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FLEXO Magazine : October 2009
50 FLEXO OCTOBER 2009 www.flexography.org BEGINNER FLEXOGRAPHER A bench-top micrometer. To borrow a line from Joe Tuccitto (FTA's education direc- tor), "You can't manage something you can't control. I would like to add to that a line of my own, "You can't con- trol something you can't measure. While color management is the buzz word, process control is the foundation that must be established first. There are many measurement devices on the market today. Let's take a look at the types of measurement devices available, where they fit in the production workflow, and what is important when considering a device. IN THE PLATE ROOM Utilizing measurement equipment in the plate room for quality control can save time and materials in the platemak- ing process. With the proper equipment and guidelines, mak- ing quality flexo plates consistently is easy. Micrometer. This device is key in establishing proper back exposure, washout, and drying times for flexo plates. There are basically two types of micrometers: hand-held and bench- top. Hand-held micrometers are typically less expensive than a bench-top micrometer. However, bench-top micrometers provide a more consistent measurement. When choosing a micrometer, make sure to take your stan- dard plate size into consideration. The micrometer should be mounted on a bench mount or handle that is long enough to reach to the center of the plate. This allows the operator to make measurements anywhere on the plate's surface, which is essential to provide the most accurate results. Transmission Densitometer. A transmission densitometer measures the amount of light that passes through a given sur- face. In analog workflows, a transmission densitometer is very important for checking and maintaining the quality of film being output from the imagesetter. By checking film density and linearity, many common analog platemaking headaches can be easily avoided. With the increasing number of digital computer-to-plate systems, transmission densitometers have been repurposed to measure mask ablation characteristics such as stain and mask linearity. This is particularly important for quantifying the performance of a laser device with a particular plate material (a key step in the initial set up of many computer-to- plate laser devices). Camera-Based Measurement Devices. Relatively new to the measurement device arena for plate rooms are dot measurement devices specifically for the ablative mask and the finished plate. Most of these systems utilize a camera and software that automatically recognizes the dot based on image contrast. The dot area is then calculated from the im- age captured by the computer. An advantage to using these devices is the ability to visually inspect the dots under mag- nification as the measurement takes place. These devices range in price and capabilities, some even offer the ability to create three-dimensional images of the plate surface. In the past, many have disputed the accuracy of these devices, but the current offerings have improved drastically in accuracy and still offer the ability to measure overall consistency in the platemaking process. Measurement Devices for Process Control The Right Tools Can Lead to the Right Results By Justin Green TECHNOLOGIES & TECHNIQUES
Sustainable Fall 2009