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  1. #1
    Hello. I bought a cnc 6040, 2.2KW on aliexpress from Chinacnczone.
    The cnc works well enough only that I have a problem.
    The spindle speed is about 20% greater than the one set as shown in the following graph:
    s1000 -> 23.60
    s2000 -> 40
    s4000 -> 74
    s6000 -> 114
    s8000 -> 150.80
    S10000 -> 187.60
    S12000 -> 230.80
    S14000 -> 270
    S15000 -> 290
    S16000 -> 309.6-310
    S18000 -> 356
    S20000 -> 400

    Click image for larger version. 

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    It should go to 400Hz when I set s24000 and not with s20000.
    I opened the controller and found that they connected the output of the inverter (Nowforever D100S2R2B) that is 12v to a board input (MKS-V-V02 www.cdxhctech.com) that instead expects10v, as shown in the following scheme.

    Click image for larger version. 

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    How can I solve the problem? Where to get 10v?

    Thank you.

  2. #2
    You could build an amplifier circuit which gives a % of input voltage as output, and set it to give 10v Out for 12v In
    It's a fairly basic Op Amp project, the plans for which are easily found with a Google search,
    Regards,
    Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  3. #3
    Maybe you could adjust these parameters, specifically "P0-024 max input corresponding frequency"

    But before changing anything, what are they set to now ?

    P0-021 AIN min input Setting range 0.00~10.00V
    Factory value:0.00V
    P0-022 AIN min input corresponding frequency Setting range 0.00~600.00Hz
    Factory value:0.00Hz
    P0-023 AIN max input Setting range 0.00~10.00V
    Factory value:10.00V
    P0-024 AIN max input corresponding frequency Setting range:0.00~600.00Hz
    Factory value:50.00Hz
    Last edited by EddyCurrent; 07-01-2018 at 01:44 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  4. #4
    One for the electronic experts - would a pair of resistors in series across the 12V output with values chosen to give 10V at the centre tap point work? All outputs would be 10/12 ths of the input so it would track all intermediate speeds ? If so just 2 cheap components required
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  5. #5
    Quote Originally Posted by routercnc View Post
    One for the electronic experts - would a pair of resistors in series across the 12V output with values chosen to give 10V at the centre tap point work? All outputs would be 10/12 ths of the input so it would track all intermediate speeds ? If so just 2 cheap components required
    That's a classic Voltage Divider and Yes, it will work provided your circuit can carry enough current to deliver the signal current required (V=IR)
    Do the maths in combination with the input impedance data from the controller manual.
    Remember that sourcing any current from a simple resistor based Voltage Divider will skew the output, you need to know the input impedance and available current to work out the values which will safely give the best result.
    Hence my suggestion of an Op Amp circuit with fractional gain.

    - Nick
    Last edited by magicniner; 07-01-2018 at 04:54 PM.
    You think that's too expensive? You're not a Model Engineer are you? :D

  6. #6
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 4-5 years. Has a total post count of 233. Received thanks 19 times, giving thanks to others 9 times.
    Okay, had a quick look at the data sheets for both the inverter and the controller. OP is quite correct - the controller expects to be supplied a 10V supply from (e.g.) inverter, and will presumably generate a 0-Vref for the spindle speed. What is needed is to reduce the 12V reference voltage to 10V. A simple way to do this would be to place 3 silicon diodes in series with the 12V output from the spindle.

    +12 -------->|------>|------>|------------- +10V In

    Diodes 1N4001, or similar would be good enough and cost pennies each.

    You could put a LM317 regulator inline - with 2V difference between Vin and Vout, it should manage well enough, but it's probably a sledgehammer to crack a nut.

    There is also a AO1 analogue output on the inverter, range 0-10V, but I can't figure out a way to use this to generate a constant 10V output.
    Last edited by Doddy; 07-01-2018 at 05:51 PM.

  7. #7
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 8 Hours Ago Has been a member for 4-5 years. Has a total post count of 1,128. Received thanks 201 times, giving thanks to others 5 times.
    I would go for the diode solution as well. Even if you buy from Maplin, they're still cheap enough and it's a better solution than resistors. Tweak the calibration as also suggested here (if needed - give or take a few per cent, spindle speed isn't that important) and job's done.

  8. #8
    A fixed 2 Volt drop may be acceptable for the OP's requirements and that's an elegant solution if such is the case, I had Tunnel Vision on an output proportional to the input,

    - Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

  9. #9
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 7 Hours Ago Has been a member for 4-5 years. Has a total post count of 233. Received thanks 19 times, giving thanks to others 9 times.
    I'm impressed with the inverter - the manual claims the electrolytic caps within are "wearing parts" and must be replaced after 5 years.

    At least they're honest.

  10. #10
    ..Clive
    The more you know, The better you know, How little you know

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