The record breakers!

AMFeb19Features - coppinger1
AMFeb19Features - coppinger1

Tooling made fast and cheaply could end the reputation for high cost and long lead times that has bedevilled the likes of the mould and die industry. Rob Coppinger reports.

 

The Guinness Book of World Records is not something that would automatically be associated with the drier world of aerospace tooling, but just such an award was given in 2016 for a 3D printed trim-and-drill tool; at the time the largest solid 3D printed item ever, according to the record reference book.

The tool was made from the composites of carbon fibre and the polymer, Acrylonitrile, Butadiene, and Styrene, known as ABS thermoplastic. It is 17.5ft long, 5.5ft wide and 1.5ft tall, with a mass of 748kg (1,650lbs). For Boeing’s 777X airliner programme, it was made by the US government’s Department of Energy’s Oak Ridge National Laboratory (ORNL). Guinness World Records awarded ORNL the record.

The tool was made in 30 hours and perhaps another record could have been awarded for this. As Jason Susnjara, Thermwood’s marketing vice-president, says: “An aerospace company can wait 20 weeks for a tool.”

He makes similar short lead-time claims for his company’s technology, a tool in a week, “depending on the shape”. Susnjara explains that Thermwood is producing a blade tool for a helicopter and while that would normally take 20 weeks, it will be made in less than five days. The blade tool would then go into an autoclave to create the blade.

Getting bigger

The 777X wing trim-and-drill tool was printed on what the ORNL calls its, “Big Area Additive Manufacturing machine,” at its Manufacturing Demonstration Facility. The tool secures the aircraft’s composite wing skin allowing operators to correctly drill holes in it before assembly. Boeing will inform the laboratory about the tool’s performance. Production began for 777X test aircraft in 2018, but Boeing was not available for comment. In the ORNL’s 2016 announcement, though, the aerospace giant’s director of structures and materials, Leo Christodoulou, says: “The existing, more expensive metallic tooling option we currently use comes from a supplier and typically takes three months to manufacture using conventional techniques.”

Other companies developing 3D printed tooling are CPI Aerostructures and Bristol Aero. CPI Aerostructures has started working on 3D printed tooling and created a tool for the Embraer Phenom 300 engine inlet for hole drilling. On Bristol Aero’s website, a statement dated 28 June 2018, says: "Bristol Aero is actively investing in R&D for large aerostructures additive manufacturing tooling with the ability to withstand temperature gradients for composite material curing in autoclaves." Bristol expects the autoclave production of tooling to replace traditionally built ones.

But the firm recognises that there are technical challenges and solutions have to be found for issues such as the expansion of components and joints of different 3D printed parts due to their dissimilar materials. However, there are long term advantages in Bristol's view. Tooling can be printed in a matter of hours, accelerating the production process, and composite tools are lighter, making handling easier. Iterations of tooling design are also expected to be more efficient to achieve.

Boeing and Thermwood used additive manufacturing technology to produce a large, single-piece tool for the 777X using Thermwood’s LSAM machine

This acceleration of lighter tooling manufacture will help because its development has not been quick enough in recent years to match the innovation in composite structures.

“It is a challenge to develop tooling systems to keep pace with the rate of innovation. Automated layup equipment that used to be large and extremely cumbersome is now much lighter and faster,” says Ascent Aerospace’s technical engineering director, Colin Birtles. Ascent produced the wing skin moulds for the Airbus A350 XWB and 777X.

A two in one solution

Susnjara’s company has built an additive manufacturing machine that also has CNC routers for finishing operations to produce a final printed tool to the precise geometry needed in hours.

“About maybe four years ago, we started developing the Large Scale Additive Manufacturing (LSAM),” Susnjara explains. “We have just printed a tool that was about, 12 or 15ft long, about 5ft tall and about 3ft wide, in one piece,” says Susnjara. There has been no Guinness world record for Thermwood, but it has also supplied Boeing.

Thermwood’s LSAM machine uses what it calls Vertical Layer Print (VLP) 3D printing technology. This prints an object from one side to another, not from the base, horizontally up to the top of the object. It prints a one-piece tool with no joints or need for assembly. For Boeing, Thermwood printed and trimmed a 12ft-long R&D tool at its southern Indiana demonstration laboratory and delivered it to Boeing in August 2018.

Using VLP, the tool was printed as a single piece from ABS thermoplastic reinforced with carbon fibre. Boeing has also purchased an LSAM, with the VLP print system, for its Everett, Washington-based Interiors Responsibility Centre facility. The VLP uses plastic pellets infused with carbon fibre that are melted and extruded through a nozzle with a 12.5mm diameter. This size of nozzle leaves ridges along the exterior and interior of the printed part and these need to be machined.

“These ridges need to be machined and smoothed so that they can then create the part, or a mould, off of that particular tool, depending on what they're using it for,” Susnjara adds. Thermwood’s machine can print objects up to 30m in length.

Cheaper and quicker

Thermwood has found that it can produce a tool whose material cost is 34% cheaper and whose labour cost is 69% less than the same tool produced with conventional methods. It knows this because an unnamed customer had the same tool made the conventional way to compare processes.

“It took us three days to produce that tool and it took them eight days. There's a huge cost savings in it,” he explains. And Susnjara’s firm is continuing with LSAM’s development, with a faster output head and nozzle. It has already improved from an extrusion rate of 86kg of composite an hour, to 258kg.

Ascent Aerospace produces moulds for fuselages

Composite tooling is also expected to help solve another issue, how composite structures and the tool itself respond differently to the heat in an autoclave. Coefficient of thermal expansion (CTE) matching is where the tool expands like the composite product to ensure the final dimensions are correct when it all eventually cools. A composite tool can expand just like its composite product. However, this may be a short-term argument for composite tooling.

“The trend towards out-of-autoclave curing means that CTE-matching becomes irrelevant and tools don’t have to perform under extreme heat and pressure,” Ascent Aerospace’s Birtles concludes.

Tooling, historically, has been subject to long lead items and high costs. Cheaper, faster tooling manufacture will have an impact for product and production development and improvement and so, ultimately the entire value chain.

www.thermwood.com

www.ascentaerospace.com

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