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  1. #231
    Hi Rob. I had the same thought initially. A water level. Although old fashioned, for long distances, I do not know a better method today.
    But still, the question remains, what do to first. Rails or bearings?

  2. #232
    An easy way to check the coplanarity of the two rails is by stretching two diagonal strings and check if they touch in the middle. With thin fishing line and eventually compensating the thickness of the line for the one above you could get very good accuracy. When you have the ends coplanar then you can straighten the rails with a straight reference (the hardest part).

    For the perpendicularity of the gantry to the x axis, draw with the cnc the corners of a rectangle, and measure the diagonals which should be equal. The larger the rectangle, higher the measured accuracy.

  3. #233
    One more great ideea. Thank you paulus.v

  4. #234
    Quote Originally Posted by Radu_Andrei View Post
    Hi Rob. I had the same thought initially. A water level. Although old fashioned, for long distances, I do not know a better method today.
    But still, the question remains, what do to first. Rails or bearings?
    Work from bottom to top i.e Frame, X rails, Gantry, Y rails, Spindle, then you are not so likely to be re-iterative with your adjustments.
    Albert Einstein may have been a genius, but his brother Frank, was a monster

    Having just moved to Windows 10 (which is crap) My stress levels are through the roof !!!

  5. #235
    Ok. Thank you.

  6. #236
    Quote Originally Posted by Radu_Andrei View Post

    Regarding your post, ˇˇThe difficult part is bolting down the first rail absolutely straight.ˇˇ, before doing that, is it not necessary to set the y axis linear bearings/rails absolutely perpendicular to the x axis rails?

    Actually, getting the gantry square to the other rails is one of the easiest adjustments, and it was almost the last thing I did. I am assuming that you are able to adjust the gantry - in my case, I can loosen the bolts between the gantry and the plates which carry the bearings so that if I turn one ballscrew, I adjust the "squareness" of the gantry. So, get it as close to square as you can - I used a carpenter's square - and then cut a test piece. As someone has suggested, drill four holes on the corners of a square and measure the diagonals. I used the shanks of drills as pegs in a piece of MDF, having used the same size drill to make the holes. With a little bit of schoolboy trigonometry, you can then work out how much you need to turn just one of the ballscrews driving the gantry to bring it into square. Tighten bolts and check again. I wrote a short piece of gcode to drill the holes so that I could ensure that I always approached the holes from the same direction to remove backlash from the process.

    My very final adjustment was to use the machine itself to skim the strips of wood I use as bed supports so the the bed was reasonably flat once I screwed down a sheet of plywood. Not good enough for precision metalwork, but this is a woodworking machine. I machine a smaller spoil board if I want more depth accuracy for a particular job.

    Good luck!
    Last edited by Neale; 1 Week Ago at 10:54 AM.

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