Revo-Equipped CMM Helps Cut Part Inspection Times

Ant Industries has cut inspection times on complex parts by up to 83 per cent using Renishaw's Revo five-axis measurement system fitted to a Metris co-ordinate measuring machine (CMM). In 2008, when aerospace subcontractor Ant Industries carried out a study on its production processes with the aim of making improvements, it was clear that inspection was a major bottleneck. Shaun Rowley, Ant's manufacturing and sales director, said: 'There were thousands of non-productive hours a year where parts were either in inspection or waiting to be inspected.

'These are expensive parts without any value being added,' he added. To solve the problem, the company purchased a CMM equipped with a Renishaw Revo five-axis scanning system. Ant produces more than 1,000 different machined parts, approximately 85 per cent of which are supplied to the aerospace industry, requiring a high proportion of final part inspection. The company has to offer the CMM inspection of finished parts to its customers as part of the manufacturing process.

Some parts need 100 per cent inspection, while others must have at least one in 10 inspected. According to Alan Naylor, Ant's technical director, the new CMM reduces inspection time and measures complex features, such as the leading edges of blades. With an efficient machining operation, the company also uses Renishaw's spindle-mounted touch probes and tool monitoring systems for process control on its multi-axis machining centres and CNC lathes. However, Ant needed an improvement in post-process inspection. Rowley said: 'Our inspection method now uses a completely different approach.

'We have taken a big jump in a very short time from slowly taking multiple touch-trigger points with the old Tesa CMM to rapid five-axis scanning. 'The old CMM really struggled to maintain the accuracy needed; there were small but frustrating inconsistencies all over the measuring volume, which we had to correct to keep an acceptable standard,' he added. According to Rowley, the Revo system measures one type of turbine blade with a very complex form. 'Each of these blades used to take two hours to measure; now it can be done in 20 minutes,' he said.

Prior to the new Revo-equipped CMM, Ant had to analyse the form using a projector technique to measure the shape - a long and laborious task, according to the company. Now, the Revo system does the same job with a rapid profile scan, overlaying measured data onto the computer-aided-design (CAD) model and applying variable tolerances in different areas. The system has also helped to improve the calibration of the probe. Previously, it took around two hours to calibrate all the different probe angles needed for a measurement routine, whereas the Revo system calibrates in 20 minutes.

Ant needed the new CMM to be supplied quickly to satisfy the measurement needs of a large blade contract. The company decided to purchase a ceramic CMM frame from Metris (now Nikon Metrology), without a probe system or controller, with axis travel of 2m in Y, 1.2m in X and 1m in Z to enable the measurement of large engine rings. Renishaw then fitted the frame with its Revo five-axis measuring head and probe system, together with its UCC2 universal CMM controller. The work was done at Renishaw's Gloucestershire assembly plant prior to installation at Ant.

The system uses Renishaw's new Modus metrology software. 'The customer gives us some part designs as 3D CAD models, but most parts are defined with 2D drawings, which our CAD department turns into 3D models to enable the calculation of machining paths in a CAM [computer-aided-manufacturing] system,' said Rowley. The plan now is to train one of Ant's CAD/CAM team to also program the Revo inspection routines so that they have an overview of the whole production process.

'He or she will then be able to consider all the implications for machining and inspection when creating the CAD model,' added Rowley. Ant's machine shop includes 14 machining centres, most of which are fitted with Renishaw spindle-mounted touch probes or tool-setting systems. Simple load-bearing clamps are now used to provide approximate positioning, with the Renishaw probe systems and software automatically measuring the position of key features in seconds and adjusting the co-ordinate system to prepare for machining.


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