The main goal of the CARCIM project was the integration of the two-component ceramic injection moulding (2C-CIM) as a low-cost and large-series production technique for development of complex shaped ceramic components for automotive and railway applications offering a high degree of structural and functional integrity.
To achieve the main project goal the following tasks had to be fulfilled:
- specifying four functional components as case studies including material choice and freezing of the final design;
- adaptation of powder surface properties to the requirements of feedstock production;
- development and supply of new feedstock suitable for low/high pressure 2C-CIM and environmental-friendly debinding processes;
- linking of tools for simulation techniques of 2C-CIM parts enclosing the complete processing chain, i.e. tool design, injection moulding, debinding and co-sintering processes;
- design and construction of a 2C-CIM tool for testing parts;
- establishing of a test rig for non-destructive testing (NDT) by thermography for injection moulded ceramic green parts;
- to develop debinding concepts for co-debinding of the feedstock couples;
- to predict final distortion of testing and prototype parts after sintering by FEM analysis;
- to develop testing samples by high and low pressure 2C-CIM and to characterise these parts;
- to produce powders and feedstock couples with refined properties according to the results achieved the testing parts;
- to design prototype parts and to simulate the mould filling process for these parts;
- to design and to construct tools for the four prototype components;
- to develop prototype parts by high and low pressure 2C-CIM;
- to fix the final composition of the feedstock systems for large-scale production of the prototype parts;
- to investigate the prototype parts in the green and in the sintered state by non-destructive testing methods;
- to establish technical guidelines for high-volume production of the case study components;
- to test the prototypes under practically relevant conditions;
- to estimate the production costs for the specified components;
- to validate and to verify the results of the simulations results of the different processing steps;
- to perform a comparison between traditionally used materials and the ceramic materials chosen for the ceramic components with respect to the main environmental impact and
- to organise two technical workshops.
As a result of the work implemented under the project the following conclusions were defined:
- Two-component ceramic injection moulding is a very promising shaping technique for large-scale production of ceramic parts with novel functionalities and complex geometries. The advantage of this technology can be seen in the fact that two different ceramics can be combined without any additional time-consuming and expensive assembling or joining steps. However, two-component ceramic injection moulding is a very challenging shaping method. For each processing step of the technological chain both ceramic materials have to be adjusted to each other. Following principle requirements should be taken into account for the development of two-component ceramic parts:
- The powders chosen for two-component injection moulding must be sinterable to full density at comparable temperatures and under the same gaseous atmosphere.
- For avoiding critical stresses during sintering the powders shall have a similar sintering behaviour, i.e. the onset of shrinkage shall fall in a narrow temperature range for both powders and the shrinking rate shall be comparable.
- For ensuring a precise adjustment in total shrinkage the volume content of solid in the feedstocks must be the same.
- Since differences in the thermal expansion coefficients of the feedstocks may cause cracks, distortion or delaminations of the compounds already in the green state the same binder system or binder systems with comparable thermal expansion behaviour must be used for feedstock preparation.
The thermal expansion coefficients of the sintered ceramic materials play also a very important role as shown in this article, because differences in this property can result in stresses in the two-component part during cooling after sintering or during application of the part under cyclic heating and cooling conditions.
If stresses between both components cannot be excluded totally, they should be taken into consideration already in the design of the injection moulded parts.
The CarCIM project showed the feasibility of ceramic components with novel functionalities by two-component injection moulding. It emphasized the importance of non-destructive testing methods for ensuring the quality of the products in each processing step. Simulation of the processing chain can also be a helpful tool for avoiding problems in mould filling or with distortion and delamination of components. However, for improvin