Metallics i Machining
attended by Lockheed Martin, Northrop
Grumman and BAE Systems. This
collaboration has involved development
of the Siemens Sinumerik 840D
controller to include the capability to
compensate for measurable machine
tool axis inaccuracies in all five axes
simultaneously. Northrop Grumman
Corporation Aerospace Systems is now
strongly and unequivocally encouraging
its supply chain to explore the use of
Siemens’ Sinumerik 840D sl CNC
and its VCS to achieve high tolerance
machined parts for the F-35 Joint Strike
Fighter programme. The technical
requirements from Northrop Grumman
have been listed as robust machine
tool design, repeatability, machine
Measuring geometrical accuracy: VCS in practical use on a 5-axis Breton Flymill 1000
tool responsiveness, environmental
temperature stability, and stable machine
tool foundations. the VCS technology was carried out plays a part here too, and there is no
Volumetric errors can be initially by Siemens in conjunction with Italian way of achieving very high repeatability
determined using state-of-the-art laser machine tool manufacturer Breton. without taking into account external
measuring equipment. The VCS has In this trial, a Breton Flymill – was factors such as thermal stability of
been configured to interact seamlessly calibrated using Renishaw XL-80 laser the shopfloor environment. Coast
and automatically with many popular interferometry equipment, with optics Composites in Irvine, California, has
systems by equipment suppliers like for measuring position, rotation and made something of a science of this
Renishaw, Automated Precision and translation. Without the integration of technique in high accuracy machining
Etalon to dramatically reduce the time measuring equipment, machine shops of Invar composite mould tools, not
and cost of using these systems to map were only able to identify errors and did necessarily controlling the shopfloor
a machine tool’s working space in all its not have the possibility of being able to temperature, but in understanding how
various dimensions. To perform the task directly make improvements. Users with this affects the dimensions of machine
of mapping data points and creating a the new VCS as part of their machine tool beds and axes. Part of the Hampson
high fidelity set of compensation data control capability can now directly use Industries group of companies, Coast
manually would in most cases not be the error curves that they have measured Composites has devised its temperature
viable as it is so resource intensive. for use in volumetric compensation. In compensation system to overcome these
A case study of the effectiveness of cooperation with Siemens, Renishaw variables in ambient factory conditions
developed an automatic converter for whilst still maintaining an accuracy that
this purpose. This simply and reliably often exceeds the customer specification
converts the data recorded using the in a range of typical materials.
XL-80 into the VCS data format. It has proved that it is possible to
A significant improvement during effectively retrofit the VCS enabled
this trial was indicated by the Renishaw controller to its older machine tools,
circularity test, which uses a number of with specific experience in using this for
axes moving together to provide an easily Henri Liné, Nicolas Correa, SNK and
verifiable toolpath. This was carried Amura machines. Coast also reports a
out in all three planes in space. In the changing philosophy on the shopfloor
YZ plane, the rectangularity error was of turning every machine tool into its
reduced from 8.6µm/m to 0.1µm/m and own coordinate measuring machine.
circularity deviation was improved from Laser trackers are now only used for final
Finding the sweet spot: Numerous rotational and
24µm down to 18µm. checking of machined parts. y
Cartesian errors build up at the tool centre point
Good shopfloor housekeeping always www.siemens.com
AEROSPACEMANUFACTURING | jANUARy 2010 29
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