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Rapid Prototyping Techniques
Prototyping ServicesRapid Prototyping

The RP techniques currently available in the industry are described next. These includes,

  • Stereo Lithography (SLA).
  • Fused Deposition Modeling (FDM).
  • Laminated Object Manufacturing (LOM).
  • Selective Laser Sintering (SLS).
  • Three Dimensional Printing (3DP).

Some of these processes are explained as below with their relative advantages and disadvantages.

Stereo-Lithography (SLA)

Principle and Process

  • This is based on selective polymerization of a photosensitive resin using ultraviolet light.
  • In this system, an ultraviolet laser beam is focused on the top layer of photo sensitive resin contained in a vat.
  • The beam is positions and moved in horizontal X and Y directions to polymerize the resin within the boundary a particular cross-section.
  • The cured layer of polymer is lowered by a platform attached to it, so that a fresh layer of liquid resin covers the cured layer.

Advantages

  • Achieving accuracy in industries.
  • Market shares and industry presence.
  • Capable of high detail and thin walls.
  • Good surface finish.

Limitations

  • Requires post-curing.
  • Some war page, shrinkage and curl due to phase change.
  • Limited materials (Photo polymers).
  • Support structures always needed. Removal of support structures can be difficult.
Selective Laser Sintering (SLS)

Principle and Process

  • In this process a high power laser beam selectively melts and fuses powdered material spread on a layer.
  • The powder is metered in precise amounts and is spread by a counter-rotating roller on the table.
  • A laser beam is used to fuse the powder within the section boundary through a cross-hatching motion.
  • The table is lowered through a distance corresponding to the layer thickness (usually 0.01 mm) before the roller spreads the next layer of powder on the previously built layer.
  • The unsintered powder serves as the support for overhanging portions, if any in the subsequent layers.

Advantages

  • The main advantage is that the fabricated prototypes are porous (typically 60% of the density of molded parts), thus impairing their strength and surface finish.
  • Variety of materials.
  • No post curing required.
  • Fast build times.
  • Limited use of support structures.
  • Mechanical properties of Nylon & Polycarbonate parts.

Limitations

  • Rough surface finish.
  • Mechanical properties below those achieved in injection molding process for same material.
  • Many build variables, complex operation.
  • Material changeover difficult compared to FDM & SLA.
  • Some post-processing / finishing required.
Fused Deposition Modeling (FDM)

Principle and Process

  • The FDM technique relies on melting and selectively depositing a thin filament of thermoplastic polymer (ABS - engineering and medical grade - plastic, Polycarbonate and investment casting wax) in a cross-hatching fashion to form each layer of the part.
  • The material is in the form of a wire supplied in sealed spools which is mounted on the machine and the wire is threaded through the FDM head.
  • The head is moved in the horizontal X and Y directions for producing each layer through zigzag movements.
  • The supporting table moves in the vertical direction and is lowered after the completion of each layer.

Advantages

  • No post curing.
  • Variety of materials.
  • Easy material changeover.
  • Office environment friendly.
  • Low end, economical machines.

Limitations

  • Not good for small features, details and thin walls.
  • Surface finish.
  • Supports required on some materials / geometries.
  • Support design / integration / removal is difficult.
  • Weak Z-axis.
  • Slow on large / dense parts.

Rapid Prototyping Services
Rapid Prototyping
SLA Process
SLS Process
FDM Process
3D Printing Process
Vacuum Casting
Medical Models
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