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Posted on July 13, 2020

Rapid prototyping is a fast design process that involves an idea, prototyping, and testing of a physical part, model, or building using a 3D computer-aided design (CAD). The building of the part, model, or assembly is typically accomplished through additive manufacturing which is also known as 3D printing. Additive manufacturing describes the technology that is used to build 3D objects by adding layer-upon-layer of material. 

There are two types of prototypes that are used to describe a product. A high-fidelity prototype is when the design matches the projected end product. Whereas a low fidelity type is where there is a clear distinction between the prototype and the final product.

How Does Rapid Prototyping Work?

Rapid prototyping (RP) describes a lot of different manufacturing technologies. The most used RP is additive manufacturing.  However, other technologies that are generally used for RP are casting, molding, extruding, and high-speed machining. 

When using additive manufacturing for the rapid prototyping process, various established processes can be used to build prototypes. 

These processes are:

  • Subtractive: A chunk of material is sliced to create the preferred form using grinding, turning, or milling. 
  • Compressive: A semi-solid or liquid material is altered into the preferred form prior to hardening, just like with casting, molding, or compressive sintering.

What are the Different Types of Rapid Prototyping?

Stereolithography (SLA) or Vat Photopolymerization

This is an additive manufacturing process that is quick and affordable. This technique was the very first method of 3D printing to work. It works by using a tank of photosensitive liquid. This liquid is then turned into a solid layer-by-layer through the use of a computer-controlled ultraviolet (UV) light. This process is irreversible, and the SLA parts cannot be reverted back to liquid form.

Selective Laser Sintering (SLS)

SLS is an additive manufacturing technology that is used for metal and plastic prototyping. It uses layers of powder to create a prototype using a high-power laser to heat and sinter the powdered material. SLS parts are weaker than SLA. However, SLS is low cost, requires minimal time and labor, and offers high productivity. Also, the surface of the finished product is rough and requires more work to obtain the finished product.

Fused Deposition Modelling (FDM) or Material Jetting

FDM is an additive manufacturing process that is affordable, fast, cheap, and an easy-to-use process. This makes it ideal for product development. FDM can be located in a lot of non-industrial desktop 3D printers. It creates a physical object from the bottom up by using thermoplastic filament that is melted inside a printing nozzle barrel. The printer nozzle moves back and forth placing liquid plastic down layer-by-layer using a computer deposition program. 

Selective Laser Melting (SLM) or Powder Bed Fusion (PBF)

This is a fan favorite additive manufacturing technique because its process is relatively inexpensive and makes high-strength, multifaceted parts. SLM is typically used by automotive, aerospace, medical, and defense companies. The PBF method uses either an electron beam or high-powder laser to melt layer-by-layer and fuse material powder together to create either a prototype or production part. PBF uses any powder base material but the most frequent materials used in RP include cobalt chrome alloys, aluminum, stainless steel, copper, and titanium. 

Laminated Object Manufacturing (LOM) or Sheet Lamination

This is a relatively low-cost process that is not as complex as SLM or SLS. The benefit of LOM is that there is no need for specially control conditions. LOM works by assembling layer-by-layer plastic, metal, and ceramic materials that have been already cut with laser beams or a different cutting mechanism to create the CAD design. Each layer of material is bonded with glue on top of the prior one until the component is finished. One problem with this style of additive manufacturing is that ceramic parts need to be decubed making it labor-intensive, involving longer processing times.

Digital Light Processing (DLP)

DLP is a lot similar to the SLA technique in that DLP also uses the polymerization of resins that are cured(hardened) using a light source. DLPs light source comes from UV light from a projector whereas SLA light source comes from UV laser beams. Even though DLP is quicker and is cheaper than SLA, DLP typically needs support structures and post-build curing. 

A different form of DLP is Continuous Liquid Interface Production (CLIP). CLIP uses digital light projection to form a part that is continuously pulled from a vat and does not use layers. As the material is pulled from the vat a sequence of UV images is projected onto it to change its form. This hardens the part and creates the prototype.

Binder Jetting

This additive manufacturing technique enables one or more parts to be printed at the same time. When compared to SLS, the parts created are not as strong. This process works by using nozzles to spray liquid binding agents to join powder particles creating one layer of the piece. Layer-by-layer, powder is added, compacted and spread by a roller, and binder added. Ultimately, the part is created through layering of powder and binder. When finished the part is cured in an oven to singe off the binding agent which merges the powder into the finished product.

Applications

These processes are used by product designers, engineers, and development teams for rapid manufacturing of prototypes parts. Prototypes are extremely beneficial for product designers because the parts aid in visualization, designing, and developing of the manufacturing process prior to mass-producing it.

Rapid prototyping has been around since the late 1980s and was originally used to create parts and scale models for the automotive industry. Since then, it has been applied to a wide range of industries such as medical and aerospace. One application in the dental industry is where RP is used to create various dental moldings such as crowns.

Finally, rapid tooling is another application of RP that enables a person to produce a product quickly and cheaply. It is the creation of a mold in a shortened period of time. In rapid tooling, a part like an ultrasound sensor wedge is created and used as tool in a different process.

What are the Advantages?

The list of advantages of rapid prototyping is endless. RP enables a product designer, engineers, and product development teams to see a more complete view of how their product will appear or work in the beginning of the design and manufacturing process. This enables alterations or improvements to be made in the early stages of the process, saving a designer time and money. The length of time RP takes can range from a couple of days to months and it is largely dependent on the additive manufacturing technique used. 

Two other major advantages to RP are cost-effectiveness and precision. RP is an extremely affordable way to prototype products because it is an automated process that does not require a lot of people to operate. It is also cost-effective because RP can act fast and solve any problems in order to lessen the risk of costly errors while in the manufacturing stage. RP is a tremendously precise technique because of its ability to be used with computer-aided designs (CAD). This enables it to lessen the amount of material that is wasted and there is no need for specialized tools in order to prototype each specific product. 

RP enables designers to show their unique ideas to board members, clients, and investors in a way that allows them to comprehend and approve of the product. Customers and clients are able to provide designers with more accurate feedback because they are able to see what the product will actually look like, based on the physical product they can see and touch, rather than something they have to imagine or visually observe in a 2D drawing. 

Lastly, the RP process gets rid of the need for customized products to be created from scratch. It is an interactive process that enables its customers’ needs to be integrated into designs through affordable means. This process enables RP to provide greater choice and flexibility for customers.

How Much Does It Cost?

The cost varies greatly depending on a multitude of different factors. These factors include the physical size of the part, machining method, quantity, surface finishing, volume or the amount of material used to create the part, labor costs, and how much post-production processing needs to be done.