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  1. #1

    Join Date
    May 2020
    Posts
    3

    Chinese cnc not square

    I just purchased a Chinese cnc, it my first CNC, so I quickly found myself craving expensive software. I've since purchased hopefully all the software I'll ever need.
    And now I'm finding flaws of a Chinese cnc
    The work bed is t-slot aluminum. And isn't square to the Gantry ever so slightly with about .7mm difference over the span of 14"
    I'm considering milling the t-slot into submission, it feels like there is or should be a better way. I'm hoping to get some advice from everyone
    Googling "Chinese 3040 CNC" will show what machine I'm up against

  2. #2
    Registered
    Join Date
    Dec 2003
    Posts
    582

    Re: Chinese cnc not square

    Does the longitudinal axis have a single ballscrew or is there one each side?

  3. #3

    Join Date
    May 2020
    Posts
    3

    Re: Chinese cnc not square

    The gantry, has one ball screw, and two guide rails near the edge of the machine

  4. #4

    Re: Chinese cnc not square

    Quote Originally Posted by Razrburn View Post
    I just purchased a Chinese cnc, it my first CNC, so I quickly found myself craving expensive software. I've since purchased hopefully all the software I'll ever need.
    And now I'm finding flaws of a Chinese cnc
    The work bed is t-slot aluminum. And isn't square to the Gantry ever so slightly with about .7mm difference over the span of 14"
    I'm considering milling the t-slot into submission, it feels like there is or should be a better way. I'm hoping to get some advice from everyone
    Googling "Chinese 3040 CNC" will show what machine I'm up against
    Maybe try to adjust the screws of machine's feet.
    http://cncmakers.com/cnc/controllers/CNC_Controller_System/CNC_Retrofit_Package.html

  5. #5
    Registered
    Join Date
    Dec 2003
    Posts
    582

    Re: Chinese cnc not square

    I would be surprised if fiddling with the screws at the base of the gantry achieved very much.When doing the cut that revealed the defect,was the machine conventional cutting or climb cutting?I would suspect the drift was due to a cumulative amount of play from the base of the gantry and the Z axis combined with some cutter flexing.It would be interesting to know whether running the cut in the opposite direction resulted in an equal and opposite inaccuracy.

  6. #6

    Join Date
    May 2020
    Posts
    3

    Re: Chinese cnc not square

    I wrote a simple gcode file to just around and pause, and I used a plastic card and tried to slide it under the bit in the spindle while off. I didn't try to flex the machine while doing it. The gantry seems rather solid I didn't visually notice any flex while moving (taking out of the box). I'm talking about .7mm so maybe I need to try and lift on the gantry and see if I can find slop in the accuracy first

  7. #7
    Registered
    Join Date
    Jun 2013
    Posts
    40

    Re: Chinese cnc not square

    Use a spoilboard, flycut it then check to see if everything is level. If not then tram the spindle. I would not expect that the aluminum base it going to be flat. Mine wasn't but it does not matter because you should be using a spoilboard anyway.

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