Precision Casting

The casting method of choice for complex components. 

The Exacast® ceramic precision casting process is an interesting alternative to casting methods like investment casting and shell moulding. The Exacast Process was developed by Wolfensberger and registered under the Exacast® brand name. As the name suggests our precision casting process allows for the accurate casting of complex components. Reusable patterns made of plastic, metal, wood or silicone rubber are coated with a quick-hardening ceramic and then fired. The alloy that is then cast into the preheated moulds is able to flow into extremely thin walled sections. A wide choice of steel and cast iron alloys can be cast as per customer requirements.

Our Strengths – Your Benefit

The Process For Complex Castings.

  • First-class surface roughness: N8/N9 (Ra 3.2 - 6.3 µm) 
  • Tolerances in accordance with VDG instruction sheet P 690 for investment casting
  • Radii > R 0.2
  • Large wall thickness differences possible 
  • Weight of parts 2 to 400 kg 
  • Size of parts up to 1000 x 1000 x 400 mm 
  • Up to 100 cast iron and steel materials

Tolerances In The Exacast® Precision Casting Process.

The tolerances for Exacast® precision casting are based on VDG instruction sheet P 690 for investment casting. The tolerances specified in the sheet can be largely complied with. The only non-compliance that occurs relates to the non form-bound dimensions, for example over the mould partition or from the core mould to the outer mould, and even these do not exceed D1 in VDG standard P 690. If the precision casting tolerance is not adequate, a machining allowance must be added .

 

 

Precision Casting References

Precision Casting Exacast® Products

FRANCIS IMPELLER

Characteristics

Unit weight: 50 to 200 kg
Material: GX4CrNi 13-4 (1.4317)
Batch size: 1 to 5 pieces

Solution

The specially-developed ceramic core permits a surface roughness of Ra 6.3 µm without post-machining for the interior spaces that are not readily accessible. Casting into the hot mould ensures complete discharge into the 3 mm thin blades. The blade end can be generated without any machining allowance. Fulfilment of the tight measurement tolerances, quality-tested delivery with inspection certificate.

GRINDING CONE

Characteristics

Unit weight: 2.5, 4.0 and 5.6 kg
Material: G-X35 CrMo 17 (1.4122) or all common wear-resistant alloyed cast iron, depending on the field of application
Batch size: 1, 3 and 6 pieces

Target Setting

Fine surfaces (N8) of the raw remaining areas, corrosion and/or wear resistant material.

Solution

Diagonal undercut grinding cones realised without a core thanks to a silicon rubber pattern part. Tight tolerances lead to even distribution of the mass: minimal machining allowance and low balancing resources. Supplied ready-to-install.

PELTON ROTOR

Characteristics

Unit weight: 30 to 200 kg
Material: GX2CrNiMoN 26-6-3 (1.4468)
Batch size: 3 to 10 pieces
various sizes with a pattern combination

Target Setting

Casting of a bucket profile without machining allowance, possibility of pattern combination in order to reduce pattern costs.

Solution

The complete bucket profile can be cast without a machining allowance with our Exacast© ceramic precision casting technique, guaranteeing high dimensional accuracy and surface roughness from Ra 3.2 to 6.3 µm. Considerable machining effort is consequently saved. Pattern costs can be substantially reduced as a result of ingenious pattern design and pattern combination.

PELTONLAUFRAD-SEGMENT

Characteristics

Unit weight: 2.5 kg
Material: G-X 4 CrNi 13-4 (1.4317)
14 per pelton rotor

Target Setting

Better quality than sand casting, also cost effective in medium sized batches, minimal post-machining.

Solution

Surface roughness of Ra 3.2 to 6.3 µm and high tolerance of the cup shape, tapering mid-cutting edges fully cast with just minimal machining allowance, tempered under inert gas, machined ready-to-install and quality-tested.