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Making Measurements that Matter

(May 2008) posted on Tue May 27, 2008

Teaching employees to use measurement tools correctly and assess the results accurately can significantly improve both production speed and product quality. Discover how proper measurement techniques can help you correct for registration errors and compensate for dimensional changes in substrates.


By Tamas S. Frecska

click an image below to view slideshow

Using ¼-in. registration pins for accurate alignment of these substrates is out of the question. The fact that they are soft (and often more than ¼ in. thick) makes it impossible to align them on a ¼-in. pin. Furthermore, punching holes in foam rubber or T-shirts may also prove to be impractical. The only method we can recommend to evaluate these substrates is a controlled printing experiment.

To perform a controlled printing experiment, you will need the following:

1. A printing press (manual or automatic) with proven registration accuracy. A press with proven accuracy is a press capable of printing images in identical locations as long as the sub strate is placed in the same position and the screen setup is not changed.

2. Six sheets or pieces of the substrate to be evaluated, cut to the appropriate size to fit on the press, but not smaller than 14 x 14 in.

3. A screen with four registration targets and an image that covers 50% of the substrate (Figure 5). Note that the design in Figure 5 is only a suggestion. You may use any existing design that covers 50% of the stock.

4. A skilled employee to print and cure the samples, then record the results.

 

Since placement of the substrate on the printing table will affect the accuracy of the experiment, you must take the following precautions:

• Make sure that the alignment edges of the substrate are straight and perpendicular to each other. Use a guillotine cutter to trim them.

• Use a three-point registration guide system (Figure 6). The registration guides contacting the substrate edges must be at least 1 in. long.

• Use adequate vacuum to firmly hold the substrate down. If the substrate is more than 0.06 in. thick, build a nest around it to prevent the squeegee from knocking it around. If the substrate is a woven material or T-shirt, it must be held onto the printing platen with a reliable adhesive.

 

Performing the experiment with non-textile materials

Follow this procedure when conducting a dimensional change test on soft, nontextile substrates:

1. Prepare any type of ink that is compatible with your drying system and can also be air dried. Do not use UV or plastisol inks—remember, this is a test, and adhesion to the substrate is irrelevant as long as the ink prints well).


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