THE IMPORTANCE OF FOUNDRIES
The processes of casting metal in foundries were first documented in the Middle Ages for the production of bronze and iron bells, canons, and cannon balls. Thereafter, the metal casting industry grew to supply the demand of expanding towns and cities, for which more advanced and stronger tools were developed.
Nowadays, foundries continue to play a vital role in the development of critical parts and components used in the automotive and aerospace industries, such as car and truck transmissions and aircraft engines, to name just a few. Consequently, these major industries rely on metal castings produced in foundries.
Although the process of casting molten metal into a mold was developed a long time ago, foundries must continue to optimize their processes and remain attentive to new technologies in order to push forward the development of better castings. Their clients are aware that poor castings will have a serious impact on the reliability of manufactured goods used by a majority of consumers around the world.
THE CASTING PROCESS
A foundry is the factory where metal castings are produced. The general steps involved in the casting process are patternmaking, molding, melting metal, pouring liquid metal into a mold, then removing the mold material after the metal has solidified, cleaning and fettling the casting, and, finally, inspecting the casting.
The final casting shape corresponds with the mold it is poured into, so molds are carefully shaped with a pattern—a wax, wood, plastic, or metal replica of the object to be cast. The mold is constructed using different operations depending on the type of foundry, metal to be poured, quantity of parts to be produced, size of the casting, and complexity of the casting.
Among castings, die casting is a modern technique developed to improve the quality of casting finish and the dimensional consistency. Die casting is characterized by forcing molten metal under high pressure into a mold cavity. Because manufacturing die casting is relatively simple, production cost per item is low, making this process specifically suited for a large quantity of small- to medium-sized castings.
CHALLENGES IN PRODUCT DEVELOPMENT
The first steps of the casting process—patternmaking, molding, melting, and pouring—lead to a first raw casting that is compared to the computer-aided design (CAD) file in order to verify that it presents enough material for the subsequent steps of cleaning and fettling. If the casting does not match the specifications, the mold must be corrected. From this moment, an iterative process begins, which consists in making modifications to the mold as long as the casting does not correspond to the required parameters of the nominal part.
Throughout this iterative process, inspections are performed on the casting—not the mold—in order to make the necessary corrections on the mold. For example, if a hole is too wide on the part, modifications are made at this precise location on the mold. If a surface is too thin, corrections are made on the mold to obtain a greater thickness on the precise surface that will be machined later on. And so on. This iterative process takes place until the part with the required dimensions and thicknesses is obtained.
Once, and only once, a first casting corresponds to the required specifications and fits within tolerances, then product development is completed, the mold is suitable, and volume production of castings can begin. Consequently, the more the foundries can speed up this iterative process of inspections and modifications, the more quickly production can start.
CHALLENGES IN QUALITY CONTROL
It is normal that, after producing large quantities of castings, molds and dies will wear and chip, leading to products that no longer meet the specifications. Knowing that this wear is inevitable, quality control and maintenance of the molds and dies is required to avoid production deviation. However, quality control and maintenance interrupt the casting production, resulting in a loss of money for foundries. Therefore, they must find ways to accelerate the inspection time in order to restart production as soon as possible.
Nevertheless, using traditional equipment, such as a coordinate measuring machine (CMM), to inspect molds and dies risks creating bottleneck issues and, therefore, lengthening the time required for quality control. On the one hand, moving the molds and dies, which are often heavy and bulky, to the metrology lab, where the CMM is located, is time-consuming and non-ergonomic. On the other hand, the time required for programming and acquiring data, combined with waiting for the CMM’s availability, will be added to the maintenance and repair time (if necessary).
This is happening in a context in which foundries and casting manufacturers face rigorous quality expectations and just-in-time delivery mandates. Consequently, quality assurance practices and predictable shipping schedules are critical to uphold brand equity. The foundry industry must, then, try to balance between the delivery and quality realities. Quality control, while necessary, interrupts capital asset utilization and profit generation. Therefore, it is important for foundries to minimize the time required for quality assurance and control and optimize the shutdown required for the maintenance and repair of molds and dies.
OPPORTUNITIES TO SAVE TIME AND MONEY
In all stages of the casting process, as well as during product development and quality control, foundries must question activities that bring no added value and are time-consuming. Among them, machine disassembly, die and mold transport to the metrology lab, and CMM programming certainly represent the largest opportunities to save time and money during casting inspections and quality control operations.
What actions can foundries and casting manufacturers take to save time and money during product development and quality control?
The first, and far most important, action is to reduce production downtime by accelerating control quality. They must also find ways to reduce the number of iterations during development time. To do so, they need a fast solution that is capable of quickly measuring a large amount of data and making it available without delay to any operator, regardless of their level of expertise and experience.
The second action is to facilitate shop floor inspections that do not require the casting to be moved to the CMM in the metrology lab. Because castings are often large and heavy, the measuring solution must be portable and come to the part—not the opposite. Consequently, the measuring instrument must be insensitive to environmental instabilities, such as vibrations and changes in temperature and humidity, which are common in foundries.
The third action is to eliminate CMM inspections when they are not necessary. Because CMM inspections take a long time to program and operate, bottlenecks are frequent. Therefore, if noncritical inspections are redirected to an alternative solution that offers the needed accuracy, CMM time is saved and made available for other, more critical controls. Ideally, the alternative solution should also improve inspection and analysis with high-density, high-resolution, and non-contact measurements.
The fourth action is to opt for a single metrology instrument that can be used for measuring various shapes, sizes, and levels of complexity, with no powder required for shiny surfaces. Whatever the casting’s size, shape, geometry, or surface finish, operators can always use the same measuring solution, with which they are familiar.
Now, the question that many foundries and casting manufacturers have is this: What is this solution that offers speed, portability, accuracy, and versatility? Because, only with this combination will they be able to solve their challenges in product development and quality control efficiently.
CREAFORM 3D SCANNING SOLUTIONS
With Creaform’s 3D scanning solutions, such as the HandySCAN 3D, foundries and casting manufacturers get a fast, portable, accurate, and versatile instrument for measuring, inspecting, and validating castings during the iterative processes of product development and quality control and maintenance.
In addition, they can quickly see the discrepancies between a casting and its CAD file with the colormap feature. The software displays results in a clear and intuitive way, which facilitates analysis. Unlike touch probing, 3D scanning illustrates the overall view of the inspected part and measures surface profiles rather than just discrete points.
Steven Kennerknecht, VP of Engineering at Alphacasting, explains the importance of Creaform 3D scanning solutions for his team: “The team used the HandySCAN 3D to scan the entire casting very quickly. Having 100% of the surface and the inspection report was so vital for us to understand the changes to be made and also to make sure there was enough material before machining. The quality of the scanned data enabled us to make better decisions and reduce development time.”
For foundries and casting manufacturers, using 3D scanning solutions helps to reduce the number of iterations and shorten development time. Moreover, quality control is accelerated and improved by unloading the CMM—reversing it for critical inspection—and keeping inspections on the shop floor. Not only is downtime limited, but also production is optimized to manufacture castings of better quality, resulting in satisfied customers and more business contracts.
Author: Daniel Brown, Director - Product Management