Mimaki’s ink jet pad printer

EP 2 546 058 A1
Imaging device and imaging method
Mimaki Engineering Co., Ltd.

Here Mimaki seeks to replace the pad printing processes that are widely used in industry for printing and decorating products.  With pad printing a master plate is formed by etching the image.  The plate is inked and an elastic pad, normally made from silicone rubber, contacts the plate and picks up the ink image.  The pad then presses against the object to be printed transferring the image.  The ink is then dried or cured and the process repeated for the next object.  Although the process works well, the major drawback is that the image is fixed and it takes time and expense to change to a new design.

Jan13The proposed process uses an ink jet printhead 2 to print UV-curable ink on to a transfer sheet 6.  The transfer sheet is thin silicone rubber stretched within a circular metal holder 7.  After printing the ink is partially cured by UV lamp 3.  This raises the ink viscosity from 3-20 cP to 30-300 cP, so the image ends up as a soft paste.

The transfer sheet then passes to the next part of the machine A2.  Here the object to be printed M is pressed against the transfer sheet, which stretches and wraps around the surface, aided by the flexible pad 10.  Almost all of the ink is transferred to the object.  Although the printed object is shown here as a sphere it can of course be any shape.

In the next part of the machine A3 the image on the object is fully cured with UV lamp 11.  If need be the lamp can be moved around the object to ensure all of the image is exposed to the UV radiation.

Finally at section A4 the transfer sheet is cleaned for re-use.  Pads 10 and 12 above and below the transfer sheet press cleaning web 12b against the upper surface to clean any un-transferred ink.