MMS Blog

By: Timothy W. Simpson 9. December 2018

Additive Manufacturing for Large Parts

For most of my columns, I focus on additive manufacturing (AM) using laser powder-bed fusion (PBF). This AM process is what is driving much of the hype given PBF’s ability to build complex and intricate shapes as well as organic structures that were previously too expensive or impossible to make via traditional manufacturing operations. For example, the design freedoms enabled by laser PBF can be exploited to lightweight components, to build intricate lattice structures for more efficient material usage, to consolidate multi-component assemblies and to optimize a part’s shape for functionality. Of course, laser PBF also has its drawbacks including difficult-to-remove support structures, thin-walled/high-aspect-ratio parts that might fail during a build, layering effects on surface roughness and different process parameter settings (e.g., laser settings for up-skin versus down-skin surfaces).

Despite PBF’s many advantages, its big limitation is the size of the part that can be printed in the build envelope. For a variety of reasons, most commercial laser PBF systems offer a build envelope measuring 250 by 250 by 325 mm (roughly 10 by 10 by 12 inches), though some laser PBF systems can accommodate taller parts, and larger systems are in development. For instance, GE’s Concept Laser X Line 2000R boasts an 800 by 400 by 500 mm build envelope, and the company plans to build a system that starts at 1.1 by 1.1 by 0.3 meters.

By: Timothy W. Simpson 8. December 2018

Smoothing out the Rough Edges

So, is machining the only way to finish your metal part after additive manufacturing (AM)? You might think so from everything you see and read, but there are countless other post-processing techniques to improve the surface finish and dimensional integrity of your part. Besides, if you have to machine your AM part, you will likely need fixtures and jigs to orient and hold your part, especially if it is a complex organic shape. You will also need to establish datums and references on the part once it is removed from the build plate so that you know how to orient and align it. In short, doing all of this extra work to machine your AM part will quickly undermine all of the benefits and advantages of using AM in the first place.

The big challenge with metal AM parts is that they are not “smooth” when they come off the build plate. The close-up of the lattice structure in Figure 1 is a great example of this. Partially melted powder particles adhered to the part, stair-stepping effects of the layer-by-layer process, tessellation of the 3D solid model and differences in up-skin and down-skin surfaces all contribute to surface roughness as I discussed in my October column. Smoothing out these rough edges and surfaces adds time and cost for post processing too and is critical for meeting specifications and tolerances, especially mechanical properties and fatigue life.

Imagine voice-recognition technology as the star of your machine shop. Imagine a hands-free way to execute a number of control and information functions on every piece of digitally connected equipment. Imagine getting instant access to CNC machine info that otherwise would require wading through the interface to find things such as machine settings or maintenance history.

Too good to be true? All the components of this technology already exist, and now it’s a matter of integrating them with more production equipment and software applications that control the shop.

The 2019 Capital Spending Survey projects accelerating growth for the machine tool market next year. This latest report from Gardner Intelligence, the research arm of Modern Machine Shop’s publisher, Gardner Business Media, sees machine tool consumption increasing 11 percent to $7.748 billion in 2019. (See chart 1.) This follows increases of 3 and 6 percent in 2017 and 2018, respectively. In 2018, machine tool prices rose and delivery times lengthened. Given the planned spending by machine shops detailed in the report, prices are likely to climb higher and delivery times will remain lengthy.

Answering the question about what is driving the accelerating growth, higher prices and longer delivery times of machine tools is complex, but a good place to start is with the old economics maxim: “Prices are set at the margin.” This important concept explains supply and demand and, in this case, machine tool prices.

Robotics have advanced to the point in which CNC machine shops’ expectations might outnumber questions about practical applications. In fact, many successful shops are already benefiting from machine-tending robots or have researched various robot offerings with an eye toward adding them.

Global robot sales bear out this notion. According to the International Federation of Robotics’ 2018 World Robotics Report, a record number of 381,000 robots were shipped worldwide in 2017, an increase of 30 percent compared to 2016. For 2018, that number is expected to increase by 10 percent to 421,000 robots shipped.

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