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Is it possible? z axis move to account for cylindrical etching

Discussion in 'Laser Cutters' started by NickEng, Sep 7, 2022.

  1. NickEng

    NickEng Well-Known
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    I use lightburn, fusion360, and openbuilds CONTROL to do designs/run Gcode. I know there are rotary axis that will turn to keep the focal point correct while lasering, but is it not possible to adjust the z height to do the same? For example, if I am going to laser etch a cylinder cup, If I focus on the peak of the cup, and put the circumference of the cup in to the program, could it not calculate and produce a Gcode that would raise/lower the z axis as the x (or y) axis moves during the laser etching process? Is there something like this out there? Would it not work?

    Thanks!
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
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    You can use bCNC to probe the surface and then use the probed mesh to correct for the curvature.
    Your Gcode is generated as for a flat surface, and bCNC will warp it for you.
    Engraving Curved Surfaces

    Keep in mind that OpenBuildSCONTROL is designed as a starting point, to get the beginner going in the CNC world, it is not 'full featured' and never will be because that would introduce a level of complication that would detract from its beginner friendly nature.
    bCNC is more complicated but gives you the options like surface scanning.
     
    Rob Taylor likes this.
  3. NickEng

    NickEng Well-Known
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    I have no experience editing gcode really. Once bCNC has corrected for the curvature that you have probed (with a bit or metal pointer I assume?) , does it add in the necessary Gcode for a laser's strength and when to turn on/off? Or, is that something you have to do manually? Thanks for your answer!
     
  4. David the swarfer

    David the swarfer OpenBuilds Team
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    if you watch the video in the link i gave you can see that it is purely a setup operation.....
    1 - bcnc probes the object surface and stores the points
    2 - you set the Z=0 point for the scan (and tool 0 of course)
    3 - you run your Gcode - while it is running bCNC uses cubic splines to offset Z moves to match the probed surface.

    no editing required (-:

    and the guy in the video uses a microswitch with a plastic ball glued onto it as the probe, so he can scan plastic pipe in his example.
     
  5. NickEng

    NickEng Well-Known
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    Thanks! This is probably not the place, but I downloaded bcnc from github, but I don't even know how to open it. Do you have to download python? I don't see a .exe file

    Thanks!
     
  6. David the swarfer

    David the swarfer OpenBuilds Team
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    there were installation instructions on the wiki but I see they are missing. I have opened a bug report.
    meanwhile, follow GitHub - Harvie/bCNC: GRBL CNC command sender, autoleveler and g-code editor
    ie, install python and pip, then use pip to install bCNC
     
    #6 David the swarfer, Sep 9, 2022
    Last edited: Sep 9, 2022
  7. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    I tried this once it was very easy.
    Gary
     
  8. NickEng

    NickEng Well-Known
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    That
    That is pretty simple. Do you run the gcode from estlcam? Does it support laser?
     
  9. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    Oh good question, Yes I did run from Estlcam (with the hardware flashed) but for laser I just searched and doesn't look well supported sorry.
     
  10. NickEng

    NickEng Well-Known
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    Ok, I was able to successfully install it and I am able to run it on my machine. I probed a metal cup with the auto leveling/scanning tool and it seems to work. However, once the scan is complete if I try to run the job, the machine crashes. It runs in to a limit switch. It does not seem to start where I set my zero point to. I use inches, and the design I created in fusion is designed with inches. The gcode works fine and runs fine CONTROL (without the auto leveling of course). I wonder if it has something to do with inches/mm, but I can’t figure it out.
    Thanks!
     
  11. Giarc

    Giarc OpenBuilds Team
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    If you plan to do a lot of this, this aluminum tape is perfect for putting on the surface you are probing. I use it for a lot of things where I can't use the normal probe. It is 0.003 inches thick for your probe height. I just clip an alligator clip to the tape and clip the other end to my Openbuilds XYZ probe.
    https://www.homedepot.com/p/Everbil...TWyrAnP26IAX-T-UvcsaAtRDEALw_wcB&gclsrc=aw.ds

    The aluminum tape also makes a great capacitive touch sensor for when you need to build a life-sized robot Operation game for use with bomb/eod robots. ;) I should write this one up and throw it in the projects section.
    upload_2022-9-11_9-33-43.png
     
    #11 Giarc, Sep 11, 2022
    Last edited: Sep 11, 2022
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  12. David the swarfer

    David the swarfer OpenBuilds Team
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    are you sure you did all the setup?
    in particular, after the surface probe you must also do 2 separate Z probes, one to tell the system where the Z zero is for the probed surface (on the probe tab), and one to do the normal 'setzero' for Z (on the Control tab).

    I don't know how imperial mode will affect it so I have to suggest doing the fusion gcode in metric (just select mm on the 'units' edit box in the postprocessor options, no need to change the drawing), and doing the probe in metric as well, just to check. GRBL is all metric internally and bCNC is coded by people in metric countries, so imperial mode will not receive a lot of attention.
     
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Does the crash happen on that initial G53 Z-safe move? Incorrect start/stop Z position value (Positive instead of Negative)?
    Post the GCODE please
     
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  14. Mark Carew

    Mark Carew OpenBuilds Team
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    You guys are crazy! :D and yes you should Craig :ROFL:
     
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  15. NickEng

    NickEng Well-Known
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    No, I reset z back to zero manually with xyz zero and the zero in the margin button, but I did not probe it to find the zero after the auto leveling was complete. I am still a little lost to how the program works.

    I am going to post the gcode and a screen shot of what I show. When I tried it the other day and it crashed, I used the gcode file (state of Ga in screen shot) to get the "margin" for the autoLevel. I completed the autoLevel for that particular size on a cup. It appears the autoLevl data worked. In the viewer, the Gcode (state of Ga in screen schot) laid on top of the autoLevel data. It appeared it should work. However, I just tried to recreate it, and you can see that the Gcode (state of Ga in screen shot) is well below the autoLevel data. I don't know how to move it in the program, but it wasn't this way when I tried it the other day.

    Thanks!

    Screen shot:

    Gcode (sorry so, long, I can save it as a file if needed:
     

    Attached Files:

    #15 NickEng, Sep 12, 2022
    Last edited: Sep 12, 2022
  16. Alex Chambers

    Alex Chambers Master
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    Please do upload that as a file and delete the text - freezes my phone :)
    Alex.
     
  17. NickEng

    NickEng Well-Known
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    I deleted and saved to txt file
     
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  18. David the swarfer

    David the swarfer OpenBuilds Team
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    The probing sequence is a little tricky so please carefully read this page Engraving Curved Surfaces and also watch (on a PC not a phone) the video he links on that page several times. This is the best explanation of using the surface probe I have ever come across so it is well worth the reading and watching time.

    which clearly shows that you have not told bCNC that the Gcode goes on top of the surface scan.
    Set X and Y 0 before doing the scan so it knows where to work.
     

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