Coudray walks through screen and stencil preparation, identifiying techniques for producing accurate and durable screens that will last beyond 100,000 impressions.
You may be ready to take on jobs with long run lengths, but are your screens? Coudray walks through screen and stencil preparation, identifying techniques for producing accurate and durable screens that will last beyond 100,000 impressions.
There comes a point for all printers when they land the big kahuna, a monster job that eclipses any order they've run before in terms of run length. I can't say exactly how big this job is, but it is an order of magnitude above what is normal for the operation--it might be 5000, 50,000, or 150,000 pieces.
Orders of this size create many challenges for the production manager. One of the most demanding is making production screens that can hold up to these extra long runs. This month, I would like to discuss how to make such screens and the techniques that will help to keep them on press in excess of 100,000 impressions.
For screens to hold up over very long runs, they must resist abrasion, ink penetration, and emulsion breakdown, all while maintaining edge definition. They must hold up to repeated wipedowns and press washes. And registration should be rock solid over the entire run, with no change in image size or shape.
Many printers never have had to worry about these issues, because their runs are short enough that they never experience any of the associated weak points. For our purposes here, we'll consider a long run as anything over 5,000 and less than 150,000 prints. Our goal is to create screens that will last the entire length of the run with no loss of print quality.
It starts with mesh
The journey begins with properly tensioned mesh. We should not use screens with less than 22 N/cm of tension. Anything lower than this offers too much elastic distortion, which will eventually lead to failure. Depending on mesh type, brand, thread diameter, weave, and mesh count, printing tensions should range between 25-45 N/cm. Lower tensions usually result in higher off-contact distances on press, which ultimately lead to excess squeegee pressure and premature screen fatigue and failure.
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