HOW TO MOLD A RUBBER PRINTING PLATE

We recommend a technique called position molding to achieve the best accuracy in the finished rubber plate. There are two key points to this technique:

The plate should be molded in the same press in which the matrix was molded.

The matrix (loaded with the rubber charge) is returned to the same position and orientation as when it was originally molded.

This will, in theory, help to minimize molded plate variation by canceling out any small inaccuracies in the cure press platens.

MOLDING PROCEDURE

1. Choose the proper combination of bearers to achieve the calculated thickness and place them in position on the lower press platen or tray.
2. Cut a piece of rubber just large enough to completely cover the printing area of the matrix.
3. Brush any excess uneven dust from the surface of the rubber. A light, uniform dust coating is vital to proper molding to avoid trapped air.
4. Remove the protective film from the back of the rubber.
5. Place the rubber with the dusted side against the room temperature matrix.
6. Place the matrix/rubber charge on the lower platen tray in the proper position with the matrix side against the platen tray.
7. Cover with release paper at least two inches larger than the rubber. Do not extend the release paper over top of the bearers (if it is necessary to do so, exclude the thickness of the paper from the calculation of bearer height).
8. Close the press slowly until the bearers are just tight. Use only enough pressure to hold the bearers in place when lightly tapped. Excessive pressure will distort the press platens causing plate inaccuracies.
9. Cure the rubber / matrix charge for ten minutes (press closed time) at 310F (60 psi Steam). We do not recommend using a preheat of the rubber.
10. At the completion of the cure time, open the cure press and remove the rubber / matrix charge from the press. Carefully remove the release paper from the rubber and the rubber from the matrix to avoid tearing the rubber plate. Also avoid folding, creasing, or stretching the plate, especially while hot.
11. Trim any excess flash from the rubber plate. When cooled to room temperature, the rubber plate is ready for mounting.