today I received a question about where to get a spindle cable for a Huanyang VFD/spindle kit.
The problem is, it is difficult to fit a well-dimensionated spindle power cable to cheap chinese spindles because they use rather small so-called “aviation connectors” instead of dedicated spindle power connectors. Also these “aviation connectors” are expected to be soldered, but this is not to recommend, especially not for beginners. In professional spindle connectors, the contacts are crimped contacts, not soldered.
May I e.g. refer to these threads:
If you look at cable manufacturer’s sites, you got to know that the cable between VFD and spindle is shielded power cable. A spindle needs a shielded 3+PE power cable, since spindles are three-phaseinduction motors, and since the currents that a VFD outputs are by no means nice sine waves, the cable emits heavy EMI, so it is always necessary to use a shielded spindle cable and a VFD is meant to be enclosed into an earthed control cabinet. To prevent currents harmful for the spindle bearings, the entire CNC machine has to be properly grounded.
Note that you may have neglected grounding all the moving components of your CNC machine until now, because…
these milling motors made by Mafell and AMB (former Kress) are, like the Makita hand trim router, double-insulated Class II (IEC 61140) devices that are not grounded. However, the Onefinity CNC is a grounded Class I device. All of its components that are able to carry current must be grounded. Important: The electrical connection of the individual components of the machine via the linear bearings or the ball screws is not a valid protective ground connection. Each moving part must be connected to ground with its own protective earth conductor. As mentioned in the thread linked above, grounding the entire CNC machine in accordance with safety regulations is not only mandatory as of the safety standards, but also noticeable in terms of preventing EMI and eliminating electric shocks due to potential differences.
Note that the use of a TN−C earthing system with PEN conductor (combined PE and N conductor) breaks the protection concept of protection class I.
The additional importance of proper grounding when using a spindle is that it is earthed and that it is driven by a VFD that uses high carrier frequencies internally. Proper grounding, shielding and filtering is necessary to prevent motor bearing currents which can damage the bearings of the spindle.
By the way, switching from the router to a spindle is also the reason why then you don’t need the magnet end of Touch probe anymore. Since the spindle is earthed, the Touch probe connection only needs one wire (see here).
Regarding damage to the spindle bearings from the VFD stray currents, I have been involved with the repair of several large industrial motors damaged by stray VFD current, the only way to prevent this is either grounding the spindle shaft via carbon brush or non metallic bearings such as commonly advertised ceramic bearings, shielding and connecting ground wires does not help in this case.
yes, grounding spindle shaft with a carbon brush, use of conductive bearing grease or using non-conductive bearings would be the direct interruption of bearing currents. But you cannot always implement this. I think more possible countermeasures are listed correctly here and here. That’s why I wrote “proper grounding, shielding and filtering is necessary”. It’s high-frequency, common-mode currents that make problems, and countermeasures can also include to try to avoid or suppress them.
The conductive bearing grease is a new one to me, one other thing, my experience has been with large high horsepower motors that run 24-7 under full load, I have seen 2 identical motor / pump / VFD setups and one will fail bearings every 2 years and the twin never does, it is a mystery why some do and some don’t. I wonder if these small router spindles only running occasionally will even have any issues or if anyone would disassemble a failed motor to see if the bearings are fluted or not.
How in the heck does one achieve this from a practical standpoint? I know there are various threads on grounding, but I’m not seeing a clear path to grounding all the components that are able to carry current. Is that every single 1F component?? Is that possible without leveraging the electrical contact through the linear rails and ball screws. I’m stumped. Double drag chains?? Green wire everywhere? Looking for some actionable advice here based on the following set-up, which I think is common among many users.
1.5kW @PwnCNC Kit - older version, ordered in May of 2022, so no EMI filter, but I do see there’s an upgrade kit available. No idea which version I have, but can find out.
Kreg 44" x 64" Bench
Dedicated 120V @ 20A Breaker for Spindle
Dedicated 120V @ 15A Breaker for Dust collection, controller, monitor, lights, etc… everything else in my garage runs off of this. No other woodworking equipment is ran simultaneously.
Is it recommended to run dedicated ground wires through the drag chains that are then attached to the aluminum blocks for X and Z with some type of ground terminals? Would I need to drill and tap the blocks to do this?
Is it recommended to keep the grounds of the 2 separate circuits isolated, as mentioned here?
Given that I’m getting close to performing the drag chain installation, it would be great to implement this type of thing now to avoid doing it 2x.
there are good locations all over the machine to attach ground wires (e.g. stepper motor screws. Don’t loosen adjustment screws on the machine though!). Usually ring connectors are used that are crimped to the the protective earth wires and that have a mounting hole to simply attach them on bolts. I don’t think it is necessary to make new holes, just use bolts that are already present.
It is important to order ring connectors with the correct combination of mounting hole (given by the bolt to which you want to attach the connector) and the wire cross-section area. The superior safety of a crimp connection can only be accomplished when both the sheet metal crimping sleeve of the connector and the crimping pliers insert are matching the wire cross-section area. Otherwise there is the danger of a faulty connection. The color code is: Red: 0.5–1 mm², Blue: 1.5–2.5 mm², Yellow: 4–6 mm². In the image above ring connectors for two wire cross-secton area ranges blue and yellow, and for three different bolt sizes, M4–M6, are shown.
(For conversion of IEC 60228 cross-section area to American Wire Gauge see here:
The crimp insert shown above has two pressing surfaces one behind the other, the first to press the bare copper wires into the sheet metal sleeve, and a second behind that, which presses the entire wire together with its insulation into its own sleeve to create strain relief and kink protection. This allows to crimp both in one step. With simpler crimping pliers, you do this with two separate steps. The crimp pliers shown in the image above is rather expensive, but designed for day-long use, it features almost parallel crimping motion, consistently high crimping quality thanks to precision dies and ratchet mechanism (unlockable) and optimum transmission of force due to lever action for fatigue-reduced operation. Of course a $20 crimping pliers will also do:
Perhaps it’s what I mentioned above: The one has the motor cable wiring going through ferrite rings or uses an AC reactor on the output, uses a good shielded cable with symmetrical geometry (common-mode noise reducing) with extra low impedance or simply uses a lower internal carrier frequency (<5 kHz) on their VFD, others possibly do none of that.
thank you! Yes, it’s mentioned on different topics, e.g. here (besides LAPP ÖLFLEX® CLASSIC FD 810 CY). There are already a lot of threads about spindle/VFD wiring in this forum, but the information is a little spread around
Apologies, but I read enough of your posts to puzzle out that I could buy an igus cf31-60-04 cable to power my Huangyang 240V 2.2kw spindle, but missed the part where it was dis-recommended to attempt to so solder it myself. The cable and the spindle are sitting in my garage.
I can enlist an electrical engineer to help, but what is the correct way to build a cable for these spindles? Does one buy a crimped connector which is mechanically compatible with the spindle? Replace the male end of the connector on the spindle (held in by four screws) so that both sides of the connector are replaced? Or use judgement, knowledge and experience to make the existing aviation connector work as best as it can? I see your phoenixcontact link but am having trouble puzzling out what the standards actually are.
the main problem with the “aviation” connectors found on cheap chinese spindles is that their strain relief fits maximally a cable with outer diameter of 7.8 mm. For a 2.2 kW spindle, this is usually a too weak cable. But the cable you linked to is AWG10 / 6.0 mm² with 16 mm outer diameter is stronger as necessary.
The cheap chinese spindles have the “aviation” connectors for which you can buy cables ready-to-use here from PwnCNC. I don’t know how thick the cables are and how @PwnCNC manages to fit them in the connectors, but they offer the range of “aviation” connectors that are found out there.
If you have experience with soldering and have a strong soldering station with at least 80 W and with temperature sensor, you can of course solder it, but if you are not really experienced or if your soldering iron is too weak, due to the higher mass of connector contacts, you could get a “cold” soldering spot that may fail.
Generally a crimped connection is superior to a soldered connection, not only because solder has a much lower melting temperature than the wire material which is not ideal in cases of shorts, but primarily because when solder is applied with heat, it tends to creep in varying and unpredictable amounts along the individual strands of the wire and the area of the individual strand affected by the solder loses its flexibility. When such cables are subjected to movement, individual strands break. A crimped connection ensures that the compressed part of the wire begins and ends at a defined point and does not differ between the individual strands.
Effective crimp connections deform the metal of the connector past its yield point so that the compressed wire causes tension in the surrounding connector, and these forces counter each other to create a high degree of static friction which holds the cable in place. Due to the elastic nature of the metal in crimped connections, they are highly resistant to vibration and thermal shock.
A well-engineered and well-executed crimp is designed to be gas-tight, which prevents oxygen and moisture from reaching the metals (which are often different metals) and causing corrosion.
Because no alloy is used (as in solder) the joint is mechanically stronger.
You could do this. It is difficult to advise on this because I never tried to fit a big enough cable into these connectors. I decided that because I want to use the machine professionally, that I would buy a professional spindle, and it has the industrial connector shown above. But you could ask Daniel @PwnCNC how they make the spindle cables they offer using the “aviation” connectors.
Whoops. I pulled that gauge from the Omron manual but used the wrong inverter model; that’s the recommendation for a single phase motor. It may be difficult for me to find a connector that that cable will fit into.
I know the table you mean. There is an error in this table. They took the same value AWG10 for input and output for the single-phase input model, which can only be wrong. AWG10 is only valid for the input on 2.2 kW single-phase input model. On the output, you have the power on three phases shifted by 120° which means AWG12 or AWG13 is enough. I use 3 x 4.0 mm² (2+PE) at the single-phase input of VFD and shielded 4 x 2.5 mm² (3+PE) on the output (VFD to spindle).