pressure

Platens and Pressure: The Ideal Setting for Quality Prints

Joe Clarke has spent the past 47 years in the lab and in the engineering department, in pre-press and on-press, as an R&D / technical researcher and as a manager of screen print production. Clarke has held executive positions as President of M&R Printing Equipment and as Vice-President at Wilflex [Poly One]. He has been granted a growing number of print-related patents, including one for High-Shear printing with Smilin'Jack - he is a member of the ASDPT, is an Associate Editor for NBM and an SGIA Fellow.

Clarke has presented hundreds of technical papers, written a couple books and published over 600 technical / management articles for which he has been awarded five Swormstedts; the international standard for excellence in technical writing.

Currently Joe Clarke is the President of CPR, a Chicago-based corporation which manufactures Synergy Inks including NexGen; environmentally & financially responsible T-Shirt inks. For more information on CPR, visit http://www.cprknowsjack.com/.

Pop quiz: During the print stroke, what is the ideal pressure on the platen which leads to optimized loading on the superstructure? In case you don’t know, we will get to the answer shortly.

Before we answer that question, a far more critical feature (the benefit and incentive to buy) on a screen-printing press is how it applies force to the blade and pressure to the screen.

The universal goals for top-quality imaging are as follows:

  • Minimum force on the blade to overcome off-contact gap
  • Minimum blade angle
  • Blade dynamic interface fitted to mesh
  • Minimum blade deflection during the stroke
  • Maximum stroke speed
  • Zero net pressure on the platen

As an experiment to answer this question, we used a press with two cylinders on the squeegee and two cylinders on the flood and maximized the travel on both. We had a high-fill/low-capacity 150/45 mesh at 25N/cm², an 85A double bevel at a zero angle, 0.160" gap, and a highly shear-thinning/low tack level (less than 25 percent tack) white plastisol.

We ran a stroke speed of 40 inches per second (as fast as the press would go) and the squeegee pressure was 18 PSI. Case in point: we had near zero pressure on the platen while cleaning the non-image areas and completely clearing the mesh openings. At the settings listed herein, we easily achieved the maximum print quality, productivity, and screen/stencil life. For additional PSI suggestions, refer to the diagram above.