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On-Demand, Low-Volume Production of Aerospace Parts

April 7, 2020
The aerospace MRO market is dominated by casting suppliers — but the supply chain is at risk, apparently ready for a "step-change improvement" in manufacturing technology.

Replacing aircraft and aerospace parts (MRO) is an important and valuable segment of the overall market for castings — but buyers and suppliers are frequently beset by time delays and production costs. The demand is comparatively small in volume, and the schedule for ordering and delivery can be inconsistent, or incompatible with just-in-time standards. The issue of aircraft program longevity is a parallel concern that injects uncertainty in the supply chain.

The alternative of additive manufacturing is looming for aircraft builders and their Tier suppliers: producing parts as-needed seems to be an ideal solution for on-demand, low-volume production of aerospace parts. A veteran of this supply chain, former Zodiac Aerospace CEO T.K. Kallenbach, discusses the role for AM in the aerospace direct-part replacement market. There is much at stake for all involved, he explains: buyers, suppliers, metalcasters, AM technology suppliers, and new entries in the supply chain. The supply chain is at risk, but so is the entire aerospace ecosystem, which needs to protect its aircraft investments and consumer-and-shipping price points.

Q: What were your impressions of the MRO Europe 2019 even in October 2019, in particular of the ways that manufacturers are preparing for (or implementing) additive manufacturing (AM)?
We found a mix of skeptics: some surprised folks that hadn’t yet realized how direct-to-metal AM applies to their situations; and others that had started AM implementation on both legacy and new, optimized designs. The event was all over the spectrum in terms of what people are doing and what they thought. Overall, though, we encountered a fair amount of skepticism from the early adoption experiences versus the promises of today’s direct-to-metal AM.

I will say that those who are familiar with AM were struck by the capabilities of Velo3D and their data collection and real-time metrology to certify the quality of the print process. The information quality and real-time data gathering directly address the primary hurdle of AM adoption for certified parts, and we got very positive interest from even the toughest skeptics.

The subsequent announcement of the Velo3D Assure™ software availability is paramount for AM to have wide-scale adoption for aviation parts, and true serial production manufacturing. The other positive feedback for Velo3D concerns the lack of support structures often required for printing parts. Many of the MROs' prior experiences amount “additive manufacturing to do subtractive manufacturing." The economic advantage of Velo3D’s process was quickly recognized as a breakthrough in total part-cost reduction.

Both MRO engineers and supply chain leaders expressed a desire to get AM into their manufacturing cycles. This is especially true for low-volume, “impossible to obtain” parts that are becoming more common as the commercial aircraft fleet’s age.

Q: What makes additive manufacturing more ready for adoption now than in the recent past?
I'd say that in comparing this year to last year, there has been general improvement in AM print size, speed, and materials, which attract potential adopters. The greatest change has been advanced by Velo3D. Fundamentally, industry progress on behalf of customers must be measured by a reduction in Design for Additive Manufacturing (DfAM) work, in upfront design time of supports, compromises to design functionality, and post-processing.

There have been two things that Velo3D offers to encourage AM adoption. One is the expanded printing capabilities. They’re able to print closer to the original design intent without redesign and compromises for AM. That is, they’re able to turn parts without a DfAM reconstruction to accommodate the traditional limits of the process.

The other aspect is the quality control brought to AM; the validation of the print process. Velo3D has a suite of sensors and data-acquisition capabilities = that makes it especially fitting for aerospace over traditional AM systems, where it's considerably more difficult to certify parts because of the variation in nearly every aspect of process control.

When talking with the skeptics, one hears: "Hey, I have such major material-property variation across the build plate. How do I know that location A and location B are going to meet the same material properties?" Those kinds of fundamental issues have inhibited industry-wide adoption. And those are the problems that Velo3D has addressed with the atmospherics, powder-bed health, beam performance, in-process measurements, often support-free designs, and overall construction of their system.

Let me add that the fundamental architecture for many of the metal AM machines on the market today likely needs to be completely overhauled to capture the same results from a data-acquisition standpoint and, to many extents, the precision print accuracy and yields for very complex parts.

The third item, beyond AM capability and quality control, is the continued advance of certification authorities providing guidance to MROs for AM and the publication of AM standards. In the past year, the Federal Aviation Administration published Job Aid for Evaluating Additive Manufacturing at an MRO, which is very helpful for creating a repeatable process for MROs to follow in AM printing. And, the SAE committees continue to advance new AM specifications for metal powder and processing. Without these certification process advances, we can have the best printed parts in the world, but they still will not be certifiable.

Q: Can you outline the primary roles you see for additive manufacturing in the MRO field?
AM for MRO is about replacing the exact parts a customer needs. The nice thing about the role of additive here is that once you get over that first trial hump to the AM-engineering side, you learn that you can quickly and efficiently meet the challenging low-volume production targets in the high-value, one-to-ten-part range.

Today, if an aerospace MRO customer turns to a casting supplier for a production run of one to 10 parts, the supplier may rightfully say, "I need tools," because the previous casting tools likely are worn out. There’ll be standard time delays due to tool creation. And the customer will need to order 100 parts at a time. Lead time for some parts is 20 months or more.

But meanwhile, the buyer is thinking: “100 parts equals 10 years of supply — best case, if these planes are even still flying in 10 years! And I'll have to wait two years to get them.” These are terrible economics.

In contrast, additive manufacturing allows aircraft OEMs and their parts suppliers to right size the supply chain for the current demand. This is particularly important in regard to aging engines or aircraft. As the older model planes wind down, we have to find solutions to keep the fleet of 30, 40, or 50 aircraft flying. These aircraft still are worth millions of dollars, tons of revenue to the people who own them. Staying operational is a very big deal for them. The air cargo fleets are the perfect example. Metal AM allows them to fit the supply chain to immediate part demand and to minimize delays that hurt profits and cash flow.

Another important investment factor is that the aerospace-casting supply chain today has a very challenging problem with capacity. The aerospace industry has been and continues to operate at very high levels of output, and the investment cost of the next unit of casting capacity is measured in hundreds of millions of dollars. No one wants to make the investment, given that there is a higher probability for an aircraft build-rate decrease than a build-rate increase.

Contrast this with metal AM machines, for which investment in the next the unit of capacity is $1 millon to $2 million, and it is far more flexible capacity in terms of the parts it can manufacture. It's a straightforward cost to add another machine, and another machine. There is not such a massive step-change in capital expense around additional capacity. So that helps in terms of cash, asset management, and utilization. And in operations these machines build only build the that are needed, not 100s of them.

Q: What other core applications are there today for additive manufacturing in MRO?
First in importance is supply-chain replacement, where AM offers a new form of base metal, in powder, as a substitute for casting or milling process materials. That's just a huge value, straight out of the gate, whether it's an issue of planned, low-production parts or an “impossible to get” part. Additive manufactuirng is an immediately available, on-demand option for those situations.

Casting of parts is plaguing aviation manufacturers today because of its total cost in material, equipment, tooling, overhead, lead time, and delivery.

Secondly, we use the term direct-part, or direct-design replacement, and it's just the basic idea that, "We're going to get to the AM part of the production process with all the same pre-approved, regulated CAD drawings, specs, and parameters included, and print in, say, titanium or Inconel 718, which have better material qualities than cast metals.

There should be no reason to go back to a more manual production process with less precision. It’s almost never worth the time, compared to additive manufacturing. AM can meet and exceed the form, fit, function and mechanical aspects of the original part.

Q: What broad trends do you see today in MRO? And ,adjunct to that, what are the economic pressures on the MRO industry?
On the macro level, the trend of increasing competition between traditional OEMs and independent and airline MROs continues. OEMs want not only to manufacture but also repair aircraft and systems. They want to enjoy an aftermarket revenue stream, which is essentially the repair market.

The economic pressures on the MRO industry are very much centered around the price of parts. Any given repair job in MRO tends to involve parts that need to be procured to complete that repair. It could be a stator, a valve, a nut, a bolt, or a fan blade. All those are items that need to be repaired and/or replaced as part of the overall maintenance process of an engine, or an auxiliary power unit (APU), or actuators, or the door of an airplane. If the parts or systems are available at lower cost and, hopefully, cheaper prices—whether it's a great deal someone cut with the OEM or the ability to get them through a new manufacturing process such as additive—then obviously prices drop competitively against other offerings from another OEM, airline MRO, or the independent MRO.

We have many cases in the industry in qhich the price of the replacement part is completely out of whack with the part’s value; we need to reset that.

My overall belief is that we need to continue to push cost productivity to the airlines, for their benefit as well as the health of entire aerospace supply chain.

Coupled with procurement cost/price of parts is, in a lot of cases, just the flat-out challenge of part unavailability. This is especially true for legacy products, because the volumes are low and the scaling cost and delivery speed of traditional casting presents a real conundrum. Suppliers have left the business rather than take on the challenge. But, there are real-time cases where current, in-production, in-service engines or APUs also have parts that have long lead times from inadequate supply chains.

So, whether it's getting something cheaper or more readily, I think additive manufacturing is a very strong option both for bringing down price/cost and increasing availability throughout the aviation-component industry.

And by the way, for MROs this would apply to all three of the core competitors. Because OEMs often do not make all their parts; they get those parts from their suppliers and suppliers may not only sell to the OEM, but to the other two MROs. It’s an intertwined ecosystem, such that I think all three of these parties can benefit massively from a step-change improvement in manufacturing technology.
T.K. Kallenbach is the former CEO of
the Aerosystems branch of Zodiac Aerospace, now SAFRAN Group, and currently a consultant to Velo3D, and additive manufacturing equipment developer and supplier.