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Fine Tuning for Fine Details

(December 2012) posted on Tue Dec 18, 2012

Use these pointers to start making the adjustments needed to produce high-quality work.

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In Figure 3, the carriage rails and table are parallel, but the screen is not. The parallelism of the rails and table will maintain even pressure, and the elastic nature of the screen will allow the stencil to compensate for its alignment—within reason.

It would be ideal to have all three parallel to have predictability within the screen-printing operation. On most presses, the screen is constantly the easiest of the three elements to adjust, and the most difficult to keep adjusted. It is usually designed to be adjusted a lot to change off-contact distances, but it’s the most difficult to keep adjusted because people often tweak the off-contact in ways that aren’t calibrated to very exact standards. In addition, you must also consider peel adjustments, which actively and deliberately move the screen out of parallel to the table and squeegee as part of their function.

Addressing the problem
Fixing the press-alignment problem requires aligning the squeegee-carriage rails to be parallel to the press table. The first step on any press is to measure the degree of misalignment and to be able to check that measurement during the alignment process. With no screen in the press, a squeegee holder should be inserted into the machine. Place a true, straight, freshly sharpened squeegee into the holder. If you don’t have one, substitute a piece of rigid material. The key is to have a straight and true edge that can be brought nearly in contact with the table.

Run the press to the end of the stroke that prints first. Using the pressure adjustment, bring the squeegee down until it nearly touches the table. Either a feeler gauge or a piece of stock used as a feeler can be used to set each end of the squeegee edge an equal distance from the table surface. Then run the squeegee to the opposite end of the stroke and measure the gap between the edge and the table. the difference in distance from one position to the other is the amount of adjustment required to bring the press into parallel. The following tips will help you adjust clamshell and four-post presses.


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