1. #1
    Hi,

    I have been operating an enhanced Ox CNC for the last few months and all has been going smoothly.

    I operate a 400W 48v Chinese spindle which performs flawlessly apart from one electrical issue I think I have introduced. I operate it at max rpm via the potentiometer which is stated to be 12000r/min on the datasheet, although I do not currently have a way to measure the rpm. I decided to extend the cabling from the spindle to the speed controller in order to tidy up the cables. This involved an extra metre of same gauge wire to what the manufacturer supplied. Now, when I reconnected and powered up, the rpm seems to be slower based on the sound and additional bit chattering when operating at the same feed rate and depth of cut as before. (3mm depth 1400 mm/min). It feels like a 20% reduction if I had to make a guesstimate.

    My question is, as I have extended the cabling, has this introduced a voltage drop due to increased resistance over the length and thus caused a reduced rpm? And secondly, what can I do to regain the previous max rpm? Would changing select cables out to a thicker wire help reduce voltage drop?

    I extended the following wires,
    Motor U, V, W
    Hall Sensor Hall+, Hall-,HA, HB, HC

    Many thanks in advance for any assistance,

    Mike

  2. #2
    It probably is voltage drop if thats all you have done and sure you haven't messed up the wires. Thou the Speed reference voltage must have been on the low side to start with for only 1mtr to affect it that much.
    Often the Voltage source is 10V but using a Pot etc you never actually get 10v which the speed controller needs for full rpm.

    Start by measuring the voltage at full speed and see what you get. You may need a higher voltage source like 12V to get full 10V for the speed controller.

  3. #3
    Thanks for your response. The wiring is all correct as the spindle spools up smoothly as before but seems to top out at a lower RPM. For further info, the wiring was about 1.2m in length, now extended to about 2.5m.

    I lack some electrical knowledge. Which pins on the speed controller should I measure between to get the voltage reading mentioned above. And should it result in being lower than the 10v suggested, how would I go about boosting it? The speed controller itself is supplied with 48v.

    Many thanks,

  4. #4
    Quote Originally Posted by TheMike View Post
    I lack some electrical knowledge. Which pins on the speed controller should I measure between to get the voltage reading mentioned above. And should it result in being lower than the 10v suggested, how would I go about boosting it? The speed controller itself is supplied with 48v.
    Well to be fair if your not electrically minded then I suggest you don't mess around because depending on the Speed controller type the voltages can be at mains potential and dangerous if poking around not knowing what your doing.!! Suggest you try to find someone electricly savy to help with this.

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