Wax injection Mould

The first step in the development of a component that must be cast with the lost wax method is the engineering and production of a matrix. This matrix is developed in-house at CIREX in the tooling department and is a “negative” of the final cast piece. Once the design phase is completed, the matrix is milled or spark-eroded and assembled by a specialised toolmaker. CIREX is responsible for the design and development so that the matrix can be produced externally using the most advanced processing machines.

With the matrix, a “positive” of the wax model is injected, with precise dimensioning and excellent contour relief. These wax models are “treed up” into a so-called wax tree, which includes both a large number of wax models and the casting funnel in which the steel will be poured later in the process.

At CIREX, various types of wax injection matrices are used. For a clear picture of the various types, please see the summary below.

General features of wax injection moulds

  • suitable for both small series and large series of castings
  • nearly unlimited lifespan
  • single investment for nearly infinite production capacity
  • wax injection matrices are made of aluminium or steel
  • extremely high dimensional accuracy
  • the form is corrected for a constant shrinkage factor during the coagulation of the liquid wax
  • no release angle required because the wax model shrinks
  • provided with cores and slides in case the wax model has non-releasing facet(s)
  • good heat conduction
  • wax model identical to final cast piece
  • excellent contour relief
  • matrix produced using processing machines or spark erosion
  • matrix contains injection channels to guide liquid wax to the cavities
  • provided with cavity numbers for good traceability of the products

Pre-series moulds

The pre-series matrix is mainly used for making the first series products quickly and reliably. We get feedback from the customer after the first delivery as to whether additional optimisations must be implemented to the product design. These changes can often be performed quickly and easily. In addition, a pre-series matrix provides good technical insight into the product and the production process. This information is used later to ensure the series production runs optimally from the start.

  • suitable for first production series to determine whether the product design functions
  • used for smaller series, up to approximately 200 pieces
  • usually made of aluminium
  • manual operation
  • favourable price level due to low production costs

Single series moulds

This matrix is often used in the industrial sector in which relatively small series of castings must be made.

  • used as a series production matrix throughout the entire life cycle of the product
  • consists of a single cavity, hence the name single matrix
  • matrix can contain multiple cores or slides
  • suitable for medium-size series (250 to 5000 units)
  • usually made of aluminium
  • manual operation
  • favourable price level
  • product prices relatively slightly higher because the products are injected piece by piece

Multiple series moulds

A multiple series matrix is usually used in the automotive and industrial sectors in which large series of castings must be made. Whether the series mould must be controlled manually or automatically is decided on the basis of the expected annual production and duration of a project. For the production of extremely large series of castings in the automotive industry, for example, steel moulds are always automatically controlled. Both manual and automatic control are possible in the industrial sector.

  • used as a series production matrix throughout the entire life cycle of the product
  • consists of multiple cavities, hence the name multiple matrix
  • matrix can contain multiple cores or slides, operation can be hydraulic or using springs
  • suitable for large to very large series of castings
  • fabricated from either aluminium or steel
  • usually automated operation
  • often complex matrices
  • higher price level
  • product prices relatively low because several products can be injected simultaneously

Manually operated versus automatically operated moulds

There is considerable confusion about the use of a manually or automatically operated matrix.

As the word indicates, a manually operated matrix is operated manually by a CIREX employee. However, the wax injection cycle itself runs completely automatically: processing times and injection pressures are controlled by the wax press.

When using an automatically controlled matrix, not just the wax injection cycle but also the operation of the matrix is electronically controlled by the wax injection press. The production of large series of wax models runs entirely automatically (without personnel).

Manual

  • this matrix is operated manually on a wax injection press
  • favourable price level matrix
  • matrix can contain multiple cores or slides
  • suitable for both small series and medium-size series of castings
  • fabricated from either aluminium or steel

Automatic

  • this matrix is operated automatically on a wax injection press
  • no manual activities are performed here
  • often very complex matrices in terms of design and dimensions
  • often contains complex electronics and hydraulic and pneumatic systems
  • suitable for large series of castings and/or long-duration projects
  • always made of hardened steel, so nearly unlimited lifespan

Aluminium moulds versus steel moulds

The matrices that CIREX uses in its production process are made of either aluminium or steel. Below is a brief summary of the differences:                                       

Aluminium

  • suitable for both small series and medium-size series of castings
  • less wear-resistant than a steel matrix
  • less conduction of heat than with steel
  • good dimension retention and high precision
  • favourable from a price standpoint
  • applicable to multiple or single-series injection
  • relatively simple matrices

Steel

  • nearly unlimited lifespan
  • suitable for large to very large series of castings
  • very good retention of dimensions and precision
  • good heat dissipation
  • high cost price is compensated for by long lifespan
  • primarily automatic and multiple matrix

The series size and expected lifespan of a project determine whether the mould is installed on a manual press or on an automatic wax injection press and whether it should be made of aluminium or steel. The decision is also affected by geometry and the manufacturability of the component to be produced.