When new technologies enter a market, it usually brings with it new
opportunities for customers to take advantage of. The use of 3D printing in
investment castings now brings with it the opportunity for customers to
save money on their prototypes and also speed up the process significantly.
Within this content you will find:

1. The different types of 3D printing used in investment casting.
2. The advantages and disadvantages each method could have on your
   project.
3. How it can be used in investment casting to save you both time
   and money.

The types of 3D printing used in investment casting.

Fused Deposition Modelling (FDM)

This technique utilises a form of extrusion to deposit a thin bead of
molten plastic onto a flat platform. Utilising a moving print-head, this
leaves a thin trail of quickly hardening plastic.

These trails are deposited very close to one another so that when they
harden after exposure to air, they fuse together to form a single layer of
plastic. This process is repeated continuously on top of each deposited
layer, eventually forming a fully finished plastic part.

Advantages

• The products made through this technique are dimensionally accurate
• This is an excellent technique for proof of concept models.

Disadvantages

• The materials use predominantly low density plastics such as ABS
  and PLA.
• FDM printing does not produce parts that are robust enough for long
  prototype testing cycles and the adhesion between different
  materials is often very weak.
• Parts need a large amount of support material, which must be
  removed when finishing the part and can lead to dimensional
  irregularities and cosmetic blemishes.

Fused Deposition Modelling (FDM)

Stereolithography (SLA)

Stereolithography uses a beam of ultraviolet light to cure a liquid
polymer. This is done layer-by-layer as with FDM, but does not include any
reaction with air in the solidification process, instead the layers are
chemically bonded through a curing reaction rather than being melted
together.

Advantages

• Parts produced by this technique perform well in mechanical tests
• Parts are relatively inexpensive to produce in comparison to other
  techniques
• The parts produced are far stronger than those made through FDM
  with much better dimensional accuracy. This makes the SLA process
  exceptionally useful in the production of prototypes.

Disadvantage

• This process requires the use of expensive polymer resins
• Takes much longer to complete a full model than FDM, whilst still
  requiring a large amount of support material that must later be
  removed.

Stereolithography (SLA)

 

Selective Laser Sintering (SLS)

Like Stereolithography, Selective Laser Sintering forms stronger components
than Fused Deposition Modelling

 

Advantages

• The parts made through SLS are much tougher than those made through
  FDM
• No support structure is needed when printing the parts, since the
  model is surrounded by powder at all times. This makes it a
  particularly useful technique for the manufacture of parts with
  complex geometries that can go directly into prototyping functions.
• SLS can be used for a variety of different materials including
  glasses and metals. As a result, this is the preferred AM technique
  for prototyping in the aerospace industry

 

Disadvantages

• The Parts require a number of procedures to be performed after they
  are printed to remove surface porosity

 

Selective Laser Sintering (SLS)

 

Polyjet printing

This is a hybrid form of printing that combines the print-head style system
of FDM with the strong bonding of SLA. In this process, photopolymer powder
is sprayed onto a flat print bed in ultra-thin layers and cured using a
moving UV lamp.

 

Advantages

• This produces fully cured parts that require no post processing
  except to remove a minimal amount of gel-like support material
• Parts made through this technique can be used immediately for any
  application from medical implants to working components in small
  production projects
• the most versatile method of 3D printing

Disadvantages

• This technology is still very expensive
• It is limited to polymeric materials for the time being

Polyjet

 

How rapid prototyping can benefit you

When a new part is designed, the 2D drawing and 3D model are used to make a
concept for an injection tool. This is subsequently built by precision
machining large blocks of aluminium and brass and is usually first stage in
the investment casting process.

Advantages

• To reduce this initial lead time, 3D printing can be used to make
  waxes within a number of days which can immediately be put into an
  assembly and used to make a ceramic mould.
• These waxes can be made with the same properties as a traditionally
  injected wax to produce quality parts without the need to invest in
  tooling before finalising the design.
• The parts made in this technique can have multiple design features
  that differ between individual waxes so that many ideas can be
  prototyped simultaneously.

Disadvantages

• This process is costly and takes approximately two weeks to
  complete, which makes it prohibitive in the early design stages for
  a new product. As a result, new products are traditionally tested
  using prototypes made through a different technique.
• This increases the prototyping stages by a number of months for new
  projects, since further testing will be needed once parts are made
  through investment casting.

Wax Assembly

CNC Machining

Polyject

Shelling

 

Ultimately, the use of 3D printing allows us to:

 

• Design 3D models specifically considering the melting behaviour of
  the wax material used so that we can ensure minimal scrap once the
  parts are poured in metal.
• Build wax models with a polyjet printer within one week, compared
  to four weeks when injecting waxes through a traditional tool.
• Collaborate with product designers from the earliest stages of a
  project and as a result, the final part design requires far less
  revision once the products are in regular use.