Jerky rigid tapping G84 cycle
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    Default Jerky rigid tapping G84 cycle

    Hi,
    First time trying out rigid tapping on my 1995 vf-oe and I'm slightly concerned about the jerky motion.
    (Ordinary machining of flat and contoured surfaces all seems fine.)
    Initial movement is like a shudder and as it's approximately 10mm into a 25mm tapping cycle it smooths out and appears "normal".

    I have only tapped fresh air so far as I daren't and don't see the point in needlessly smashing a tap...

    Any idea what it might be? acceleration rate? Not looking ahead enough?
    No other Z movements behave like it.

    Thanks in advance,
    Tom.

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    I might be inclined to look at the cog belt that drives the encoder located just on top of the spindle motor, a couple of missing cogs can do this

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    What software does your machine have? and what rpm is your spindle running during the taping cycle? when the machine powers up , it will momentarily show you the machines software level should be something like M9.xx

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    Hi,

    Thanks for the replies both. New to this game and it's a job to trust my intuition when it comes to the unknown.

    Fusion 360, machine software I'll fire it up and take a look...

    Attached a video of the action and a photo of the code, with regards to the latter I really don't see how it could be a cause of the issue. I've got setting 57 ON for repeat rigid tapping which is why the spindle pauses to orient itself after already starting up, I guess I could avoid the jerkiness by switching that off but peck tapping is obviously a very handy thing to be able to use on tougher materials.



    20200104_204811.jpg

    Will take the spindle cover off and check the belt out for tension and wear etc. and report back.

    Thanks guys,
    Tom.

    P.S. Where would I find the "line rate" the machine reads its code at? Keen to see if I can tailor future code to be more compatible with the rate it can be read.

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    To me it looks like the feed and rpm are just syncing up. The lathe i ridge tape on will do it some.

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    I had a 1992 VF0 did the same exact thing, and I had that machine from 2004 until 2018.

    When tapping, the max RPM I would use is 1,000 RPM, and I would start my "Z" feed at plus .500".

    The more course the pitch, the more the shudder, but never any issues with gaging the threads as the feed synced with the speed before engaging the material.

    Best Regards,
    Russ

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    Thanks everyone!

    Reassuring to hear that it's pretty normal. Re-tensioned the encoder drive belt, belt was ok but I think the toothed wheels are a little worn and the extra tension seemed to reduce the issue, but it's still not gone away.
    I spent the rest of the day playing with some of the machine settings but none of them seemed to make a lot of difference. Parameter 140 for instance, but somehow it barely made any difference.
    Big thing I noticed was the unnecessary spindle start prior to the tapping cycle, will eliminate that from the code and see how it goes this afternoon.

    Will also try the raising of the reference plane trick while I'm at it.
    Thanks again, Tom.

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    why is your R value below the initial Z plane? that, and i'd make sure that the machine is in metric mode rather than inches.

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    you still haven't answered my question on what software does your haas have?

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    I have a year 2000 vf0e and it doesnt do that? just runs smooth from start to finish, but i create all my tapping cycles etc in fusion 360

    The encoder belts are a 5 minute job to change once the covers are off but i didnt see anyway to adjust the tension on mine as all bolt holes for the encoder and bracket etc are captive so tension cant be adjusted?

    Thanks
    Marc

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    The extra spindle start will go away if you drop the "m3" however it is important that the previous tool spindle command was m3 and not m4.

    You should answer Hoss710, he is pretty sharp on these things:

    "you still haven't answered my question on what software does your haas have?"

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    Quote Originally Posted by kustomizer View Post
    The extra spindle start will go away if you drop the "m3" however it is important that the previous tool spindle command was m3 and not m4.

    You should answer Hoss710, he is pretty sharp on these things:

    "you still haven't answered my question on what software does your haas have?"
    Should not worry about the last G03, as the codes are different for left and right hand threads, G84 Vs G74. The code determines the spindle direction.


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