Precision Casting

The process for complex castings. 

e Exacast® ceramic precision casting process is an attractive alternative to conventional methods like investment casting. Further developed by Wolfensberger and registered under the Exacast® brand name our precision casting process allows the precision manufacturing of demanding components. Reusable patterns made of plastic, metal, wood or silicone rubber are coated with a quick-hardening ceramic and then fired. The choice of material for steel and iron applications is virtually unlimited.

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

NOZZLE RING

Characteristics

Unit weight: 2 to 120 kg
Heat-resistant steel casting, nickel-base alloys
Diameter: 200 to 1000 mm
Dimensional tolerance up to D3 (VDG information sheet P 690)

Solution

Wolfensberger developed special pattern facilities that can be combined. The flow diameter of the nozzles machined ready for assembly is measured with a computer-controlled test system and logged. Tolerances are called for here in excess of the D3 degree of accuracy required for investment casting in compliance with VDG specification P 690. Unlike the previous welded construction, Exacast© ceramic precision casting means less rejects because of a lower likelihood of cracking, as well as higher strength and resistance to wear. At the moment, ABB Turbo Systems takes delivery of over 12,000 nozzles in 300 variations annually.

IMPELLER WHEEL

Characteristics

Unit weight: 5 to 100 kg
Material: GX5 CrNiMo 19-11-2 (1.4408)
Batch size: 5 to 100 pieces

Target Setting

Hydraulic pump parts with high finish quality, strict tolerances, complicated blade geometry, minimal post-machining.

Solution

With Ra 3.2 to 6.3 µm in the pre-cast interior spaces that are practically inaccessible for machining, there is a very high level of effectiveness, optimal shaping of even the thinnest blade parts beside thick-walled areas and high flexibility in terms of material and shape variations (e.g. diameters from 200 to 800 mm). Delivery with inspection certificate.

REGULATING BLADE

Characteristics

Various types and sizes, Unit weight: 0.6 to 50 kg
Material: EN-GJSA-XNi22 (Ni-Resist) GX4CrNi13-4 (1.4317) and GX5CrNiMoNb19-11-2 (1.4581)
Batch size: 12 / 24 / 48 pieces
supplied machined, ready to be installed, with 3.1 certificate

Target Setting

Very high surface quality for high efficiency, lower tool costs, short lead time without storage and the possibility for casting different materials.

Solution

The usage of ceramic moulding material results in a very fine surface condition and a perfect net shape which does not require additional machining of the blade area. According to the required application varies materials can be cast with one and the same pattern equipment.

STATOR / ROTOR

Characteristics

Unit weight: approx. 4 kg
Diameter: 200 mm
Dimensional tolerance up to D3 (VDG), Surface roughness N8
Material: EN-GJS-400-15 (GGG-40) and GX4 GNi 13-4 (1.4317)
Batch size: 1,000 pieces

Target Setting

Cleanly designed blade tips and connecting surfaces, complicated part geometry, high quality requirements (surfaces, tolerances, materials).

Solution

The high degree of effectiveness is provided by the well-formed 2.5 mm thin blades with R 0.2 mm jagged edges and the low surface roughness of Ra 3.2 µm in the blade section. Exacast© ceramic precision casting provides these values without post-machining, partly because of the fine ceramic shaping material and partly because of the complete flow of the molten metal into the hot shaping parts. Because there are no cores for the undercut blade sections, close tolerances can be observed.