British Airways Boeing 747-400 on final approach;
image courtesy of NPL Crown copyright 2004
january 2008
The production of gas turbine blades is dependant upon heat treatment, which is
controlled by noble metal thermocouples. Thanks to a joint programme of
research their unprecedently fine calibration is now possible
Thermal metrology thrusts ultra-efficient jet engine forward
AIRLINES are under mounting pressure to
reduce CO2 emissions and fuel consumption.
Improvement of energy efficiency of jet aircraft
is achieved by operating gas turbine engines at
higher temperatures. To facilitate this, gas
turbine engine manufacturers are continuously
developing new alloys for hot zone turbine
blades that will withstand the increased inservice
temperatures. A critical part of the
manufacture of these blades is heat treatment to
ensure that they attain the necessary
metallurgical characteristics. Turbine blades for
the next generation of engines undergo heat
treatment at over 1310˚C to attain these required
properties.
The heat treatment, which is controlled by
noble metal thermocouples, is performed at
Bodycote Heat Treatments (Derby). This process
has exacting control requirements (±3˚C), at the
limits of the lowest accredited uncertainty
currently available from thermocouple
manufacturers. With conventionally calibrated
thermocouples, the heat treatment process is
limited by available uncertainties, and
additional detailed inspection is required to
verify the process efficacy. Bodycote wishes to
attain ±1˚C temperature uncertainty in-process,
but until recently this was not possible at the
industrial level.
However, thanks to a joint programme of
research between NPL, thermocouple
manufacturer CCPI Europe (Rotherham) and
Bodycote, the calibration of noble metal
thermocouples with world-beating
uncertainties of better than ±1˚C is now possible
at CCPI Europe. NPL has enabled this by
Laser deposition welding, a process which is becoming more widely accepted, provides a solution
to the problems of wearing on expensive tools, or design changes just before production starts.
New routes to mould repair
DEPOSITION laser welding, also known as Laser Metal Deposition (LMD), is a generative laser process in which metal is built
up in layers on existing tools and components. It offers great savings potential via the ability to make small modifications or
design changes to the end product and for correcting processing faults. Volume build-up can be used to compensate for
failures, achieve specified nominal dimensions and make old components useable again with little effort. The material
characteristics and the load capacity of the original component are retained, and the durability of the repaired form is
comparable to that of a newly made mould insert.
One specific solution comes with the Trumpf TruLaser Station 5004 laser. This is a compact and ergonomic workstation,
incorporating integrated TruPulse 156 solid-state laser. The machine made its debut at EuroMold 2007, and embraces a number of
innovations. For example all linear motions are performed by the laser beam while the workpiece remains stationary. This makes it
possible to weld with great precision with long travel distances and high workpiece weight. The 5004 is nevertheless compact
with a footprint under 1.5m2. The operator also benefits from an integrated microscope: the view into the microscope can be
individually set to a wide variety of positions; the same applies to the arm rest. The most important laser parameters can be displayed in the user’s field of
vision in the microscope. The control system, which addresses three linear axes and an optional rotational axis simultaneously, allows three processing types:
manual welding and setup; guided welding with supplementary wire; and automatic NC welding without additional material. www.trumpf.com
Micro bore finishing: alternative to honing
for technical ceramics
ENGIS’S new Micro bore finishing machine has been designed specifically
to make components with bores 2mm to 20mm, particularly automated
production of ceramic components in the medical, precision valve and
aerospace sectors. This flexible, small-footprint machine provides lower cost
per bore throughout a long tool life, with consistent and predictable results,
improved bore quality and fewer rejects. At the same time, its high level of
automation offers shorter cycle times and higher production rates, while
reducing labour cost per part. The system provides manufacturers looking
to avoid the drawbacks of conventional honing - for example rapid tool
wear and high skilled-labour costs - with a more cost-effective alternative,
which can be used for virtually any bore finishing application and
workpiece material. Using the single-pass process, extremely tight
tolerances can be held reliably and consistently in a production
environment, at a lower overall cost per finished piece. www.engis.com
process development
implementing a novel high temperature fixed
point into CCPI Europe’s calibration chain.
These novel high temperature fixed points mark
a watershed in high temperature metrology and
have extended the range of reference fixed
points from the previous limit of 1084˚C
(copper) to approximately 3200˚C. Their
development has been the subject of vigorous
research at NPL for the last 3-4 years. The ideal
candidate for this aerospace application is the
Co-C eutectic, which melts at 1324˚C, very close
to the heat treatment temperatures required. The
resulting improvement in process control
should yield an increase in effectiveness of the
heat treatment process at Bodycote, allowing
them to respond effectively to the increasingly
stringent demands of engine manufacturers.
jonathan.pearce@npl.co.uk
Intelligent light created by plastic laser sintering
ADDITIVE layer manufacturing technology using a machine built by EOS
GmbH, near Munich, is helping internationally acclaimed designer, Assa
Ashuach, to produce interior furnishings that could not be made any other
way. Laser sintering of plastic powder in successive horizontal slices taken
through a 3D CAD model, is a technique normally used in engineering to
produce prototypes and products quickly.
A good example is Ashuach’s AI light. Endowed with artificial
intelligence, the light incorporates five digital sensors that cause it to move
and morph its structure in response to changes in the space that it is
illuminating. The owner is able to interact with it using movement, sound
and other lights. Over time it develops new behavioural patterns and a
unique character, becoming so familiar with its surroundings that it can
behave unpredictably if moved elsewhere.
‘Layer manufacturing from my 3D software allows me to create
seemingly impossible designs’ says Ashuach. www.eos.info
MWP
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