3D printer wire gauge

How to Choose Wire Gauge and Length for Your 3d Printer


Duet Wifi

How to Choose Wire Gauge and Length for Your 3d Printer

How can you calculate the wire gauge and length for 3d printer wiring? Most 3D printers use either 12V or 24V. The hotend of a 3D printer may draw up to 4A, while a heated bed draws nearly 12A. If the wire is not large enough or longer than needed, it will have more resistance which means less watts going through the wire. Copper wire size uses American Wire Gauge (AWG) which determines how much current it can handle safely. To calculate 3d printer wiring calculations, divide Current in Amps by Length in Feet to identify the correct size of wire material needed for your 3D printing project.”

Stepper Motor Wiring

Rated Current is the maximum current that can pass through both windings at the same time. Set the motor current to no more than about 85% of the rated current. To get maximum torque out of your motors without overheating them, you should choose motors with a current rating no more than 25% higher than the recommended maximum stepper driver current.  

  • Nema 17 Stepper Motors: 22 AWG wire with 4 conductors
  • NEMA 17 motor wires are 26 AWG

Most motor torque data assumed 24 Volts, at 1.1 amp to 1.5 amp. Roughly 26 to 36 Watts, but remember that’s “chopped” or pulsed.

Wire size is based on power transmission requirements and length of wire.

If your wire gauge is not large enough or longer than needed the resistance will be higher This means less watts going through the wire. Copper wire size uses the American Wire Gauge (AWG). The lower the gauge number, the less resistance the wire has and therefore the higher current it can handle safely.

Most motor torque data assumed 24 Volts, at 1.1 amp to 1.5 amp. Roughly 26 to 36 Watts, but remember that’s “chopped” or pulsed. Wire size is based on power transmission requirements and length of wire.

Recommended Wire Size
  • 10 gauge wire – 30 amps
  • 12 gauge wire – 20 amps
  • 14 gauge wire – 15 amps
  • 16 gauge wire – 10 amps
  • 18 gauge wire – 7 amps
  • 20 gauge wire – 3 amps (or slightly more)
  • 22 gauge wire – 2 amps
  • Maximum motor current 1. 5A peak => Stepper motor rated current <= 1.9A
  • Maximum motor current 2.5A peak  => Stepper motor rated current <= 3.0A
  • Maximum motor current 1.6A peak with good fan cooling  => Stepper motor rated current <= 1.7A. 

3d printing at a higher speed uses more current and can cause wire overheating if wire thickness is not thick enough. Use motors with lower rated current (e.g. 1.0 to 1.2A) and 24V power, then the drivers will run cooler.

Duet 3 Current

Duet 3 Mainboard 6HC and Expansion board 3HC has a recommended maximum motor current 6.3A peak/4.45A RMS) => Stepper motor rated current <= 6A

Duet 3 Toolboard has a recommended maximum motor current 1.4A peak) => Stepper motor rated current <= 1.75A

One solution is twisted pairs of wire to have one wire carrying the current while the other brings the current back. Use a shielded 4-core high current wire, so that the wiring creates much less capacitive and induced interference or a twisted pair of twisted pairs.

Each individual winding should have a twisted pair, and these two pairs should be twisted (in the opposite sense) together. Twisted pair will reduce induced interference to a minimum, and twist-on-twist is a very flexible way to combine 4 wires. Alas the construction will couple capacitively to nearby signal cables, so it pays to keep separate from them, or ensure all signal cables are shielded. Signal cables are things like limit switch wiring, encoders, etc….

Using a cordless drill and a bench vice, keep enough tension to prevent kinking, and reverse briefly to lose any torsion before releasing the wires.

Wire Connectors

The Molex 4 pin connector are rated at about 14 Amps (.093 inch / 2.36 mm diameter terminals.

Calculating the wire size

A higher voltage means a lower current for the same amount of power. This gives you the opportunity to use smaller wires for the same job. Voltage is proportional to the current.  A higher voltage means a lower current. Wire size influences the amount of current that can pass through it.

  • A thicker wire will have less resistance per length
  • Less resistance means loss
  • The less loss means less temperature increase

In terms of wire size, 24V has an advantage over 12V, as the wires can be much smaller. A power supply of 300 watts running at 12V or 24V, will use less wire.

Wire Sizing Chart and Formula

Calculate the Voltage Drop Index (VDI) using the following formula:

  2. Determine the appropriate wire size from the chart above.

To compensate for voltage-drop, heat and current changes it is recommended to use 6 gauge wire and 4 gauge for over 15 feet.

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electronics - Using CAT6 cables for 3D printer motor / sensors / fans


Modified 5 years, 10 months ago

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I'm considering using CAT6 cables to connect my printer's extruder assembly to the control board. They seem like an elegant solution, but I've read conflicting opinions online on whether or not this would be feasible.

I would like to know if CAT6 cables can handle the required current, whether I should be worried about electromagnetic interference or other problems, and how I should pair up the wires. Cable length would be 30cm max.

Here are the relevant parts:

  1. E3D heater cartridge (2 wires)
  2. E3D thermistor cartridge (2 wires)
  3. 30mm hotend fan (2 wires)
  4. Z-axis auto-leveling probe (3 wires)
  5. NEMA 17 extruder motor (4 wires)
  6. 50mm part cooling fan (2 wires)

[cable A] I imagine I would use one CAT6 cable for parts 1-4, which form a logical unit (and in the future I might combine them into a removable module). I've been given to understand that power for the fan can be spliced from the z-probe or heater cartridge, so 8 wires should be enough.

[cable B] I would use a second CAT6 cable for parts 5 and 6. There will be two spare wires, so I could potentially double the bandwidth for the motor.

  • electronics




The ampacity question is not completely answerable because CAT6 does not specify wire gauge, so the current limit will depend on the specific gauge you get. CAT6 can be anywhere from 22 AWG to 24 AWG, and depending on who you ask this can be good for as much as 7A or as little as 0.5A. Given that you will have a bunch of wires in a bundle, this may cause them to heat up more than if they were in free air. For the steppers (1-2A) a single wire should suffice, but for the heater (around 3-4A) you might want to double up.

EMI will likely not cause any problems regardless of how you wire things up. CAT6 cables have the wires twisted in pairs of 2. Some people recommend to take advantage of these pairs: the +12V and GND of the heater should use a pair, each of the two coils of the steppers should have their own separate pairs. The reasoning behind this is that with equal current flowing in opposite directions in each wire of the pair, the generated electromagnetic fields will cancel out.

Twisted pairs are usually used when dealing with multiple pairs of wires that are carrying high frequency signals that might affect each other. The main concern for crosstalk in this application is if the stepper motor might cause the endstop to be erroneously triggered, but this is only a concern during homing when the feedrate (and thus frequency of the signal) is low anyways.



I did this for some of the wiring on my printer, and it's working fine so far. The two cautions are:

  • At @tom pointed out, the heater is the high current item, so be careful of the wire gauge, and avoid running the wire where air can't circulate well to cool it. Wire ratings differ greatly depending on whether they're in a bundle (poor air circulation) or free.

  • For the most part I agree that EMI shouldn't be a problem -- but if you switch to thermocouples it might become a problem -- they're much more sensitive, and this might have been part of the problem I described at How to get consistent and accurate readings from thermocouples? (though alternate wiring didn't completely solve the problem in that case).



CAT6 cable by itself is not a problem, it is typically 23 AWG solid core wire which can take you to 4A just fine. The real problem comes from the connectors you use. CAT6 usually goes hand in hand with 8p8c ethernet connectors which only have contacts rated to 500mA.

Also typically CAT6 cable is meant to be stationary (hence the solid core wires), so I'd go for something stranded. McMaster sells some nice cheap cabling that fits your needs, and it's actually meant for moving platforms like a CNC machine.




I've used some cat 6 in one of my printers and just to be safe I used 4 wires for the extruder heat block, 2+, 2-

On the thermistors 1 is more than enough for each +/-.

I also stripped the thick shielding off and used some 'curly' cable organizer in it's place, not the shielding on the wires but the cord. So i could fit 2 cables in slightly more than the same space as one. You are probably doing this to keep it organized too but this is an option if you run out of space in your wire runs.


How to safely extend silicon heating wires?

heated bed wiring

I'm in the middle of building a D-Bot printer and I'm running into a bit of a problem when it comes to heated bed wires. The heated layer is an aluminum plate with a silicon heater attached to it, and the heater wires are not long enough to pass through the resistance circuit when the Z-axis is fully extended.

Silicone gasket 120VAC / 750W and will be turned on/off with Fotek SSR. The heater wires are cloth covered and probably 22-24 AWG in length. (Sensor not marked)

I suspect I will need to extend the wires by inserting some kind of sleeve at the top of the resistance circuit, but I'm not sure if there are specific wire requirements for an AC powered heat table.

For this purpose, I was wondering:

  • Is there a specific wire gauge that I should use for heater wires, and should it have a specific sheath?
  • Which type of connector is best for safe wiring in this case?

Thank you in advance!

@Bluetopia, 👍 0