1、AECMA STANDARD NORME AECMA AECMA NORM Edition approved for publication 30 April 2004 prEN 3475-706 Edition P 1 April 2004 Comments should be sent within six months after the date of publication to AECMA-STAN ICs: Descriptors: ENGLISH VERSION Aerospace series Cables, electrical, aircraft use Test met
2、hods Part 706: Laser markability Srie arospatiale Luft- und Raumfahrt Mthodes dessais Prfverfahren Cbles lectriques usage aronautique Partie 706 : Marquabilit laser UV Elektrische Leitungen fr Luftfahrt-Verwendung Teil 706: UV-Laser-Markierung This “Aerospace Series“ frestandard has been drawn up un
3、der the responsibility of AECMA-STAN (The European Association of Aerospace Industries - Standardization). It is published for the needs of the European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following member comments. Subsequent to the publicatio
4、n of this frestandard, the technical content shall not be changed to an extent that interchangeabilify is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of AECMA-STAN, it will be submitted as a draft Europea
5、n Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to full European Standard (EN). The CEN national members have then to implement the EN at national level by giving the EN the status of a national standard and by withdrawing any national standards c
6、onflicting with the EN. Electrical Domain I I Copytight 2004 O by AECMA-STA1 Page 2 prEN 3475-706:2004 Contents Page O In trod uction 3 1 Scope 3 2 Normative references 3 3 Definitions 3 4 Requirements . 5 4.1 General 5 4.2 Sample marking . 6 4.3 Sample measurement 6 4.4 Requirements . 7 Page 3 prEN
7、 3475-706:2004 O Introduction UV laser wire marking is the aerospace industry standard method for marking identification codes on to the surface of electrical wires or cables. UV laser wire marking was developed in 1987 to provide a safe, permanent means of marking thin wall insulations in particula
8、r, as an alternative to hot stamp wire marking, which is considered to be an aggressive process. 1 Scope This standard specifies the test method to establish the ultra violet (UV) laser marking performance of aerospace wire and cable for use in conjunction with UV laser wire marking systems in accor
9、dance with TR4543 “UV laser wire marking systems for aircraft wire and cable identification” and EN 3475-100 “Aerospace series - Cables, electrical, aircraft use - Test methods - Part 100: General”. 2 Normative references This European Standard incorporates by dated or undated reference, provisions
10、from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amen
11、dment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 3838, Aerospace series - Requirements and tests on user-applied markings on aircraft electrical cables. I) EN 3475-100, Aerospace series - Cables, electrical, aircraft use -
12、 Test methods - Part 700: General. EN 3475-705, Aerospace series - Cables, electrical, aircraft use - Test methods - Part 705: Contrast measurement. TR 4543, UV laser wire marking systems for aircraft wire and cable identification.2) 3 Definitions For the purpose of this standard the following terms
13、 and definitions apply. 3.1 Laser Laser is an acronym for Light Amplification by the Stimulated Emission of Radiation. Lasers are a source of intense monochromatic light in the ultraviolet, visible or infrared region of the spectrum. The “active” or lasing medium may be a solid, liquid or gas. The l
14、aser beam is generated by energising the active medium using an external power source, which is most commonly electrical or optical. 3.2 Ultraviolet (Abbreviation UV) Electromagnetic radiation in a wavelength range from approximately 200 nm to 400 nm. 1) Published as AECMA Prestandard at the date of
15、 publication of this standard 2) Published as AECMA Technical report at the date of publication of this standard Page 4 prEN 3475-706:2004 3.3 UVLaser A laser that produces a beam of UV radiation. 3.4 Fluence The energy density, measured in J cm-* (Joules per square cm) of a single pulse of the lase
16、r beam, which, for the purposes of this document, is at the surface of the wire insulation or cable jacket. 3.5 Pulse Length The time interval between the laser energy crossing half the maximum energy on the rising and the falling edges of the pulse; referred to as FWHM - full width half maximum. Pu
17、lse lengths are measured in nanoseconds, ns. 1 ns = lO-s. 3.6 Wavelength (A) Wavelength is measured in nanometres, nm. 1 nm = IO- m. A = c/f where c is the velocity of light and f is the frequency. 3.7 Damage For the purpose of this document, damage is defined as an unacceptable reduction in the mec
18、hanical or electrical properties of a wires insulation, .e. specifically a measurable reduction in the performance of the wire which is outside of its defined and acceptable specification. Wire surface defects that are visible only through x 10 magnification or greater, such as bubbles or flakes, sh
19、ould not be considered as damage unless they would affect marking performance (contrast, legibility, or other behaviour according to EN 3838) or other properties of the wire insulation. 3.8 Nd (Neodymium) Neodymium is an elemental metal that forms the active laser material in the most common type of
20、 solid state laser. The neodymium is held in an optically transparent solid “host” material, and is energised by optical input, either from a flash lamp or from the optical output from a diode laser. The host material does not play a direct role, but can slightly influence the laser wavelength. Typi
21、cal host materials are specialised crystal materials, such as Yttrium Aluminium Garnet (YAG) and Yttrium Lithium Fluoride (YLF). These lasers are commonly referred to as Nd:YAG or Nd:YLF respectively. The primary wavelength of Nd solid state lasers is in the infrared (IR) at a wavelength of approxim
22、ately 1064 nm. The IR output of such lasers can be conveniently reduced to lower wavelengths suitable for wire marking by use of harmonic generation (see 3.1 O). 3.9 Excimer A gas laser deriving its name from the term “excited dimer”. The laser is energised by means of a gas discharge. Excimer laser
23、s are available operating at a number of discrete wavelengths throughout the UV, the most common of which are 193 nm, 248 nm, 308 nm and 351 nm. The wavelength is dependant only on the gas mix used; 308 nm is commonly used for UV laser wire marking. 3.10 Harmonic generation The use of non-linear opt
24、ical processes to change the wavelength of a laser by frequency conversion. This enables the output of an infrared laser to be converted to shorter wavelengths. In the case of Nd lasers this results in a frequency doubled output at 532 nm in the green and a frequency tripled output at 355 nm in the
25、UV, which is used for wire marking. Page 5 prEN 3475-706:2004 4 Requirements 4.1 General 4.1.1 Preparation of wire samples Take a sample of the wire for marking. Before marking the wire ensure that the wire surface is clean and dry and free from dust and dirt. For initial production it should only b
26、e necessary to clean the wire with a dry cloth. However, in some situations, for instance if the wire is contaminated with oil or is very dirty, it may be necessary to wipe it clean using Propan-2-01 (Isopropyl alcohol). 4.1.2 Laser marking system A suitable laser must be used to mark the wire sampl
27、es. Based on commonly used laser sources employed in UV laser wire marking systems within the aerospace industry, it is recommended that either one of the ultra violet (UV) laser types listed in the following table is used for marking the wire samples. These are pulsed lasers that provide the very s
28、hort pulse lengths and intense, high power pulses of UV light required for creating marks on aerospace wire insulation. The laser pulse length shall be within the range of 1 to 30 ns. Laser type I I Wav;rgth I Pulse lengtha ns I I 355 I 4to20 Frequency tripled Q-switched Neodymium YAG, (Nd:YAG), sol
29、id I state laser I Xenon chloride (XeCI) excimer gas laser I 308 I loto30 I I a The pulse length ranges quoted are typical of commercially available lasers. I Important note Other laser types may only be employed provided they comply with the requirements of TR 4543. To measure the marking performan
30、ce of the wire it is necessary to measure the contrast of the mark made by the UV laser beam. The mark should be made using a laser and optical beam delivery system that incorporates a mask with a suitable cut out, e.g. in the shape of a square or rectangle, so that a clearly defined mark can be mad
31、e on the wire surface for measurement. See Figure 1. To enable the mark contrast to be accurately measured, a well-formed mark with minimum dimensions of 1 mm x 1 mm is required, subject to the wire gauge being large enough to accommodate this. See Figure 2. It is important that the intensity of tha
32、t part of the laser beam used for marking the samples and subsequent contrast measurement should be uniform to within k 10 % when projected on to a flat surface at the focal point of the beam delivery system. This is to ensure that fluctuations in the mark contrast due to changes in the laser intens
33、ity within the marking field are kept to a minimum. To ensure that this is the case suitable, purpose designed test equipment must be used for the laser marking, or alternatively, appropriate diagnostic equip- ment must be used to confirm that the laser beam intensity is within the required limits.
34、Figure 3 shows an acceptable laser beam profile. Important note The contrast achieved may vary for certain combinations of wire types and lasers, in particular wires with ethylenetetrafluoroethylene extruded insulations, whether cross linked or non-cross linked, are likely to exhibit a higher contra
35、st with 355 nm Nd:YAG lasers than with 308 nm excimer lasers. It is therefore important to record the type of laser used in the tests. In general, wires with insulations made from polytetrafluoroethylene are unlikely to exhibit this tendency. Page 6 prEN 3475-706:2004 4.1.3 Laser marking fluence Mar
36、king should be carried out as follows: A marking fluence of 0,9 J cm-2 k 0,l J cm-2 should be used unless the wire type under test is specified for marking at a different fluence. This fluence level has been determined to be satisfactory for achieving the maximum contrast, or satisfactory contrast l
37、evels, on all common aerospace wire and cable types and is representative of the majority of equipment in use, albeit that some equipment does function with higher fluence levels. It should be noted that the fluence is specified here for the purposes of defining the requirements for determining the
38、laser markability of the wire only. The system used must ensure that the laser fluence delivered to the wire remains within the specified range for all markings. NOTE For marking on the smallest gauge wires in production situations, e.g. 24 and 26 gauge, it may be necessary with some wire types and
39、equipment to utilise higher fluences at the wire centre. This is to ensure that the fluence at the edge of the mark remains above the minimum required to achieve the desired contrast while accommodating the geometric affects of the wire curvature, which reduces the fluence as the laser beam rolls of
40、f at the edges. WARNING: Care must be taken that maximum permissible fluence is not exceeded in such cases: refer to the appropriate product or other specification. 4.1.4 Determination of laser fluence The laser fluence should be determined by first measuring the laser beam energy after it has passe
41、d through the mask aperture (see Figure 1) using a suitable calibrated laser energy calorimeter. The area of the laser beam should be determined by making a mark on a suitable piece of flat plastic material held at the focal point of the laser system. NB when marking wire samples, take care to ensur
42、e that the top centre of the wires are positioned in the same plane as the flat plastic sample to ensure that the marking is carried out at the same fluence. After making a mark on the flat plastic material the area of the laser beam should be determined by measuring the mark dimensions using a suit
43、able microscope and graticule. The fluence may be calculated by dividing the laser beam energy by the mark area. 4.2 Sample marking Take the sample of wire and mark it according to the above instructions at appropriate intervals along the length of the wire. It is important to ensure that the laser
44、marks do not overlap when doing this. Make sure that the laser beam is centralised on the wire axis to ensure accurate marking. For the purposes of determining the laser markability of a batch of wire during manufacture, samples of wire should be marked taken from the wire at both the start and the
45、end of a run. 4.3 Sample measurement 4.3.1 Contrast measurement After marking the wire measure the contrast of the resulting marks on the wire insulation using a suitable contrast measurement system in accordance with EN 3475-705 “Aerospace series - Cables, electrical, aircraft use - Test methods -
46、Part 705: Contrast measurement“. Page 7 prEN 3475-706:2004 4.3.2 Sample area When measuring the contrast of the marks ensure that measurements are made on the marked and unmarked areas about the central axis of the wire and just either side within a band equal to k 20 % of the diameter of the wire o
47、r cable, to ensure that the most uniform part of the mark is measured so that errors are not introduced caused by changes in the laser fluence resulting from the curvature of the wire. See Figure 2. 4.3.3 Mark contrast Take the contrast values established according to 4.3 and take an average of the
48、measurements made at the various points along the wire. This is the mark contrast of the wire. 4.4 Requirements The measured mark contrast shall meet the requirements of EN 3838. 1 3xND:YAG (355nm) 2 UV Laser beam 3 Mirror 4 Mask 5 Projection lens 6 Marking area Figure 1 - Schematic of typical arran
49、gement for laser marking wire samples Page 8 prEN 3475-706:2004 Figure 2 - Photograph of laser marked wire showing rectangular laser mark and box area defining typical measurement area along wire axis Figure 3 - Laser beam profile in two dimensions demonstrating minimal intensity variation within the selected marking and contrast measurement area
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