Optimizing Shrink Sleeve Applications on HP Indigo Digital Presses

Substrate Compatibility: Not all substrates perform the same. Many PETG films have different skins, thus can perform differently when seaming through the primer. Trying different film grades and/or manufacturers may yield better results.

Primer Coat Weight: As a rule of thumb, a lower coat weight will make it easier to seam through the primer, allowing faster speeds and creating better bonds. On the press, use the lowest coat weight available, and consider pre-diluting the primer for even lower coat weight. (Add no more than 20% water vs. total volume.)

Seaming Solvent: To properly seam through the primer layer, you must ensure the solvent has enough time to penetrate through before it dries. Often, pure THF will dry too quickly and prevent seaming. Use a solvent mixed with dioxolane to lengthen drying time. You may find press-ready seaming adhesives on the market.

Wick vs. Needle: A wick is always preferred, as it is more effective at breaking through the primer layer and helping the solvent penetrate through it.

Seaming Machine Speed: When testing a new primer-film-solvent combination, start with slower machine speeds and verify seam bonds before increasing speed. Michelman's seamable primers typically allow successful operation at speeds of 50-200 meters (150-600 feet) per minute.