Whether it’s for prototypes or end-use, metal parts that must meet high standards of strength, density, and durability are traditionally produced by CNC machining. Newer printing technologies like DMLS shortcut that process and offer manufacturers a fast, cost-effective way to make such critical metal parts.
However, to take full advantage of the design freedom offered by AM, several elements must come together to deliver quality parts that meet industry standards. These elements include:
1. Material Qualification
Creating accurate and precise metal 3D prints requires attention to more than just the printer itself. It’s crucial to consider the entire AM workflow, from build preparation to post-processing. For example, the quality of the metal powder used for printing must be maintained to avoid contamination. Impurities in the raw material can significantly affect the final part’s dimensional accuracy, especially when building for safety-critical applications like aircraft parts or medical devices.
The most significant source of model inaccuracy is human error, but this can be minimized by ensuring that all relevant processes are followed. Then, software-driven inspections and closed-loop melt pool control can correct mistakes before they become major issues.
When it comes to manufacturing precision parts, traditional techniques have decades – if not centuries – of history behind them. Compared to this, the development of industry-wide standards for AM is still in early stages. Nevertheless, the right strategies and solutions can dramatically reduce the time it takes to qualify a metal 3D print for production. This will help companies to take advantage of the unrivaled design freedom and cost savings that metal AM offers. The following proven methodologies can help metal 3D printers achieve this:
2. CAD Model Checking
The CAD model is the basis for the whole print process, so it’s imperative that the model is accurately measured and verified. A QA team should consist of several members from different disciplines: surgeons or physicians who know the clinical need and the intended outcome of the models; medical physicists to optimize scanning and reconstruction techniques and to ensure that the resulting DICOM files can be processed in the imaging system; radiologists who interpret the models; and engineers and technicians for segmentation, model design, printer maintenance, and more.
The accuracy of a 3D metal printing machine is directly related to the quality of the printed part. For this reason, regular testing and preventive maintenance recalibration is a critical step in the QA process. This includes assessing the accuracy of the forming and material cylinders, as well as confirming the precision of laser overlap during a build. The Eplus3D QA protocol also involves evaluating the performance of the laser and powder bed, to ensure they are operating within their optimal ranges.
However, the latest generation of Sapphire machines has integrated Assure, a revolutionary real-time quality control solution that predicts bulk material properties in real time using multisensor, physics-based excursion detection algorithms. This allows engineers to understand the state of their print and verify it against an approved master print before a production run begins. The result is a more reliable, safer and higher quality print, while eliminating the risk of a costly production setback caused by uncontrolled fluctuations in printing parameters.
3. Pre-Print Inspection
As with every fabrication method, metal 3D printing has its limitations. To overcome these limitations, a thorough QA program is critical. The QA process is typically a manual step, wherein an engineer matches a 2D image of the part to the physical print and checks off a list of requirements. Fortunately, solutions exist to streamline this process, making it a valuable tool for enabling high-value applications with 3D metal printing.
The system, called Assure, combines a laser beam scanning system with an automated software process for assessing build quality. It can predict bulk material properties in real time and offers a detailed build report that can be used to verify compliance with an approved master print. It also speeds up the move to production by detecting any defects during the build, which allows for corrections to be made in advance of the finished part.
Metal 3D printing has the unique ability to create a number of end-use parts that cannot be fabricated through traditional manufacturing methods. These parts range from highly complex — like topology optimized parts created by generative design software — to those with conformal cooling channels and custom manifold designs. These parts have one thing in common: they all require complex curves and shapes that would be impractical to fabricate using conventional methods.
4. Post-Print Inspection
When it comes to metal 3D printing services for production parts, QA is critical to ensure the part’s strength and quality meet rigorous standards. The end-to-end digital workflow of a part from a CAD file through to a finished product requires a series of highly complex steps that need to work together in order to deliver consistent, high-quality results.
This includes everything from build planning to monitoring to feedback control. For example, simulation helps engineers test how a design will behave in a virtual environment to understand its potential issues like warping or distortion, and avoid them during the print process.
A successful QA program is a team effort, and it’s important to bring together people from across the business in order to understand and meet the needs of the different stakeholders. The QA team should include engineers, metallurgists, designers and operators. Each person will have their own priorities and expertise, but it is crucial that they all work together to ensure that the end product meets the required quality standards.
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