1. Visual Inspection
The visual inspection involves using the human eye to detect surface defects, tears, misruns, cracks, cold shuts, gas evolution, molding flaws, metal penetration, slag adhesions and sand inclusions. This inspection is essential to ensure the casting adheres to visual acceptance standards.
2. Dimensional Inspection
The dimensional inspection ensures a part of the casting meets dimensional requirements or tolerances. This inspection can be performed manually or via a coordinate measuring machine (CMM) that utilizes probes for precise measurements. CMM is the most accurate way of testing the products’ dimensions.
3. X-Ray Inspection
An X-ray inspection of the castings can ensure they meet a quality standard. X-rays can reveal small breaks, crevices of heat cracking and shrinkage cavities. Cracks, inclusions and voids will display as a dark area due to the radiation the X-ray uses. If a casting’s mechanical properties have been compromised by holes, inclusions or shrinkage, the item can be fixed before shipment. In some cases, common surface irregularities may not affect the use of the otherwise sound casting.
4. Liquid Dye Penetrant Inspection (LPI)
With a liquid dye penetrant inspection (LPI), small surface imperfections like pores or cracks that are hard to see in metal castings are identified. First, the tester cleans the casting to eliminate dust or grit that could prevent the liquid dye from getting into the metal’s cracks.
After the metal is clean and dry, it is bathed with a penetrant solution. Different solutions are used depending on the type of LPI used, though the solution is typically an oil with low viscosity and high capillary action, which allows it to flow freely into the casting’s cracks. This dye is given dwell time to work into invisible crevices. Eventually, the excess is removed with a damp cloth. After a special developer is applied, casting defects are clearly visible.