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Thread: Some Advice

  1. #1
    Hi All,

    First post on here but been stalking everyone's builds for a while and still very very new to CNC.

    Does anyone have experience with these https://leantechnik.com/en/products/lifgo/, if so would there be any advantage of using them over ball screws for a Y axis cutting area of 1500mm? The DIY CNC will be used to cut molds for wings, I safely really need a cutting length of 1800 or so. Then there is the driven ballnut vs the above as well..

    Many thanks in advance

  2. #2
    They will be very expensive with the only advantage being no rotating screw. The disadvantages of cost and lower resolution/efficiency would far outweigh the one advantage.

    However, with only 1500mm travel required there is no reason why you can't use a standard ball screw without any issues provided you are not wanting ridiculous feed rates.
    The trick is keeping the screw speed down and this can be done by choosing a higher pitch and then gearing it down with a ratio. The gearing brings it back to the desired pitch to give speeds required but it halfs the Screw speed which stops any whip. ie:

    Let's say you want 10mtr/min cutting speeds and you are using typical stepper system that provides usable torque up to 1000rpm.

    Normally you'd select a 20mm Diameter with a 10mm pitch that will spin the screw at 1000Rpm to give 10mtr/min, however at 1800mm then you are likely to get whipping.
    But if you use 20mm pitch and 2:1 ratio then screw speed drops to 500Rpm and you still get 10/mtr/min speeds and keep the same resolution because the ratio effectively halfs the pitch back to same as 10mm.
    The ratio also effectively doubles the torque but this is offset because of the 20mm pitch as a lower linear torque than 10mm but still, you can see the advantage this method gives.

    I've built several 8x4 machines using this method and they work fine. My preference is a rotating ball nut but it's much more costly and complex but for a 4 x 4 machine I wouldn't hesitate to use this method.
    -use common sense, if you lack it, there is no software to help that.

    Email: [email protected]

    Web site: www.jazzcnc.co.uk

  3. #3
    Many thanks for the reply! You knowledge is much appreciated. Im still ways to go with this but I'm sure i will have many more questions along the way. Im going to aim for a granite build, its costly i know, i have quotes from suppliers but i believe it would be something i could use well for future. I like going to war with an A Bomb so to speak. I want the option of cutting Ali without any issue but most likely hard plastics and acrylics. Before i begin any build i need to secure a more permanent home for a 1000kg+ granite CNC. The 2000 x 1000 x 150mm surface plate is 950kg..

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