Need Help! Some problems when cutting


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Thread: Some problems when cutting

  1. #1
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    Default Some problems when cutting

    Hello all!

    Finally I finished building my Joe's and I couldn't be more happy.

    The thing is that I am having a few problems (see image below):
    - The part where the cut is "flat" insted of being a circle > Notice that the flat part is always in the same section of the cut (at the end and begging of the circle). I have watched the motors turn but havent been able to see anything wrong.
    - The jiggling > I can notice that sometimes the bridge jiggles a bit and makes the cut sort of "snake like".
    - The missalignment (probably related to the first issue).



    Also I don't know if the motors are tuned properly
    I bought this kit.
    Motors are tuned to 1574.80315 (4000 divided by 2.54) and mach3 matches the units (when jogging the axis anually) to my machine dimensions. I dont know if my weird math is correct. Also Mach3 is set to MM.
    Another problem I am having is that the rapids are way too fast and makes the top of my table jiggle also.

    Any help would be highly appreciated.

    Kind Regards!

    PS: Sorry for my English, it is not my main language.

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  2. #2
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    Default Re: Some problems when cutting

    I think you have a serious backlash on X or Y (depends on which one you call X or Y). Best to measure that first. Once you have eliminated backlash you have to square the machine axes. I don't know why you have 1574.80315 (steps per?) and what you mean by 4000 / 2.54. The "steps per" value is a calculated value based on your lead screw pitch and microstepping. Without more detail about your machine it is not possible to say which values you should have. The problem of too fast rapids is easy to fix. set the value you are comfortable with.

    Another thing, if you are using Mach3 it is a good idea to read the manual. It explains also how to tune your motors, measure and eliminate backlash and explains every item in the configuration menus and a whole lot of other things.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: Some problems when cutting

    I was having some problems like that my steppers work miss steps when they have to go really slow i changed my steppers out for smaller ones from nema34 1600 oz to nema 23 340oz they have plenty of power to do what i need to and stopped my problems your rapids are set in motor tune



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    Default Re: Some problems when cutting

    I think it`s a CAM issue, since it produced a line pattern, this things sometimes appear when you do the CAM using lazyCAM, happened to me few years ago, there`s one way to find out sir, can you post the measurements of that circle? I`ll give you a code and try it out and see if it happens again, that`s the time you can eliminate the software issue and could be just a minor adjustment issue or a backlash on the machine`s machanical system...



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    Default Re: Some problems when cutting

    It's not a CAM issue, it's backlash, as was stated above.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

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

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


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    Default Re: Some problems when cutting

    Quote Originally Posted by ger21 View Post
    It's not a CAM issue, it's backlash, as was stated above.
    OK sir one way to find out, if this code still does the same thing then I guess it`s a very big backlash on the mechanism.

    Code:
    ( T0 : 0.0 )
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    G1 X-40.4937 Y102.2754
    G1 X-46.8357 Y99.531
    G1 X-52.9929 Y96.3937
    G1 X-58.9409 Y92.8761
    G1 X-64.6564 Y88.9919
    G1 X-70.1166 Y84.7565
    G1 X-75.3002 Y80.1865
    G1 X-80.1865 Y75.3002
    G1 X-84.7565 Y70.1166
    G1 X-88.9919 Y64.6564
    G1 X-92.8761 Y58.9409
    G1 X-96.3937 Y52.9929
    G1 X-99.531 Y46.8357
    G1 X-102.2754 Y40.4937
    G1 X-104.6162 Y33.9919
    G1 X-106.5441 Y27.3559
    G1 X-108.0516 Y20.6119
    G1 X-109.1326 Y13.7867
    G1 X-109.7829 Y6.907
    G1 X-110.0 Y0.0
    G1 X-109.7829 Y-6.907
    G1 X-109.1326 Y-13.7867
    G1 X-108.0516 Y-20.6119
    G1 X-106.5441 Y-27.3559
    G1 X-104.6162 Y-33.9919
    G1 X-102.2754 Y-40.4937
    G1 X-99.531 Y-46.8357
    G1 X-96.3937 Y-52.9929
    G1 X-92.8761 Y-58.9409
    G1 X-88.9919 Y-64.6564
    G1 X-84.7565 Y-70.1166
    G1 X-80.1865 Y-75.3002
    G1 X-75.3002 Y-80.1865
    G1 X-70.1166 Y-84.7565
    G1 X-64.6564 Y-88.9919
    G1 X-58.9409 Y-92.8761
    G1 X-52.9929 Y-96.3937
    G1 X-46.8357 Y-99.531
    G1 X-40.4937 Y-102.2754
    G1 X-33.9919 Y-104.6162
    G1 X-27.3559 Y-106.5441
    G1 X-20.6119 Y-108.0516
    G1 X-13.7867 Y-109.1326
    G1 X-6.907 Y-109.7829
    G1 X0.0 Y-110.0
    G1 X6.907 Y-109.7829
    G1 X13.7867 Y-109.1326
    G1 X20.6119 Y-108.0516
    G1 X27.3559 Y-106.5441
    G1 X33.9919 Y-104.6162
    G1 X40.4937 Y-102.2754
    G1 X46.8357 Y-99.531
    G1 X52.9929 Y-96.3937
    G1 X58.9409 Y-92.8761
    G1 X64.6564 Y-88.9919
    G1 X70.1166 Y-84.7565
    G1 X75.3002 Y-80.1865
    G1 X80.1865 Y-75.3002
    G1 X84.7565 Y-70.1166
    G1 X88.9919 Y-64.6564
    G1 X92.8761 Y-58.9409
    G1 X96.3937 Y-52.9929
    G1 X99.531 Y-46.8357
    G1 X102.2754 Y-40.4937
    G1 X104.6162 Y-33.9919
    G1 X106.5441 Y-27.3559
    G1 X108.0516 Y-20.6119
    G1 X109.1326 Y-13.7867
    G1 X109.7829 Y-6.907
    G1 X110.0 Y0.0
    G1 X109.7829 Y6.907
    G1 X109.1326 Y13.7867
    G1 X108.0516 Y20.6119
    G1 X106.5441 Y27.3559
    G1 X104.6162 Y33.9919
    G1 X102.2754 Y40.4937
    G1 X99.531 Y46.8357
    G1 X96.3937 Y52.9929
    G1 X92.8761 Y58.9409
    G1 X88.9919 Y64.6564
    G1 X84.7565 Y70.1166
    G1 X80.1865 Y75.3002
    G1 X75.3002 Y80.1865
    G1 X70.1166 Y84.7565
    G1 X64.6564 Y88.9919
    G1 X58.9409 Y92.8761
    G1 X52.9929 Y96.3937
    G1 X46.8357 Y99.531
    G1 X40.4937 Y102.2754
    G1 X33.9919 Y104.6162
    G1 X27.3559 Y106.5441
    G1 X20.6119 Y108.0516
    G0 Z3.0
    G0 X0 Y0
    G0 Z0
    M5
    M30

    It keeps me thinking that if it`s a backlash on the Y section then why is the lower part somewhat curved? selective backlash? I guess?



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    Default Re: Some problems when cutting

    OK sir one way to find out,
    You don't need to do anything to find out... It's backlash.

    Gerry

    UCCNC 2017 Screenset
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    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

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    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

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


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    Default Re: Some problems when cutting

    Quote Originally Posted by KH0UJ View Post

    It keeps me thinking that if it`s a backlash on the Y section then why is the lower part somewhat curved? selective backlash? I guess?
    Ha ha...

    There is a serious backlash, how serious it is, is easy to measure but may not be easy to fix. The backlash can be on X or Y or on both, and may also be on Z. I think there is also a pretty serious misalignment, squaring issue. No need to run long code with circles. Backlash is easier measured through straight moves. Milling more circles is totally pointless. Besides, each circle can be just one line of G-code, but it is pointless at this stage.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: Some problems when cutting

    There`s also one reason to let him try the code I posted, the code he`s using is causing the rapids too fast, I coded my circle @ 800 feed rate and a plunge rate of 300 to eliminate the rapids going too fast, usually noticed backlashes on worn out worm screws like for example Y section, it should occur in the north and in the south, for X backlash east and west straight lines on circles, backlash = play right? sorry im not a native english speaker.



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    Default Re: Some problems when cutting

    Wow thanks for all the replies

    The details of my machine are:
    Driver: G540 (10 of microstep).
    Steppers: 3 x NEMA23 381 oz/in.
    Screw: 1/2-10 5 start.

    Regarding "steps per" I arrived to that number (1574.80315) because I used a "step per" calculator (see image below) where I input the data of my machine and got 4000 as a result. Since the result was in inches, I figured I should divide it by 2.54 to get it in cm. Once again, I don't know if that is the correct "steps per" value.



    Regarding backlash I have to comment that I am not using ACME nuts as it is stated in Joe's Manual. Instead, I am using 3 x Anti-backlash Leadnuts. I use one for each axis and it is placed in the "moving" part of each axis.
    In the past I posted a problem in which the leadscrew moved from it's position and tried solving it by putting springs between the Lovejoy and the bearing, but that didn't solve it.
    Finally (and luckily), I had 6 Thread Clamps from dumspterCNC laying around so I put 2 of these (and some washers to make it as tight as possible) in each axis between the lovejoy and the bearing (can add some mages if desired).

    What can I do to eliminate backlash? I though that the 3 AB Leadnuts + 6 thread clamps would be enough

    @KH0UJ: The circles in the test are 10, 8, 6, 4 and 2 cm each and yes, I used LazyCam to generate the Gcode. Can't hurt to try! Will get back to you with the results

    Can't thank you enough for all the replies



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    Default Re: Some problems when cutting

    Do you have any thrust bearings holding the screw in place?
    How exactly are the screws mounted?

    Gerry

    UCCNC 2017 Screenset
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    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

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


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    Default Re: Some problems when cutting

    Quote Originally Posted by ger21 View Post
    Do you have any thrust bearings holding the screw in place?
    I don't think so. The assembly manual didn't specify that bearings should be of that kind so I bought the "common" ones.

    Quote Originally Posted by ger21 View Post
    How exactly are the screws mounted?
    I dont understand what do you mean by this. I followed the assembly manual



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    Default Re: Some problems when cutting

    Quote Originally Posted by inicdam View Post
    I don't think so. The assembly manual didn't specify that bearings should be of that kind so I bought the "common" ones.



    I dont understand what do you mean by this. I followed the assembly manual
    I think the best would be if you'd post some pictures. Right now, I honestly don't have an idea about how your machine looks like. Also, like I said before, milling more circles won't make any sense. Better to mill in straight lines to check where the problem is because you definitely have some serious problems. Did you change your rapids? It is a simple configuration setting in Mach3. Did you check the manual about backlash measurement? Also, what sort of lead screw is that? Is it 1/2" diameter and 10 threads per inch? What is the 5 (thread starts) in that calculator? The diameter is not important, but the pitch (inch or mm per turn) is what matters. The Mach3 manual also explains how to calculate the "steps per" value.

    BTW, Rapid = G0 moves and that only happens in the air, you should not mill with G0 moves. Use G1, so for example assuming your X axis is at zero the line: G1 X100 F100 will move the X axis 100 mm from zero at 100 mm/min in your case, if the machine is set up for mm. That's a very slow move, it will take one minute. Likewise and obviously, G1 X0 F100 will move the X back to the zero. Of course, same if you enter G1 Y100 F100 and on the next line G1 Y0 F100 should return to the starting position. This is a more efficient way of identifying problems than milling circles, but if you mill circles you might as well record a short movie to show what is happening.

    Anyway, if you like milling circles here is the code for your circles. No need for a lot of straight moves, better use the codes which are made for the purpose.

    Code:
    (Generated with: DXF2GCODE, Version: PyQt5 Beta, Date: $Date: Sun Oct 4 21:49:52 2015 +0200 $)
    (Created from file: C:/CNC software/DXF to G-code/DXF/Circles.dxf)
    (Time: Fri Mar 24 18:13:53 2017)
    G21 (Units in millimeters)  G90 (Absolute programming) G64 (Default cutting) G17 (XY plane) G40 (Cancel radius comp.) G49 (Cancel length comp.)
    G0 Z  20.000 
    
    (*** LAYER: 0 ***)
    T14 M6
    S22000
    
    (* SHAPE Nr: 0 *)
    G0 X  -7.071 Y  -7.071
    M3
    G0 Z   1.000 
    F200
    G1 Z  -2.000
    F700
    G3 X   7.071 Y   7.071 I   7.071 J   7.071
    G3 X  -7.071 Y  -7.071 I  -7.071 J  -7.071
    F200
    G1 Z   1.000
    G0 Z  20.000 
    
    
    (* SHAPE Nr: 1 *)
    G0 X -14.142 Y -14.142
    G0 Z   1.000 
    G1 Z  -2.000
    F700
    G3 X  14.142 Y  14.142 I  14.142 J  14.142
    G3 X -14.142 Y -14.142 I -14.142 J -14.142
    F200
    G1 Z   1.000
    G0 Z  20.000 
    
    (* SHAPE Nr: 2 *)
    G0 X -21.213 Y -21.213
    G0 Z   1.000 
    G1 Z  -2.000
    F700
    G3 X  21.213 Y  21.213 I  21.213 J  21.213
    G3 X -21.213 Y -21.213 I -21.213 J -21.213
    F200
    G1 Z   1.000
    G0 Z  20.000 
    
    (* SHAPE Nr: 3 *)
    G0 X -28.284 Y -28.284
    G0 Z   1.000 
    G1 Z  -2.000
    F700
    G3 X  28.284 Y  28.284 I  28.284 J  28.284
    G3 X -28.284 Y -28.284 I -28.284 J -28.284
    F200
    G1 Z   1.000
    G0 Z  20.000 
    M5
    G0 X   0.000 Y   0.000
    M30 (Program end)
    Load this into Mach3, it will mill your circles at 2mm depth (material top is Z zero). It will go slow (700mm/min), so you can observe what is happening. X and Y zero is in the center. Takes about a minute to run, maybe more on your machine if you don't have fast rapids. Note that the final diameter of the circles will be the actual diameters minus half the diameter of the cutter you use. The code is not compensating for the tool in my code since I have no idea what you plan to use.

    Last edited by A_Camera; 03-24-2017 at 02:26 PM.
    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: Some problems when cutting

    Quote Originally Posted by A_Camera View Post
    I think the best would be if you'd post some pictures. Right now, I honestly don't have an idea about how your machine looks like. Also, like I said before, milling more circles won't make any sense. Better to mill in straight lines to check where the problem is because you definitely have some serious problems. Did you change your rapids? It is a simple configuration setting in Mach3. Did you check the manual about backlash measurement? Also, what sort of lead screw is that? Is it 1/2" diameter and 10 threads per inch? What is the 5 (thread starts) in that calculator? The diameter is not important, but the pitch (inch or mm per turn) is what matters. The Mach3 manual also explains how to calculate the "steps per" value.

    BTW, Rapid = G0 moves and that only happens in the air, you should not mill with G0 moves. Use G1, so for example assuming your X axis is at zero the line: G1 X100 F100 will move the X axis 100 mm from zero at 100 mm/min in your case, if the machine is set up for mm. That's a very slow move, it will take one minute. Likewise and obviously, G1 X0 F100 will move the X back to the zero. Of course, same if you enter G1 Y100 F100 and on the next line G1 Y0 F100 should return to the starting position. This is a more efficient way of identifying problems than milling circles, but if you mill circles you might as well record a short movie to show what is happening.
    Thanks for the reply!

    The Leadscrew is exactly this one. 5 is the number of starts the screw has.

    Right now I am not where my machine is so I can't do much, but I will get some pics later today.

    Regards!

    EDIT: Just saw the Gcode above, will try it in the afternoon!



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    Default Re: Some problems when cutting

    Ok, so here are some pics of my machine, if more are needed please reply

    @A_Camera I loaded the code you gave me but it measures 80 x 80 cm (bigger than my cutting area)

    Attached Thumbnails Attached Thumbnails Some problems when cutting-dsc_0048-jpg   Some problems when cutting-dsc_0047-jpg   Some problems when cutting-dsc_0046-jpg   Some problems when cutting-dsc_0045-jpg  

    Some problems when cutting-dsc_0044-jpg   Some problems when cutting-dsc_0043-jpg   Some problems when cutting-dsc_0049-jpg  
    Last edited by inicdam; 03-25-2017 at 05:25 PM.


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    Default Re: Some problems when cutting

    Quote Originally Posted by inicdam View Post
    Ok, so here are some pics of my machine, if more are needed please reply

    @A_Camera I loaded the code you gave me but it measures 80 x 80 cm (bigger than my cutting area)
    OK, thanks for the pictures. Sorry, but now I am even more convinced that you have huge play, back lash, misalignment and everything you can think of. I didn't know your machine was an MDF machine. I don't think you can make a good CNC out of MDF, especially not in this size. I know some people disagree with me, but I can live with that.

    The code I gave you supposed to be 80mm x 80mm, center is zero and is -40 + 40 mm moves maximum. I have no idea how you can have 10 times as much, other than your screw pitch (steps per) is wrong.

    BTW, did you find out the screw pitch? What is it?

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: Some problems when cutting

    So, you have a clamp on connector connecting the leadscrew and one half of the lovejoy? What's keeping the screw from moving axially?

    Gerry

    UCCNC 2017 Screenset
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    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

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    Default Re: Some problems when cutting

    Quote Originally Posted by A_Camera View Post
    OK, thanks for the pictures. Sorry, but now I am even more convinced that you have huge play, back lash, misalignment and everything you can think of. I didn't know your machine was an MDF machine. I don't think you can make a good CNC out of MDF, especially not in this size. I know some people disagree with me, but I can live with that.

    The code I gave you supposed to be 80mm x 80mm, center is zero and is -40 + 40 mm moves maximum. I have no idea how you can have 10 times as much, other than your screw pitch (steps per) is wrong.

    BTW, did you find out the screw pitch? What is it?
    Hey! The step per in mach3 is correct since if I make a square of 10x10 cm and run the code, the square measures are correct. I also used Mach3 tool that sets the "steps per" for you and gave me a similar number to what I have set it to.
    I used Lazycam to reduce the given code to 25% (or so) but got the same results as my first post.

    I am afraid I don't agree with what you say about MDF CNCs, because Joe made this same model out of MDF and got good results. I probably didn't because I had to make some adaptations to the files provided by Joe due to the fact that some materiales where imposible for me to get in my country

    Quote Originally Posted by ger21 View Post
    So, you have a clamp on connector connecting the leadscrew and one half of the lovejoy? What's keeping the screw from moving axially?
    There is 1 AB nuts on each axis plus the lovejoy has a screw to tighten it to the leadscrew.



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    Default Re: Some problems when cutting

    It sounds like you don't have the screw mounted properly. The screw needs to be held in place by thrust bearings, so that it can't move axially.

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

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

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


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    Default Re: Some problems when cutting

    Do you have an image of those because I don't know how it translates in my language



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Some problems when cutting

Some problems when cutting