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  1. #1
    Member
    Join Date
    Jan 2020
    Posts
    6

    How to achieve clean cuts?

    Hi,
    Seems that no matter what endmill I try, or wood type, I can't achieve a clean cut. The worse part for me isn't tearout, but the irregular inside part of the cut. Any suggestions? Right now I'm using 2 flute, downcut, Yonico 31212-SC.

    Note: My machine is a DIY machine, so I know that there's a lot of room for improvement. SO my question isn't just for what bit to use, but what should I focus on solving to achieve a cleaner cut.

    Thank you very much
    Attached Thumbnails Attached Thumbnails índice.jpg  

  2. #2
    Gold Member
    Join Date
    Apr 2004
    Posts
    5052

    Re: How to achieve clean cuts?

    It's probably not a problem with the endmill you're using, but your home-made machine's lack of rigidity. Try this - with all the motors locked up so you don't backdrive the axes, lean on the spindle in various directions, and note the deflection (a dial indicator can help with this). If you see more than a few thousandths (or hundredths, if you're in mm) of motion, then it's likely the tool is bouncing around as it tries to cut, which leads to poor surface quality. If you post pictures of your machine, perhaps someone will weigh in with suggestions on how to beef it up so this is minimized.
    Andrew Werby
    Website

  3. #3
    Member
    Join Date
    Jan 2020
    Posts
    6

    Re: How to achieve clean cuts?

    Well Andrew, that explains a lot. I haven't checked with a dial (I will now that you mention), but I can notice some shake especially in the Y axis direction, which means it's way too much (deffinitely a lot of hundredths). I will make a new post seeking for help to improve the structure.

    Thank you for taking the time!
    Last edited by maguru; 07-16-2020 at 10:47 PM.

  4. #4
    Member
    Join Date
    Dec 2012
    Posts
    183

    Re: How to achieve clean cuts?

    Hello.

    Perhaps this comment is unnecesary but I´l say it anyway.

    Have you checked the direction of movement of the cutting bit in respect to the workpiece?

    I have found that in some instances even professional furniture makers make the error of not considering that and end up ripping the wood instead of cutting it. Also if the turn of the cutting bit is incorrect forces are generated that pose extra stresses on the machine sometimes so big that the structures are deflected or even bent. Of course that depends on the size of the bit and the mass of the workpiece.

    I suggest you check it in case you haven´t done that.

    Regards.

    PS: I´m pretty sure you have done that but as I mentioned even seasoned professional workers tend to forget that when dealing with CNC machines or any automated process for that matter.

  5. #5
    Member
    Join Date
    Jan 2020
    Posts
    6

    Re: How to achieve clean cuts?

    Quote Originally Posted by BBMNet View Post
    Hello.

    Have you checked the direction of movement of the cutting bit in respect to the workpiece?
    I haven't done that. I do that when routing with a hand router, but I'm not sure I know how to do that on a CNC cutting shapes that on some parts go with the grain and on others go against. But now that you mention, as expected, the parts that go against the grain are the worse in terms of tearout.

    How do you plan that beforehand? Thanks

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