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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > What would cause inconsistent "lines" like this?
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  1. #1

    Join Date
    Nov 2019
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    What would cause inconsistent "lines" like this?

    I am confused as to why I am getting inconsistent lines when surfacing my spoil board with a 2" cutter (1" step over) after tramming to .004" difference over 6" inches. The existence of the lines is not so much the greatest concern (should it be at .004"?), but the inconsistency of the lines is what I do not understand. Why would I get lines is some areas but not consistently across the spoil board?




    I trammed my Joe's Hybrid CNC using a tramming squaring from SST with two dial indicators. With the gantry near centered on the x and y axis, the front to back measurement is about .004" different and the left-to-right is about .0005" different. Both of those measurements are across 6" from dial indicator to dial indicator. The dial indicators are measuring against a 1/4"x20"x20" piece of glass that has been made parallel to the x and y axis prior to the measurements/adjustments above. Example: https://cdn.thingiverse.com/assets/8...132807_200.jpg (not my image, but that is the technique I used)

  2. #2
    Gold Member
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    Re: What would cause inconsistent "lines" like this?

    Is this the first series of surfacing cuts or the second? If it's the initial surfacing pass, the unevenness is probably happening because your bed wasn't flat.
    Andrew Werby
    Website

  3. #3

    Join Date
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    Re: What would cause inconsistent "lines" like this?

    2 full passes using the same pattern (front to back). Taking 1/32" off the first pass. And not changing the Z depth for the second pass (aka it stayed at z-0.0032 without re-zeroing Z).

  4. #4
    Registered
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    Dec 2003
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    751

    Re: What would cause inconsistent "lines" like this?

    What happens if you do the skimming cut across the spoilboard?The only time i have found this kind of issue was with a badly built machine that had some flex in the rails and it dug in a touch going one way and lifted a bit going the other way.Changing direction may just help with this operation,but could in itself,be highlighting a flaw that needs further investigation.

  5. #5
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    Re: What would cause inconsistent "lines" like this?

    ...non precision machine...well oiled . sunburned wood chucker...ing chucking saw dust anymore questions?

  6. #6
    Community Moderator ger21's Avatar
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    Re: What would cause inconsistent "lines" like this?

    Does the machine use V rollers on angle iron? If it is, it could be variation in the angle iron.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  7. #7

    Join Date
    Nov 2019
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    22

    Re: What would cause inconsistent "lines" like this?

    It does use V rollers on angle iron. I did a feel test of the top angle iron and was not able to make a connection between unevenness of the angle iron with marks on the spoil board.That said, yes this was my #2 suspect.

    Do folks have a process for addressing variations in angle iron/v-bearing setups? Other than replacing them with linear bearings. :-) (want to, but cannot justify the effort or financial expense yet)



    I did recheck the tramming after the surfacing passes to confirm the Z axis had not lost its true (it did not).

  8. #8
    Community Moderator ger21's Avatar
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    Re: What would cause inconsistent "lines" like this?

    Replace the angle with the proper guide rails for the V rollers.
    https://www.pbclinear.com/Products/C...-Bearing-Wheel
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

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