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Process Standardization for Special-Effect Printing

(November 2000) posted on Tue Dec 19, 2000

Davis continues his investigation of special-effect inks by encouraging printers to standardize the methods they use to print them. The focus of this article is mesh selection and tension, squeegee characteristics, and ink modifications.


By Rick Davis

In "The Do's & Dont's of Special-Effect Inks," I reviewed the do's and dont's of special-effect printing from the standpoint of artwork engineering and process sequencing. This month, I will review the need for process standardization in special-effect printing, particularly as it relates to selection of mesh, squeegee, and printing angles. Special-effect printing requires the same amount of process standardization as any other aspect of the printing process and, in some cases, more. As opposed to standard flat colors, special-effect inks are intended to deliver an eye-catching appearance beyond what's provided by the design alone. Control and standardization of process variables are crucial for ensuring consistent results from production run to production run. In order to realize aesthetic benefits by standardizing your variables, you need to document every aspect of the production process. The additional benefit is that you can later use the documented standards as training tools for new employees. Some shops will even post standards at various workstations throughout the facility to ensure that the standards are always being met. An ability to read is the only thing an employee needs in order to properly execute a specific job. The first and most crucial step in the standardization process is documentation. Lack of documentation is the primary cause of inconsistent results from production run to production run. And for any given type of job that you print, you'll establish the standards based on an initial production run that you deem to be successful. Standards for special effects One of the challenges that special-effect printing offers from the standpoint of documenting standards is that the documentation must cover a much wider range of printing parameters and variables than you'd associate with standard flat-color printing. For example, mesh counts can range from 40 threads/in.(or coarser) for glitter inks to 305 threads/in. for highlight fluorescent inks. Squeegee parameters can run the gamut of durometer requirements and edge profiles. Screen stencils can range from conventional thicknesses to extra-thick stencils (250 microns or more) for high-density printing. Without proper documentation to guide you to the appropriate ink, screen/stencil, and squeegee combination, your ability to achieve consistent results from run to run are greatly diminished. One way to standardize your processes is to create a chart of the parameters that meet your printing requirements (Table 1). The chart could be used as a ready reference guide for screenmakers, inkroom personnel, and press operators. While the values shown in the sample chart are appropriate for most applications, you may want to develop a similar chart with values based directly on your own production capabilities and needs.

 

Table 1: Special-Effect Standards
Process Standardization for Special-Effect Printing
  1. 2. 3. 4. 5. 6. 7. 8. 9.
Mesh count (threads/in.) 40 86 86/125 86 60 86 230 60 86
Optimal tension 40 40 40/35 40 35 40 28 35 40
Squeegee durometer 75/
90/
75
65/
90/
65
65/
90/
65
75/
90/
75
75/
90/
75
65/
90/
65
75/
90/
75
75/
90/
75
65/
90/
65
Squeegee angle (degrees) 80 75 75 75 85 75 85 80 75
Squeegee profile
(round or sharp)
round round round/ sharp round round round sharp round sharp
Viscosity modifications (by volume) 5% NA 5% 5% NA NA NA 5% NA
1. Glitter
2. Metalic
3. Puff
4. Reflective
5. High density
6. Crystallina
7. Flourescent
8. Goop
9. Flocking Adhesive

Mesh-count standards On the chart, I have listed standardized mesh counts for different special-effect inks. Once again, these are only guidelines. You may employ different mesh counts for different special-effect inks depending on the type of visual effect you want to achieve. Once you have established the specific mesh counts that work best for you, documenting them on a chart (as well as the job jacket) will ensure consistent mesh selection, and it will have the overall effect of streamlining production and reducing confusion. Optimized screen tensions Standard screen tensions may already be established and enforced in your operation. If so, it's merely a matter of recording tension standards for each mesh listed on your table. If you don't have tension standards in place, you need to experiment until you identify appropriate tension levels for each mesh you use. Variations in screen tensions from run to run or screen to screen will hamper your ability to achieve desired effects on a consistent basis. When printing with inks like reflectives, which can cost as much as $200 per gallon, getting consistent results becomes imperative from a financial standpoint. Squeegee durometers and edges Squeegee durometer and edge profiles cause more havoc on press than any other variable if they are not properly selected and documented for specific specialty-effect applications. Philosophies for squeegee selection vary widely and range from the belief that one durometer/edge profile is suitable for all applications to the strategy that every specialty application requires four different squeegee types. As I recommend in Table 1, most shops can meet all their special-effect needs with two triple-durometer blade types and two edge profiles. The theory is to use the softer blade when you want a slightly thicker ink film and the harder blade for a thinner deposit. The table also shows two squeegee-edge specifications: R for slightly rounded and S for sharp. Rounded or radial edges are used with special-effect inks that are being printed through mesh counts of 86 threads/in. or lower, where a thick deposit is required. Rounding allows the edge of the squeegee to glide over the surface of the mesh without over shearing the ink film. In most cases, employing a sharp squeegee on a coarser mesh will only result in the ink being over sheared and will require a second print pass in order to get a thicker deposit and achieve the desired effect. Squeegee angles Squeegee angle is another troublesome variable that should be standardized. Some printers completely ignore angle selection, others adjust angles randomly and sacrifice consistency altogether. For special-effect printing, I suggest using one of two different angles: 75° or 85°. Generally, I recommend 85° for most standard applications and 75° for those jobs that require a slightly heavier ink deposit. Viscosity modification: In general, I recommend against making viscosity modifications because most inks don't require them. Some special-effect products, however, do occasionally benefit from viscosity adjustments. As Table 1 shows, I recommend no more than 5% modifier by volume for any special-effect ink, and then only with certain special-effect inks. Always refer to the manufactures' product information for specific modification instructions, and follow those instructions to the letter. If possible, incorporate the manufacturer-recommended modification guidelines on your chart. Conclusion Standardized procedures should be a part of every step in the production process at your facility. And documentation for these standards, whether presented in a chart or another format, should be readily accessible to employees throughout the facility. You can even apply the principles here to other areas of your business where standardization could reduce confusion and boost efficiency. Adhering to standards is the only way to ensure consistent results.


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