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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 Journeyman
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    Hello,

    I have recently mounted my new Workbee 1500mm x 1500mm for ooznest so now I play with it.
    My current issue is the precision, I have calibrate it as in they videos. Now when I say move 100 on the X axis is is exacly 1000 mm so that is ok. The same on the two other axis.

    But I still have precisions issue when you see the photos below.
    When i do two centered concentric circle they are not aligned. And when I create a line slot (photo 2) we also see that the first pass was a bit longer than the other one.
    Is is all I can expect from my machine or is it just some fine tuning?
    20190601_094447.jpg
    defaut1.jpg

    Regards,

    Benjamin
     
  2. Alex Chambers

    Alex Chambers Openbuilds Team
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    Hi @Benjamin Vg, the other clue is that your circles aren't round. You have some backlash/play in your machine. Be methodical - start at the bit (router/spindle off) - does it move side to side or back to front? See if you can see what is moving that shouldn't. Move on to the Z axis/X gantry - tighten anything (don't overtighten) that's loose. Check the adjustment of the eccentrics on the X and Z gantries . Check the X C-beam is secured to the Y gantry plates. Check there is no play in the belt drive and the belt is properly tensioned (sorry - I have a leadscrew machine so can't give detailed advice on this). Check eccentrics and belt on the Y axis. Are both X and Y moving freely? Let us know what you find.
    Alex.
    PS remind us what controller you are using - you may be missing steps which could be caused by stiffness in the axes or (more likely) you might need to adjust the motor current.
    PPS - just checked - you have the Duet so it's unlikely to be motor current - Ooznest have set that for you.
     
    #2 Alex Chambers, Jun 1, 2019
    Last edited: Jun 1, 2019
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  3. Alex Chambers

    Alex Chambers Openbuilds Team
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    Hi @Benjamin Vg, are you getting anywhere with this?
    Alex.:thumbsup:
     
  4. Benjamin Vg

    Benjamin Vg Journeyman
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    Hello,
    No for the moment I have checked everything I can without more success.
    I have juste notice a wheel on the right side of the Y axis who is not tightened enough but I had to unmount the cnc from my table so I will do that this afternoon.
    I just wonder how to check if the wheel are setup correctly everywhere it isn't an esay stuff for me.
    The router is very well attached and doesn't move for my I saw.

    Regards,
     
  5. Benjamin Vg

    Benjamin Vg Journeyman
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    Hello,

    i have also received a response from ooznest:
    Issues like your seeing is normally down to 2 things:

    - Pulleys slipping. Are you using the silver cap head bolts? And is one on the flat portion of the motor shaft?
    - Wheels being too tight, are they are all rotatable with one finger and a small amount of friction?
    So I have spend like 4h to unmount all my axes to adjust everything. But it is very difficult to have all the wheels ajusted correctly. I have run an new test with concentric circle but on a 60mm of diameter circle I have a difference of 0.7mm on the X than on the Y.
    I am a bit deseperate. :(
     
  6. Alex Chambers

    Alex Chambers Openbuilds Team
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    Hi @Benjamin Vg. Have you ever calibrated your machine?
    If not, get the tool with the smallest tip (a very pointy engraving bit is ideal). On one side of the machine use the bit to make a mark on a piece of masking tape stuck to the spoiler board. Lift Z slightly. Jog X an exact amount (say 500mm). Use the bit to make another mark on a piece of tape. Measure the distance between them.
    Do the same on the Y axis.
    Let us know what distance you told the machine to move and what distance it actually moved.
    Alex.
     
  7. Benjamin Vg

    Benjamin Vg Journeyman
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    I had done this procedure before the recalibration of the wheels. But now that is is less clamped, I guess that is it a good idea to do that agin I will do it tomorrow.

    Thank for your help!
     
  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    If the circles wer ovals, i'd expect it to be calibration.
    But as they are about the same width as height, but not round, i'd look for backlash in the driving system
    Things to check:
    - Couplers between motors and leadscrews / Pulleys on Motors: Make sure setscrews are tight and that coupler/pulley cannot rotate on the shafts
    - Antibacklash Leadnut properly adjusted / Belts properly tensioned
    - No free play if you move the leadscrew axially: If there is check your stop collars are pressing the bearings tight into their recesses
    - Mechanical backlash (loose wheels, loose bolts, anything thats not solid. Grab the top of the endmill (with router unplugged) and give it a wiggle, see if you can deflect it, if yes, follow the looseness until you find what isnt tight, but should be

    This could be skipped steps: Stepper drivers current adjusted properly? Not too little, else you have little torque, not too much or the drivers could go into short periods of thermal shutdown
     
  9. Alex Chambers

    Alex Chambers Openbuilds Team
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    Hi @Benjamin Vg, have you got a picture of your last test?
    Alex.
     
  10. Benjamin Vg

    Benjamin Vg Journeyman
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    Here is the picture of my last test...
     

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  11. Alex Chambers

    Alex Chambers Openbuilds Team
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    I'm busy tonight and most of tomorrow @Benjamin Vg, but if you want me to help calibrate your Duet post a message on here and I'll get back to you as soon as I can.
    Alex.
     
  12. Benjamin Vg

    Benjamin Vg Journeyman
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    Ok, I have recalibrate the X and Y axes (the M92 command) so now when I say move 1m on the X or Y axe it is ok again. But this doesn't change the precision of my circles at all. I still have 0.8 mm of delta. But I saw that my right motor of the Y axe is not tight engough now...
     
  13. Alex Chambers

    Alex Chambers Openbuilds Team
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    Good luck with that @Benjamin Vg, let me know how you get on.
    Alex. :thumbsup:
     
  14. Benjamin Vg

    Benjamin Vg Journeyman
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    I have rerun the test of printing a circle of 60mm of diameter but I still have 58.5mm on the X axe and 59.2mm on the Y axe I have run the test twice and the measures of the other one are: 58.7 on X and 59.5 on Y.
    I have tried to move the bit with my hand, when I move it on the Y direction it move a bit more on the right Y axes, when I move on the X direction if move also a bit but I guess that it is normal. The router, the support and the z axis doesn't move at all (Z in screw based)

    Benjamin.
     
  15. Alex Chambers

    Alex Chambers Openbuilds Team
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    It would seem that you are almost there - Ooznest only claim +/- 0.2mm for the belt drive. Also, because of the side forces on the bit and the fact that you can compress materials like mdf you won't necessarily get a very accurate cut unless you use acrylic or aluminium. The milling direction (climb versus conventional) also has an effect.
    It's up to you to decide whether it is worth the work to get slightly more accuracy.
    The bad news is that these machines need fairly frequent checking and adjustment.
    You could try doing a roughing cut (leave about 0.2 - 0.5 mm of stock on the first cut pocket rather than contour) and then a finishing cut to take off the last little bit - one pass at full depth.
    Alex.
     
  16. Benjamin Vg

    Benjamin Vg Journeyman
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    Here is both the circle and the lines tests.
    I have a lot of time a gap of 1 mm...
    20190604_150353A.jpg

    It is not very readable but the right circle is 58.7 x 59.5...
     
  17. Alex Chambers

    Alex Chambers Openbuilds Team
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    You said when you move 1000mm it is accurate, but if you go back 1000mm does it go back to exactly the same place? - try that for both X and Y.
    Alex.
     
  18. Benjamin Vg

    Benjamin Vg Journeyman
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    Hi,

    Here are the latest news.
    The ooznest support asked me to adjust all the exentric spaces to largest position (the 6mm text facing the bottom of the cnc). And I also unmout an exentric space and looked at this video: It is stupid but in fact I didn't had fully understood how they worked.
    So now I think that I have been able to adjust it correctly.
    After that I did a calibration based on a square of 10cm x 10cm and then by using the formula of this video:
    With those two steps, I have been able to create a square with a difference of 0.3mm and a circle of 0,2mm so that is really great.
    But I still have a latest issue. With the new calibration my 10x10cm square is correct but the movement of 1m go 13mm too far away so I guess that I can change another parameter somewher to manage it but I don't know wich one...
    I am almost there ;-)

    Regards,
     
  19. Benjamin Vg

    Benjamin Vg Journeyman
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    Hello,

    Just to give you some updates. I am in contact with the support of ooznest everydays since 15 days and test some stuffs everydays most of the time twice a day. I am really really tired about it and my hope to have something correct is really really low. My morale too...

    I am always at the same poistion. I am able to cut a almost perfect squate of 100mm x 100m but when I adjust like this I am not able draw a simple line of 399mm for example the long distances are never exact.

    Here my example of 100x100 square:
    20190614_100545.jpg

    And my line of 399mm who is about 1.5mm too long (we see the end of my square who is exacly 39.9mm long)
    20190614_100539.jpg

    If you still have ideas they are welcome but I guess that something is defect I don't know excally what...

    I have already done:
    • adjust the excentric spacers to the maximum
    • adjust the excentric spacers to the minimum
    • adjust the excentric spacers to be able to turn the wheels but still be in contact with the rail (as in every videos)
    • adjust the belts with more or less tension
    • check if the pulleys are not slipping on the motors
    • check if the pulley are fixed on the flat portion of the motor
    • undo the top bolts and tighten them back up again to relieve any pressure.
    • calibrate the parameter to match a 1m distance but then my square is not correct anymore
    • calibrate to have a perfect square but then the 1m is not correct anymore
    • perform the test with or without a router
    I am really out of ideas and I feel that the support too. I have already asked to have replacement wheels and belts but they said that it will not solve my issue. I have also tried to have a skype to show them but for the moment they didn't have accepted.
    If I didn't had invested so much money and time for the kit, the cnc bits, the torsion box, ... I had already left the cnc world I think...

    Regards,
    Benjamin
     
  20. Alex Chambers

    Alex Chambers Openbuilds Team
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    Hi @Benjamin Vg, sorry to hear you are still having problems. A couple of messages ago I asked whether, after moving 1000mm, the machine would go back exactly to the start point. Also you are not telling us which axis is which - do you have the same problem with lines on both X and Y?
    With your permission I would be happy to talk to Ryan at Ooznest to see if between us we can think of a solution.
    Alex.
     
  21. Rob Taylor

    Rob Taylor Master
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    CNC is often, unfortunately, more difficult and technically demanding than a lot of these maker websites suggest. Considering the price of these machines, it doesn't feel right to me, but I suppose that's the cost of doing business.

    I think Ooznest are right, wheels and belts won't solve the issue. Belts aren't really ideal for a router build, it may just be that you're pushing too hard and need a shallower depth of cut. You could try cutting at smaller depths but at higher speed, to keep the cycle time the same.

    I'd calibrate so that 1000mm is 1000mm under no load. Make sure that 500mm and 100mm are also good under no cutting load, just using a pointer, and that if you draw a rectangle (or very shallowly engrave one, say 0.2mm depth of cut at high spindle speed) the corners are precisely square and that your two end points meet perfectly (within 0.2mm). That way you know that in-software, all your numbers are correct and your frame is set up perfectly. After that, it's about the deflection of the motion chain and the motor/driver capacity, there has to be some kind of issue there.

    One random thought, I'm not sure how much it may apply or not, but it's been an issue for other people on occasion: routers are electrically very noisy. Are all of your wires shielded, your machine frame grounded, and your drivers inside a grounded enclosure?

    I know the morale feeling, I just had a couple of weeks of banging my head against the electronics for my mill. Got there in the end, but when the solution isn't obvious and it feels like you've tried everything, it's not fun.
     
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  22. Alex Chambers

    Alex Chambers Openbuilds Team
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    @Rob Taylor's advice is spot on @Benjamin Vg, while trying to work out what is going wrong just scratch the surface - 0.1 - 0.2 mm deep so that you are not putting too much sideways strain on your machine. If things are too large then it is almost certainly a calibration issue - too small could be several things.
    Alex.
     
  23. Benjamin Vg

    Benjamin Vg Journeyman
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    @Alex Chambers
    • A couple of messages ago I asked whether, after moving 1000mm, the machine would go back exactly to the start point => Yes that test is working I come back to the same point that is not and issue even with longer distances.
    • About the axes. I mainly testing it on the X axis currently. I didn't have done a lot of tests on the Y axe but it look that the problem is less present. I will do more test on this one if it can help
    • About the communication with Ryan : of course you can communicate with him. both of you are doing your best to help me and I am grateful for it.
    @Rob Taylor
    • About the belt: I have choose ooznest and this design because I wanted to be able to cut a mdf sheet on it and in they video they say that both beth and screw have the same precision. Only the hard material like meta could be more difficult to cut in a precise maner with belt. I am a total beginner so that is why I cannot juge about it.
    • About the kit: I was aware of the fact that it is more expensive but again without any experience at all it was clearly easier and now I am happy to have support. When I will have more experience it is possible that I will create my own...
    • About the depth: I have already tried a lot of time to calibrate my machine with my router turned off and a V bit on it. I had even uploaded this video for Ryan to make sure I was doing it correctly: (don't juge my english please ;-) )
    • Still about the depth: for the moment I have done all my tests with 2mm depth on eache pass because I am still afraid to break my bits... (usuall I using one or two passes)
    • About the calibration: I cannot have at the same time even without any load both 100mm, 500mm, and 1000mm correct. I need to choose one and then calibrate it with the G92 command and the correct numbers
    • About the noise: again even without turning it on. I have the same issue so I don't thing that it could be my issue. And I use the Makita rt700cx3j for what I saw it is avery classical one in the cnc world
    Thank to both of you for your support!

    Benjamin
     
  24. Benjamin Vg

    Benjamin Vg Journeyman
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    Btw, I have also checked the machine is mounted on a torsion box so it is very well flat and I have measure the diagonals it is squared...
     
  25. Alex Chambers

    Alex Chambers Openbuilds Team
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    When you say you are using the M92 command do you mean that you are changing the settings in the config.g file using the system setting editor in Duet Web Control?
    Alex
     
  26. Benjamin Vg

    Benjamin Vg Journeyman
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    Yes that is what I mean.
    I have just have executed the test on the Y axe (I have recalibrate again this morning) and it is almost perfect now. the 100mm measure 99,9mm and the 399mm only have a few tenth of a millimetre. So it look a lot better than on the X axe.

    Here is the result:
    20190614_130405.jpg
     
  27. Alex Chambers

    Alex Chambers Openbuilds Team
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    Please take much shallower cuts Benjamin. What is happening with the X axis?
    Alex.
     
  28. Benjamin Vg

    Benjamin Vg Journeyman
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    My cut is 4mm deep and on the X it is only 2 mm depth.

    The X axe give me this: 99.8mm for the 100mm and something like 405 for the 390mm
    20190614_100533.jpg

    If you look in the video even without turning on the router the problem is there.
     
  29. Alex Chambers

    Alex Chambers Openbuilds Team
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    Hi @Benjamin Vg, Yes - I saw that in the video. I've started an e-mail conversation with Ryan - while I'm waiting for his response could you post a copy of your config.g file here (it must be the one from your sys folder - use system settings editor to download it to your computer or select all and paste it into a notepad file)
    Thanks
    Alex.
     
  30. Benjamin Vg

    Benjamin Vg Journeyman
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    Here is my config file
     

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