-by-layer, by tracing the required shape direct from a 3D CAD model via a .stl file. Where SLS is very different from SL is in the format of the materials used and the reaction of the laser with these materials. Selective laser sintering processes finely powdered materials that are tightly compacted and housed in a powder bed within the machine. As the laser interacts with the powder it is fused — or sintered — to form the selected shape and as each layer is completed the powder bed drops down fractionally so the next layer can be traced, sintered and bonded to the previous layer.
Materials: Glass Filled Fine Polyamide, PA 2200 nylon, PA 2210 FR
Advantages: greater strength, generally cheaper compared to SLA
Disadvantages: Less accurate, porous surface finish, Color models cannot be created
Stereolithography (SL)
Stereolithography (SL) is generally recognised as the first and most widely used additive process for building prototypes and parts. Utilising original photopolymer materials in resin format, the stereolithography process builds plastic parts layer by layer to form a complete 3D object direct from 3D CAD data via a compatible format (.stl file). The stereolithography machine processes the .stl file and builds (prints) a 3D part directly proportional to the data supplied.
The stereolithography process employs a solid-state laser, the beam of which traces the required shape across the surface of a vat of liquid photopolymer held in the build chamber of the machine, thereby solidifying the material it touches. On completion of the first layer, the vat is lowered incrementally for the second layer to be solidified with the laser and simultaneously bonded to the first. This process continues until the part is complete. The speed at which the part is built is fully dependent on the nature of the part itself — for smaller, thin-walled models the build time will be quick, however, for larger, denser models the build time will be increased.
The advantages of the stereolithography process include the precise accuracy of the parts built, with good repeatability and superior surface finish. It is also possible to build relatively large parts using this process. The disadvantages of the stereolithography process include the necessity to post-cure parts for improved stability, which can lengthen the overall process.
Materials: Accura 25, Acura 55, SL Grey, SL Clear
Advantages: more accurate, smooth surface finish
Disadvantages: more expensive compared to SLS, Colour models cannot be created
3 Dimensional Printing (3DP)
Three-dimensional printing is a quick, low-cost rapid prototyping process used for concept modelling. The system applies a thin layer of powder on a chamber surface. The ink-jet style spray head deposits a liquid adhesive onto the powder in a 2-D pattern, bonding the layer to form the object. Materials are starch or plaster based which a fragile when handled. The process yields a slightly rough textured surface with lower accuracy than other popular RP systems
Materials: large variety such as plastics, metals and ceramics as long as they can be deposited in powder form.
Advantages: colour prints possible,
Disadvantages: rough texture, lower accuracy, lower strength