scouringpad
Member
Hi - I'm new to this site, but have looked over past posts and don't see a definitive answer for my current problem. I'm using HSC1 in a Micrologix 1500 and an Allen-Bradley 600 PPR 2 channel encoder to measure rubber matting on a shear line. The encoder has a 1 foot wheel on it, and rides on the matting. About 33 feet of matting come by the encoder every 7 minutes or so, and are cut into rough lengths entered by an operator into the panelview hooked to the PLC. The problem is in the 6 minutes or so that the matting is essentially sitting (it creeps slowly backward as it shrinks while cooling). The encoder counts fine forward or backward while things are moving along, but while sitting still, or almost still, I'm getting erratic false counts. Sometimes none, sometimes a few inches forward or backward. There is slight vibration from an air table under the matting, but not much, and the rubber will normally shrink back about 3 inches between pulls out of the press. Encoder is connected with Belden shielded cable about 15 feet long.
As sometimes the reading is just what it should be, I suspected some noise on the line, but am not sure what else I might look at. Filters, scan times? Another encoder of the same type yields the same results. Though I did make the program that runs this shear line, I am fairly new to this, and have little experience with HSCs. The operators not knowing whether the first cut of the cycle will be long or short makes them generally cut on the long side for the whole pull, and this generates a lot of wasted trim. If anyone has an idea that would steer me in the right direction, I'd sure appreciate it!
As sometimes the reading is just what it should be, I suspected some noise on the line, but am not sure what else I might look at. Filters, scan times? Another encoder of the same type yields the same results. Though I did make the program that runs this shear line, I am fairly new to this, and have little experience with HSCs. The operators not knowing whether the first cut of the cycle will be long or short makes them generally cut on the long side for the whole pull, and this generates a lot of wasted trim. If anyone has an idea that would steer me in the right direction, I'd sure appreciate it!