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  1. #1
    Neuer Benutzer
    Join Date
    Mar 2013
    Posts
    15

    Citizen L32 Turning help

    Im running an older Citizen L32 5/8 416 material not ground but within .0003 roundness . I'm turning in one pass 6000rpm .003 feed down to a .4945 dia. over 1.5 length to a shouler then up to a .600dia for .5 length.
    My issue is on the .4945 dia. my dia. is out of round over .001 but on the .600 dia within .0002. I tried breaking the turning down to rough and finish passes in sections taking only a .012 finish but still have the same issues. I am going to replace the bearings is my first thought just looking for suggestions and if most of you do your turning in one pass or multiple passes. Thanks for any help
    My insert I am using is a Sandvik VBMT221-MF 2220

  2. #2
    Member
    Join Date
    Jun 2015
    Posts
    3195

    Re: Citizen L32 Turning help

    hy, you just hit into setup stability machine is performing fine on the 0.6dia, but not fine on the 0.4945dia

    i am going to replace the bearings is my first thought just looking for suggestions and if most of you do your turning in one pass or multiple passes.
    no, not yet, especially on gang lathes, because the problem may not be with the machine, and there are cases, when, after a service, the machine geometry is even worse then before

    look, for example, a new machine may come with a geometry alignment tolerance < 0.003mm, and inside the " alignment paper" you may find that the maximum accepted value is 0.030mm

    there had been cases, when, after service, machine geometry was within the maximum tolerances recomanded by the cnc producer, but now as low as when the equipment was new; this means that the result of the service intervention was bad, but officialy, it was within factory specs

    this being said, let's return to your machine, so 0.6is ok, 0.4945is not :
    ... try to begin cutting values in between those 2, and locate the linearity of the effect, see how it changes when you continously change diameters; thus cut 0.6, then 0.57, 0.55, 0.52, 0.5
    ... also, try to cut a 0.4945 from a piece of material that is shorter enough to be clamped ok inside the machine, thus check contact surface with guide bushing and main spindle collet to be maximized; longer materials may induce vibrations during cutting, and those vibrations have a bigger effect on smaller diameters, because there is no room to dump the vibration
    ... you said that also during finishing, still the tir was bad : try to run finishing directly, thus cut a 0.4945dia starting with a smaller stock, because, if you rough, and then you finish it, you may loose contact with the guide bushing, and this means that the material is not clamped/guided as it should be

    dia. is out of round over .001
    do you check the roundness inside the machine, thus right after the turning, and before cutting; do you use a dial inside the cabinet ?




    unfortunately, my advices are general, i can not be specific, since i don't see the machine working

    however, before considering the bearings, i would invest a few days to locate the issue / kindly
    Ladyhawke - My Delirium, https://www.youtube.com/watch?v=X_bFO1SNRZg

  3. #3
    Registered
    Join Date
    Mar 2009
    Posts
    35

    Re: Citizen L32 Turning help

    Quote Originally Posted by jimwjr89 View Post
    Im running an older Citizen L32 5/8 416 material not ground but within .0003 roundness . I'm turning in one pass 6000rpm .003 feed down to a .4945 dia. over 1.5 length to a shouler then up to a .600dia for .5 length.
    My issue is on the .4945 dia. my dia. is out of round over .001 but on the .600 dia within .0002. I tried breaking the turning down to rough and finish passes in sections taking only a .012 finish but still have the same issues. I am going to replace the bearings is my first thought just looking for suggestions and if most of you do your turning in one pass or multiple passes. Thanks for any help
    My insert I am using is a Sandvik VBMT221-MF 2220
    I know this is an old post, but to potentially help others who search in the future I will give my two cents...The insert you're using has too big of a radius. If you're running parts that require runout/roundness tolerances lower than .0005" you NEED a smaller radius tool. What's happening here is because the nose radius on the insert is too large it is putting too much cutting force into the material. The insert geometry and grade may also play into this. I would suggest something like a VCGT 2203-UM 1125 (.004r) or VCGT 220-UM 1125 (.008r) especially considering Sandvik doesn't make a VBMT insert under .016r.

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