Forum Comments

Electronics instructions
In Technical support
Robin Whittle
Aug 10, 2021
The existing documentation on mains wiring looks OK in principle for the power supply and for power to the VFD. However, it is far from clear how the very thick 4 core shielded cable should be connected to the spindle motor. The connector is too small for that cable, so the three wires or some other three wires to a junction box would need to be soldered into that connector, with some kind of sleeving to protect them from the body of the connector, and in all the circumstances of movement. Then there needs to be junction box or at least heatshrink and cable clamps for the transition from the thick cable to these three wires. What are the relevant Australian Standards regarding mounting 230V cables which flex repeatedly like this? I doubt if the local electrician would know this off the top of his head - but if he is going to sign off on the safety and legality of the installation, he will - or should - want to know. Then there needs to be the fourth wire going to the z chassis which holds the spindle motor. I don't accept - and neither should an electrician - that the spindle motor body will be grounded by being clamped in the thickly black anodized motor clamp. So it needs to be grounded via its 4th pin (not documented, but it is pin 4 - my multimeter shows this). Yet, according to the instructions, some (unspecified) spindle motors lack this and the instructions tell the electrician to connect ground via one of the four screws which hold the motor together. (On mine, the screws are deep in a plastic end piece. If raised to be high enough for a lug, the screw would not be screwed into the metal body of the motor at all, and so would perform no mechanical or grounding function.) Also, once the electrician gets things wired up, I will need to improvise a voltage source to get the VFD to power up (no time to set up the controller, PC and software while the electrician is waiting), so we can see the spindle motor turn. If it is in the right direction, good. If not, the electrician needs to change over two wires to the motor. Please bear in mind that an electrician is trained to wire houses. He has probably never worked on an CNC machine before. So I am supposed to ring up the local sparky and get him out here, show him the wiring diagrams, and get him to do it - including soldering the motor connector, which is very tight for space inside, with a metal body and no insulation between the pins and the body just 2 or 3mm away, with 3mm thick wires soldered . . . . . . . and he is supposed to be happy to do all this, as if he knows what he is doing, and then professionally certify it is all safe? What if he needs to run a high voltage insulation test on all this? The VFD surely would not like this. Now you are suggesting that the lack of documentation for the Emergency Stop switch is intentional, and that while the fellow is working on this strange stuff, he is supposed to call you for instructions? I cannot see how the emergency stop function is purely a wiring matter if it really does remove power from the controller and the VFD. If it wires into the controller and causes it to turn off current to the steppers, and turn off the control voltage to the VFT, then this is fine. But why deny DIYers this information? The headache and likely extended cost of getting a local electrician to successfully navigate all this is daunting enough apart from me expecting him to call you to get instructions on to wire up a possibly life-saving safety feature. My QueenBee is mechanically complete now. I didn't bother much with the instructions, since there was no clear path through the various documents which was clearly marked as the correct path for my particular machine. I referred to some instructions and videos in a piecemeal way. I found this mechanical build process *highly satisfying*. The lack of clear instructions was not a problem for me - but it would be for some other people, I think. However, this wiring and grounding of the spindle motor looks really difficult, at least if it is to be done by an electrician according to whatever Australian Standards apply to it. I would be asking a professional to come out and deal with stuff he has probably never dealt with before, with very scrappy documentation, with him certifying it to be safe and legal. Is he really supposed to do this professional work on the emergency stop button without written documentation? This doesn't sound legal or sensible.
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Robin Whittle

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