How Mitsubishi Hitachi benefits from additive manufacturing technology

In this Q&A, Paul Browning of Mitsubishi Hitachi explains how additive manufacturing technology helps build gas turbine parts that are more cost-effective and energy-efficient.

Additive manufacturing technology has not yet reached critical mass in manufacturing, but there are areas where it has become an essential ingredient of the process.

Many companies are finding that there are things that additive manufacturing can do that simply can't be done with traditional manufacturing processes. Design freedom enables you to design for the part, not the manufacturing process, and new techniques and materials enable you to manufacture parts that are lighter weight, but that have greater strength and heat tolerance.

Mitsubishi Hitachi Power Systems Americas Inc. is an early adopter of additive technologies, and it has discovered these benefits; additive enables it to manufacture gas turbine parts that can tolerate much greater pressure and higher temperatures. This, in turn, makes for greater efficiency and lower costs for the power plants that run Mitsubishi Hitachi's gas turbines.

In this Q&A, Paul Browning, CEO of Mitsubishi Hitachi Power Systems Americas, explains how and why the company uses additive technologies to create better products that improve outcomes for its customers.

What kinds of additive manufacturing technology does Mitsubishi Hitachi use, and what are some of their main benefits?

Paul Browning: We use a single crystal technology that was developed for the silicon wafer industry, and [we] have applied it to some of the most challenging parts of the gas turbine.

The way that you create value for customers with a gas turbine is to get to higher temperatures and higher pressures, which allows us to provide better efficiency.

Paul BrowningPaul Browning

We use these single crystal technologies to produce directionally solidified parts, which means that all the crystals in the component, which can be a foot tall, align in one direction across the component's stress access point. Our parts have a weakness in the grain boundaries between those crystals, so aligning the axis of weakness along the stress axis greatly improves the components' temperature capabilities.

We've also used a different form of additive technology called plasma spray thermos barrier coatings, which uses multiaxis robotic systems to apply a coating to that same component one layer at a time, allowing us to add about another 150 degrees Celsius to our temperature capability.

This combination allows us to dramatically increase the fuel efficiency of our products, which has a big economic value for our customers, and also dramatically reduces the CO2 emissions per unit of energy produced, so it has benefits for climate change.

How does this additive technology differ from manufacturing processes you used in the past?

Browning: In the single crystal technology, we would have cast that component, and the grains would have all had random orientation relative to one another.

Instead, we grow that part one atomic layer at a time through a very controlled solidification process so that, as the part grows, it maintains the same crystal orientation for all those grains, and they are all uniformly aligned. That's the additive part of it; it's a very tightly controlled solidification process that allows those atoms to deposit one layer at a time and grow the part rather than casting it, as we would have done normally.

Does this change the way you design parts, and even change the types of parts that you are able to manufacture?

Browning: The neat thing about that is that we're now able to take additive manufacturing up to a whole new class of components in our gas turbines.

These are parts that we would have produced in the past, either by the old fashioned casting methods or by very complex and expensive multiple brazing operations. These parts have very complex internal cooling passages in them, and the only way that we [were] able to produce those complex cooling passages was either through multiple brazing operations or through some very expensive cord castings.

Now, we can just print those parts, and our design engineers have a whole new degree of freedom; they're no longer constrained by what we could manufacture.

So we were able to change the game in what we can do, and that's not only having benefits in improving the fuel efficiency of our products, it's also helping reduce pollutant emissions because, in some of our combustion technology, we're able to do a better job of mixing fuel and air [to] reduce emissions of nitrous oxides and other pollutants.

We used to have big debates between our manufacturing team and design teams; the manufacturing team would complain that the design team was always intentionally designing something that they couldn't actually manufacture. That whole argument just goes away when you get into additive manufacturing because you can print anything you can think up.

Additive manufacturing has been used primarily to produce prototype parts, but that has been changing lately. Are you using additive primarily for prototyping, or are you using it for production parts, as well? And does that impact other processes, like your supply chain?

Browning: Particularly [in] the combustion parts area, there's a lot of science in combustion, but there's still a little magic, so we need to prototype parts when we design new products.

There are things that we don't perfectly understand why [they] happen, and there's an iterative process required where we manufacture a prototype component. It's very expensive and time-consuming to produce those prototype parts using standard manufacturing techniques.

Additive manufacturing enabled Mitsubishi Hitachi to make more energy-efficient gas turbine parts.
Additive manufacturing enabled Mitsubishi Hitachi to make more energy-efficient gas turbine parts.

Now, with additive technology, the time is days rather than months between when our engineers design a part until we've got a part that's ready to go into an engine. So that has just dramatically changed our product development.

When we get into more production-ready parts, it will be interesting to see how this really impacts our supply chain. Right now, we have these additive capabilities in house, but I think, as we move more into a full production mode with these 3D printed parts, we'll look more to our supply chain to add this capability and provide us [with] these components.

What are the cost implications of additive manufacturing? Is it more or less expensive than traditional manufacturing processes?

Browning: We're willing to spend money if it creates value for our customers, and we can create tens and hundreds of millions of dollars in value for our customers by investing a bit more in our components. We're an early adopter in this [and] we can create so much value for our customers that we can afford to spend money on one of these parts.

We can produce parts for one class of components -- fuel nozzles -- cheaper and faster using additive than we can with our traditional, multistage brazing operations. We have other components where we think the 3D printed part will actually cost more than the conventionally cast part, but the performance benefits more than offset the additional cost of 3D printing.

We also think that, over time, the costs of additive manufacturing [are] going to fall rapidly, so even if we have to spend more today, we're willing to do that because we feel that, in future years, the costs are going to come down.

One of the traditional liabilities of additive technology is that it can sometimes take a long time to build a part. Have you seen this in your additive processes?

Browning: In the prototyping stage, I would say additive is a huge speed enhancer. In the full production phase, typically additive is going to be slower than our traditional process, particularly when we're replacing conventionally cast parts.

But when we look at the lead time of our components, we have longer lead time items than these 3D printed parts, so we can fit them inside of our standard lead times for the overall final product.

What does the future hold for additive technology in general, and for your manufacturing processes at Mitsubishi Hitachi specifically?

Browning: The big story here is that we've been using additive for a while, and it makes sense in our industry that we're an early adopter because we can create so much value for our customers with it.

As we move now from the additive technologies that I described earlier into 3D printing with metallic components, we'll see a whole new wave of additive technologies that we'll be able to bring to bear for our products.

As the cost curve comes down on these, we'll see it penetrating not only the BOMs [bills of material] of our products, but also moving into other industries that [Mitsubishi Hitachi] is active in, so we're going to see additive move into more and more applications for our company overall, not just our gas turbine business. 

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