¶ Note: There is a newer v3 version of this page that can be found here
¶ Required Wiring for Spindles
Double-shielded (braided and foil) 4 conductor VFD wire. Shield and ground needs to be terminated to both VFD and spindle.
- 2.2kW 120V spindle use #16 AWG or 1.5mm2 VFD cable.
- 2.2kW 220V spindle use #18 AWG or 1.0mm2 VFD cable.
- 1.5kW 120V spindle use #16 AWG or 1.0mm2 VFD cable.
- 1.5kW 220V spindle use #18 AWG or 0.75mm2 VFD cable.
HP is typically used as the method of determining motor strength and required cabling. Metric and British horsepower are slightly different, so I'm going to use the median of 740W = 1HP. A 2.2kW spindle is a 3HP motor, and a 1.5kW spindle is a 2HP motor.
Reference for calculations: https://www.lapptannehill.com/resources/technical-information/vfd-cable-selection-guide
Reference for shield requirement: https://www.wireandcabletips.com/how-much-importance-does-shielding-have-on-my-vfd-cable-selection/
¶ Recommended Wiring for Stepper Motors
Shield connected to ground at an electronics enclosure only.
Foil shielded 4 conductor wire. Up to 5A steppers can use #18 AWG or 0.75mm2 cable. Logan: 24 is too small. 20awg is better, 22 bare minimum
NOTE: The power path to the motors should be PSU → (stepper) DRIVER → (stepper) MOTOR.
Logan: Running DC straight to the (stepper) MOTORs WILL BREAK THEM.
The control path should be LinuxCNC PC → Break Out Board (parallel or Ethernet Mesa) → (stepper) DRIVERS.
The sensor signal path is Sensor → (optional) Sensor Connection Block → Break out Board sensor input pins. Consult your BOB documentation for information regarding any required pull-up or pull-down resistors.
The sensor power path is left as an exercise for the reader.
¶ Recommended Wiring for Endstop Switches or Sensors
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¶ Q – Can I use Cat5/Cat5e for motor wiring and end stops?
Yes for end-stops, it makes a lot of sense and is easy to work with. Patch cables are normally stranded wire, and some people use break out boards to expose the lines to screw terminals at either end but that is not a requirement.
Boxes of Cat5 wire meant for in-wall installation are normally solid core and don’t have the same bend radius as the stranded patch cables. You SHOULD NOT USE Cat 5 for wiring motors as it is not rated for the typical amp load the motors generate.
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¶ Q - Are folks powering their prox switches with 5V? Do they support 5V?
Mishkan said: usually 6v-36v. A majority of us are using 24V, just because thats a usual standard
Logan said: I'm using 12V because that's what my Cisco PSU has
¶ Recommended Lengths for Cable
For a standard sized PNC with the controller mounted within 1m of the end of the Y cablechain:
- 5m (16.5ft) VFD cable
- 15m (50ft) Stepper cable
- 15m (50ft) endstop cable
¶ Wiring example
/cnc_wiring_example-201122.pdf
¶ Frequently Asked Questions - Wiring
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¶ Q - Can I use Cat5 to connect my drivers to my Mesa or BOB?
You can use Cat5 patch cables (which are stranded, versus plenum cable which is usually solid core) to wire your Mesa BOB or Parallel BOB to your drivers. If you do so, use both cables in a particular twisted pair for each signal pair. For example, use Orange/White Orange for Step + and Step -, and Green, White Green for Dir + and Dir -. Use of the twisted pairs will minimize the potential for interference.
Stripping the sheath on Cat5 cable is a pain without the correct tool. Kelin makes a very nice tool that allows you to quickly and perfectly strip the shield without damaging any of the pairs.
Trader, BC CA: If anyone is going to be using Cat5 cables they have laying around for signal lines, this tool makes it heavenly: https://www.amazon.ca/Twisted-Radial-Stripper-Klein-VDV110-261/dp/B073YDM1J6/Mine just arrived. Beautiful, perfect strips of the outside sheath in seconds.
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¶ Q – Any wiring best practices?
Logan: Make sure you're using direct paths to a common terminal strip for your DC and ground (don't jumper between steppers) and same for your signals. (I did and I need to fix it) and use colored wires so it's easy to double-check your wires are going to the correct terminals.
Kotlikm: And always power down before changing driver settings. I did reach out to a few more name brand suppliers to ask if they know what a flashing green might mean. Nothing yet.
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¶ Q- I was watching some videos and the guy said that you should ONLY use solid wire for CNC for safety.... I feel like that is a bit over the top right? Using stranded is ok? I’m assuming it is since the shielded cable I have is stranded and the wire I use between components would probably be stranded too?
@rcw: Just avoid soldered connections to stranded cable anywhere that will see any repeated flex. My understanding is that ferrules are what you want there instead.
@Cybran Nakh: Yeah I’m putting ferrules on everything everything really. His video just made me second guess myself
Logan BC 🇨🇦: That's competely backwards. Solid is for permanently installed (unmoving) wires. Stranded is for motion.
rcwToday: Stranded, is what you want for flexible cable
Logan BC 🇨🇦: He's [guy in internet video] just 100% wrong. Are extension cords solid core? No.
m0jo QC 🇨🇦: That guy is also the one recommending to ground the spindle to the screw in the VFD that's actually not connected to anything, he sounds like he know his stuff, but I now have my doubts.
J1mbo: It's possible that he was referring to the control box wiring only. As Logan says, solid core wire can help in situations where the wires are not expected to move after installation, eg the control box. They can be bent to the path to and from components within the control box and maintain their shape meaning its probably easier and neater than using flexible wires. Either will work but good cable management is required in both instances. Additionally, provided you have the correct gauge wire for your components, solid core wiring doesn't require ferrules and can be terminated directly to the screw terminals. Finally, if you expect to be swapping/replacing components, stranded is better (with crimped ferrules) as it won't suffer microfractures in the wire from bending back and forth.
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¶ Q - I am going to order some 4 pair shielded wiring. Any reason not to go with 20 AWG rather than 22? My compound stripper only goes up to 20 so I'd rather use 20 just for ease of use if there are no down sides.
@logan: I used 18ga for my steppers, but I'm using 5.6A. bigger wire hurts nothing.
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¶ Q - So 18ga would future proof my wiring in case I beef up motors or drivers? And stranded not solid core?
@Logan: correct, stranded is the right type.
¶
¶ Q – I'm not very good at soldering, can I use Wago 221 connectors to joint my motor wire pigtails to my motor lines?
Yes. A 2 port Wago is fine to join each of the four lines from the controller to their corresponding line in the motor pig tail.
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¶ Q – If I want to use Wago 221 lever nut / lever lock connectors for my wirings, how can I easily mount them?
J1mbo: https://www.thingiverse.com/thing:4711150
That is for the older style connectors but the idea is solid and can be updated for Wago 221s.
Wago offer an official DIN rail mounting kit: https://www.wago.com/global/installation-terminal-blocks-and-connectors/mounting-carrier/p/221-500
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¶ Q – What are the correct connectors to crimp on the ends of wires going in to screw down terminals?
@logan: It's called a ferrule. You can get it and a crimper for about $25 on amazon, and it's completely necessary for stranded wires into screw terminals.
https://www.amazon.ca/Ferrule-Crimping-Terminals-Stripper-Projects/dp/B07H2K89DV/
¶
¶ Q – Do I need a compound wire stripper?
No, any good wire stripper will do. That being said, they are lovely to have and very fast and satisfying to use. I have had a good experience with this one: https://www.amazon.com/Capri-Tools-20010-Precision-Stripper/dp/B01018CVM0/
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¶ Q – Is there an easy way to step down my 24V power supply to 12V or 5V for accessories?
Trader: I have had good luck with these units. Less than $15, nice visual display, adjustable. However, max input is 32V and they are NOT rated for 36V unfortunately: https://www.amazon.com/DROK-Adjustable-Converter-Transformer-Protective/dp/B07JZ2GQJF/
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¶ Q - What is the formal name for the green screw terminal connectors the stepper drivers use? I want to see if there are right angle versions, the cabling may thwart my plans
Myatt: They are a “pluggable terminal block” and are created by Phoenix Contact.
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¶ Q - I am not using a spindle and my router power cord is 10' long but I don't think that is long enough, may be close. I guess the outlet it is fed from needs to be integrated in to the contactor/estop/safety model via a relay controlling that circuit?
Yes, you want your router to cut off when the emergency stop fires. You should consult with a professional electrician to ensure you have a safe outlet integrated in your design.
¶
¶ Q – What about fuses and cable raceway for the wiring diagram?
@logan: Maybe some 1A DC fuses for your power supply 12/5V outputs and a couple 10A for 42V to your drivers
@bob: din fuses?
@Logan: Yep just make sure they're rated above 42V for the 10 (or 1 - 20A if you can find it). Typically DC fuses are either 32V max or 400V max.
@bob: I have to figure all of the DIN stuff out as I have never used it but LOVE how clean it looks (when done properly).
Logan: The cheap wiring channels are for home theaters, but will work just as well for this. No need for the $100/m stuff
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Q – Where should you place fuses?
Logan: @J1mbo I put a 1A fuse between my 12 and 5 V lines and my loads, and a 10A DC meter fuse between my 42V supply and each pair of motors. X & Z together, both Y together, so if the fuse pops it won't rack the gantry
J1mbo: and what fuse holders?
Logan: Just cheap din inline ones. If I did it again I'd probably get the ones for solar.
Like this C$ 2.30 13%OFF | PV Solar Fuse 1000V DC Fusible 10x38 gPV, LED Fuse Holder for Solar System Protection ZTPV-25X
https://a.aliexpress.com/_mqONETJ
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¶ Q - If I don't go with aviation connectors, would I just use an electrical strain relief connector like you see in junction boxes?
Yes, something like this should be fine, if your box will be mounted: https://www.amazon.ca/MGI-SpeedWare-Strain-Relief-Cable/dp/B07KBFLF8X/
@logan: the "1/2" " needs a 7/8" hole. you can find them at a hardware store too, probably don't need 20.
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Wago also make a nice feed-through 12-pole (24 connection. 12 in/out) termination block. You can find it here: https://www.galco.com/scripts/cgiip.exe/wa/wcat/catalog.htm?searchbox=wago%20826-172
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¶ Q - If I use the strain relief outlets, would I run each motor out separately through different outlets direct from its stepper driver or could I group them all through one?
@logan: you'd need one for each motor probably. You could just get a 1" one but it wouldn't grip each cable individually very well.
Also one each for the axis prox sensors and a few spare maybe? I'm just running a single cat5 stranded for the sensors. Other considerations are VFD lines, parallel port and USB for LinuxCNC or USB for GRBL connection. Plan for USB jack for easy movement of PC.
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¶ Q – What are the wire connectors you typically need?
36V PSU – Ring screw down
Steppers – Ferrule
Motor pig tails – Wago 221 or XT60
Terminal Blocks – various terminal blocks with counts per your wiring design
Step drill is a good idea for drilling holes in enclosure box if plastic or metal.
¶
¶ Q - Are there any instructions on how to modify the drag chain?
BTownPilot: I did find the video below that might help some folks: https://www.youtube.com/watch?v=s2Gj_ONr8aw