At MACH 2022, GTMA member LK Metrology (Hall 19, stand 422) will launch two larger sizes of co-ordinate measuring machine (CMM) in the company’s entry-level ALTERA C range. The machines are an ideal solution for manufacturers looking to purchase their first motorised CMM as well as those that need additional measurement capacity.
With easy-to-use software and a choice of probing options including touch-trigger, analogue scanning and non-contact laser scanning, ALTERA C machines provide accuracy and flexibility for a range of metrology tasks. The compact design conveniently fits into the smallest of spaces and should a user’s requirements change, the future-proofed platform can be upgraded with new technology.
The original ALTERA C variants introduced in August 2019 were offered in three sizes, 7.7.5, 10.7.5 and 10.7.7, the biggest having X,Y,Z axis movements of 1,000 x 650 x 650 mm. The two extra machines, designated 12.9.7 and 15.9.7, extend the inspection envelope to 1,200 x 850 x 650 mm and 1,500 x 850 x 650 mm respectively and feature a new 900 x 700 mm ceramic bridge.
The largest machine model, which will be demonstrated at MACH, nearly doubles the previous maximum measuring volume, greatly expanding the range of applications for which the affordable ALTERA C is suitable. Typical applications are likely to be found in the aerospace, automotive and medical industries as well as in other sectors with demanding metrology requirements.
Through the ability of all machines in the range to include automatic tool change in the inspection program and to capture data flexibly from multiple types of sensor sequentially, dimensional measurements at discrete points and the acquisition of complex freeform surface data may be combined seamlessly in a single, high-speed, CNC inspection routine, without manual intervention.
The result is efficient throughput for quality control tasks in laboratories and shop floor environments, avoiding metrology bottlenecks. The data obtained provides a comprehensive awareness of component conformance, reliably meeting today’s requirement for a measuring platform that underpins concurrent engineering practices to speed time to market for new products.
The accuracy of an ALTERA C is high, starting at 1.7 µm + L/333. Repeatability of 1.5µm, 720 mm/sec traverse speed and 1,900 mm/sec2 acceleration are all industry-leading in this class of machine. The inclusion of Renishaw encoders with 0.05 μm resolution optical scales for high volumetric accuracy not only leads to outstanding metrology but also provides immunity to contamination.
The machines harness the power of the latest software, such as LK’s powerful CAMIO 2021 R3 for programming and multi-sensor measurement and reporting based on 3D CAD data. The latest release even includes a module for automated inspection of gears. Further options are ArcoCAD metrology software from Metrostaff; and the Industry 4.0-compatible Metrology Gate portal, which provides remote access to quality data and CMM status from any internet-connected device anywhere in the world. LK’s offering is rounded off by a vast array of automation options.
Intelligent Machine Design
Innovative features incorporated into the design of the ALTERA C have resulted in a surprisingly compact footprint, even for the largest model, making the multi-sensor platform an attractive proposition when floor space is limited and/or expensive.
Three CMM stands are available to allow customers to choose a configuration that best suits the installation site and application. One stand provides the possibility to integrate an on-board PC and includes a monitor arm to support a controller with keyboard, replacing the stand-alone controller by the side of the machine and thus saving space. Another stand incorporates pneumatic mounts that isolate the CMM from nearby sources of low frequency vibration such as production plant.
The CMM structure has been optimised using computer-aided solid modelling and finite element analysis, 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 it offers an unparalleled 10-year guarantee covering dimensional stability.
All guideways use LK-designed, low maintenance, pre-loaded air bearings of wrap-around design, offering 3.5 times higher stiffness than standard air bearings. They run with a reduced air film thickness for low energy consumption and give repeatable measurement results, even at fast axis speeds. 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. It is more than three times stiffer than aluminium yet only one-third heavier by volume, resulting in higher acceleration and speed. Ceramic does not stress-relieve like aluminium, leading to better long-term dimensional stability. The thermal expansion coefficient of the material, which is similar to that of granite but four times lower than aluminium’s, 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.