When Additive Manufacturing/3D Printing was introduced to the market, it was called rapid prototyping which was an accurate description of the process—a method to quickly create physical prototypes from virtual representations of a product. The name has evolved over the years to additive manufacturing (AM) to capture the goal of the industry to rapidly create functional components in a more agile manner. This is the stated goal of the AM industry, but few have developed robust additive manufacturing production systems.
For traditional manufacturing production, quality and verification processes are in place to certify and qualify the material, manufacturing process, and end-use components. Materials are generally produced in bulk form and qualified by material sampling. Material performance data is generated through physical testing to provide input to design engineers, so they know the right shape and size of the component to meet the performance requirements. For most metals and plastics, the test procedures are well understood, and testing can be carried out relatively quickly. For composite materials, the test procedures can be very involved, time-consuming, and expensive.
This is because composites are generally made of two distinct materials, so the testing has to account for all of the variables in material composition, form, fiber direction, and how they are manufactured. Manufacturing processes, including cutting, molding, stamping, curing, and finishing are then qualified using a combination of machine monitoring and inspection systems. Finally, quality processes are put in place to verify final components meet all required specifications.
"Material and process qualification is simply a means to the end goal of a functional component or system"
For additive manufacturing, the industry is still learning how to fit a new manufacturing process into an established manufacturing ecosystem. For many additive manufacturing processes and materials, they are more like composites rather than plastics or metals since the material properties are dependent on material deposition or consolidation direction, processing parameters, and the part geometry. In general, material properties are not uniform throughout an additively manufactured part which is also the case for composites. Below are three areas where the overall industry, including equipment manufacturers, material suppliers, and end users can work together to move additive manufacturing from prototyping to production.
1) Qualify the Material
Many AM systemsare open-material systems which can use a variety of material systems. In reality, these open material systems are usually relegated to prototyping. At the other end of the spectrum, machine vendors qualify certain materials for their systems and ensure the materials meet specifications. These materials are much more expensive than open-material systems, but they come with reliable batch data on the material quality. Even with this data, many companies will still conduct their own material qualification effort. In addition to qualifying the materials, how the material is stored, the age of the material batch, and the processing parameters used during the build all affect the material properties. As mentioned, the material properties are generally not uniform so print direction, processing parameters, and part geometry all factor into the qualification of the material. A streamlined and robust material qualification process for additive manufacturing will be required for production applications.
2) Qualify the Process
For many manufacturing processes, it is a series of discrete processes that produce the end component. For example, a bulk material is cut down, machined, finished, and painted. Each processing step can be monitored and qualified. For AM, it is more of a continuous process that can present some advantages but also complications. Machine vendor qualified materials often come with processing recipes for the material that are dependent on part geometry, machine parameters, and environmental factors to produce parts with as consistent material properties as physically possible. In some cases, the machine parameter settings such as power, path speed, and path trajectory are proprietary to the machine vendor so the user must simply trust that the process will yield a component that meets specifications. One of the advantages touted by the AM industry is the ability to selectively change material properties by varying the process. We have yet to figure out how to qualify such material property variable components.
3) Qualify the Component
In the end, users want end components that meet required specifications. Material and process qualification are simply a means to the end goal a component or system that meets requirements. Here, many of the traditional quality systems for checking dimensional tolerances, surface finish, and internal material consistency are adequate. Quality methods are available to detect voids or defects but they are not well established to detect material property variations due to processing variations. For example, material properties are often a function of temperature so areas of the part that cool down more quickly than others will have different material properties. AM component qualification processes are sometimes more stringent since the process is relatively new to many companies. As the industry gains more confidence in AM, these processes will become less expensive and more streamlined.
For many in the AM industry, the focus is on developing and selling machines, developing and selling materials, or selling end components. To move the entire industry from prototyping to production, all players will need to work more closely together. As an example, Hexcel focused first on qualifying the material, then qualifying the process, and finally producing final parts that are flying and qualified on several aerospace programs. In this case, Hexcel is responsible for each part of the process from materials, to process, to end components so all can be coordinated and traced. Where these functions are done separately, the supply chain will be required to work together to achieve the quality to which we have become accustomed with traditional manufacturing. Companies that have been successful with production applications have treated Additive Manufacturing as any new manufacturing process and have developed manufacturing and quality procedures that conform with the overall manufacturing and quality systems they have developed and established for the components and systems they produce. The key to accelerating the move from prototyping to production is treating additive manufacturing as any other manufacturing process and integrating it with the overall manufacturing production systems in place today.