I have a strange dip in the middle of my turns - Page 2
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  1. #21
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    Quote Originally Posted by DMF_TomB View Post
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    you using coolant ? temperature changes will cause problems

    Yes, using coolant. I'm not talking about a change that happens in the middle of a run, I'm talking about a consistent problem, that only disappears when the taper move gets reversed in direction.

  2. #22
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    Quote Originally Posted by Dave K View Post
    Yes, using coolant. I'm not talking about a change that happens in the middle of a run, I'm talking about a consistent problem, that only disappears when the taper move gets reversed in direction.
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    all cnc have backlash and the slides often tilt when reversed. like a 4 legged chair with one leg short upon direction reversal it tilts and effects position. i often see .0004", if you use .0001 indicator and move back and forth .0001 in handle mode rarely see only .0001 movement back and forth
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    i also see servo oscillation where the servo is moving back and forth sometimes fast and sometimes slow. sometimes if .0001 indicator setup up and in handle mode you move .0001" you might see it bounce back and forth .0005" for a few seconds or longer.
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    i also see where spindle is warming up and it can change position just running as heats up. some jobs i use 5 minute delay spindle turning to stabilize spindle temp so it does not change .0003" while machining a part
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    i also see parts with hardness variations requiring many small cuts in the .0005" range. reminds me of sparking out with a surface grinder. keep cutting back and forth til it finally stops cutting.

  3. #23
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    May not be this, but if running negative/large radius/high edge hone (more tool pressure), it can make the middle come out bigger due to deflection. Same tool path run with positive/small radius/sharp edge could actually cause part to suck in (make the middle smaller) if diameter is not large. Finish allowance makes a difference too. Just something to consider.


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