Details:
Summary:
With the increasing emphasis on internal register of printed work, a test method for accuracy of machines is suggested. Four basic tests are described in detail: testing the base mechanism, testing the loading mechanism, testing the pin system, and testing machine-to-machine accuracy. Recommendations for a step-and-repeat room and stripping recommendations are also discussed. The considerations for evaluating a new or used step-and-repeat machine are voluminous. Test the accuracy of the machine using a GATF Register Test Grid. The GATF Register Test Grid is a new quality control device used to test the register accuracy of a vacuum frame. The test grid is a 24 x 36-in. (600 x 900 nm) film negative containing a precisely ruled pattern of lines and 8 percent (approximately dot measures 0.00275-in.--0.06875 nm) tint patches, imaged on a dimensionally stable 7 mil (0.007-in. or 0.175 nm) polyester base. Misregister as slight as 0.001-in. (0.025 nm) can be detected with this device. The degree of misregister that is acceptable in your step-and-repeat machine depends upon the press equipment on which the final job will be run. You must also consider the quality required by your customer. For many markets, registration within 1/4 of a dot would be more restrictive than needed. For other markets 1/4 of a dot movement may not be acceptable. How often the step-and-repeat machine should be tested depends upon its condition as well as the desired accuracy. Many printers perform the full test on a monthly basis; others test their machines quarterly.