Martin Baker uses Mitutoyo CMMS for precision inspection

Citation

(2002), "Martin Baker uses Mitutoyo CMMS for precision inspection", Aircraft Engineering and Aerospace Technology, Vol. 74 No. 3. https://doi.org/10.1108/aeat.2002.12774cab.009

Martin Baker uses Mitutoyo CMMS for precision inspection

Keywords: Aircraft industry, Safety, Inspection

To ensure the thousands of safety-critical components in each Martin Baker ejection seat are manufactured to within the strictest tolerances, Mitutoyo coordinate measuring machines (CMMS) are employed to inspect fully mechanical parts prior to assembly (Plates 8 and 9).

Plate 8 Mitutoyo CMMs provide support for Martin Baker in ejector seat manufacture

Plate 9 TRW Aeronautical Systems gets it right every time with bespoke Mitutoyo gauge

With over 250 customers worldwide, UK based Martin-Baker Aircraft Company has to date supplied over 69,000 ejection seats for a total of 87 air-forces. Customer requirements vary for different conditions of use. For example, the terrain over which the aircraft are to be flown determines the survival pack contents of each seat. Different contents are used for flying over the desert to one where the aircraft will be predominantly flying over the sea, when a life raft is incorporated.

BHN 504 and BHN 506 models were the first CMMs to be purchased by MartinBaker from Mitutoyo about five years ago, to replace two old Ferranti machines. According to Mitutoyo the company soon realised how easy it was to use the Mitutoyo machines, prompting further purchases of two Euro-C Apex 9166 machines in 1998, followed by two Euro-C Apex 9106 machines in 1999.

With a large measuring range, combined with high movement speed, the EuroC Apex 9106 and 9166 machines combine integrated, fully digitised CNC control, automatic temperature compensation and high precision, claim an accuracy of Ul:(2.9+0.4L/ 100)µm, with a resolution of 0.0005mm.

The versatility and ease of operation claimed of the Mitutoyo CMMs enables four programmers to write complete programs for the components produced at Martin-Baker. This allows a team of 12 inspectors to operate the machines by simply entering the part number of the component to be inspected – the machines then automatically carry out a full inspection of the part.

Inspection supervisor at Martin-Baker, Mr. Jim Kelly, commented, "With the newer machines the operators don't need to know a great deal about the machine they are using – it takes over for them. The service has also been excellent."

It is also reported that a special pneumatically powered, gauge manufactured by Mitutoyo Gauging Technology Division has enabled TRW Aeronautical Systems (Lucas Aerospace) to "get it right first time" when calibrating flap actuator torque limiters for Airbus aircraft prior to assembly. This has considerably increased first time throughput by eliminating the need for stripping down, adjusting and re-testing the complex units.

TRW Aeronautical Systems is a supplier of high integrity systems and equipment to the global aerospace industry. The manufacture of the flap actuators requires the correct size shim to be fitted into the torque limiter before being tested under load. Once assembled, the only way that adjustment can be performed is by stripping down the actuator to change the shim. Using the new gauge, TRW is reportedly now able to fit the correct shim every time, eliminating the need for stripping down and retesting.

Prior to utilising the bespoke gauge, approximately 50 per cent of the flap actuator torque limiters failed under test, with each unit taking over an hour to strip, re-calibrate and retest – the company producing 10 flap actuators for the Airbus A320 aircraft family.

During operation, the pneumatically powered gauge inspects three key elements of the assembly by compressing a spring pack and simultaneously measuring two critical dimensions. The required shim thickness is displayed on a computer monitor, the operator then selecting and fitting the correct size shim. A fool-proof system built into the gauge will only allow the mechanism to be removed from the gauge when the correct size shim is inserted.

The gauge is used for calibrating nine different types of gearbox, all requiring different setting and gauging – each actuator has a different loading depending on its position on the aircraft wing. The shims used for calibration are to within ±0.0005", with the gauge having repeatability to within ±0.0002".

Substantial benefits have been gained by the company using the new gauge, explained Mr Simon Burr, operations manager at TRW Aeronautical Systems: "The gauge has given significant time savings on production and freed up test capacity by getting every actuator right first time. As well as the time savings, it has also provided Health and Safety benefits because the gearboxes are filled with a semi-fluid grease/oil mixture that is hazardous to the skin and had to be disposed of every time an actuator had to be stripped down."

Prompted by the success of this project, TRW Aeronautical Systems is now working with Mitutoyo on further projects. Simon Burr explained, "We are currently working on more metrology projects with Mitutoyo – most of what we do when building gearboxes is concerned with measurement to reduce backlash and end-float and we can probably reduce our build process workload by at least 20 per cent by using the right gauges."

Details available from: Mitutoyo (UK) Limited. Tel: +44 (0) 1264 353123; Fax: +44 (00 1264 354883; E-mail: janice.cook@mitutoyo.co.uk