All manufactured components used in all industries, aerospace, automotive, medical, etc. go through product design and development towards the end of designing a final product. During this process there is a necessity having high-quality functional prototypes is enormously helpful, and if these prototypes can be made in-house using prototyping technology and concept models, it makes the design process so much more streamlined and efficient before venturing into large-scale mass production using different manufacturing methods.

All methods of rapid prototyping - 3D printing technology, additive manufacturing, Rapid Prototyping, stereolithography, etc. - have immensely helped in product design and new product development.

Rapid Prototyping vs 3D Printing

Additive manufacturing - This technology uses computerized 3d model and by adding material layer by layer. The word additive manufacturing was derived from the word ‘adding’. Conventional machining is exactly opposite to Additive manufacturing and can be referred to as Subtractive manufacturing since material is removed.

3D Printing - 3D printing and Additive manufacturing can be used interchangeably. 3D printing is much more widely used in the general public, while additive manufacturing is used mostly by professionals in certain industrial sectors.

Rapid Prototyping - As the name suggests, Rapid Prototyping is an application used in additive manufacturing or 3D printing to create a model ‘faster’ than the normal process. Rapid Prototyping can be done either by additive manufacturing or 3D printing.

Stereolithography - Stereolithography belongs to a family of additive manufacturing technologies known as vat photopolymerization, commonly known as resin 3D printing. These machines are built using a light source (laser or projector) to cure liquid resin into hardened plastic. SLA 3D printers use light reactive thermoset materials called ‘resin’.

Are Rapid Prototyping and 3D Printing the Same?

Rapid Prototyping is a prototyping technique used to grow or fabricate a prototype from a CAD file. Additive manufacturing / 3D printing or any other prototyping manufacturing process falls into this category.

Rapid prototyping has wide range of material options, while 3D printing is limited to PVC, Plastic materials, Nylon, certain types of rubber, etc.. With technology advancement, ceramics may be available in 3D printing in future.

3D printing technology does not require any tooling needed by conventional machining methods.

Rapid Prototyping Techniques

There are various techniques of rapid prototyping services available in market from which to choose. Depending on the lead-time, complexity, accuracy, cost and size of the part an appropriate 3D printing service is chosen, and some of the most common processes are :

• 3D printing - SLA (Stereolithography), FDM (Fused Deposition Modeling), SLS (Selective Laser Sintering) are some of the most common 3D printing technologies.

  • FDM (Fused Deposition Modeling) - FDM is the most common and popular technique in 3D printing. It is very user-friendly and cost-effective process. Models are built layer by layer using material filament. The filament will be in the form of wire and fed into the nozzle and when heats up liquifies the material and the material is extruded from the nozzle layer by layer (Z-axis). The nozzle will move in X, Y axis as per the geometry of the part. The X,Y movement route map is calculated by the machines computer.
    • FDM machines are inexpensive.
    • Material used in FDM machines is also inexpensive.
    • A wide variety of choices for 3D printing material are available, also in wide variety of colors.
    • FDM machines are comparatively slower, and build quality is also not as accurate as other methods.
    • High strength materials are available and can used, when needed.
  • SLA (Stereolithography) - SLA uses a liquid resin material and models are built layer by layer and when exposed to ultraviolet(UV) light of right wavelength, this will selectively solidify part features. The UV light continues this process for the entire part, solidifying the resin to match the 3D model from the CAD design. Structural supports are created before setup process and manually removed after printing is completed. Uncured resin is washed in a solvent solution.
    • SLA technology has size limitations and has less options for material selection.
    • Operating costs for SLA machines are higher compared to FDM machines.
    • SLA machines are more expensive than FDM machines.
    • SLA machines yield prototypes having less mechanical strength.
    • SLA is a faster process than FDM.
    • SLA is used mostly in jewelry, dental sectors where need of high quality and accurate detailing is necessary.
    • Parts made using SLA technology have very good surface finish.
    • SLA printers should be handled with care as the resin used is toxic and is not recommended for inexperienced users.
  • Polyjet - Polyjet 3D printers use UV cured liquid resin and inkjet like print head to distribute the resin onto print bed eliminating the messy, smelly and hazardous pool used in SLA machines. Polyjet 3D printed parts has various steps involved in support material removal process. Polyjet is proprietary technology of Stratasys.
  • Multijet - Multijet 3D printers are similar to Polyjet except they use paraffin wax as the support material, which results to an easy curing process. On removal of part from the print bed, it is kept in an oven for easy melting of the wax support. No effort is needed to remove the support material which makes it an easier removal process. Multijet is proprietary technology of 3D systems.
  • SLS (Selective Laser Sintering) - This technology produces highly accurate and durable parts that are capable of being used directly in end-use assemblies for low volume production. SLS materials are primarily nylon based materials. This process involves selective laser sintering with high-power laser to fuse small particles into the 3D model geometry. The laser selectively fuses powdered material by scanning cross-sections of the geometry generated from the 3D CAD model.
    • SLS materials are primarily nylon based
    • SLS machines are expensive.
    • SLS does not need any support structures unlike SLA & FDM.
    • SLS can build intricate and complex geometries.
    • Unlike SLA & FDM no post printing process is needed.

• CNC Machining - If a high accuracy and exact material requirement is needed, CNC machining or traditional manufacturing is the best option to deliver a high-quality final product. Although, it might not be a cost effective process, as it is a subtractive manufacturing technology involving material removal using a conventional or CNC turning / milling process - it yields an exact part.

• Rapid Injection Molding - This process incorporates a rapid tooling method to deliver a production grade final product quickly. Technology used in this process is also very accurate and mostly used when several prototype parts are needed. This process is more expensive than 3D printing but considerably cheaper than CNC machining.

• Vacuum Casting - Vacuum casting is used when air is an issue. Air can entrap in the mold and cause issues with finish and intricate details on the feature may not form accurately. This process is also expensive than 3D printing.

For simple prototypes, used for conceptualization - it’s most cost effective to invest in a 3D printing machine.