LK Metrology to launch compact CMMs at Advanced Engineering

LK Metrology will unveil the ALTERA C ceramic-bridge CMM range at this year’s Advanced Engineering exhibition, which takes place on 30-31 October at the Birmingham NEC. Using the latest metrology software, multi-sensor technology and CMM design, the compact systems are intended for demanding quality control applications.

Built at the company's factory near Derby, ALTERA C machines are available in three sizes - 7.7.5, 10.7.5 and 10.7.7 - their respective X, Y and Z-axis movements being 700 by 650 by 500 mm, 1,000 by 650 by 500 mm and 1,000 by 650 by 650 mm. Typical applications are likely to be found in the aerospace, automotive, medical and other challenging industries.

ALTERA C is equally at home in an inspection department or on the shop floor, especially as pneumatic mounts isolate the CMM from nearby sources of low-frequency vibration, such as large machinery. The CMM control may be either stand-alone, or integrated into the machine base with a keyboard on an arm at the side. Renishaw encoders are included with 0.05 micron resolution optical scales for high volumetric accuracy.

Measurements taken with a touch-trigger probe are increasingly being augmented by continuous-contact probing and laser scanning to allow high speed collection of data on complex freeform surfaces. ALTERA C measuring machines are able to deploy all three types of sensor. Such flexible data acquisition boosts measurement throughput to avoid bottlenecks in the metrology department, provides a comprehensive awareness of component conformance, and meets today's requirement for a CMM that underpins concurrent engineering practices to speed time-to-market for new products.

The CMM structure has been optimised using computer-aided solid modelling and FEA, particularly within the bridge section, and is finely tuned to maximise stiffness, reduce vibration and provide smoothness of axis motion, all of which are fundamental to delivering high-accuracy measurements. Such is LK's confidence in its design methods that the company offers a 10-year guarantee covering dimensional stability.

All guideways use LK-designed, low maintenance, pre-loaded air bearings of wrap-around design, which are said to offer 3.5 times higher stiffness than standard air bearings. The bearings run with a reduced air-film thickness for low energy consumption and give repeatable measurement results, even at fast axis velocities. Friction drives provide smooth motion and exact positioning at continuously varying speeds, as well as zero backlash, overload protection and low maintenance costs.

Careful selection of materials in the machine construction includes, as with all LK CMMs, the use of ceramic for the moving bridge and spindle. The ceramic deployed is more than three times stiffer than aluminium, yet only one-third heavier by volume, resulting in higher machine acceleration and speed. In addition, ceramic does not stress-relieve like aluminium, leading to better long-term dimensional stability. The thermal expansion coefficient of ceramic, which is similar to that of granite but four times lower than that of aluminium, makes the structure highly resilient to thermal movement. Moreover, ceramic is three times harder than aluminium, so is more resistant to abrasive wear and indentation.

The ALTERA C is available with LK’s CAMIO8 DMIS-based, multi-sensor software, enabling programming and measurement based on 3D CAD data and comprehensive reporting.