Investment Cast Components from 3D printed master

Investment Cast from 3D printed Master

The design of this component meant that producing investment waxes via conventional techniques was almost impossible ….

In brief

Like all defence contracts, confidentiality is a must.
Finding examples of work that we are allowed to show is therefore very difficult.
What we are showing here is our own version of a series of designs that one such MOD customer commisioned us to do.

Model requirements….

The design of this component meant that producing investment waxes via conventional techniques would have been very time-consuming and very expensive.
Utilising the SLS process and Castform PolyStyrene powder was the ideal candidate to produce 75 waxes for investment casting.

Delicate De-Caking

Prior to infiltration with wax, the castformPS components are extremely delicate. Highly skilled and patient craftsmen carefully de-cake the Castform pieces from the powder cake.

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Ready for Infiltration

Once de-caking is complete the parts are ready for infiltrating with hot liquid wax.

Delicate De-Caking

Prior to infiltration with wax, the castformPS components are extremely delicate. Highly skilled and patient craftsmen carefully de-cake the Castform pieces from the powder cake.

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Ready for Infiltration

Once de-caking is complete the parts are ready for infiltrating with hot liquid wax.

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How it was achieved…

CAD data was loaded into the SLS machine which sliced the data into hundreds of "slices" ready to be processed.
The SLS machine, loaded with CastformPS polystyrene powder, sinters each slice on top of the previous one building the component from top to bottom.
After a few hours the SLS process is complete and the "Cake" is removed from the machine. Delicate de-caking follows to seperate the components from the unused powder.
The component is then infiltrated with hot liquid wax which soaks into the part similar to a sponge soaking up water. Once the hot wax has cooled, the now red "Wax" can be handed to an investment foundry.
The foundry can then process the CastformPS "Wax" in an almost indentical fashion to that of standard investment waxes to produce, in this case aluminium, castings.

Detailed Views

Under close inspection, some areas show evidence of the stair-stepping that can come from the SLS process.

The surface finish of the resultant casting is slightly rough. The roughness is a direct reflection of the roughness of the SLS CastformPS

Under close inspection, some areas show evidence of the stair-stepping that can come from the SLS process.

In this instance the castings needed to be functional only. The surface finish was left as-is. Finishing techniques are available for castings that require aesthetics also. The finishing techniques are applied to the Castform "Waxes" resulting in a smoother surface finish on the subsequent casting.

Why Castform?….

At MNL we have three choices for producing "waxes" for investment casting. Firstly we can produce actual wax from silicone tools, secondly we can produce QuickCast "waxes" using the SLA process and thirdly Castform as in this example.
So why did we choose Castform?
Perhaps a quick look at the following chart may give a good indication to the pros and cons of the three options.

Real Waxes via silicon tooling

Best Surface Finish

  • Geometry constraints due to tooling design
  • Best Surface Finish Achievable – similar to die casting
  • Slower Processing Speed especially for higher quantites
  • Waxes process EXACTLY the same as standard waxes

QuickCast Waxes via SLA process

Largest Build Envelope

  • Few Design Constraints
  • Surface Finish Shows layering – Can be improved with Surface Finishing to Wax
  • Largest Build Envelope – Parts up to 500x500x580mm can be built in one piece
  • Burn-Out Procedure has to be tailored to suit QuickCast Process

In conclusion….

Within 2-4 days Investment casting waxes can be ready to undergo the investment casting process to produce virtually any metal casting.
In just over a week, 75 "Waxes" were shipped to a foundry ready to be cast.

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