Solved How to maintain starting point on Turning project with Fusion 360


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Thread: How to maintain starting point on Turning project with Fusion 360

  1. #1
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    Default How to maintain starting point on Turning project with Fusion 360

    This is part of a compound problem, and I'm trying to work it to the problem. I am going to assume that it's somewhere in the setup.
    The machine: Scratch Built CNC Lathe + Fusion 360 + home made Post Processor running arduino GRBL. Basically, it's an XZ Axis sitting next to the Lathe. The goal is to cut profiles out of a spinning dowel.

    The projects are built in Fusion 360, and I have a hacked up linuxCNC post processor that generates clean GCode for GRBL.

    Here is the problem I'm currently having. Here is the part with the path. When I simulate it, it does exactly what it should. It starts in the corner, moves across the Z axis, moves in as it needs to cut off more stock, etc etc.
    How to maintain starting point on Turning project with Fusion 360-screenshot_1-jpg
    The code when it is generated has a 'glitch' in it somewhere. See below where I have it listed as 'THIS CODE'
    Code:
    %
    (1001)
    G7
    G18
    G90
    G20
    
    (PROFILE1)
    G54
    G94
    G90 G0 X1.45 Z0.2575  // THIS CODE
    G0 Z0.149
    X1.3038
    G1 X1.3031 F40.
    X1.19 Z0.0925
    Z-9.
    X1.25
    X1.13
    Z0.1237
    X1.2431 Z0.1802
    G0 Z0.1989
    X1.1831
    G1 X1.07 Z0.1423 F40.
    For some reason, it's moving the X Axis 1.45 inches away from the stock before it begins the program. That's 1.25 of the stock, plus .1 offset from the WCS setup of the origin (Stock Front) and Home position .1in and then in the Radii tab of the profile 1 cut, the clearance stock OD has a .1 in offset. Without those, the line is generated as X1.25 insted of X1.45.
    At this point, i'm a little lost as to what should be in there, or what the gcode should look like.. maybe I am missing something in the setup. So, before I get into GCode programming section, I figured i'd try here first, and make sure that everything is setup the correct way first. I'll attach the f3d file in here if you want to take a look at the settings for the profile, setup, etc..

    Thanks for the extra pair of eyes. Looking forward to trying to get this thing working.

    ~D

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    Last edited by dregalia; 08-28-2018 at 01:17 PM. Reason: Updating the Prefix to solved.


  2. #2
    Community Moderator Jim Dawson's Avatar
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    Default Re: How to maintain starting point on Turning project with Fusion 360

    I think that G code is correct, at least it would work on my lathe. Internally the program works off of the radius but the G code reads in diameter. If the G code tells the machine to cut 1 inch diameter, the machine sets to tool 1/2 inch off of the spindle centerline. The DRO also displays diameter.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: How to maintain starting point on Turning project with Fusion 360

    So, are you saying that I need to set the X axis output * .5 to get the right distances since my controller isn't going to compensate for it itself?
    Also, if you don't mind me asking, what are you using for your controller?

    Thanks for the quick reply, btw



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    Community Moderator Jim Dawson's Avatar
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    Default Re: How to maintain starting point on Turning project with Fusion 360

    Yes, * 0.5 That's what I had to do with mine the first time I tested the lathe software. I thought the G code was wrong or that there was a setting in Fusion that was not correct. Took me a couple of minutes thinking about it, then I just made a code change in the software and end of problem. You might be able to do that in the post processor.

    I wrote my own CNC software. I wrote the UI in VB.net, and use a Galil motion controller for the machine controller.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: How to maintain starting point on Turning project with Fusion 360

    Okay, so this is different now. I need to give this a try tomorrow and see how it works.
    I set the scaling on my post processor to 1 instead of 2 and now my code looks like this:
    %
    (1001)
    G7
    G18
    G90
    G20

    (PROFILE1)
    G54
    G94
    G90 G0 X0.725 Z0.2575
    G0 Z0.149
    X0.6519
    G1 X0.6516 F40.
    X0.595 Z0.0925
    Z-9.
    X0.625
    X0.565
    Z0.1237
    X0.6216 Z0.1802
    G0 Z0.1989
    X0.5916
    G1 X0.535 Z0.1423 F40.

    Thanks Jim, I'll give this a try and see how it turns out tomorrow night. Getting excited. Hope this works out right.



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    Default Re: How to maintain starting point on Turning project with Fusion 360

    BTW, Got any information on your software? Kinda curious to see what you're doing with it..I'm an old VB Developer.



  7. #7
    Community Moderator Jim Dawson's Avatar
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    Default Re: How to maintain starting point on Turning project with Fusion 360

    That G code looks like it might solve your problem.

    Not sure what you want to know about my software. But I'll be happy to answer any questions.

    Here is a screen shot.

    How to maintain starting point on Turning project with Fusion 360-clipboard01-jpg

    Attached Thumbnails Attached Thumbnails How to maintain starting point on Turning project with Fusion 360-clipboard01-jpg  
    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: How to maintain starting point on Turning project with Fusion 360

    Looks really nice..so that's your GCode sender?
    BTW,
    I've been able to compensate for just about everything inside of the Post processor in Fusion 360 to dump working GCode to a generic GRBL Controller, I think the only thing I have left to figure out is how to manipulate the G54 command to automatically set to the Stock OD from the setup.

    Thanks for your insights.. that really helped me out.



  9. #9
    Community Moderator Jim Dawson's Avatar
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    Default Re: How to maintain starting point on Turning project with Fusion 360

    Thank you for your kind words Not exactly a G code sender, you load the G code file into the CNC program, then the software translates it into a command code that the controller can understand, the controller does not understand G code. It drip feeds command code to the controller, with deep look ahead. The largest file I have run was about one million lines of G code, it would handle more than that. During a job run, it's primary job is to keep the 512 line command buffer full, secondary is keeping the DRO and tool path graphics updated.

    It's my pleasure to help out where I can.

    Jim Dawson
    Sandy, Oregon, USA


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How to maintain starting point on Turning project with Fusion 360

How to maintain starting point on Turning project with Fusion 360