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Designing with prepainted metal

In many ways, designing with prepainted metal is just like designing with any other form of sheet metal, but with the additional freedom of surface aesthetics.  However, there are a few peculiarities of prepainted metal which the designer would do well to remember to ensure that the design works well.

  • The first and most obvious point to remember is that the paint finish is present before forming.  The coatings used on prepainted metal have been formulated to flex with the base metal, but some are more flexible than others.  In many cases, coatings will retain their adhesion even at a 0T bend radius, but it is important to confirm this before starting the design.  The coatings have also been formulated to be very scratch resistant, but again some are better in this respect than others, so it is worth checking with your supplier first.  When assessing tooling to be used for forming operations, it is important to remember that a scratch in forming is a scratch on the finished product, but this can be overcome with good quality tooling, good design and, if all else fails, the use of a temporary protective film.
  • The second important point to remember when designing with prepainted metal is that the finish is applied before any joining takes place.  The most important consequence of this is that conventional welding is not possible.  However, there are numerous joining techniques which are possible, so this should not hamper the design.
  • The third point to consider is that the back-side of the prepainted metal sheet may well have a different appearance to the front side.  This is sometimes very useful, where, for example, the inside of a cabinet has a simple grey coating or a bright white finish applied before construction, but when designing it is important to remember that front and back surfaces may look different.  However, if this is important, it is usually possible to specify the same finish on the reverse as on the front side.
  • Finally, it is important to think about the edges of metal sheets within the design.  Prepainted metal sheets will always have at least two edges (and usually all edges) which are uncoated, since they will have been cut from a much larger metal strip.  These bare edges can look slightly unattractive and in the worst case, they will be the initiation point of eventual corrosion.  However, there are well established techniques adopted to hide bare edges.

Learn more about forming and joining prepainted metal sheet, including the common solutions to some of the issues raised above, in the following pages...