The wax patterns of these special turbine components (cored) are injected in WAX Area in one solution in dies provided by core housing.

The ceramic cores used in EMA for components with equiaxed (EQX), directional (DS) and single-crystal (SX) grain structure have dimensions ranging from a few centimeters to 70 cm, with different and highly complex geometries.

The operations performed on the ceramic cores within this production Area are finishing, impregnation with a material that ensures the increment of the mechanical resistance during wax injection, CMM and GOM (3D industrial scanner) dimensional inspection, preparation for wax injection (e.g. spacers (chaplets) insertion, partial filling with wax, core-wax adherence optimization) and visual inspection for verifying their integrity and compliance with the quality specifications.

Wax Area is equipped with a series of semi-automatic systems for wax injection into steel/aluminium dies for the manufacturing of the wax patterns of the final components. These systems ensure the control and monitoring of the thermo-fluido-dynamic production parameters during the whole wax injection process. In particular, the main process variables are subjected to a continuous control by means of complex feedback systems in order to ensure the stability of the injection process so that full compliance with the set standards and high product quality are always guaranteed.

The wax patterns thus manufactured are then manually processed on workbenches equipped with the most modern tools for components finishing and preparation to subsequent process operations. Subsequently, the wax patterns are subjected to a series of non-destructive tests such as visual inspection, digital X-ray inspection, dimensional measurements with CMM machines, optical scanning of the whole pattern with newest GOM cameras based on Blue Light Technology, wall thickness measurement by means of Ultrasonic Thickness Gauges to verify their compliance with the quality standards. The wax patterns are then assembled in a variable number, according to their type and dimension, on specific assemblies in order to increase the production efficiency in terms of raw and ancillary materials and productivity.

The environmental thermo-hygrometric conditions of the Wax Area (temperature and relative humidity) are in-line monitored to guarantee the dimensional stability of the wax patterns during their permanence in this production Area.

The robotic cells offer maximum working flexibility so that there can be produced a wide range of shells in terms of:

• materials - there are available three different shell systems with specific mechanical characteristics able to meet the casting requirements for all alloy types used in EMA and for the three solidification processes i.e. directional (DS), single-crystal (SX) and equiaxed (EQX);
• weight - up to 150 kg;
• dimensions - maximum cylindrical envelope of 1000 mm in high and 800 mm in diameter.

The anthropomorphic robots (6/7 axis) are of the latest generation and guarantee accurate and delicate (vibration-free) handling of small and large wax assemblies. All rotary tanks containing ceramic slurries are equipped with automatic-lids and cooling paddles to avoid contaminations and maintain a controlled slurry temperature.

The rotary and vertical rain cabinets guarantee an uniform stucco powder distribution onto the wax assemblies.

All the ceramic slurries are prepared by means of an automatic mixing plant that ensures the transfer and mixing of the various constituent materials (i.e. binders, refractory powders, wetting and antifoaming agents) in automatic mode.

All the ceramic slurries are regularly checked during their use in production by measuring a series of physico-chemical characteristics (e.g. viscosity, plate weight, temperature, pH, total solids, silica content, specific gravity, gel test).

The granulometry of the incoming stucco powders are regularly checked.

In order to guarantee the stability of the shell manufacturing process, the control systems of the Shell Area ensure, through complex feedback systems:

• the full management of the robot handling programs (rotation, translation and time interval of the individual movements);
• the control and monitoring of all process and environmental parameters such as slurries temperature, environment temperature and relative humidity, ventilation and air flux inside the drying rooms for forced shell drying.

Continuous development activities are carried out for the selection of new, increasingly performing materials and new in-line measuring instruments.

• preparation for the casting, where the following operations take place 

- internal cleaning of the ceramic mould/shell by means of vacuum technique and water washing to ensure the complete removal of all debris that can be potential causes for metallurgical defects

- integrity control of the ceramic mould/shell by using tracers able to intercept even the most imperceptible cracks

- application of insulating blanket onto the ceramic moulds/shells of the equiaxed components with size and shape guaranteed by CAD/CAM cutting machine;

• casting.

The equipments used for the casting, the real heart of our manufacturing process, are of three kinds:

- Resistive furnace for high vacuum casting of small dimension components (up to 10 kg per cast) by using the Bridgman controlled solidification in single crystal or multigrain structure.

- High vacuum induction furnace for casting mediante un processo di tipo tilt pouring components up to 70 kg per casting with equiaxed solidification; each furnace is feeded by a dedicated pre-heat furnace

- High vacuum induction furnace for casting , mediante un processo/tecnologia di tipo Bridgman, components up to 32 kg per cast on big assemblies, and with controlled solidification, single or multi grain.

All the equipments are provided with feedback systems for the control and recording of each casting key process parameters such as vacuum level, temperatures, pouring velocity, withdrawal velocity. All furnaces are integrated to a manufacturing execution system that ensures the possibility to access the on going casting activities from any computer workstation within the factory and to monitor, at any moment, the castings key parameters and eventually correlate them with any other process parameters and with the results of the post cast non-destructive controls.

• DRESSING: is carried out by using belts with cloth and coarse abrasive support such as to remove material from the surfaces. Subsequently, to reduce roughness, nylon fiber tapes impregnated with fine abrasives are used. The aim is to remove the indications coming from the previous processes and from the post finishing DIM/NDT controls.
• HEAT TREATMENT: at high vacuum to modify the material characteristic as requested by the customer; some components received also heat treatment at very high pressure (up to 130 atm), to remove possible internal retirements due to the cooling process of the mouldings after the casting: the equipment used for such treatments have technology workstation for the check, the monitoring and registration of all the process parameters such as pressure, temperature and time
• CHEMICAL TREATMENT: for the preparation of the surface for the following inspections; the components with ceramic core are submitted to leaching operation in autoclave using soda solution with pressure cycles and temperature supervised; the solution used in the process are regularly monitored and eventually correcte or scrapped in function of the result of the analysis done in the EMA laboratory
• SURFACE TREATMENT: such as vibro polish, abrasive sandblasting, dryhone sandblasting, polishing, to prepare the surface in terms of clearing and ruggedness to the following processes.
• MARKING: is carried outby a stylet with a vibrating tungsten carbide tip, pneumatically or electrically operated, which generated micro impacts on the surface of the product and does not produce chips or waste materials. The aim is to uniquely identify the components.

- Product Introduction by the research and definition of optimal and robust combination of main process parameters, enabling reduced time and cost for the new component development;

- Continuous Improvement by yield increment and cost reduction activities.

Investment Casting Modelling is applied to the production of components with directional, single crystal and equiaxed grain structure.

The ceramic shell heating and filling with alloy as well as the casting solidification processes are simulated by the application of finite element method (FEM), using QM00 proprietary software and ProCAST software. In this way thermal and mechanical induced defects, specific to each process configuration modeled, are predicted.

Using Casting Modelling, different process methods can be developed, tested and optimized within virtual environment, reducing the number of physical casting trials, by the variation and trialling of such items as:

- part and core geometry;

- assembly geometry;

- shell material and thickness;

- alloy material;

- casting programs.

In the list of the metallurgical checks we can find the NDT (visual inspection, x-ray and penetrant test) and the check for the grain structure, a non-destructive method, used on metals, for testing the structural indications visible on the surface after selective etching, in an illuminated room with visible radiation. The method for visual grain inspection allows to highlight indications through contrast.

In the dimensional inspection group we can also find the checks go / no go (profile scan, gauge, calliper clock, calliper ect..) and the checks with Coordinate Measuring Machine (CMM) and with Structured Light (GOM). Moreover, in case of castings with cooling passages, wall thickness is measured by ultrasonic technique.

In case of particulars components, it is possible to perform  further test, for example measure of air/water range, inspection of the cooling passages, conductivity test.. The high precision machines used for the dimensional tests, together with tools monitored periodically by visual inspection and by metrological checks, ensure the production of components of excellent quality.

The main metallographic equipment are:

• Cut-up machines
• Mounting pressers
• Automatic grinding and lapping machine
• Optical Microscope with CCD camera and Image analyser system
• Stereo Microscope with CCD camera and Image analyser system
• Scanning Electron Microscope with EDX probe

The main equipment for alloy chemical analysis are:

• XRF spectrometer for the analysis of the main elements
• Microwave Reaction System and ICP-MS spectrometer for the analysis of residual and trace elements.
• Analyzer for the determination of Carbon and Sulfur by combustion
• Analyzer for the determination of Nitrogen and Oxygen by fusion

The main equipment for the chemical-physical analysis of the other materials used are:

• Titrators dedicated to  control of ceramic leaching, acid etching (GSA and FPI preparation), neutralization cleaning and degreasing solutions.
• Furnaces muffles, weight scales and picnometers for total solids, specific gravity and binder solids determination in ceramic slurry.
• Centrifuge and portable XRF spectrometer for silica content analysis of slurry binders.
• Sieves and optical granulometer for size analysis of ceramic powder and flours.
• Optical dilatometer for deformation measurements of ceramic samples.
• Water autoclave for porosity measurements of ceramic samples.
• Simultaneous Thermogravimetric & Differential Scanning Calorimetry equipment.
• Adhesion test machine for ceramic material.