BS/EN 9132-2017 pdf download.Aerospace series-Quality management systems-Data Matrix Quality Requirements for Parts Marking.
3.4.7 Stencil material
Stencil material and stencil generation are critical to producing repeatable quality of coded identification. There are four common types of stencil material currently available, these are:
a) Photographically etched stencils:
These are manufactured in precut sizes containing impressions of the required image. The ‘marking vendor’, who will then generate the image onto a finished plate, supplies the image. The plate is then used to form the image onto the stencil, which is a high precision polyester mesh material. Once the image is photographically etched into the stencil material, the stencil will withstand marking of large volumes of parts depending on the set parameters of the marking unit. If a high current is used to provide the mark the stencil will degrade with fewer marks. This method could be used for applications where the marking data does not change between markings, but although quality produced is good, the stencils may be relatively expensive.
b) Thermal wax stencil:
This Is a coloured permeable paper with a wax surface. The data matrix image is printed onto the thin wax surface by means of a thermal process, which removes the wax to leave an image of the identification required. The method tends to be fragile; the wax degrades easily under marking processes using a high current and tends to produce a mark of poor quality in these conditions.
c) Die-impression:
Die-impression stencil paper is widely used for producing electro-chemical etch marks in many applications. The stencil Is made from a coloured permeable fabric with a thin non-permeable laminate surface on one side of the stencil. A dot matrix printer is used to punch holes through the laminate coating in the shape of the data matrix image. Die-impression stencils are durable and can produce marks of a good quality. The most significant quality concerns derive from the way the stencil is produced. A 24-pin dot matrix printer is normally used to produce the images onto the stencil. Problems can occur with inaccuracies in the printing process (e.g., misalignment of the holes in the stencil paper with the pins in the printer).
d) Thermal transfer printed stencil — Disposable:
This type of stencil material is similar to the die-impression paper, with a permeable fabric and a non-permeable laminate. The main difference being that the laminate is only microns thick The laminate is thermally removed from the stencil using a thermal printer leaving the image on the permeable fabric. The process is generally reliable and produces a good quality mark The stencils are normally used once and then disposed of. Slight variations in print quality are mainly due to the weave of the permeable fabric structure.
3.4.8 Electrolyte solutions
A large number of electrolyte solutions exist; the compositions of which may vary according to component material type. However, as they are all designed to produce some form of chemical attack of the material, it is vitally important that all traces olelectrolyte are washed/removed/neutralized from the entire component immediately after the marking process is complete. It is vitally important to note that when applying or removing the electrolyte, the electrolyte and washing solution shall not be allowed to flow Into any openings or cracks between parts. The type/composition and use of the electrolyte fluid shall be the responsibility of the engineering design authority.
3.4.9 MarkIng requirements
a) Inspection of surface colour — Contrast:
Surface colours and mark contrast will affect the quality of component identification. In general, dark colours are applied to light surfaces and light markings applied to dark surfaces. The minimum contrast level between the marking and its substrate as a grey density difference should be no less than 20 % (see Figure 11). In order to maximize quality, original surface discolouration should be minimized.
b) Module fill:
The module size fill shall be 60 % to 105 % of the nominal module size; overlapping of 5 % is permitted.
c) Visual appearance:
To maximize quality, the process output shall be controlled within acceptable visual limits (see Appendix D for process guidelines).BS/EN 9132-2017 pdf download.
BS/EN 9132-2017 pdf download
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