1. #1
    Hi All

    I am considering building a gantry type cnc vertical mill. I am trying to decide if I will go for a moving table or a moving gantry. I have read that the moving table is less "efficient" in terms of space usage, my question relates to this.

    All the moving table designs that I have seen have the long rails on the bed and short bearing blocks on the table, i.e. bed length = table dimension + maximum possible travel.

    However, in a standard vertical mill the opposite arrangement is universal, i.e. The table is on top of the saddle and the table dimension is longer than the saddle, overhanging on both sides, so the equation is changed around to be: table dimension = bed (saddle) length + maximum possible travel.

    So my question is this: Would a moving table gantry machine with table overhanging the bed for a significant portion of travel be a really bad idea?



  2. #2
    phill05's Avatar
    Lives in Derbyshire  UK, United Kingdom. Last Activity: 10 Hours Ago Has been a member for 6-7 years. Has a total post count of 145. Received thanks 10 times, giving thanks to others 4 times.
    I have the choice of both, I have been running a fixed gantry with a 700mm x 600mm table now for a few years with no problems whatsoever, and with a 2.2kw W/Cooled spindle capable of taking large cuts in wood, metal and stone and even fine engraving on glass, If I were to design a new machine I would decide on the maximum size of bed I want to work with and add 150mm for clamping and you need the rails as the bed of the machine and twice the length of the table and the blocks fixed to the table.
    The moving gantry machine is a 7.5kw spindle 2.2m x 1.2m is on rack and pinion and has had problems racking, losing steps, also an inconvenience is the depth of sides when loading you can only load from the ends.
    If you have the space to use a large machine I would go for fixed gantry over moving gantry everytime so much more ridged.


  3. Moving table with the rails attached. Keep overhangs to a minimum

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