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Thread: YOOCNC 3020Z-D52 losing steps

  1. #25
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    I tried the fixes that Max put out but to no help. X is still skipping. So I put my scope to it and found noise on the oscillator capacitor as long as the motor is connected to the board, but is clean when the motor is not connected. The noise is there when the motor is connected even if it is not moving. This leads me to think it is feedback from the charge pump in the chip. I looked and foundthat there are no decoupling caps on the chips, so I put a .47uF 100v ceramic on the bottom of the board between pins 6 and 20 of each chip. The cap lays flat and fits between the board and the heatsink. Since then, no missed pulses and a much cleaner clock signal. I also made the pulse pins active low in mach3. Hope this helps.

    Tim



  2. #26
    Registered helisat's Avatar
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    Hi Tim,

    Yes, I also added these capacitors to the supply line, which completely fixed the problem (big thanks to Rak for his advice). My machine is no longer skipping steps. Even after running a machine job for 2hrs, the machine had not lost its position.

    I recommend anyone with the "YOOCNC-NT65-3X" board should check and add these capacitors if required. Users should also ensure their pulse timings are correct (no guessing values here), and take into consideration your max CPU Jitter time. I had to modify BIOS settings to optimize/minimize my CPU Jitter.

    Regards,
    Luke



  3. #27
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    Hi,

    I'm having the same problem but I'm not that good at PCB board design / electronics. I think I can find the components you all suggest but I'm having a bit of a hard time figuring out what the "easiest" thing to do is as I now read multiple solutions? I'd like to fix as much as I can to prevent losing steps. As I'm Dutch, some English tech info isn't all that obvious to me...

    So, i.Is my following conclusion correct? :
    1. Make some hardware adjustments:
    - Adding the 470nF capacitors (ceramic or polyester both work fine?) to the pin 15 and ground of every TB6560 as suggested in the picure uploaded by Rak.
    - Adding .47uF 100v ceramic capacitator on the bottom of the board between pins 6 and 20 of each chip: This part is not really clear to me, I haven't got a clue which pin is 6 or 20... (where to start counting and in what order?). Could you please make a picture of the adjusted board?
    2. Use a software workaround in Mach 3 as suggested by Max:
    - Select Sherline 1/2 pulse mode (kernel speed at 25kHz is fine on my system according to the Mach3 drivertest so I don't need to change that).
    - In "motor Tuning" setting "Dir Pulse" to 15
    - What to do with the step pulse? Leave it at 3 as suggested by the manual? Or also put this at 15? Luke suggests "no guessing values here" but how do I do that? I'm not really getting what's meant in the Mach3 documentation on this subject.

    If that all is done, do I need to change anything else? I have the motors now at 400 steps, velocity at 1999.8 and acceleration at 50.

    I use the router to make model railway buildings etc. that need to be cut in different layers / depths with manual toolchanges inbetween and quite good accuracy (+/- 0.1mm is ok). I use polystyrene sheets and sometimes MDF.
    Hopefully you can help me with these last bits of info so I can modify my machine and really get it to do what I've got it for!

    Thanks,

    Maykel



  4. #28
    Registered helisat's Avatar
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    Hi Maykel,

    You only need to add the 470nF capacitors (ceramic or MKT) to the pin 15 and ground of every TB6560 (as shown in picture uploaded by Rak). This will fix the missing steps issue.

    I use LinuxCNC, so I'm not sure of the Mach3 config. Here are some screenshots of the Mach3 config from the manual that came with my machine. It worked for me when I first tested my machine:
    YOOCNC 3020Z-D52 losing steps-1-jpg

    YOOCNC 3020Z-D52 losing steps-2-jpg

    YOOCNC 3020Z-D52 losing steps-3-jpg

    YOOCNC 3020Z-D52 losing steps-4-jpg

    YOOCNC 3020Z-D52 losing steps-5-jpg



  5. #29
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    Hi,

    Ok, so I will try this first before buying an new controller. If it doens't help (engough), I'll let you know...

    Thanks all,

    Maykel



  6. #30
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    Hi Maykel,

    If you need any help just let me know.

    Regards,
    Luke



  7. #31
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    Thank you guys the solution, i also had the problem with x axis (cnc3040 machine) and now it's OK. Before the 3 470nF in a 10 minutes work i had 0,3-0,8mm position lost, now it's only 0,03mm (i can't measure 0,03mm of course but i marked the wheel and the house on the stepper motors and i have very little differences after a 10min work. i can fix it by moving 0,03mm) which is i think the general accuracy of the stepper motors. What do you think?

    Thanks again and best regards
    Thomas



  8. #32
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    Hi Thomas,

    That's good to hear. There are a few other factors that can cause missed steps.

    I'm using LinuxCNC, and in the configuration process it checks the CPU jitter time. From this you configure the Timings. From my understanding, if the timings are mis-configured, then it may miss sending some of the step pulse to the LPT, as the CPU is not ready to process the interrupt.

    I'm using an Intel P4 2.6GHz, and initially the CPU jitter was greater than 90ms (not good). I needed to disable the Intel SMI, and make a few tweaks in the BIOS, and now my CPU jitter is 12ms.

    You can still work with high jitter time, you just need to configure the timings accordingly.

    Since there is no motion feedback, the software will assume that every movement command was executed successfully. Therefore its critical that everything is configured correctly. From the PC side, the CPU and Pulse Timings are critical. In some cases is better to give yourself some buffer on the timings.


    Some people have also advised that all motor wires need to be shielded. Personally I haven't had any issues with unshielded wires.

    Hope it helps..

    Luke



  9. #33
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    A little update to my comment above.
    First time i used 2x 1uF MKT capacitor serial (that was at home only), now i replaced with 470nF ceramic wich is theoretically must be better.
    But no! i got a little bit more position lost in the usual 10min work (0,05mm). Then i solder a 47nF caramic cap paralell with each 470nF, now after 5 10min work i can't measure position lost at all

    Best
    Thomas



  10. #34
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    Default YOOCNC 3020Z-D52 losing steps

    Hello all,

    Thanks a lot for this thread. I got a CNC3040Z+D52 with the YOOCNC controller for Christmas and had exactly the same problems as described here: lost steps in the negative X-direction. Y, Z and positive X (to the right) worked fine. I couldn't believe that, I thought it must be some mechanical problem. The problem is gone after I added additional capacitors across the electrolytics as described above. I choose 1uF||0.1uF ceramics, but the precise values are probably not very important. So far I didn't change any Mach3 settings, but will probably do that later.

    I found another problem, with the board. I connected reference switches for X, Y and Z to the LIMIT socket and found that operation was highly unreliable. It turned out that the pull-up resistors for the optocouplers (R52) were much too low. They used a resistor network of 4 x 330 ohms (the fourth one is for E-Stop), which draws 15mA per channel. My parallel port input draws anther 2 mA, so that a closed switch pulled the voltage down to just a little below 1 V (which is exactly what the coupler spec says, but the designer has probably not read or understood it). That was sometimes recognized by the parallel port as low, but most of the time is was not. I removed the entire resistor network and replaced it with four single 1k resistors (size 0805). Now the reference switches work reliably.

    And finally I turned the front panel switches into their correct positions. They were mounted upside down. It is a good convention probably since Edison's days, that switches go up, right or in for “on” and down, left or out for “off”.

    And by the way, I happened to kill the IRF740 of the spindle driver just by stalling the spindle while it was powered. The fuse was blown as well, but obviously not fast enough to rescue the power MOSFET. I replaced both and now everything is back to normal. I reverse-engineered the spindle drive board and could provide the schematics, in case someone is interested.

    Cheers,

    Michael

    Attached Thumbnails Attached Thumbnails YOOCNC 3020Z-D52 losing steps-r52-jpg   YOOCNC 3020Z-D52 losing steps-switches-jpg  


  11. #35
    Registered Rakounet's Avatar
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    Hi Michael,

    Welcome to the club

    In a different thread, I have already posted the schematic diagram and layout. May be you can check them in case I made a mistake.

    Hope it can help.

    Rakounet

    Attached Thumbnails Attached Thumbnails YOOCNC 3020Z-D52 losing steps-yoc-3024pw_diagram-jpg   YOOCNC 3020Z-D52 losing steps-yoc-pw3024-layout-jpg  
    Last edited by Rakounet; 01-05-2014 at 11:24 AM.


  12. #36
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    Hello Rakounet,

    >> Welcome to the club
    Thanks a lot!

    >> In a different thread, I have already posted the schematic diagam and layout. May be you can check them in case I made a mistake.
    Oh great, that would have saved me some time. Please see my version attached. Note that I did not spend the effort to enter the correct reference designators. I used DesignSpark (free PCB program, DesignSpark - Home » DesignSpark) to draw the schematics (DesignSpark file attached as well). I can see a few minor differences. My board is called PW3618 and it uses the IRF740A as power MOSFET. Also the input voltage for the spindle is 36V, not 85V and the capacitors after the rectifiers are 22uF/250V, not 220uF. Maybe one of us made a mistake or we use a different spindle. I'll verify it next time when I open the enclosure.

    Btw., do you happen to have the schematics of the stepper drivers as well? I did not spend the time yet to analyze the board.

    Michael

    Attached Thumbnails Attached Thumbnails YOOCNC 3020Z-D52 losing steps-spindle-driver-pw3618-yoocnc-pdf  
    Attached Files Attached Files


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