Q&A: Hot Stamp/Heat Transfer Tooling and Application
A resource sponsored by SPE’s Decorating & Assembly Division
by Bill Morey
In 2016, are there any “typical” hot stamp or heat transfer applications?
If “typical” refers to smooth, flat surface decoration or even raised letter “tip stamping,” the answer is yes.
Because of the benefits of the completely “dry” process of hot stamping – particularly the wide range of colors and the bright metallic finishes of hot stamp foil, as well as multi-color heat transfers – there is a strong desirability in the industry for the heat-applied decoration processes of today. Also, thanks to the digital machining world of today's toolmakers and engravers, fewer restrictions exist for hot stamping curved or shaped surfaces, which actually are becoming more “typical.”
Are there any differences in the tooling or application parameters between flat and multi-curved parts?
Certainly, there are substantial differences in the tooling. With shaped or curved surfaces, the print detail of a hot stamp die must follow the part surface exactly, but restrictions still apply to the decoration area of curved parts. Mostly, for any “radius” less than ½-inch total, deco “wrap” should be 70 degrees or less for low scrap results. In addition, the support fixture must support and locate the part more precisely. Thankfully, today's modern hot stamp machines have superior controls and servo drives that allow for very fine settings of motion with repeatable setups.
What is required from today's plastic decorator in order for the toolmaker and engraver to produce such detailed dies and fixture?
Well, as we are in an advanced digital era, all artwork – as well as 3D part surface files – are created using computer programs. Therefore, the most accurate, fast and least expensive development of everything from basic flat dies to complex shaped tooling must start with Illustrator-type artwork and CAM-type 3D computer surface files. If these files are not supplied, then the art department must develop images. These images can be patterned after anything from the most basic lunch discussion napkin sketch to a photo.
If the parts are from 20-30 years ago (or even modern era, but from unknown offshore suppliers), then they must be computer-digitized to create accurate machining paths for the toolmaker to reproduce the shapes.
Please note that two-dimensional flat drawings are of no use in creating compound surfaces because they typically lack the many points of reference that are used to create the blended surfaces that we are trying to match. The days of pouring a cast of a part section and using an antiquated mechanical duplicating machine to create a master are reserved for only the most valuable (expensive) projects – and still is not as accurate as original 3D surface files.
The bottom line is all of these “fixes” are expensive to re-create and really wasteful knowing that the modern files do exist most of the time. You only need to ask the right person for the correct file. As engravers and toolmakers, we are all familiar with and agree to privacy contracts, so that should never be a problem in getting the correct computer files.
Are the tooling requirements without regard to substrate material or are they particular to the substrate?
The basic premise is that all tooling must match the part decoration surface, be it flat, contoured or simply dealing with common shrinkage. The foil makeup must match the substrate chemistry. Product comparability tests may require certain protective foil layers to protect the decoration. This is more common in cosmetic packaging and other beauty products, such as creams, lotions and fragrances.
That said, the die material choice – be it metal or most commonly, custom-blended silicone rubber – requires the same tooling approaches to matching the part.
As an example, nylon and polypropylene decorate well with silicone or metal, but with certain fillers or additives, metal dies may work best. Polystyrene, PET blends or PVC most always are better with silicone. As long as the foil or transfer chemistry is formulated for the correct die material, all components should work well together.
What trends are on the horizon in hot stamp/heat transfer applications?
What I see, not only in the cosmetic packaging world but also in POP and automotive, is a combination of the product designers’ search for a new “WOW!” look while understanding the need to deal with government legalities of product safety ingredients, point of manufacture, etc. – which all may have to be print-decorated – sometimes stretch the laws of geometry and practicality when it applies to the decoration process. Some may say this structure actually forces the advancements of the tool making and application processes, which may well be correct. However, I believe that a more open discussion earlier on in the design process would accomplish shorter, less costly product launches when all suppliers have input prior to being contracted to produce working tooling.