Everyone wants to know the castings they receive from their foundry suppliers are correct, but quality is doubly important when the parts are going into high load, safety-critical applications. A particular challenge with castings is that defects can be hidden from view inside the bulk of the metal, so buyers should satisfy themselves of their supplier’s ability to manage quality. Here’s what happens at Impro.

The Importance of Quality Control in Investment Casting

This process is used to create complex geometries that save weight and reduce or even eliminate operations like welding and machining. It’s often used for casting parts that will go into challenging environments where they will be exposed to high loads and temperatures and corrosive atmospheres or fluids.

In many of these applications the cost of failure can be extraordinarily high. At the same time, casting is a complex process. Metal flows and solidification are influenced by many variables, which can result in flaws and defects inside the cast part. Consequently, a rigorous attitude to quality control is vital to ensure dependable in-service operation.

Defect Prevention

At leading investment casting foundries like those Impro operates, quality begins by optimizing the process to minimize the creation of defects. Metal flows and cooling are modeled to identify potential problems like non-fills and shrinkage defects, and the design revised accordingly.

Only after all options have been analyzed and the design completely optimized are patterns molded and parts cast. These are then inspected carefully for geometric accuracy and the presence of defects. If necessary, the models will be updated and more optimization work done to ensure the integrity of the parts being made.

Quality Control Methods

After casting, part is cut away from the metal feeding “tree”, cleaned up, and inspected. While the tooling design and casting parameters are being finalized, these parts go through both visual and dimensional checks. This is to verify conformance to the drawing and find external casting flaws like non-fills or poor quality surfaces. Dimensional inspection of complex, investment cast parts is almost always performed on a coordinate measuring machine (CMM).

Investment casting is a very repeatable process. This stems from the use of injection molding to make the wax patterns that in turn, produce the mold cavities. Thus, once tooling is correct, dimensional checks are seldom necessary.

In addition, the first parts cast are usually subjected to non-destructive testing (NDT) and also sectioned for access to internal features. NDT can be x-ray imaging, ultrasonic inspection, eddy current inspection, or any combination of these. This will find defects like cracks and gas porosity. Sectioning, which is a destructive process, is used to verify microstructure, and to check surface finish and the dimensions of internal features. It also provides another check for internal defects like cracks.

Once a part enters production, quality control checks are carried out as agreed in the quality plan. This takes into account the intended application and the risks posed by any defects.

Choose Impro for Flawless Investment Cast Components

Investment casting is accurate and repeatable, but as with any casting process, variations in metal flow and solidification can give rise to defects, particularly inside the part. Impro uses a mix of advanced tools and technologies to first optimize the casting process, and then verify the completeness and integrity of the parts produced. Together, these ensure our customers only receive parts that meet and exceed their needs and expectations.

If you would like to know more about our investment casting capabilities, or need a quote for a specific project, please contact us to arrange a discussion.