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Cantilever Diode Laser Engraver V821

Discussion in 'Laser Cutters' started by David Bunch, Aug 17, 2021.

  1. JustinTime

    JustinTime Veteran
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    He also had this video with more shutter options.

     
  2. David Bunch

    David Bunch Veteran
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    Those are pretty cool. I am going to give this turntable idea a rest for now as I have some other things to work on.
     
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  3. David Bunch

    David Bunch Veteran
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    Someone on the V1engineering forum mentioned using springs and then that made me think about using rubber bands. They are a perfect simple solution with no other electronics needed. I will have to adjust the sliders a little to give a little lip under the pegs & make the pegs probably a little longer. Here are a couple of photos to show proof of concept. Just when I am ready to put this project aside, I get pulled back in to finish it.
    IMG_1503_640x480.jpg IMG_1504_640x480.jpg
     
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  4. David Bunch

    David Bunch Veteran
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    I had to try the straight slots to see what the problems were with them versus the curved slots. During the design, one problem that is quite apparent is the end of the slots are a lot closer to the sides of the other slot next to it. They also don't move well along the straight lines as they do along the curve. I am printing the new design today & maybe try it tomorrow.
    IMG_1505_640x480.jpg SlotCamTurnTable.jpg
     
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  5. David Bunch

    David Bunch Veteran
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    Here is the 1st test of the self centering rotary axis. Seems like this painters tape core has a coating that does not burn well in some spots. It also seems like the rotary axis is moving faster than the linear axis. I posted a message to lightburn forum about it, but maybe someone here also knows what the problem might be.

    In the rotary section of Lightburn, I have 32 mm per rotation (DRV8825 drivers) and Chuck rotary type set. Y-axis is the rotary axis & X-axis is the vertical linear axis in my current configuration.
    You can see this problem in the 1st part of the linked video below when it is drawing a rectangle around the object.


    Below are the GRBL settings I am currently using in this configuration.
    Grbl 1.1h [’$’ for help]
    $0=10 ;Step pulse time, microseconds
    $1=255 ;Step idle delay, milliseconds
    $2=0 ;Step pulse invert, mask
    $3=3 ;Step direction invert, mask (invert x & y)
    $4=0 ;Invert step enable pin, boolean
    $5=0 ;Invert limit pins, boolean
    $6=0 ;Invert probe pin, boolean
    $10=1 ;Status report options, mask
    $11=0.010 ;Junction deviation, millimeters
    $12=0.002 ;Arc tolerance, millimeters
    $13=0 ;Report in inches, boolean
    $20=0 ;Soft limits enable, boolean
    $21=0 ;Hard limits enable, boolean
    $22=0 ;Homing cycle enable, boolean
    $23=0 ;Homing direction invert, mask
    $24=25.000 ;Homing locate feed rate, mm/min
    $25=500.000 ;Homing search seek rate, mm/min
    $26=250 ;Homing switch debounce delay, milliseconds
    $27=1.000 ;Homing switch pull-off distance, millimeters
    $30=1000 ;Maximum spindle speed, RPM
    $31=0 ;Minimum spindle speed, RPM
    $32=1 ;Laser-mode enable, boolean
    $100=160.000 ;X-axis steps per millimeter
    $101=200.000 ;Y-axis steps per millimeter (200 * 32 = 6,400 rotates 1 revolution with 1.8 nema17)
    $102=200.000 ;Z-axis steps per millimeter
    $110=500.000 ;X-axis maximum rate, mm/min
    $111=500.000 ;Y-axis maximum rate, mm/min
    $112=500.000 ;Z-axis maximum rate, mm/min
    $120=100.000 ;X-axis acceleration, mm/sec^2
    $121=100.000 ;Y-axis acceleration, mm/sec^2
    $122=10.000 ;Z-axis acceleration, mm/sec^2
    $130=435.000 ;X-axis maximum travel, millimeters
    $131=435.000 ;Y-axis maximum travel, millimeters
    $132=0.000 ;Z-axis maximum travel, millimeters
     
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  6. JustinTime

    JustinTime Veteran
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    Is there an option to enter the diameter/radius of the object since that will determine the rotary axis speed?
     
  7. David Bunch

    David Bunch Veteran
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    There is a setting for that & it was set to the diameter of the object I had.

    After some trial and error today, I have it pretty darn close by watching the video test I shot & checked frame by frame near the end of each movement to get the time it took to run a 100mm square in both directions. I switched to using Z-axis since I got that to work, so less firmware settings to change. Since rotational axis was 7.296x faster than linear, I used 200/7.296 = 27.412. Since I am using DRV8825 (200*32=6400) 6400/27.412 = 233.47mm.

    I set:
    $102=27.412.000 ;Z-axis steps per millimeter
    and 233.47mm = mm per rotation in Lightburn rotary setup

    It was a little off, but speed difference between linear & rotation seemed close. I wanted to see if I could use whole numbers, so I changed the $102=27 and starting adjusting the mm per rotation until it made one full rotation correctly. It came out to a nice whole number for that also.
    $102 =27 and 245 =mm per rotation in Lightburn rotary setup. With those settings, it does one rotation right on the money & speed difference between linear & rotational movements seems correct. I am seeing a little stuttering in the rotary axis, so am thinking that is the DRV8825 doing that.

    I tried the LV8729 drivers (1/128 microstepping) but they did not seem to work properly. Either the Eleksmaker board does not support them or they are bad drivers. I did check the vrefs on them before putting them on and from my previous notes I have the correct voltages. I will just stick with the DRV8825s. After putting the DRV8825s back in I rechecked the rotatary setup & had to change that 245 to243 as it overshot the 360 by a little bit.

    So my final numbers for DRV8825 drivers are $102=27 & 243 for lightburn rotary setup. I don't see a rhyme or reason for how those numbers came out that way, but seems to work. I was expecting those numbers would be a multiple of 6400 (200*32), but it is 6561. I might do another video test to verify the speeds are still exact.
     
  8. David Bunch

    David Bunch Veteran
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    The other day while looking at the grabcad terms of service, it was not clear to me whether I could release a derivative of that cam & follower design. The next morning I realized that design was very much like the Trammel of Archimedes design & I had remixed a version of that 3 years ago: Remix of Trammel of Archimedes by GeoDave - Thingiverse Rather than concern myself with grabcad, I redrew that portion of the design and cut out some volume of plastic in the process.

    I am getting very close to releasing this turntable design to thingiverse, probably tomorrow. One problem I was running into was smaller objects less than about 1" in diameter, which probably is not used much. Dowels are a good example of that small a diameter & would be a good test burn. The bracket attaching the top to the motor would interfere with making those pegs get closer to the center. So what did I need, Spacers inserted over the pegs. Another simple solution. Here is what the final design will probably look like. I estimate $15-$20 in parts and almost no cost if you have the motor & bearings.
    DoveTailTurnTable.jpg
     
  9. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    We always have lots of Pen Turners asking for recommendations on a build to laser their Pens (;
     
  10. David Bunch

    David Bunch Veteran
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    I have a plethora of 3/8" dowels I could test this on. Might have to make the spacers a little taller to make sure it stays vertical. With the spacers, I can get it down to holding about 5mm diameter objects. This turntable portion of this build is turning into quite a useful & inexpensive project that @Mark Carew inspired me to work on.
     
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  11. David Bunch

    David Bunch Veteran
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    That was good to know about the pens before releasing this. I had 5.6mm diameter hole in the center & changed it to a 3mm hole so a small object won't accidentally go thru it. Of course you could put a piece of tape over the hole also. Here is what it looks like with at 5mm cylinder in the center.
    5mmDowel_DoveTailTurnTable.jpg
     
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  12. David Bunch

    David Bunch Veteran
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    Here is what a 3/8" dowel looks like attached to this turntable.
    IMG_1611_800x600.jpg
     
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  13. David Bunch

    David Bunch Veteran
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    Here is a 3/8" dowel burn running at 3000 mm/Min & 90% power. 1st image is what the design looks like. I wanted it to wrap all the way around to see how close it came to meeting other side. I did a video of this burn also, but probably won't get to that for a few days.
    DowelTest.JPG
    Came out good for a 1st test, but is not quite aligned with length of dowel. This dowel was quite straight, so probably dowel was not quite parallel with the cantilever arm.
    IMG_103549606_800x600.jpg
    You can see a slight overlap here. Measuring with digital caliper, it is about .65mm overlap.
    IMG__103604557_800x600.jpg
     
  14. David Bunch

    David Bunch Veteran
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  15. David Bunch

    David Bunch Veteran
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    Here is a video of engraving that 3/8" dowel. Think I see some flames in part of that video.
     
  16. Juan Cruz Fernández

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    Can it cut through metal? Or it just engraves?
     
  17. David Bunch

    David Bunch Veteran
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    This uses a diode laser which is not capable of cutting or engraving metal. You can probably engrave the anodizing on metal.
     
  18. David Bunch

    David Bunch Veteran
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    Someone on V1engineering forum asked if I could do a toothpick, so I have to try it. Reprinting to drop it down 4 more mm to keep it straighter. Not much room for not being perpendicular here. Definitely need to start at lowest power & work up from there. Toothpicks are about 2mm in diameter with just a hair less than 1/4" in circumference. Laser is about .5mm width, so should work.
    IMG_20210910_182016630.jpg
     
  19. JustinTime

    JustinTime Veteran
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    And next is engraving on a grain of rice! :D
     
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  20. David Bunch

    David Bunch Veteran
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    Not sure I would attempt that, but toothpicks do work.

    I had it at 30% power for the 1st one running at 1200mm/min & acceleration is at 100. I was waiting for it to burn in half, but never did. You can see the patterns. I had the laser probably 3 inches or so away on the 1st couple of burns since the holding cylinders around the part would get hit by the laser. I changed the cylinders to my smaller ones & moved it quite a bit closer & ran the last couple at 5% power & same other speed settings. You can read part of the 2mm high text. I shot a video of some of this, but might have to reshoot it before uploading.
    IMG_1685_800x600.jpg
     
  21. David Bunch

    David Bunch Veteran
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    Here is a video of it engraving text on the toothpick.
     
  22. Mark Carew

    Mark Carew OpenBuilds Team
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    David, it would be really cool if you would make a pen with the OpenBuilds logo on it as it would be an honor to have it displayed on the all new shelf-of-first we are putting in the new location! ;)
     
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  23. David Bunch

    David Bunch Veteran
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    I would be happy to do that, but do not currently have a wooden pen. Where is a source for a reasonably priced wooden pen? I made another video today that should be better than my 1st video. I am still editing it though.
     
  24. Giarc

    Giarc OpenBuilds Team
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    I think you should display a toothpick with the Openbuilds logo on it in a massively oversized shadow box.
     
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  25. David Bunch

    David Bunch Veteran
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    I am not sure that logo will look good on a toothpick. I do have some 3mm diameter bamboo skewers that are about 4" long that it might show up on. That gives me about 3/8" circumference.
     
  26. Mark Carew

    Mark Carew OpenBuilds Team
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    @Giarc lol :) That would actually be cool looking, to show just how fine of detail can be. I could even make part of the front glass a magnifier lens so that if you look at it from the right angle you get a nice up close view!
    @David Bunch Awesome Dave! Thank you in advance this will be really cool! Looking forward to see your next video
     
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  27. David Bunch

    David Bunch Veteran
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    I spent more time editing the video this time & should be a lot better than previous video. I also speeded it up during the longest burn so it is not so boring.
     
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  28. Mark Carew

    Mark Carew OpenBuilds Team
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    Turned out really nice! hard to believe you can burn designs on something this small but its doing a great job at it.
     
  29. David Bunch

    David Bunch Veteran
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    I wonder what it would be like to use this for marking stringers to cut. I have cut 4 soon. I cut 8 last summer & they were a pain to mark accurately because of the rounds on edge of the wood, at least they were for me. Standard stringers you buy are a little too off for me to use. I would have to get some longer V-Slot to be useful for me.
     
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  30. David Bunch

    David Bunch Veteran
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    [Edit 9/18/2021] I put together assemblies of each alternative of this design that looks reasonable. I changed these options & didn't want to confuse folks with different info here.
     
    #90 David Bunch, Sep 16, 2021
    Last edited: Sep 18, 2021

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