Exhaustive control checks and maintenance of sensitive aircraft parts must be carried out regularly. Certain parts on which strong demands are made, such as for instance landing gear, are given to special repair companies.
As those companies often do not have the original drawings of the components available, dimensional checking in the range of quality control is very extensive. They have to work according to basic data supplied by the manufacturers. Position and diameter of bushes can be particularly difficult. Often it is not known in which alignment the part was measured.
However when it is vital to achieve the highest accuracy, the alignment of a part and the support points must be taken into account for dimensional measurement. As these details are often not available, checking of complex parts proves to be problematical. Especially with heavy parts, which are often the case in the aircraft industry, part fixturing has considerable influence on the measuring results. In order to achieve comparability of results, measuring must always take place with the part in the same situation, e.g. in installation position, horizontally or vertically.
After successful measuring the data results are sent to the part manufacturer for comparison purposes. If deviations are established, measuring with different alignment must be done again. Problems then ensue when dedicated measuring fixtures cannot be adapted and therefore are no longer of any use for changed support situations.
Additionally, it is mostly small quantities which have to be checked, whereby the manufacture of a new dedicated fixture is often not cost-effective, especially if they have to be made two or three times. In such cases the use of modular fixturing systems is called for, whereby individual and highly accurate measuring fixtures are built on the spot.
The user remains independent of fixture builders, which can lead to considerable savings.
Modular systems such as Alufix stand out through the high precision and reusability of almost all components. It allows adaptation of finished fixtures catering for changed measuring requirements at the customer’s plant. When the fixture is no longer required it is completely disassembled and all components are free to build a new fixture. Investment in a modular fixturing system pays for itself after only a few applications.
As parts in the aircraft industry to be checked are often large and require corresponding coordinate measuring machines, many repair companies in Singapore work together with measuring laboratories.
In order to achieve a comparison of results appropriate measuring fixtures have to be supplied with the part or put at the lab’s disposal. Witte Far East, one of the companies with aerospace certification based in Singapore, provides individual measuring fixtures for each part to be measured. “That is the only way we can guarantee reliable results with high repeatable accuracy,” explained Stefan Roeding, managing director of Witte Far East. Even for large parts, up to 6m modular fixtures are built at short notice, whereby all special support requirements are taken into account.
