Product category:
Form/co-ordinate, optical and vision instrumentation
News Release from: LK | Subject: Evolution
Edited by the Engineeringtalk Editorial
Team on 07 October 2003
Scanning CMMs combine speed and accuracy
The Evolution range of bridge-type CMMs has been designed specifically to provide the optimum mechanical performance for analogue scanning.
Manufacturers, especially in the aerospace and powertrain automotive sectors, need co-ordinate measuring machines that are compatible with concurrent engineering practices and help to shorten product development time Data collection, usually by taking a single point or series of points with a touch-trigger probe, is now being superseded by continuous contact probing, better known as analogue scanning
This article was originally published on Engineeringtalk on 29 Jul 2004 at 8.00am (UK)
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To meet this need, LK has introduced a new range of bridge-type CMMs, called Evolution, designed specifically to provide the optimum mechanical performance for analogue scanning.
Offered with measuring envelopes ranging from 800 x 700 x 600 to 5000 x 1500 x 1500mm, the machines combine extremely high measuring accuracy with the fast operational speed of a production line-based CMM.
This level of performance, which is usually associated with high cost measuring machines, is available with the LK Evolution at a competitive price, making the scanning revolution affordable to all companies.
The innovative design of the new machine was created using computer aided solid modelling and finite element analysis where both the material selection and structure design were finely tuned to maximise stiffness, reduce vibration and provide smoothness of axis motion, all of which are fundamental in providing high accuracy scanning systems.
The construction incorporates an increased cross-section, ceramic design for the bridge and quill.
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An LK co-ordinate measuring machine with 7m long table has since the mid 1990s carried out 100 per cent inspection of aluminium wing spars for all Airbus variants at BAe Systems, Broughton
CMMs keep wood veneer trim in tolerance
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This material is ideal for a metrology structure, being 330% stiffer than aluminium and only 32% heavier by volume, resulting in high machine acceleration and velocity.
Ceramic also has a thermal expansion coefficient four times lower than aluminium, making the structure highly resilient to thermal change, so maintaining accuracy and performance.
All guideways use LK-designed, high efficiency air bearings which run with a reduced air film for low energy consumption and employ high stiffness friction drives with stainless steel drive belts.
Axis motion is assisted further by a new S-curve profile for the servomotors rather than the traditional trapezoidal velocity/time profile, giving smooth, repeatable axis travel essential in accurate scanning systems.
Finite element analysis, as used by Formula 1 teams to maximise design efficiency, has been employed to optimise the complete machine design, which together with high build quality has prompted LK to offer an industry-leading, 10-year guarantee for the Evolution's dimensional stability.
The overall result is an extremely stiff metrology structure designed to withstand the higher forces generated by continuous contact measurement using high acceleration/deceleration, without sacrificing accuracy or risking machine deterioration over time.
ISO10360-4 scanning test results with the Renishaw SP25 probe give an MPR of 1.9um and an MPT of 68s.
Repeatability is as low as 1um at scanning speeds in excess of 12m/min.
Data collection rates can be up to 1000 points per second to provide excellent component form definition and dimensional results.
Maintaining the accuracy over the wide operating temperature range of 10 to 35C is achieved by a combination of LK's dynamic temperature compensation and dynamic probe error correction.
The latter provides temperature compensation right to the stylus tip, not just the probe head centre.
LK research shows that a 5C temperature change for a probe length of 230mm could add up to 20um of error, which would remain uncompensated for in conventional systems.
Calculation of the thermal expansion coefficient for any probe assembly is automatically generated by LK's Camio inspection software, removing the need for any complicated calculation by the user of probe assembly values.
To ensure the new Evolution range is future-proof, the controller uses advanced integrated modular technology that allows new hardware support modules to be added, with shortened development time.
Examples of this include laser probing.
To provide a complete, single-source solution, LK's full suite of internally developed, Windows-based, 3D measuring software is available.
Included are the Camio Studio DMIS-based software for measurement using CAD data, and Camio Inspect for non-CAD applications.
Recently released in their third versions, both Studio and Inspect offer functionality and a user-interface designed to meet the needs of all skill levels, from novice user to experienced CMM programmer.
To assist nonskilled CMM operators, Launchpad software provides a graphical menu structure detailing component selection, required loading position within the machine and program launching instructions.
Programs can be launched with one click, eliminating any keyboard operation with fully automatic printing of the report at the end of the inspection.
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