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Component Manufacturing dverti$ dverti $ er
Don’t Forget! You Saw it in the
June 2022 #14275 Page #39
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Which is Better: Plate Placement Method or Tooth Count Method? By Glenn Traylor
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o answer the question of which is the better method, we should start with a little background. A critical plate is a plate with a Joint Stress Index of 80% or greater. The ANSI/TPI 1–2014 Standard stipulates that critical plate inspections must be conducted when completing the three inspections per station/ per shift/per week requirement. On average, the standard requires one critical inspection for each inspection made that week. Because some trusses will not have any critical plates though, several additional inspections will need to be made on the other trusses with multiple critical plates. For more on the process, see my previous article, “How Should Defects Be Recorded When Inspecting a Critical Plate?” The critical plate inspection can be performed using the Plate Placement Method (PPM). The PPM is a tool that speeds this examination by generating a template within the truss design software used to design the component. In lieu of PPM, an old-school method, the Tooth Count Method (TCM), can be employed by counting and recording teeth and comparing “good teeth,” teeth that are installed effectively, and “bad teeth,” those teeth that are pressed in defect areas or are damaged to the extent that the tooth is ineffective. So which method of recording critical plate information is better? Let’s compare them in a little more detail.
PPM – Plate Placement Method There are three distinct elements in capturing data using the PPM. Recording defects is the most recognizable portion but there are two other elements. My previous article, “How Important is Angulation? Why is It Important?”, has additional information relating to angulation and center of connector within the computer-generated polygon. Here we will just acknowledge these because they are required essentially in both analyses. Recording defects is one aspect of using the PPM. During the inspection, defects need to be recorded to provide historical data. One example is a knot defect recorded as a percentage of the defect circle. The template is placed over the defect and, using a marker, the profile of the defect is recorded within the circle on the PPM paperwork. The shading can be used to emphasize this condition. After the defect is recorded, a determination is made as to the percentage, so this information can be recorded into other databases. Another defect example could be recording of folded teeth. Rectangles represent the area of the set of teeth that are damaged. Folded teeth are always recorded in pairs because it is assumed the opposing tooth, although not visible, is folded under the plate too. Continued next page
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