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FLEXO Magazine : November 2008
TECHNOLOGIES & TECHNIQUES A dial indicator, commonly used for measuring TIR. ’Round We Go Wrapping Your Head Around TIR By Tim Reece O ver the years I have listened to many colleagues debate the meaning or definition of TIR. So, aside from being Tirupati, India’s regional airport code, what exactly does the acronym TIR refer to in the printing process? FIRST (Flexographic Image Reproduction Specifications and Tolerances) refers to TIR as “total indicated runout.” In the printing process, this refers to the measurement of the out-of-roundness of a printing cylinder or press roller. A perfectly round roller would have zero TIR. I have also heard individuals argue that TIR actually refers to “total indicated reading.” As to which term is correct, the answer to that is that both terms are correct. One cannot say that TIR, as an acronym, means one term over the other. In the scientific measurement community, TIR, as an acro- nym, has more than 40 meanings. Regardless of the two terms that we often use in measure- ment of roundness, these two terms rank far down the list of the most commonly used (22nd and 23rd). Therefore, if the individual is using the term total indicated reading, an example 42 F LEXO may be measured and stated as “TIR from -.0025 - +.001.” In this same case, if the individual is referring to this measure- ment as total indicated runout, it would be stated the TIR mea- sures .0035in. MEASURING TIR Typically, when we measure TIR it is to identify an issue with the roundness of a plate cylinder, printing sleeve, impression roll- er, anilox roller or idler roller. Any out-of-roundness can have a negative impact on print quality as well as machine performance and throughput. Some of these areas of concern stemming from excess TIR include registration issues, variable repeats, variation on solid ink density, film wrinkles, and web tracking issues. Total runout will control variations of circularity, straightness, and taper of roller features. TIR is usually measured using a dial indicator. The indicator is fixed either mechanically or magnetically, relative to the point of interest and the indicator is zeroed relative to the surface in ques- NOVEMB E R 20 0 8 www. f l e x o g r a p h y. o r g