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Workbee - precision

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

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  1. Benjamin Vg

    Benjamin Vg Well-Known
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    Hello,

    Here is the test results of the day...
    I have setup to 4 microstep and a speed of 1000 (default one was 10 000) because when I use only 1 microsteps the motor's noise is very very strange with a lot of vibrations.
    • 4 microsteps and a speed of 1000 real cut two passes of 1mm each
      • Therorical distance: 100mm Practical: 100,2mm
      • Therorical distance: 500mm Practical: ~501,8mm
      • Therorical distance: 1000mm Practical: ~1005mm
     
  2. Rob Taylor

    Rob Taylor Master
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    Looks like a ton of backlash to me. The straight lines are where the y axis is moving before the x axis has "re-caught" its lead nut.

    Hmm, interesting. Probably good settings to stick with for now. And yeah, stepper motors make some crazy noises, sometimes it's hard to tell the difference between healthy noises and bad noises with those little StepStick chopper drivers, hahaha.

    The 1000 and 100 points are great, the 501.8 is... Disappointing. You may need to do a really thorough map test for the axis, because I'm wondering where the issue is happening and then going away again. Calibrate your steps/mm to get exactly 1000.0mm on command, then do sets of shallow cuts every 100mm, making sure it returns exactly to your zero position every time. So you end up with a table:

    Distance | Actual Cut 1 | Actual cut 2
    100______|______________|____________
    200______|______________|____________
    300______|______________|____________
    400______|______________|____________
    500______|______________|____________
    600______|______________|____________
    700______|______________|____________
    800______|______________|____________
    900______|______________|____________
    1000_____|_1000.0______|__1000.0___

    Maybe then we can start to get a handle on where the non-linearity is happening.

    What's your current acceleration setting? For a belt-driven system at 24V-48V, you should be able to get it up to pretty high numbers, 5000mm/s^2 maybe. I'd try and get it up to at least 1000, because the distance it's taking to get up to speed is messing with the numbers we're getting, I suspect.

    Since you already said it was returning to your zero each time (when Alex was thinking backlash, I assume), I'm less inclined to think missed steps, too. Because it would miss steps on both the forward and return trips and end up back at say, 1.2mm instead of 0mm. I'm at a bit of a loss for now. All I can think is to try a different controller (flash an Arduino with Grbl real quick, say).
     
    #62 Rob Taylor, Jun 17, 2019
    Last edited: Jun 17, 2019
    Peter Van Der Walt likes this.
  3. Benjamin Vg

    Benjamin Vg Well-Known
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    I have unmounted my belt and examine it very carefully qithout seeing anything suspicious.
    I have also switched the motors as proposed by Alex.
    I have rerun the test after a bit of calibration (because I have moved a little bit the belt I guess) it was M92 X13.363 and now M92 X13.383.
    Now the same test give me

    Distance | Actual Cut 1 | Actual cut 2
    100______|_100,12 ________|____________
    500______|_501,5 _________|____________
    1000_____|_1004__________|____________

    Be aware also that I have the best precision of the measure of the 100mm is the best one because I am able to measure it with my caliper after that I use a standard meter and estimate the tenth of mm so of course not as precise at all.

    The test result for every 100mm is comming (execution right now)...
     
  4. Benjamin Vg

    Benjamin Vg Well-Known
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    Since the motor switch are the belt check it looks a bit better finally.
    But first forget the measures of my two previous post because I have used another meter than usual and as you see below sometimes 10cm is not equals to 10cm....
    20190617_123744.jpg

    This meter is really bullshit... so i used another one and i have measure it with my caliper this one is correct. remark, this only invalidate my two posts the other one have been measured with a correct tool not made in wood.

    Anyways now I think that I am close to the solution. Here are my measurements. (I have adjusted a little bit the parameter between the two measurements.

    Distance | Actual Cut 1 | Actual cut 2
    100______|_100,25 _______|_100 ______
    200______|_200,5 ________|_200,2 _____
    300______|_301 _________|_300,3 _____
    400______|_401.5 ________|_400,5 _____
    500______|_501,8 ________|_500,8 _____
    600______|_602 _________|_601_______
    700______|_702,3 ________|_701_______
    800______|_803 _________|_801,8_____
    900______|_903 _________|_901,9_____
    1000_____|_1003.5 _____|__1002,5___

    So it looks almost linear now. But I cannot say what have really change...
     
  5. Benjamin Vg

    Benjamin Vg Well-Known
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    More adjustement and tests tomorrow ;-)
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Looks a pulley with the grub screws all loose (;
     
  7. Alex Chambers

    Alex Chambers Master
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    The thing that has puzzled me is that the error rate has increased with distance travelled (not the actual error - I would expect that to increase, but the error/mm of travel) In a theoretically perfect system the error/mm should be constant (5 times as many steps to travel 500 mm as 100mm). If it was just a calibration issue the error/mm for each distance should be the same. If it was missing steps I would expect the error/mm to be inconsistent. Although the second set of data is closer to the desired outcome (more accurate) the first set is more linear.
    Look forward to seeing tomorrow's data, but please tell us what you are changing @Benjamin Vg - it helps us understand what is happening.
    Alex.
     
  8. Giarc

    Giarc OpenBuilds Team
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    Although it doesn't appear to be the case here, what is the diameter of your endmill? If it is supposed to be 6 mm, but in reality is 5.9, your 100 mm square will be larger than 100mm. I measure the diameter of every endmill I use and input that into my CAM software. I have yet to find an endmill that is the claimed diameter. Most are slightly smaller.
     
  9. Benjamin Vg

    Benjamin Vg Well-Known
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    Good to know I will measure it tomorrow...
    the one I currently use is a CMT so it is suppose to be a good brand.
     
  10. RV6APilot

    RV6APilot Well-Known
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    @Rob Taylor So the problem is in the X axis not the Y axis?
    Thanks for the help. I will check all of the anti-backlash blocks.
     
  11. Alex Chambers

    Alex Chambers Master
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    Check the eccentrics on the X axis as well.
    Alex.
     
  12. RV6APilot

    RV6APilot Well-Known
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    @Alex Chambers Thanks, that was the first thing I checked and they are all good.
     
  13. Benjamin Vg

    Benjamin Vg Well-Known
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    Hello,

    I think I have it.

    Distance | Actual Cut 1 | Actual cut 2 | Actual cut 3 | Actual cut 4
    100______|_100,25 _______|_100 ______ | 99.7 | 99.8
    200______|_200,5 ________|_200,2 _____ | ? | 200
    300______|_301 _________|_300,3 _____ | ? | 300
    400______|_401.5 ________|_400,5 _____ | ? | 400
    500______|_501,8 ________|_500,8 _____ | ? | 500
    600______|_602 _________|_601_______ | ? | 600
    700______|_702,3 ________|_701_______ | ? | 700
    800______|_803 _________|_801,8_____ | ? | 800
    900______|_903 _________|_901,9_____ | ? | 900
    1000_____|_1003.5 _____|__1002,5___ | 999 | 999.8

    About the M92 configuration parameter,

    Cut | Parameter Value
    Actual Cut 2 | 13.383
    Actual Cut 3 | 13.25
    Actual Cut 4 | 13.337

    But I didn't found a formula who match my result exactly the formal is supposed to be simple.

    About the changes I did:
    • Switching the two motors
    • Unmount and remount the belt so the strech is not exactly the same
    • Changing the M92 parameter

    Something is sure is the fact that my Z-axe is not correct either but I didn't have tried to calibrate it for the moment...

    As a test I have tried to execute the attached file who looks correct when I in NC Viewer // GCode Viewer and Machine Simulator
    But the result is really really strange I had to stop this test!
    20190618_181514.jpg

    What did I have done the wrong way?

    I will try to reexecute some square tests tomorrow...

    Regards,
    Benjamin
     

    Attached Files:

    #73 Benjamin Vg, Jun 18, 2019
    Last edited: Jun 18, 2019
  14. grezmel

    grezmel New
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    @Benjamin Vg definitely interesting as my machine (same as yours) gives random anomalies like this aswell :(
     
  15. Benjamin Vg

    Benjamin Vg Well-Known
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    I guess that it should come from the duet controller...
     
  16. Benjamin Vg

    Benjamin Vg Well-Known
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    I have found this on the duet site:

    Microstepping set too high. If you set microstepping too high, the processor may not be able to generate step pulses fast enough. If this happens then high speed moves may be jerky. To check whether you have microstepping set in a reasonable range, execute some long high speed moves, then run M122 and look at the MaxReps figure in the report. This value should be kept below 100 and preferably below 50.

    Source: Jerky movement when printing

    But they speak about 50 microsteps I have 16 in Y and 4 in X so I am not sure if this is the cause of my problem...
     
  17. Alex Chambers

    Alex Chambers Master
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    Hi Benjamin, I have looked at your G code file and there are some aspects of it which look a little odd. Could you please let us know what software you used to create this? (G17 is not recognised by the Duet, M3 turns your spindle on, but your machine is not set up to use this. The feed rate at 3600 is very high.

    Alex.
     
  18. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    even 8 bit CPUs can handle 1/16th so probably not the issue
     
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  19. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Not for a belted machine, on a BlackBox and my 1500mm Ox with GT3 belt I can get 7000mm/min with a 3000mm/s^2 acceleration


    Would you ever consider building a second CNC? If yes, may I maybe suggest grabbing a BlackBox as a test. If it doesnt solve this issue, you already have a controller on the shelf for your "second CNC" - this hobby tends to that to most of us, not long and you'll want two, three, more more machines for your robot army. A plasma, a mill, a laser, who knows :) (i'm sure even at minimum wage you've spent more time on this than a BlackBox costs)

    I am not saying it will solve this issue, at all, but at least it gives you an easy thing to swop in and see if it improves: We use decent 4A Max drivers, set to 1/8th by default, extensively tested to be able to run NEMA23s all day long. Silent Drivers it does not have, but is noise, or reliability the issue you want to deal with (;

    Now of course, huge chance you get one and still have issues - but then we 100% know its mechanical...
     
    #79 Peter Van Der Walt, Jun 19, 2019
    Last edited: Jun 19, 2019
  20. Alex Chambers

    Alex Chambers Master
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    I was going by the carbide speeds and feeds chart which recommends 2540mm/min feed at 19700 spindle speed for plywood.
    Alex.
     
  21. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Fair enough, in context of a cut...
     
  22. Benjamin Vg

    Benjamin Vg Well-Known
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    @Alex Chambers This code have been generated by Aspire. I didn't really have investigate the best cnc software for woodworking yet. I am use to use Sketchup but the cnc plugins are not very good in my opinion...
     
  23. Alex Chambers

    Alex Chambers Master
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    What post processor did you use? - it should have been this one; GRBL (mm) (*.g-code)

    There is also a T1 call in your g code - an instruction to use tool number one, which the workbee doesn't need.
    There are also no arc codes (G2) which the Duet can support - your code is all straight lines.
    Alex

    I am not familiar with Aspire, so I don't know for sure what G code vectric software should produce..
     
  24. Benjamin Vg

    Benjamin Vg Well-Known
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    I have checked and yes the Post-processor is Grbl (mm) (*.gcode) and that is what they use in the ooznest videos (program and post-processor).
    I guess that the not knowed code are just ignored right?

    And the M3 command looks handled by duet if I read the documentation here: Gcode but if I could really use this command it could be really great btw...

    I guess that the G2 command is alsodocumented here: Gcode

    T1 command is also present in the same doc: Gcode
     
  25. Alex Chambers

    Alex Chambers Master
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    I don't have any vectric software (can't afford it) so I was a bit puzzled by those bits of g-code I mentioned, and I am surprised that vectric doesn't do arcs. As the file ran those codes must have been ignored.
    Having said that I don't think the g code was the cause of your problems with those P clamps. I assume that you used the Duet Web Control to upload your g code file and run it?
    From the picture it looks as though two of the p clamps are bigger than the others, but they don't seem to be in your g code. EDIT - just looked at your g code in a simulator and those two are bigger.
    Is your router cable well away from any other wiring?
    Given the problems you have been having I suggest not asking your machine to work too hard - reduce the feed rate to 2000 or even 1000 and use a router speed of 19000/20000 - 3.5 on the Makita speed dial.
    Alex.
     
    #85 Alex Chambers, Jun 19, 2019
    Last edited: Jun 19, 2019
  26. RV6APilot

    RV6APilot Well-Known
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    After going through and tightening screws and correcting the backlash problems I have a circle. It measured 50mm diameter as it should. The couple of small abnormalities are due to me
    smashing the Sharpie head into the spoil board and the fact that I have it mounted in my spindle and it rotates as it draws. Let me know what you all think and thank you again to @Rob Taylor and
    @Alex Chambers for their suggestions.
    [​IMG]
     
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  27. Alex Chambers

    Alex Chambers Master
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    Now you just need to cut one with a really pointy bit.
    Alex :D
     
  28. Alex Chambers

    Alex Chambers Master
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    By the way @Benjamin Vg, that Duet G code site is very useful - I use it all the time, but you need to know that some of the things Ooznest have done with their firmware do not match what that site says. In particular Ooznest use G54 as machine co-ordinates (standard is G53) and unlike G53 it is modal - that is if you send G54 to your Duet it will stay in that co-ordinate system until you change it (G53 only applies to the line of g code it is on. Workplace co-ordinates for the ooznest Duet is G55 (would normally be G54). This means that if you select machine co-ordinates in Duet Web Control it will stay in that co-ordinate system until you select workplace co-ordinates.
    Alex.
     
  29. Benjamin Vg

    Benjamin Vg Well-Known
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    I assume that you used the Duet Web Control to upload your g code file and run it?
    -> Yes I do!
    -> Are they some other/better tools I can try for it

    Is your router cable well away from any other wiring?
    -> Yes and I was present at the moment of the issue that wasn't because of a wire in the path or something

    Given the problems you have been having I suggest not asking your machine to work too hard - reduce the feed rate to 2000 or even 1000 and use a router speed of 19000/20000 - 3.5 on the Makita speed dial.
    -> Ok I can try to change it but I am pretty sure that it wasn't the issue here because I only do 2mm passes and it was the case everywhere but on the bottom left it was really as if he "forgot" to move up the router before moving

    About the ooznest firmware
    -> What is the purpose of those changes wht did they do that? Does it have an impact of the g-code product by my CAM software?

    What software do you use with your machine in place of vetric?
     
  30. Alex Chambers

    Alex Chambers Master
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    Hi @Benjamin Vg,

    -> Are they some other/better tools I can try for it - for the Duet controller no.

    Is your router cable well away from any other wiring? - it's important to keep any mains wiring well away from any low voltage wiring - interference can cause all sorts of weird problems (you probably knew that)

    but on the bottom left it was really as if he "forgot" to move up the router before moving - that and the mis-positioning of the two clamps on the right was why I suspected interference

    -> What is the purpose of those changes wht did they do that? Does it have an impact of the g-code product by my CAM software? - most hobby cnc machines use the grbl subset of g-code. The Duet uses the rep-rap subset (developed for 3D printers as was the Duet) It shouldn't have an impact on your g-code as long as you use a post processor that has been written for the Duet - you are correct to follow the recommendations on the Ooznest site. I think the reason why Ooznest use "non-standard" machine and workplace co-ordinates is because the way the Duet used G53 was a bit odd to start with (I believe that may have changed now)

    What software do you use with your machine in place of vetric? - I use Fusion 360 - it is complex and takes a while to learn, but very powerful. Another alternative is Sketchup - search the forum and you will find references to where you can download it if you are interested. There is a plug-in for Sketchup for generating g-code, but I don't know how compatible that is with the Duet because I haven't used it. I have asked a friend who uses Vectric software for some example files to check that the g-code output you got is the best that it can do for the Duet - will let you know later if there is anything different you can do.

    Alex
     

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