Tube systems Tubeway army – measurement analysis A Test report has documented the suitability of the measuring system ‘TubeInspect’ for deployment in the aerospace industry

“Unbent tubes can only be obtained by explicitly qualified suppliers”

by Jutta thiel PFW Aerospace AG, with its headquarters in Speyer, Germany, and over 1,500 employees Quality demands on tube manufacturing in the worldwide, is considered to be a market leader aerospace industry are considerably more strin- in tube system manufacturing for the aerospace gent than in other industrial sectors. To deter- industry. EADS/Airbus, Boeing, Bombardier mine the suitability of the optical tube measur- and Eurocopter are some of their renowned ing system ‘TubeInspect’ for this sector, PFW reference customers. Aerospace AG carried out an extensive mea- surement system analysis. During the tests Special requirements PFW project engineer Martin Seibt identified All tube systems are subject to strict quality the high repeatability of the system. Even the regulations, as any imprecision could have reproducibility was five times higher than the disastrous consequences. Unbent tubes can one of the competing measuring systems. only be obtained by explicitly qualified suppli- The test results have led to Airbus, a major ers, who issue single parts with individual customer of PFW, certifying the suitability of certifications. Accordingly, during further pro- the TubeInspect measuring system for tube cessing strict tolerance specifications have to be bends of over seven degrees and PFW has been observed. At PFW Aerospace AG the tube given the official approval to deploy TubeIn- bending process has to fulfil highest demands spect in production. in regards to perfect geometry. Tube manufacturing in the aerospace indus- To remain profitable, however, the company try is much more complex that it appears at first has to be in a position to manufacture tubes in glance. Highly developed systems constructed the smallest production batches with a minimal of bent tubes which are invisible from the out- number of rejections. side run like veins through every modern air- “It is our aim to be able to manufacture prof- craft from the tip of the wing right to the land- itably even for a production batch of just one ing gear. There are tube systems for example for unit as our customers often commission us to Jutta thiel fuel, hydraulic liquids, air and oxygen. Today, produce just one part,” Seibt, explains. “Take

SHOWCASE 2011 52 | AerospaceTestingInternational.com Tube systems

Right: Tube bending within precise parameters for the aerospace industry

tem and compared this with the tactile system “TubeInspect excels in optimal conditions which had been used to date for inspecting due to its extremely low deviation, “ says Seibt. manufactured tubes. “Compared with the competing system the pre- cision is very good.” Optical measurement For the analysis, PFW chose Aicon’s measuring Second procedure system TubeInspect as this system is the only The second procedure is entitled Gage R&R- fully-optical measuring system on the market Study (Gage Repeatability and Reproducibility). today which is specialized in bent tubes. TubeIn- This measuring procedure determines the spect carries out highly precise measurements of repeatability and reproducibility of the measur- tube geometries by using high resolution digital ing process in production conditions taking cameras. Moreover it calculates the set-up and into account the influence of the operator. correction data and transfers these to the bend- Depending on the results the decision is made ing machines. The time needed for a tube inspec- whether the measuring process is suitable for tion is short: For a fuel tube measuring data is the measuring task. available within three seconds, controlling a During the analysis both TubeInspect and complex brake line with more than 40 bends can the tactile system were used to measure four be carried out in less than 20 seconds. TubeIn- completely different tubes from four different spect is capable of completely replacing cost- machine setters with three different fixturing intensive mechanical gauges. systems. In total 48 measurements per system were documented. Analysis using two procedures “We were surprised at the excellent perfor- First procedure: to carry out the measurement mance of the TubeInspect system with regards system analysis PFW used two procedures to repeatability,” comments Seibt on the result representing latest technological standards. In of this examination. “Aicon’s system performed the first test, which is the measurement capabil- five times better than the tactile measuring sys- building a satellite as an example. A tube ity test, the bias and the variance of the measur- tem. We realized that the set-up of the tactile needed here is very unique and consequently a ing system without any operator influence are measurement based on a fixturing system ‘one-off’. So you commission PFW to produce evaluated according to a calibration master. An manipulates the tube’s geometry - and this con- just this one tube.” average, a standard deviation and a bias can be stitutes an enormous error source. TubeInspect Even serial parts for aircraft can be calculated from the measuring test sequence. works with an optical positioning assistant and ordered in quantities of less than ten pieces. Carrying out a suitability test of a measuring every tube is measured in two positions. Due to Nearly without exception, production system which represents the requirements of this the system achieves significantly improved includes costly materials such as titan, stainless tube bending in the aerospace industry, PFW repeatability.” steel or Inconel, which is a non-corroding used the DKD-calibrated tube as a reference PFW presented these measurement results nickel-based alloy, and rejections have to be standard. This was measured 50 times, the tube to Airbus, one of its most important customers. kept to a minimum. was taken out of the measuring cell and replaced Due to the convincing results, PFW received “Today PFW is in a position to immediately there for each following measuring. With these from Airbus the official approval to deploy produce 20,000 components with minimal dis- results Seibt evaluated whether the measured TubeInspect in production. The system is now card,” says Seibt. “More than two tubes being values matched the established reference values implemented in the factory in Speyer and is rejected before the first good unit would be an of the calibrated tube and how the measure- used on a daily basis. unacceptable cost factor for us.” ment results related to each other, and how “Aicon’s measuring system is the most In the aerospace industry, where product much the measuring results deviated. contemporary technical method to fulfil diversity and the manufacturing of a large The result was convincing: TubeInspect is the growing demands of the aerospace indus- number of prototypes are required, a measur- suitable for the aerospace industry as a mea- try,” says Seibt. “Other manufacturers of mea- ing system which can be employed universally suring system, as 99.7% of all the measured suring systems are encountering their tech- is the ideal choice. Production methods such bending points differed less than 0.36mm nological limits. We are very satisfied with as manual gauges which have to be adjusted to (target value: 0.50mm) from the actual value. this purchase.” z fit each change of a tube and which have in The repeatability was significantly better. addition to be stored for several years, no lon- The random error was ±0.09mm (3 Sigma), CONTACT ger present an economic solution. To achieve which is considerably less than the variance Jutta Thiel more efficiency PFW analyzed for the first detected for the measuring method which Tel: +49 531 58 000 70 time the potential of an optical measuring sys- was formerly used. www.aicon.de

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