Faster and More Efficient CMM Calibration Solution

Companies need advanced measurement solutions that enable them to guarantee the reliability of key processes such as validating the quality of manufactured parts and obtaining data for analysis and critical decision making. Thus, manufacturers usually employ quality control equipment such as a Coordinate Measuring Machine (CMM) which is high technological value equipment designed to calculate the geometric characteristics of an object. Despite their precision, these machines require exhaustive and costly periodic calibration to work correctly.

In this scenario, the Basque technology centre Tekniker in Spain, a member of the Basque Research and Technology Alliance (BRTA), was accredited by the Spanish National Accreditation Entity (ENAC) for calibrating medium and large CMMs (calibration length between 1,500 mm and 13,500 mm for the 66% of the longest travel of the CMM) by using a laser interferometer as a measurement standard. The Basque centre is therefore the only entity authorised in Spain to offer a calibration service using this laser tracer technology, which replaces traditional physical calibration standards and significantly improves the calibration time required compared to the use of physical standards.

The use of this technology offers a more efficient calibration solution for the large number of CMMs with a axis greater than 1,500 mm that exist in Spain, which are being currently calibrated using manual methods. The main problem of traditional calibration systems lies in the complexity of quickly and reliably using very long physical patterns.

Compared to manual methods, this system offers a fully automated solution that combines the most advanced laser interferometry technology, the so-called laser tracer AG, which is designed by the German international company, ETALON AG, with a self-developed data management software designed by Tekniker.

This solution consists of following a reflector located near the machine probe and measuring linear displacements. It thus performs the measurement process according to the ISO 10360 standard which is comprised of 105 lengths spread over seven lines, offering two advantages over current processes. On the one hand, interferometric accuracy is maintained throughout the calibration process and, on the other, machine downtime (typically up to 6-8 hours) is considerably reduced.

The software created by Tekniker is connected via a computer to the CMM and the laser tracer AG measurement system and records the data obtained during calibration. Once all the checks have been carried out, the application generates reports that are compared with the performance data of the machine to detect possible mismatches, according to ISO 10360-2.

“Laser interferometry has made many advances concerning the calibration methods used so far,” says Dr Unai Mutilba, head of Inspection and Measurement at Tekniker. “The new approach enables companies to reduce the downtime of their CMMs, verify larger machines, generate reports automatically and assign uncertainties for each of the 105 measurements that are made taking into account the temperature at the moment of each length measurement” he concludes.

The accreditation granted to Tekniker is preceded by the introduction in 2010 by ISO (International Standards Organisation) of the possibility of using laser interferometry as a valid standard for calibrating CMMs, a circumstance that the technology centre has harnessed to develop a faster and more efficient and precise solution.

“This accreditation recognises the work undertaken in the centre and serves to generate greater confidence about the company’s activities in a key area of advanced manufacturing such as metrology,” added Dr Mutilba.

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