How can you get involved?
Some of the AM manufacturing companies that specialise in fabricating industrial metal components will aim to control all the successive steps in-house for better traceability and quality control. Others (most of them) will depend on external powder suppliers. They will also rely on sub-contractors to access post-processing facilities and take advantage of niche expertise and advanced testing capabilities.
1. Powder supply
Not all commercial powders, however, are made equal. Understandably it takes time to build process repeatability and reliability (and credibility) and the knowledge, know-how, infrastructure and costs involved to produce powder are significant. As production techniques vary from supplier to supplier and powder characteristics from batch to batch, so does the final powder composition. Even complying with the stringent industry standards allows significant composition variation that shows variable mechanical and metallurgical results in the final SLM products.
Monopoly of powder production and lack of quality reliability would affect the cost-effectiveness of AM components. It would also hinder the wide acceptance of AM as a conventional manufacturing technique.
2. Cost-effective fabrication yield with AM
The 2nd step is to find suitable laser processing parameters: ones that help you create high-accuracy, high-resolution, crack-free, 100% dense components with perfect (application-dependent) surface roughness without any stress-induced distortion. All this, of course, combined with a fast build rate and no (or limited) need for post processing and minimal operator costs. The turn-key, 1-step, high production-yield magic manufacturing technique. “Press here”. Et voilà!
Not quite. Yet.
Besides a thorough knowledge of each (supplier-specific) AM machine operation (machine preparation/maintenance and file preparation/repair/loading …), high manufacture yield relies on adequate processing parameters windows, judicious use of supports and/or sensible re-design of the components/assembly.
This depends on a combination of hands-on experience (and often machine-dependent) and hard R&D to fundamentally understand and control the complex intertwined processes (melting, re-solidification, grain growth, laser/powder interaction, melt pool lifespan, heat transfer …) on which depend the properties of the finished product (metallurgy, mechanical properties …).
In addition, the various AM machines suppliers have proprietary software controls and hardware systems. Although, the fundamentals and the key process variables remain similar across machines (Power, scanning speed, hatching distance and layer surface thickness) this makes it difficult to transfer parameters directly from one machine to another (for instance those published in scientific peer-reviewed journals) and to relate them to your own requirements. It then makes the user’s life easier to rely on the standard supplier’s parameters.
AM manufacturers also tend to guarantee their ‘standard’ parameters for their own proprietary powders only, ie powders of their own specific composition.
These standard parameters are usually conditioned for “speed” build or “performance” builds: ie fast build rates or higher density components. For a “perfect” build combining both of the above, you’ll usually need to fix this yourself. That requires access to (and understanding of) all the available commands, options in your machine. And some fundamental research or loads of time-consuming parameters investigations correlated to the mechanical properties of the finished SLM products.
Expert operators with extensive know-hows expertise of AM units and material behaviour will be sought after. CAD engineer with great understanding of the AM specifics will also be in demand to re-design components or come up with creative novel design.
And that’s just for the currently available machines. New improved units will appear that can improve build rates, efficiency and production yield and that can limit operator manipulations. For these, researchers with laser processing and material science backgrounds will be in high demand!
3. Post-processing and 4. Inspection
Understanding and improving as-built surface finish quality is still an ongoing area of research, the idea being to limit the need for post-processing or, even better, supress it altogether. Until this occurs, there is a great need for a wide range of post-fabrication surface processing capabilities and expertise to achieve application-dependent surface finish. Most techniques are mechanical although some chemical etching and laser polishing can be used on some easy access surfaces. Even though some AM companies might end up doing this in-house as part of a finished product offering, the demand will rise for reactive and reliable post-processing job-shops. Most conventional manufacturing company, especially those already set up for demanding end users and applications will be able to capitalise on this market and expand their panel of customers with minimum additional investment or expenditure.
– heat treatment
Surface quality is only one aspect of the post-processing stage in AM chain supply. Ensuring sound and reliable mechanical and metallurgical properties is obviously necessary for high value critical components. Again, research is being carried out that aims to ultimately limit or suppress post-heat treatment needs. However, like for more conventional casting methods, it is still currently required for peace of mind: ie improving or homogenising the metallurgical properties (grain size homogenisation or refinement, densification, residual stress removal, elimination of internal cracks, etc...). These heat treatments (Hot Isostatic Pressing (HIP), furnace heat treatment …) are already widely used for critical aerospace components.
Heat process specialists, materials scientists and companies already kitted out to heat-treat traditionally cast components will be able to tailor and sell their services and expertise to the AM market.
- Evaluation, inspection, validation
Once the component is built and the optional supports removed, there’s a need to evaluate its characteristics versus the original design and the mechanical requirements. Dimension accuracy, mechanical properties, temperature behaviour, air flow… are a few data points to be assessed. The associated inspection techniques can be either destructive, such as ballistics tests or mechanical tests, or non destructive (NDT) such as optical scanning, ultra-sound imaging or X-ray tomography which is typically used to detect cracks. Testing and metrology methods are already used for a wide variety of aerospace components. Each technique, with its advantages and drawbacks, is suited for the detection of specific defects (pores, cracks …). As with the detection accuracy and resolution, their respective costs vary widely and need to be shown careful consideration to achieve cost-effectiveness of the finished products. Understanding of the key advantages of each methodology as well as their cost/value ratio is indispensable within AM market. NDT companies, metallurgical and mechanical metrology companies and experts will be able to capitalise on this market.
To sum up
Companies and individuals with foresight and expertise to adapt and match typical AM requirements, demands and pitfalls (surface roughness, heat treatment …), and to match specific industries (aerospace, medical …) requirements, such as compliance to international standard criterion or traceability, will benefit greatly with the expansion of the AM market.
In addition, there is a requirement to improve the machines and technology itself in order to increase production speed and efficiency, add machining flexibility and limit operator involvement: think real-time control and feedback loop, and feature-dependent intelligent machining, etc… This still requires some hard R&D and technical development in laser/material interaction and real-time process control supported by wide range of (in-demand) skilled engineering and applied-research workforce.
Within the AM economy, economic and professional opportunities lay at each stage of the supply chainWhere will you fit in?
What else would you like to know? - Tell us what info you need to get your AM job done!
: 2014 AM research strategy agenda, Feb 2014, published by the European AM sub-platform