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Workbee - precision

Discussion in 'CNC Mills/Routers' started by Benjamin Vg, Jun 1, 2019.

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  1. Alex Chambers

    Alex Chambers Master
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    Hi @Benjamin Vg, double check that you are using the right post processor. I can't help a lot with Aspire as I have never used it, but the post processor should create arcs in the G-code (G2 or G3) and your G-code is all straight lines (G1)
    Alex.
     
  2. Benjamin Vg

    Benjamin Vg Well-Known
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    Hi Alex,

    Here is a screenshot of the available post-processors. As you see I use the Grbl (mm) but they are also some G code (mm) available for example.
    But in this video that is what they say to use: so i guess that it should be ok...
     

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  3. Benjamin Vg

    Benjamin Vg Well-Known
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    Hi again,

    Today, I have rerun the exact same code and the result is "perfect" at least I didn't have any glitch. I have an issue on my z-zxis not but I think that this one use due to the position of the router I will build another support a bit lower than this one to see if it fix the issue.
    Here is the video of my clamp test:

    I have also tried to reset to 16 microsteps and increase the maximum speed it looks better than before but never perfect I cannot have better than 99.8mm in lace of 100 and my measure of 500 should be something like 500.2 and 1000 is something like 1000.3. so I will see in practice if I can work like this or not...

    I will try to do more "real" tests with precise measures.

    Regards,
     
  4. grezmel

    grezmel New
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  5. Benjamin Vg

    Benjamin Vg Well-Known
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    I didn't had the time to work on it this weekend. I will continue tomorrow...
    For the moment, as you can see in the latest test I didn't have any artefacts. But it look that I also have issues with my Z axe now I need to take a closer look at this one first and do more tests before saying if it is fixed or not...
     
  6. Benjamin Vg

    Benjamin Vg Well-Known
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    Hello,
    New week new tests. On the Z-axe this time I have notice that it wasn't correct either.

    Here is the protocol:
    1. I use a 6mm bit
    2. Calibrate the z axe with the paper trick:
      1. Put a sheet of paper below the bit pull it down until I cannot move the sheet of paper anymore
      2. Pull up the bit of 0.015 mm to remove my paper
      3. Pull down the bit of 0.015 mm to come back to the same position
    3. Set the work coordinates
    4. Switch on the router
    5. Executing the gcode file (4 holes executed in one batch with a distance between the holes of 2mm: 5mm, 10mm, 15mm, 18.75mm)

    Microsteps | M92 Parameter | 5mm | 10mm | 15mm
    16 | 435.73 | 4.74 | 9.84 | 14.84
    16 | 439.986 | 4.8 | 10.3 | 15.67
    16 | 453.577 | 4.88 | 10.58 | 15.96
    16 | 435.73 | 4.7 | 9.9 | 14.3
    16 | 453.577 | 4.88 | 10.58 | 15.96

    So again it is not consistent...
     

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  7. Benjamin Vg

    Benjamin Vg Well-Known
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    And the results with a microstep of 8:
    Microsteps | M92 Parameter | 5mm | 10mm | 15mm
    8 | 427.475 | 4.74 | 9.8 | 15.18
    8 | 435.73 | 5.1 | 10 | 15.58
    8 | 441.148 | 5.2 | 10.2 | 15.61
    8 | 434.312 | 4.84 | 9.86 | 15.5

    So I am able to have a pretty correct 5 and 10mm but they ar a huge gap for the 15mm again...
     
  8. Benjamin Vg

    Benjamin Vg Well-Known
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    Well now that I think about it, my X axe is better since I have switch my motors and now my Z axe have a lower precision.
    So I guess that it is completelly possible that I have received one or many motors with an quality issue...
    Do I have a way to check this?
     
  9. Benjamin Vg

    Benjamin Vg Well-Known
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    Hello,

    Here are some news 2 weeks later. I still spend a lot of time to try to fix it even if it is "only" 2-3h every two days to try to calibrate and fix this ** machine...
    So I have received a new motor for my z-axe because the previous one was defect.
    Since I have change it the precision is better even if it is still not uniform when I drill three holes of 6mm each with a 6 mm bit.
    Theoritical | Practical
    5 | 4.85
    10 | 8.98
    15 | 15.2

    Btw, I have notice the exact same effect of flexibility on the X axe as @grezmel you can see it here:



    Today, I have try to execute a new project.
    Here is what it is suppose to looks like: (gcode is in attach to this message)
    Theory.png
    Here is the result:

    Face:
    20190710_092836.jpg

    Back:
    20190710_092841.jpg

    Side:
    20190710_092846.jpg

    Hole:
    20190710_092908.jpg

    Measure (first one is the theoritical the second one is the actual measure):
    measures.png

    So a lot of deception:
    - The 3 6mm holes are not round because of the fexibility of the x-axe
    - The 2 squares in the center are not squared at all. The first pass of 2mm is almost ok but the deeper we go the less it looks like a square
    - The 2 tenons have drilling marks
    - The measure are not correct at all even if my calibration tests are ok now...
    result.jpg


    And it is made in pine so it is a very soft wood!
    So I am very very very disappointed by this machine!

    Regards,
    Benjamin
     

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  10. Rob Taylor

    Rob Taylor Master
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    This is the inherent downside of extrusion machines. They're not several tons of steel being pushed around by multi-kilowatt servos. You just can't run them like industrial machines.

    Eg. for the holes, try using a smaller cutter than the hole diameter and do a helical ramp down. Since this is a relatively deep part, maybe try using up-cut (right hand flutes) bits as well.

    I think you're trying to use too much cutting force or too little spindle speed; even soft woods have some density to them, and you're essentially trying to rapid through the material. Try running the exact same file but cut your Z feed down to 500mm/min and your X-Y feed down to 1200mm/min. The spindle speed you probably need for these small cutters for the high feeds is probably unobtainable with normal routers.

    Are these the feedrates that your chipload per tooth calculations originally gave? Feed rate is proportional to end mill diameter, and these look like rates for maybe a 1/2" or 3/4" bit. Not 1/4".
     
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  11. grezmel

    grezmel New
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  12. David the swarfer

    David the swarfer OpenBuilds Team
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    no it is not (-:
    for the purposes of machining it with this type of machine the entire block of wood has to be regarded as being as hard as the hard part of the ring structures, ie as hard as a dark parts of the wood.
    this means we have to set the depth of cut and feedrate to the best for that hardness of wood (and the soft parts of the wood will cut just fine).

    also, in that video it appears you are drilling holes with a router bit, is that correct?
    if so then you really need to avoid doing that, router bits are not drills, they have a gap in the middle with no cutting edges.
    also your peck distance is too long.

    as someone else said, use a smaller bit and do a helical bore operation to cut the hole.
     
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  13. Giarc

    Giarc OpenBuilds Team
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    Recently I cut a round disk out of 3/4 inch particle board, but I forgot to make my holding tabs only 3 mm high. So, I did a quick CAM file to trace the original path and cut 16 mm off the tabs in one pass. The tabs were only 3 mm in length so I thought it would be no problem. The disk was a perfect circle except at every tab where the 1/4 inch cutter bit into the disk because of flex in both the extrusion and the cutter due to the overly aggressive removal of the tab material. It looked like what you have going on. I knew this was a possibility, but I did not care because the disk did not need to be a perfect circle for what it was being used for.
     
  14. jtovar78

    jtovar78 New
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    20190902_165911.jpg 20190902_155841.jpg Need some help. Tried cutting this file with 2 different bits. One cut is with a 60 deg v bit and the other was done with a 15 deg engraving bit. I hope you can see it in the attached pics but the sharpness I was expecting just isnt there.

    Anyone have any suggestions or more info needed?

    Thanks
     
  15. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Specifics of your machine? Belt or lead?
    Looks like backlash in Y (loose coupler on leadscrew, loose lock collars, or loose setscrew on pulley on motor)
     
  16. Benjamin Vg

    Benjamin Vg Well-Known
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    Hello,
    I took a lot of holidays without touching this ... machine... also I have waited for someone who have more experience in woodworking to come and recheck everything.
    He have recheck everything and everything look ok for him too.
    He also didn't understand the non linearity of the measurement and confirm that I use it correctly.

    But, even after I have continue to work on it and now with a very very simple gcode program with slow speed, 1mm deep passes.... I am able to have a correct measurement when I engrave 3 lines (100mm, 500mm, 1000mm) on the X axes in a MDF sheet with 0.3mm of delta only. So that was a very very good news for me.
    Now that I have this result I have tried to do the same on the Y axes but of course it isn't as easy and it doesn't work. Again I have inconsistent measurement even with the same program adapted for the Y axe and also 1mm passes.

    Each time I see this machine I am a bit disgusted of the hours I have spend for a so poor result until now and it is hard to remotivate to continue on it.
    To reply the the message about the drilling I agree that it isn't the best way to use this machine and I have abandon this test for the moment because as you said it doesn't make sense!

    Regards,
     
  17. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    At the end of the day its either mechanical, or electrical.

    Can you load up the X job again, then swop X and Y motors connections (run Y off the X driver. And X motor off the Y driver)
    If it then has issues in X there's a problem with the controller (Y driver now running the X motor acting up)
    Of it its still Y then theres something mechanical (completely strip down and rebuild Y actuators). You have a Duet right? (we evaluated Trinamic drivers extensively when we designed BlackBox - theres a reason we didnt end up going for them after all)
     
  18. Benjamin Vg

    Benjamin Vg Well-Known
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    I don't think that this test will be possible because they are two motors for Z and only one in X. Well I guess it could be possible by software but not easily by hardware. (I am not in front of my machine for the moment)
    And yes I have the Duet. And I have already experiment multiple times some bugs. For example the Z axes who wasn't calibrate correctly even after a soft reset, I had to power off power on to make it work. Sometimes when I change the number of steps per mm in the settings I also need to do a hard reset to make it work. Bugs in the execution of the program itself, ...
     
  19. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Doesnt the two Y motors plug into one header at the board?

    Ps my money is not on the hardware either but doing that test will just cement it so no one ever dares question the hardware again :)

    If its the board, perhaps the vendor you got it from can RMA it. If you prove it with the test they kinda have to (we would, at least)
     
    #109 Peter Van Der Walt, Sep 3, 2019
    Last edited: Sep 3, 2019
  20. Benjamin Vg

    Benjamin Vg Well-Known
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  21. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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  22. jtovar78

    jtovar78 New
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    Workbee 1510, belt driven. I had just check set screws on both Y motors, along with their respective belts.
     
  23. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    I noticed what looks like a bit of backlash but maybe not quite it then. You mentioned "the sharpness I was expecting just isnt there." - not sure I 100% understand then, what exactly bothers you? The little leftover islands like inside the E and P of the right side cut, the fuzziness of the wood fibers (Router RPM of bit sharpness) or something I am not seeing immediately?
     
  24. Rob Taylor

    Rob Taylor Master
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    I'm assuming the clear stuttering and tearout is the problem. In which case, the usual; sharper tooling, lower feed, higher speed. Any lash seems to be more of a product of the tip digging in due to zero effective tool speed at the tip; using a rounded-end V-bit- usually called a tapered ballnose, I believe- would probably help with that too. Polished flutes, HSS instead of carbide, whatever it takes to get the edge sharpness, but tool life will be reduced to gain surface finish.
     
  25. Benjamin Vg

    Benjamin Vg Well-Known
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    Hello,

    I have unmounted most of the pieces of my workbee. I have also replaces the screws of the pulley on my Y-Axe.
    I also use a new procedure to calibrate my cnc to avoid time consuming operations and also spend some wood in useless operation. I do that now: with an ip cam (my phone) and VLC in a target picture in it.
    Now, I have those results:
    Expected | Actuals
    0 | 0
    100 | 99.1
    200 | 199.2
    300 | 299.4
    400 | 399.8
    600 | 600.1
    700 | 700.3
    800 | 800.8
    900 | 901.0
    1000 | 1001.1
    900 | 901.5
    800 | 801.2
    700 | 700.1
    600 | 600.9
    400 | 400.2
    300 | 300.1
    200 | 200
    100 | 99.8
    0 | -0.1
    100 | 99.1
    200 | 199.2
    0 | -0.1
    200 | 199.2

    They are two things I can observe here:
    - The fact that the values < 500 are too low and after it is too high => What is the parameter I need to change for it?
    - More strange and I think that it will be more an issue, the values I have when I do a positive move or a negative one are different but stay coherent each time I do a positive move.

    Regards,
    Benjamin V.
     
  26. Benjamin Vg

    Benjamin Vg Well-Known
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    I just have perform another serie of tests with a maximum speed of 5000 in place of the 10000 of the previous test because I had do that for the X axe. But the result are almost the same:
    Max speed : 5000
    0
    99.2
    199.3
    299.6
    399.8
    600.1
    700.5
    800.8
    901.1
    1001.2
    901.6
    801.2
    701.1
    601
    400.4
    300.2
    200
    99.9
    0
    99.1
    199.3
    0
    199.3
     
  27. Rob Taylor

    Rob Taylor Master
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    Step deltas:

    100, -0.9
    200, +0.1
    300, +0.2
    400, +0.4
    600, +0.3
    700, +0.2
    800, +0.5
    900, +0.2
    1000, +0.1
    900, -0.4
    800, +0.3
    700, +1.1
    600, -0.8
    400, +0.7
    300, +0.1
    200, +0.1
    100, +0.2
    0, -0.1
    100, -0.8
    200, +0.1
    0, -0.7
    200, -0.7

    Seems fairly clear there's 0.7-0.9mm of backlash in the system and a roughly general 0.2mm precision, but that doesn't explain the wild variations during a move in a single direction- like the +1.1 at 700 followed by a -0.8mm at 600?! I'm not sure where to go with that; it must be electrical but there's no consistency... Can't diagnose a random pattern.
     
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  28. Alex Chambers

    Alex Chambers Master
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    Just to confirm what @Rob Taylor said about the backlash - if @Benjamin Vg followed the video and went from 0 to 100, 100 to 200, 200 to 300 etc then the important figure is the actual distance moved between each step. If you look at the attached file you will see moves are fairly consistent (and close to the tolerance claimed by Ooznest for a belt drive workbee - +/- 0.2mm) until there is a change of direction - indicating a small amount of backlash.

    Alex


     

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  29. Benjamin Vg

    Benjamin Vg Well-Known
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    How could I avoid the backlash?
    And the tolerence of ooznest is suppose to be 0.2 so when I see a difference of 1.5mm it sound a lot to me.
    If I go from 0 to 1000 directly I have the same difference it didn't looks related to the fact that I am doing some extra steps...
     
  30. David the swarfer

    David the swarfer OpenBuilds Team
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    stretch the belts tighter, and know how tight they are.
    I use a spring balance to set mine. I pull to 12 to 15kg on the scale and then tighten the screws.
    I did have to put plates under the screws to protect the belts as I had some screws go right through the belt.
    Focus on getting the 2 Y belts to the same value.

    after doing this you will need to recalibrate.
     
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