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  1. #21
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    Default Re: Waves/Chatter

    could it be from runout of the bit. or the tolerance level of the spindle. I have a 12HP Itallian HSD spindle that is only 2 years old?



  2. #22
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    Default Re: Waves/Chatter

    Its really likely a combination of things:

    Acceleration, backlash, mechanical slop, speed, collet, tool extension from collet, spindle runout etc. I've just tried to eliminate them one by one as I can or at least work out where my issues lie.

    Even though my machine is thick steel, like yours is I think, I think the linear bearings are the weak link. The machine should be rigid as hell but it can be flexed at the head when under power (but not moving) by +/- .01". I've tightened everything (though they do loosen sometimes). I've tried new collets and less tool extension. I've tried higher speed and lower. Runout on the collet and my HSD spindle are minimal (spindle is barely anything). Backlash is low too if not under force but as I mentioned the z axis can flex a bit and that would happen when the machine was changing directions a little. If its not backlash (ie belt and rack/pinion) then it must be from the bearings not being 'tight' enough on the rail.

    The biggest differences after mechanical issues that I can adjust seems to be acceleration - ie reducing the force it applies as it is changing directions.

    Anyhow. For me its a issue that bugs me but its not a huge issue otherwise. So dig in and see what you can figure out - get a dial indicator and check your backlash, deflection under stress etc.

    I don't know it will go away totally but hopefully it will get a lot better. Mine is only a pain on that acrylic as I need to sand out the ripples to get a glass like polish on it afterwards.

    In case anyone is wondering, I'm the twin of the other gfacer on cnczone...


  3. #23
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    Default Re: Waves/Chatter

    Nic I noticed that you were the guy I was talking about the syntec with. Did you get this one instead?

    In case anyone is wondering, I'm the twin of the other gfacer on cnczone...


  4. #24
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    Default Re: Waves/Chatter

    Yes, This Laguna machine became available for a better price so I grabbed it. This one runs B and R controller. I think its made in Austria or Australia



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    Default Re: Waves/Chatter

    Hey Guys,

    I detached the Y pinion from the rack and pushed the machine by hand during a cut and I still had the waves in my finished product. So this is telling me that the problem is not there. It also seems to move quite smoothly on the Hiwin bearing blocks and square rails. So now I am moving on to my spindle. Could this also be happening if the bit is slightly canted backward/forward or left to right? any suggestions?



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    Default Re: Waves/Chatter

    Quote Originally Posted by Nick12 View Post
    any suggestions?
    Could this be a problem with resonance of the system?

    Have you tried cutting at different RPMs? Have you tried using different bits with a different number of flutes?

    What bit (length and diameter) and feeds and speeds are you cutting with? Chatter will leave a wave pattern? If you grab onto the spindle nose when the z axis is extended and you push and pull on it, does it move (flex)? Just trying to figure out if there is something with your Z that is making it not as stiff as it should be, or perhaps you have a resonance problem with the rpm and feeds/speeds/bit that you are using.



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    Default Re: Waves/Chatter

    I am using a 1/4" two flute upcut and 1/4" O flute. I have tried both of these bits with new collets and nuts. I have tried them RPMs ranging from 10,000-24,000 and Feed rates from 60-300 IPM and the wave are very consistent at all levels.



  8. #28
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    Default Re: Waves/Chatter

    Quote Originally Posted by Nick12 View Post
    I am using a 1/4" two flute upcut and 1/4" O flute. I have tried both of these bits with new collets and nuts. I have tried them RPMs ranging from 10,000-24,000 and Feed rates from 60-300 IPM and the wave are very consistent at all levels.
    How long is your bit?

    What DOC are you using?

    Can you do a finishing pass?

    Can you try a half inch diameter bit?

    That's all I can think of.



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    Default Re: Waves/Chatter

    I am using a 3/4" CL on 3/4" material. I do 4 passes (the 4th is a .05 onion skin)
    What is DOC?
    I tried a finishing pass, stepping in .0625 (1/16") and same results
    My toolpaths will not allow for a 1/2" bit, not enough room in between pieces.



  10. #30
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    Default Re: Waves/Chatter

    Here is Pic

    Attached Thumbnails Attached Thumbnails Waves/Chatter-thumbnail_20170713_182848-jpg  


  11. #31
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    Default Re: Waves/Chatter

    DOC = depth of cut.

    I'd also recommend a larger diameter tool.

    Are you climb, or conventional cutting?

    Do a climb cut finish pass, full depth, but only .015-.02"

    For a finish pass, I'd recommend a low helix 2 flute bit. But I think a 3/8" tool will give a better finish.

    Gerry

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  12. #32
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    Default Re: Waves/Chatter

    Quote Originally Posted by Nick12 View Post
    I am using a 3/4" CL on 3/4" material. I do 4 passes (the 4th is a .05 onion skin)
    What is DOC?
    I tried a finishing pass, stepping in .0625 (1/16") and same results
    My toolpaths will not allow for a 1/2" bit, not enough room in between pieces.
    DOC is Depth Of Cut. Meaning how deep you cut on each pass.

    I wasn't talking about the Cutter Length, I was talking about how much sticks out from the spindle. So for a 3/4" cut, you'll have about what, 1" minimum that sticks out from the spindle?

    So you have a 1/4" bit and you are cutting the first three passes at about 1/4" deep with a bit that sticks out 1" from the spindle.

    I don't have any experience using these bits or cutting plastic, BUT, it seems obvious to me that you should not be cutting at the same depth as the diameter of your bit and expect to have a perfect finish. Perhaps someone with experience cutting plastics and using these bits can give an opinion.

    I also think 1/16 is way too much to take off on a finishing pass using a 1/4 inch bit.

    You could try:

    Get a 1/2" bit and use a piece of scrap to see what difference it makes.

    Try using a shallower depth of cut that is less than 1/2 of your bit diameter.

    Trying doing 1 or 2 finishing passes with far less step over.

    Hand scrape or sand the piece when you're done cutting.

    That is all I can suggest to you. I don't think it's your machine, your pinions, or your spindle that's at fault. I think you expect too much from a 1/4 inch bit that you are pushing aggressively. Like I said, perhaps someone with experience cutting plastics can give an opinion on feeds and speeds, bit types, and depth of cut.

    But that's just my opinion and it could be wrong as I don't have the experience with plastics.



  13. #33
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    Default Re: Waves/Chatter

    Quote Originally Posted by ger21 View Post
    DOC = depth of cut.

    I'd also recommend a larger diameter tool.

    Are you climb, or conventional cutting?

    Do a climb cut finish pass, full depth, but only .015-.02"

    For a finish pass, I'd recommend a low helix 2 flute bit. But I think a 3/8" tool will give a better finish.
    Just saw this post. Yes, what Ger said. I also forgot about climb or conventional.



  14. #34
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    Default Re: Waves/Chatter

    Thank you for all the advice guys. I really appreciate it. I just ordered a new ISO30 Tool holder, 1/4" Low Helix Upcut spiral bit, collet, and nut. I am going to run all these new parts tomorrow just to eliminate it being anything to do with that. If that does not work then I am going to try adding more passes. I am going to cut .125 (1/8") and do 6 passes. I am also going to buy a 1/2" bit and try that. I will get back on here with results tomorrow. Thanks again.



  15. #35
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    Default Re: Waves/Chatter

    If your doing a finish pass, it doesn't matter if you do 3 or 6 roughing passes.
    And a 3/8" bit will do just as well as a 1/2" bit, for less money.

    Gerry

    UCCNC 2017 Screenset
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    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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