Introduction
Rapid prototyping is a manufacturing technique used for fast fabrication of any physical part, model or assembly. It uses, 3 Dimensional Computer Aided Design (CAD). The term additive manufacturing, or 3D printing. is used for producing any part, model or assembly.
Working
Several manufacturing methods fall under Rapid prototyping (RP), and most of which adopt layer by layer material addition process.
Materail in different form (powder, filament, liquid, etc.) is fed to the machine and usually melted, applied layer by layer, to finally produce the desired part.
Different Types of Rapid Prototyping methods
Stereolithography (SLA) or Vat Photopolymerization
It is the first commercial method of 3D printing. Photosensitive liquid is used as raw material, which is applied layer by layer. Each layer is solidified susing a computer-controlled ultra violet (UV) light.
Selective Laser Sintering (SLS)
SLS uses a powder bed for manufacturing of prototype. Laser is used to heat and sinter the powdered material. The strength of the part produced is poorer as compared to SLA, The output surface finish is poor. Secondary surface finish is needed for achieving better surface finish. Application-Metal, plastic
Fused Deposition Modelling (FDM) or Material Jetting
A long thermoplastic filament in coiled form is used in FDM as raw material. The filament is melted inside the barrel of the nozzle, before the liquefied plastic is laid down layer-by-layer according to a computer deposition program. The process is in continuous improvement in terms of output quality, speed and cost of manufactured product. It is widely used for making prototypes as desktop 3D printers.
Selective Laser Melting (SLM) or Powder Bed Fusion
Also called, powder bed fusion process is preferred for making high-strength, complex parts. A fine metal powder is used which is melted in a layer by layer manner to produce either prototype or production parts using a high-powered laser or electron beam. Commonly used materials include, titanium, aluminium, stainless steel and cobalt chrome alloys. Selective Laser Melting is often preferred by the aerospace, automotive, defence and medical industries.
Laminated Object Manufacturing (LOM) or Sheet Lamination
LOM process is less sophisticated than SLM or SLS, but it does not require specially controlled conditions. LOM produces a series of thin laminates which are perfectly cut with laser beams to produce part as per the CAD pattern design. Each layer is bonded on top of the previous one until the part is complete.
Digital Light Processing (DLP)
DLP is similar to SLA, as both use polymerisation of resins. But curing is achieved using a more conventional light source than SLA. It is also cheaper than SLA. Support structures and post-build curing is often needed after printing. .
Binder Jetting
It can print more than one parts simultaneously. The produced parts are not as strong as compared to SLS. One layer of part is produced by spraying micro-fine droplets of a liquid using nozzles onto a powder bed.
Before applying the next layer, the previous layer is compacted by a roller. After all the layers are applied, the final part is cured in an oven.
Applications
Rapid manufacturing of prototype parts to facilitate, visualisation, design and development of the manufacturing process before actual production starts.
Create parts and scale models for the automotive industry, medical and aerospace.
Rapid tooling, to manufacture parts as, injection mould plug or ultrasound sensor wedge, to be used as a tool in another process.
Advantages
Able to gain a more complete picture of how a product will look or perform in the early stage of the design and manufacturing cycle, allowing changes or improvements to be implemented earlier in the process. The time this takes can vary from a few days to a number of months, depending on the methods used.
Cost effective way to prototype products as it is an automated process, requiring less staff to operate. This process is also extremely precise, being able to use computer aided design (CAD) to help reduce the amount of material wastage and does not require special tools for prototyping each new product. Being able to act quickly and solve ay problems also reduces the risk of costly errors during the manufacturing stage.
Rapid Prototyping helps designers present new concepts to board members, clients or investors so that they can understand and approve a development or product. This visualisation can also allows designers to gain ready feedback from customers and clients based on an actual physical product rather than a concept.
As rapid prototyping is an iterative process it allows customer requirements to be incorporated into designs cost-effectively. The process cuts out the need for customised products to be designed from scratch while providing greater choice and flexibility for customers.
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