Metal process

Advances in in-process monitoring software

It’s no wonder that AM has caused such disruption in the manufacturing industry over the past decade. Its ability to produce complex geometries that cannot be achieved with conventional manufacturing processes coupled with short lead times and often at reduced cost, AM offers many advantages in most industries.

However, one gap exists in the way of mass adoption of this technology: quality assurance.

Many pre-made templates are offered to Dashboards customers, this template called “FormUp Monitoring” includes the highest level of machine-generated detail. These templates can be used as is or modified to meet the needs of each individual. New designs can also be custom created by users. (All images provided by AddUp)

When a part is produced by AM, many post-production checks must take place to ensure its compliance and compliance with geometric tolerances, its level of porosity, the detection of defects and its reproducibility. Most of these checks are carried out on coupons and samples included in the production drawing and carried out under the same conditions as the main parts. These samples are then tested for porosity level, fatigue and other aspects to meet the contractor’s expectations. However, a coupon or sample representation of a primary part and its associated quality may be limited, particularly when considering the use of multi-laser production. In addition, these checks are often costly and time-consuming, which can have an impact on lead times and productivity.

AM is complex, layer by layer

AM, especially PBF, is well suited for the use of monitoring solutions during production. With an average layer thickness of 60 µm, typical production will require approximately 3,000 successive layers to complete a part. On paper, this seems like a slower process compared to conventional manufacturing processes, but in addition to all the already well-known advantages of AM, such as complex geometry or turnaround time, the successive fusions of these fine layers of material provide a unique perspective on the state of the part during manufacture. Using in-process monitoring solutions could replace, or at least reduce, the number of post-production inspections needed and build confidence in build quality. This type of software innovation will help move AM into a fully industrialized technology.

AM is a complex technology to master due to the different scales we have to deal with: generating millions of vectors corresponding to kilometers of trajectories, at a speed of several meters per second being drawn by a “pencil” having the diameter of ‘a strand of hair. Additionally, dozens of components such as the platform, laser, and airflow for inerting conditions will all need to work together to create the part as intended. For these reasons, a tiered approach to in-process monitoring would be inadequate to provide the level of quality assurance required of a fully industrialized technology.

Key elements of in-process monitoring

AddUp, a global metal AM manufacturing OEM, launched a full suite of monitoring solutions earlier this year to unlock the full potential of its FormUp machines. At the heart of AddUp’s monitoring strategy are three key elements.

The first is a macro view of what’s going on inside the machine. AddUp’s FormUp 350 PBF machine has dozens of sensors collecting data in real time: oxygen level, humidity level, state of the lasers, forces measured in all moving components, powder consumption or gas flow . Previously, these datasets were separated and consolidated only after production, limiting potential actions during production. But now it can be viewed in real time on an intuitive platform called AddUp Dashboards.

For further analysis, molten pool data can be evaluated in AM Explorer. This level of detail is made possible through a partnership with Interspectral, a 3D visualization software company that worked with AddUp to create a user-friendly tool that can show any anomalies that may have occurred during the merging process.

Collecting and evaluating this data can provide a powerful indication of part quality, providing a complete understanding of production conditions. This solution can also be adapted to meet the different needs of different manufacturing roles. Maintenance personnel will track moving component drifts and track firmware and software updates. Manufacturing managers will track their shop load and ensure they don’t encounter any bottlenecks or supply chain disruptions. Quality experts will have access to a build report that includes every single event during production, with an automatically generated OK/INCOMPLETE/FLAG status. Finally, process experts will have full control over dozens of variables, with advanced features for cross-referencing key process parameters (KPP).

It is important to note that all this data is fully compliant with the highest traceability standards thanks to the AddUp GUID system which tracks end-to-end compliance of the production file.

But all this is only a first step.

The second step is to analyze the execution of the production, but on a microscopic scale. AddUp measures KPPs at very high frequency: physical position of the laser spot, real power delivered by the laser and emissivity of the weld pool. Meltpool Monitoring makes it possible to characterize any defects without destroying the part, which is particularly useful for single unique constructions. The volume of data generated using this monitoring solution can be very large, which is why AddUp offers a set of PNG files, a lighter and more readable format than raw data, which can be viewed in AddUp Manager, the solution of CAM dedicated to FormUp. These visualizations are provided in real time after each subsequent layer. These images are automatically repositioned and overlaid on the nominal scan strategy, allowing comparison with expected trajectories. For mass production, this type of monitoring can be used to create a baseline fingerprint that can be used as a point of comparison for future production releases.

A fleet of AddUp FormUp 350 machines.

Finally, the last key element of the AddUp monitoring suite is the analysis of the quality of the layering. The innovative technology of AddUp (Recoat Monitoring) proactively corrects defects during production. This element was designed to improve part productivity. As explained previously, AM is based on the generation of several thousand successive layers. When powder bed quality is substandard, due to a number of issues, several hours of production can cause the build to fail. The impact can be dramatic. AddUp’s Recoat Monitoring system not only verifies the homogeneity of the powder bed, revealing the possible presence of deposits or a lack of powder, but it also triggers a correction sequence if necessary, ensuring that the powder will be nice and smooth before melting resumes. These overlay fixes are fully tracked and reported in the AddUp dashboards and in each room’s build report.

The combination of these three key elements will accelerate the adoption of the technology by not only providing confidence in the quality of flawless parts in limited run applications, but also in the mass production of AM parts.