The extruder heater outputs on Duet boards should be capable of supporting most standard 3D heater cartridges, or old-style heating resistors. These usually come in capacities specified in Watts, and for either 12V or 24V supply. From this you can work out the resistance and current draw of the heater.
Some high capacity heaters, such as the E3D 12V SuperVolcano 80W Heater, can draw up to 8A, and are usually supplied with an external MOSFET board to provide power. Consult manufacturer's documentation for wiring.
| Watts | Volts | Resistance (Ohms) | Current (Amps) |
|---|---|---|---|
| 30W | 24V | 19.2 | 1.25A |
| 40W | 24V | 14.4 | 1.66A |
| 80W | 24V | 7.2 | 3.33A |
| 30W | 12V | 4.8 | 2.5A |
| 40W | 12V | 3.6 | 3.33A |
| 80W | 12V | 1.8 | 6.66A |
WARNING! DO NOT run a 12V heater on 24V!
As you can see from the above table, the 30W 12V heater has a resistance of 4.8 ohms. If you run this on 24V, the current draw is 24V / 4.8 ohms = 5A and power is 24V x 5A = 120W! Even running with a 25% PWM duty cycle, this means the heater will be on full power 25% of the time. PWM does not modify the voltage, it modifies the amount of time the output is turned on. Use a heater with a resistance that suits the supply voltage.
Most cartridge heaters come with long leads to connect to your controller, which should be suitable. If you need to lengthen wiring, make sure your heater wiring is capable of handling the current the heater will pull. Here are some things to consider:
As a general rule of thumb, 20AWG / 0.5mm2 multistrand wire can carry 3.5A. 18AWG / 0.8mm2 multistrand wire can carry 5A. But please check the specification of the wire you are using.
The extruder heater connectors vary with the Duet version.
| Board | 'Extruder heater' outputs | Connector type | RRF3 pin name | RRF2 heater number |
|---|---|---|---|---|
| Duet 3 Mainboard 6HC | 3 x 6A | JST VH | out1, out2, out3 | - |
| Duet 3 Mini 5+ | 2 x 5A | JST VH | out1, out2 | - |
| Duet 3 Expansion 3HC | 3 x 6A | JST VH | out0, out1, out2 | - |
| Duet 3 Toolboard 1LC | 1 x 5A | screw terminal | out0 | - |
| Duet 2 WiFi/Ethernet | 2 x 6A | screw terminal | e0heat, e1heat | 1, 2 |
| DueX2 and DueX5 | 2 (DueX2) or 5 (DueX5) x 6A | screw terminal | duex.e2heat to duex.e6heat | 3 to 7 |
| Duet 2 Maestro | 2 x 6A | screw terminal | e0heat, e1heat | 1, 2 |
Duet 3 Mainboard 6HC, Duet 3 Mini 5+ and Duet 3 Expansion 3HC use JST VH series connectors for connecting the extruder heater wires. You will need to crimp the supplied pins on the end of the heater wires, and push them into the supplied connector housing.
Duet 3 Toolboard 1LC, Duet 2 Wifi/Ethernet and Duet 2 Maestro use screw terminals for connecting the extruder heater wires.
In RRF 3.x, no heaters or temperature sensors are defined by default.
; Heaters
M308 S1 P"temp1" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 1 as thermistor on pin temp1
M950 H1 C"out1" T1 ; create nozzle heater output on out1 and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
M143 H1 S280 ; set temperature limit for heater 1 to 280C
; Tools
M563 P0 D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C
; Duet 2
; Heaters
M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
M143 H1 S280 ; set temperature limit for heater 1 to 280C
; Tools
M563 P0 D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C
In RRF 2.x, heater outputs are defined by default. Use M305 to configure the temperature sensor for the heater channel. Use M143 to set a maximum heater temperature. Finally, create a tool with M563 using the heater (including associated temperature sensor), motor, and fan.
; Heaters
M305 P1 T100000 B4725 C7.060000e-8 R4700 ; set thermistor + ADC parameters for heater 1
M143 H1 S280 ; set temperature limit for heater 1 to 280C
; Tools
M563 P0 D0 H1 F0 ; define tool 0
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
G10 P0 R0 S0 ; set initial tool 0 active and standby temperatures to 0C
M307 sets the heating process parameters. Tuning this with M303 should allow for finer control of the heater; more stable temperatures during printing, and less overshoot when setting temperatures. Each heating controller also performs temperature monitoring to try to detect fault conditions such as a heater of thermistor falling out of an extruder heating block. The temperature monitor relies on the model parameters to decide what is reasonable behaviour. See the wiki page on Tuning the heater temperature control.