The key to consistency in screen printing lies in the screen. Discover how discipline and science can help you fine tune the screenmaking process.
Somebody from your screen-prep area needs to be at major industry trade events every year, researching new products. I recently spent a few days at a shop and discovered that they were paying a premium for mesh that had to be specially ordered just for them. When I asked them why, they said it was what they had always used. It turns out that the mesh had been all but discontinued because it’d been replaced by an improved and far cheaper version. The company’s rep had done his job of informing them when the new mesh was introduced, but the shop’s resistance to change prevented it from taking advantage of the better product. The result was that the printer paid a premium for old technology. Don’t get set in your ways. Complacency will cost you in the long run.
Now we come to stretching screens. I will not go into great detail, because I’ll end up muddying the waters with generalizations that will help nobody. Choose your screens carefully and then insist upon receiving thorough hands-on training on screen stretching from the company that sells them to you. Listen to everything they tell you, and make sure you implement what they instruct you to do. Buy a good tension meter, and use it on every screen. Don’t coat anything until you are satisfied that the mesh is stable and properly tensioned.
Monitor every part of this process daily, and make sure you don’t let things drift. Use the piece of very expensive ground glass that comes with the tension meter and calibrate it every morning. Go check it right now. You might be surprised. And remember, if you have ever dropped that baby, it probably isn’t working right. Check it against the one your rep carries with him whenever he visits. This is an excellent test of the mesh company’s commitment to its products. If the rep doesn’t have one on hand, then you probably need a new rep.
I remember telling somebody at a trade show 20 years ago that we were screen printing down to tolerances of ±0.002 in. in circuit-board applications, after being told that it was impossible. Now, the best process printers in our business print to those tolerances routinely and repeat-print it hundreds of times through the same screen.
In my next column, we will get into the world of coating screens and discuss the vagaries of the exposure process. Let me leave you with something to think about. Over the years, I have made a good living applying a lot of the troubleshooting techniques and process-control knowledge that I learned from that team of engineers years ago. They had no special interest in screen printing beyond the way that it fit into their production of complex printed circuit boards. They approached problems in the same scientific manner that they approached every other aspect of the process.
When I became a consultant in the screen-printing business, I always built into my contract a nice bonus for times when I could improve my client’s overall productivity by 20% in three months. Thanks to those process engineers, I have never failed to cash that check—and usually well ahead of schedule. What should interest you the most about this is that nearly all of the production increases came about due to the changes made in the screen-prep area. Worth thinking about, isn’t it?
Gordon Roberts has a history in screen-printing production management that spans more than 25 years. He has held supervisory positions in shops that represent a broad spectrum of application areas and markets, including printed electronics, apparel, signage, and retail graphics. Roberts has presented training courses on the basics of screen-printing production and on shop management for the Screentech Institute and is presently a consultant for the screen industry. He can be reached at firstname.lastname@example.org.
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