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noxcuses

Kenetix 300

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I have a Kenetix 300 setup that is indexing a belt 15" each cycle. I calculated the index pulses based on drive pully diameter and gear box ratio. It indexs exactly 15" which makes me feel my calculations are correct. The problem is that over time the stop position drifts about 1/8" over 50 or so indexes. Since the belt is position dependant it is a really big deal. I'm running out of ideas on what could be causing this. During setup, tuning the drive was very difficult. The autotune function would give vastly different gains each time I ran it. The belt moves freely with no snags or binding points throught the entire travel. After manually tuning it runs smooth as silk.. Can the tuning still be off causing the positioning error??? Any suggestions?

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Is it a positive transmission (timing) belt drive or a friction (V grove) one? The latter could allow slippage. Could the load variation cause some sort of stretching to develop? It seems to me that the mechanical transmission from the feedback point (pulse counter) to the targeted (monitored) end point "doesn't hold calibration" or losses the timing of the original calibration. If anything within the motion control loop generates any position error the system will immediately declare it and, if the control logic is monitoring the eventual position error, "decisions" will be made and/or alarms will be "posted". Edited by dmargineau

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The belt from the gearbox to the drive pully is a timing belt.. Also the conveyor belt is actually a timing belt with a near zero stretch rating. I'm going to measure the drive rollers with a caliper instead of using the printed specs. Hopefully there will be a variation.

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Let's analyze you situation -- after 50 indexes you notice a variation of 1/8" or 0.125 inches. This would occur if you were having an error of 0.0025" or 2.5 thousandths each index. Was your original measurement of 15 inches done with calipers or a micrometer and accurate to +/- 0.00025" or .25 thoudandths of an inch? If not you're most likely seeing accumulated error. Not uncommon for systems like this.

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I agree with Bob, it's accumulated error. Do you have a way to rehome the belt every so many indexes?

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