Additive Manufacturing (AM) is rapidly gaining in popularity to the point that it is challenging to have a conversation about manufacturing process options without mentioning it. You might ask, “What is all the excitement about AM processes?” or “How can this new technology be used to resolve real daily challenges?”
To help answer those questions, this article will focus on Directed Energy Deposition (DED). Looking at the history of manufacturing, DED is not a new process. At a high abstract level, it can be described as creating a melt pool and adding material to an existing component — such as welding two parts together, which is not very exciting. But the way DED is intended to be used today is new because the goal is to automate the process, to precisely control it, and to do much more than weld two parts together.
As a comparison, when computer numerical controls (CNCs) first came on the scene for material removal manufacturing processes, coming up to speed on using CNCs was certainly quite challenging but they were a game-changer all the same. Once introduced, it was clear this was the way to proceed for subtractive manufacturing. After many years and enhancements, we have collectively learned quite a lot about this topic and the knowledge base is substantial. Now we are facing the same learning curve challenges with DED, as we are still in the discovery phase of computer-aided DED processes.
The following general information is about what to look for when selecting computer-aided manufacturing (CAM) programming software for the DED/hybrid manufacturing process, as well as some real-life manufacturing application examples in which the DED process is already in use and providing manufacturers with key benefits.
The subsequent DED applications are broken out by market segments including Aerospace, Automotive, and Medical.
Aerospace. Aerospace manufacturers have been using the DED process for several decades to perform blade repair. Repair processes continue to expand as DED technology improves. What’s new is the usage of the DED process to build the parts themselves. Cost savings are achieved due to a better buy-to-fly ratio, especially for expensive and difficult-to-machine alloys where there is a significant reduction of both the cost of the raw material required and the amount of material to machine out afterward.
DED adds flexibility to the manufacturing process by easily enabling design variations. For example, DED processes can be used to build part variants on demand and requires minimal tooling, so there is a reduction in the number of components used in the manufacturing process. With the DED process, it is also possible to build parts with composite and functional graded materials.
Automotive. The tooling used by the automotive industry is one obvious segment where an automated DED process can advantageously replace a manual one. Car manufacturers have already experimented with extending the life of tooling (to last three times longer) by rebuilding wear sections with a harder alloy. Cost savings can also be found by modifying existing expensive tooling to produce new parts. For special car models, it is possible to add material on existing standard parts, avoiding the need to have a new setup to produce those parts. Finally, fast tooling repair can keep the assembly line in production and avoid costly and counterproductive downtime.
Medical. Because each human body is different and unique, customized parts are required when making implants or fixtures for medical applications. Medical manufacturers recognized this quickly and took advantage of various possibilities offered by the powder bed additive processes. The DED process can also help here to produce better parts by coating some areas with a dissimilar material to prevent wear or by reinforcing highly stressed areas.
As seen on the various aerospace, automotive, and medical application images featured here, the additive process is not generally being done on a flat area of the part. The DED process provides benefits when building models of any shape, compared to the Powder Bed Fusion process where the build occurs layer by layer. DED can also be applied to more complex geometry and without designing, building, and removing supports that are required in Powder Bed Fusion.
Implementing the DED Process
First, it is important to confirm that your CAM software has the needed functionality for additive and hybrid processing. A second important factor is to establish on which type of equipment the DED process will be performed. Machine tool manufacturers have started to offer additional equipment enabling the DED process. These machine tools are expensive and often have additional devices such as lasers, powder delivery systems, etc. for the additive process. Other machines are focused exclusively on additive processes.
CAM Software and Hybrid. Selecting reliable CAM software is critical to success and the following questions need to be addressed. Is the software capable of working within a hybrid process? Are you able to create machining and additive operations in the same programming environment? Are the operations limited to planar slices or can 3D sections be used for build layers? How does the software keep track of the stock between different types of operations? The stock tracking is very important if performing multiple operations in the same setup and/or additional operations. The stock model should also be capable of being used for toolpath generation and for collision check with the tool assembly, machine components, etc.
5-Axis. As mentioned in the previous application examples, the DED process will most likely not happen on flat surfaces. Since the best conditions for the build process are normal to the base surface, 5-axis trajectories are beneficial when applying material on shaped components. Another reason why 5-axis is key is that the additive device might need to be tilted to avoid existing features or to access challenging areas.
While smoothness of the 5-axis motion is a big factor in the machining performance and surface quality of a part, it is also critical for DED. CAM software plays a significant role in the 5-axis path generation. If the motions are not smooth, the machine will not be able to maintain its speed, resulting in the additive process potentially overbuilding or overheating.
Simulation. Key functionality to have is simulation of the hybrid or additive process directly from the CAM software via NC-code simulation, which considers and optimizes the movements based on the machine kinematics. It offers significant advantages over using a second, additional software program only for machine simulation. CAM software that offers a single environment and interface with straightforward integration between job planning and simulation is a key benefit, resulting in having comprehensive data available such as NC code.
During the additive manufacturing process, CAM software should be able to display the build during simulation to ensure that the workpiece is built correctly. This might sound obvious but some CAM software offering DED options is not offering this capability. The simulation module should be able to react to axis limits and collision potential with large additive delivery nozzles that are common on DED machines. This is especially important when performing 5-axis motions during the build process.
Technology Parameters and Post-Processor. In subtractive manufacturing, the technology parameters are known and should be streamlined from the CAM to the NC code. In additive manufacturing, it should be the same case but there are usually more parameters to control. In addition to this, there are special cases such as local conditions requiring different parameter sets or functional graded material, where the parameter sets are changed to create a different alloy. All this must be managed in the CAM software and properly streamlined to the NC code. If you intend to perform complex 5-axis motions with an expensive machine tool, it is better to use NC-code simulation, as this is the safest approach. There are already enough variables associated with a new process.
Choose the Best Software Partner
Since the computer-aided DED process is quite new, confronting unexpected issues can be anticipated, so it is important to consult with a knowledgeable software developer/supplier. Some questions to consider when choosing a software partner include: What is their experience in additive? Are they willing to help to find solutions? Does the software developer have a pioneering mindset and will act as a partner to find innovative solutions to address new challenges based on ongoing feedback from their customers? In addition to this, does the CAM software supplier have partnerships with machine tool manufacturers/research centers who are involved in the research and development of additive technology?
This article was written by David Bourdages, Product Manager, OPEN MIND Technologies, developer of the hyperMILL® CAD/CAM software suite (Wessling, Germany with worldwide subsidiaries including Needham, MA, U.S.A.). For more information, visit here .