Impressions - January 2014 - (Page 64)

talking SHOP Screen Printing Technique Controlling Variables, Part 4 In this continuing series, we explore the variables surrounding squeegee applications. By Rick Davis, Contributing Writer Editor's note: To read Parts 1-3 of the "Controlling Variables" series, visit our website at impressionsmag.com and search the Impressions digital edition archives for the August, September, and October/November 2013 issues. t o start this series on controlling the variables of the screen printing process, we ﬁrst addressed prepress functions. In Part 3 of "Controlling Variables," we addressed the speciﬁcs surrounding the physical squeegee itself. Now, we come to the remaining variables of the squeegee's printing parameters, ﬂood bars, ﬂashing and curing. Here, we will continue with the actual squeegee applications. There are two basic rules of thumb when it comes to squeegee selection: Fewer is better and more is better. I have come across both schools of thought in shops throughout the industry. I espouse the fewer-is-better philosophy and here is why: When working in a facility with multiple manual and/or automatic screen printing presses, the fewer choices (variables) you introduce to the process, the better. Assume you have three different squeegee durometers in your facility and you are printing a six-color halftone reproduction. If the exact squeegees used in the initial production run are not properly documented for the next reorder, it will be a turkey shoot when the reorder hits the press trying the ﬁgure out the correct squeegee selection. The basic rule of thumb to follow is to minimize your selection of available squeegee durometers (to two if possible) and always document the squeegee durometers that were used in each screen to eliminate issues for future reorders. 64 Impressions | January 2014 Whether you are working on a manual or automatic press, the basic rule of thumb to follow is to minimize your selection of available squeegee durometers (to two if possible) and always document the squeegee durometers that were used in each screen to eliminate issues for future reorders. SQUEEGEE PRINTING PARAMETERS There are several variables that determine the correct squeegee speed. We already know what durometers of squeegee you will want to use based on the application. The squeegee speed is determined by many additional inﬂuencing factors. These include: Ink Viscosity/Shear Characteristics: How the ink shears from the action of the squeegee pressing the ink into the mesh will be the most inﬂuencing factor on squeegee speed settings. This applies to both automatic and manual printing. Printing at a speed greater than the ink's ability to properly shear will minimize its ability to properly clear from the screen and results in the need for a second pass. Higher viscosity inks will require a slower squeegee speed. Keep in mind that as the ink warms up from the shearing effects of the squeegee repeat (and heat from the platens, if ﬂashing), the ink's viscosity will drop and become easier to print. This can allow for an increase in squeegee speed. Always remember that once a run is started and looking good, press adjustments, such as squeegee speed, can alter the color of a wet-on-wet print or opacity of an underbase. Thus, such adjustments must be made with caution. Screen Tension/Off-Contact Distance: The screen tension/off-contact distance also is another large factor in determining proper squeegee speed. When printing with standard screen printing plastisols, impressionsmag.com http://www.impressionsmag.com http://www.impressionsmag.com

Table of Contents for the Digital Edition of Impressions - January 2014

Impressions - January 2014
Contents
First Impressions
From the Show Director
FYI
Product Gallery
ISS Long Beach Product Pick
ISS Conferences
In the Details
How to Make Your Website Into a Prospect Magnet
Tees Stand the Test of Time
Shop Spotlight
Embroidery Technique
Embroidery Production
Screen Printing Production
Screen Printing Technique
Digital Decorating
Classifieds
Online Directory
Ad Index

Impressions - January 2014