Contamination screening at LPW using SEM and EDX analysis.
On July 19th, 1989 United Airlines Flight 232 departed Denver; Colorado bound for Chicago with 296 souls on board. One hour and seven minutes into the flight, during a shallow right turn at 37,000 feet, the fan disk of the DC-10’s tail-mounted engine disintegrated. The plane lost all hydraulics, and the captain declared an emergency to air traffic control.
With the odds stacked against them, the crew attempted to land the aircraft on runway 22 at Sioux City, Iowa, travelling and descending almost at double the speed as would be required for a safe landing. The plane’s right wing hit the runway first causing the vehicle to cartwheel landing upside down and immediately catching fire. Remarkably the actions of the crew and emergency services on the ground meant 185 lives were saved; there were 111 fatalities.
The National Transportation Safety Board identified the cause of the accident as a failure by United Airlines maintenance processes and personnelto detect an existing fatigue crack. That fatigue crack, however, resulted from a microscopic contamination of tungsten in the titanium used to make the engine’s fan disk.
Contamination of this kind keeps Dr Phil Carrol, CEO of LPW Technology, up at night:
“If you go into some powder mills making nickel and steel alloys, it’s like going back 100 years. There’s a wake up call required for this industry. Within the titanium powder that people are using for their AM processes there are risks around tungsten contamination.”
The devil particle
This is an output from a CT scan of titanium alloy powder, the CT scan differentiates material by density. Materials of higher density, relative to one another, appear brighter, the bright particle in the image must be of significantly higher density than the rest of the powder particles, and in this case is an unwanted contaminant or the Devil Particle.
LPW refers to this type of contaminant as a High Density Inclusion (HDI). Often, the HDI has a significantly higher melting point than the bulk powder, and therefore does not dissolve into the material during the melting process. This creates a point of weakness within the material, and can cause premature part failure, especially in high stress environments.
A pharmaceutical philosophy
The tungsten contamination conversation was brought on by a recent visit to LPW’s soon to be former HQ in Runcorn (the company is set to move to a larger, purpose built premises across the new Mersey Gateway bridge in Widnes within the next six months). Upon entering, at reception, we were asked to hand in any ball-point pens. Ball-point pens often contain, you guessed it, tungsten. This level of thoroughness makes its way past reception throughout the premises as a whole.
“At LPW, we’re taking a pharma mindset and putting that into powder manufacturing environment so that we don’t have a repeat of the DC-10 incident in AM,” explains Phil. “We need to instil a clean-room discipline and develop a culture with all our employees to think about contamination at all times.”
Dr Phil Carrol attained his PhD in Alloy Development from the University of Sheffield. After working with companies like Siemens, TWI and Trumpf developing machines and AM processes, Phil realised that no matter how good the hardware and processes were, if the materials weren’t consistent, parts never could be.
Phil has a mantra, which if you meet him he’ll be sure to repeat, it’s a slightly less clean version of, ‘you get out what you put in.’ He set up LPW to ensure what was going in was good enough for stringent aerospace qualifications.
Since employee number two, hired in 2012, the company has grown to 90 employees and within the next 12 months is predicting to have upwards of 200 members of staff on board, dotted in locations across the globe.
“The numbers miss a couple of subtle points,” explains Phil. “It has been a challenge to grow from a consultancy of a couple of engineers with PhDs through to all the skills you need to run a lean manufacturing facility that makes powders, develops software and manufactures hardware.”
A smart solution
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LPW's PowderTrace smart hopper designed exclusively for the transport and storage of metal AM powders.
A significant challenge for Phil and his ever-growing team is the fact that nobody has done this before, everything LPW is doing from its array of materials called PowderRange to its material lifecycle solution, PowderLife, is brand-new R&D.
“In traditional manufacturing a company would buy material, get a certificate of conformance to say the material is good, they’d go off and use it, and that’s it,” states Phil. “The difference for metal AM is that the economics only work with the reuse of the material.
“The elephant in the room for AM is the powder surrounding the part during build; it changes, and it can degrade. For example, some [of the powder] might pick up oxygen; a higher oxygen content means a stronger but more brittle material. If you’re making a paperweight, nobody cares, but if you’re in production, you need a component to have consistency no matter if the powder used once or used ten times.”
To achieve said consistency Phil believes the solution lies in PowderLife, LPW’s platform consists of five products; PowderTrace - a hopper for controlled metal powder storage and transport; PowderEye - sensors to measure powder condition; PowderFlow - a simple powder ow measurement kit; and PowerLab - LPW’s analytical testing and consultancy services. All of which provide data for powder lifecycle management software, PowderSolve.
“With PowderLife, operations teams have the benefit of traceability,” says Phil. “The second benefit is that data generated by PowderEye means you can start to do predictive trends, you can start to see before the material goes out of specification before making a part, saving a lot of time and money.”
Futureproofing
A keyword in Phil’s quote is data. In a world where GE is bringing its “Brilliant Factories” to fruition complete with digitisation at every juncture, firms will begin to require their entire supply chain to be ‘smart’. As a materials supplier with a complete monitored solution and a prestigious Queen’s Award for Enterprise in International Trade in its trophy cabinet, LPW looks to be way out ahead of the competition, and Phil believe big data will be the driver for further success.
Decanting metal powder into a container for delivery
“In the consumer world, we’ve talked about the use of big data with Apple, Facebook and Google trying to utilise our data to sell us products,” says Phil. “In an industrial environment, it is harder to integrate because you’ve got the encumbrance of big machinery that you’ve spent a lot of money on and it’s not just about putting sensors in left right and centre you have to change cultures.
“But AM, and specifically us at LPW, can get that right from the outset. We’re building a new factory; we’re not inheriting a powder atomisation factory that has been there for ten or twenty years, we’re building an AM materials plant, specifically to be digital.”
There’s a further benefit to gathering data at every step, by monitoring processes and analysing trends the ability to develop new alloys is significantly improved. In August this year, LPW announced a Royal Academy of Engineering fellowship with Professor Pedro Rivera of Lancaster University - a world leader in alloy development.
Phil believes that the data gathered will help this LPW / Royal Academy of Engineering Chair develop statistical models, which consider powder size, composition and atmospheric conditions, as well as component properties, like strength and ductility, allowing for the creation of robust processing parameters and novel alloys.
All this points to a rosy future for manufacturing in the UK, but Phil offers a word of warning about the current state of AM affairs:
“It is important the focus, for now, should be about doing what we do now with more stability. Everybody talks about production, but there are very few in full production. So let’s iron out the creases and deliver on the hype, let’s walk before we can run.”
We can start by handing our ball-point pens in at the door.
